Archivo Digital UPM: No conditions. Results ordered -Date Deposited. 2019-11-18T13:21:52ZEPrintshttp://oa.upm.es/style/images/logo-archivo-digital.pnghttp://oa.upm.es/2018-12-17T06:34:19Z2019-04-26T07:21:51Zhttp://oa.upm.es/id/eprint/53263This item is in the repository with the URL: http://oa.upm.es/id/eprint/532632018-12-17T06:34:19ZComparative Saturn‐Versus‐Jupiter Tether OperationSaturn, Uranus, and Neptune, among the four Giant Outer planets, have magnetic field B about
20 times weaker than Jupiter. This could suggest, in principle, that planetary capture and operation using
tethers, which involve B effects twice, might be much less effective at Saturn, in particular, than at Jupiter. It
was recently found, however, that the very high Jovian B itself strongly limits conditions for tether use,
maximum captured spacecraft-to-tether mass ratio only reaching to about 3.5. Further, it is here shown that
planetary parameters and low magnetic field might make tether operation at Saturn more effective than
at Jupiter. Operation analysis involves electron plasma density in a limited radial range, about 1–1.5 times
Saturn radius, and is weakly requiring as regards density modelingJuan Ramón Sanmartín LosadaJesus Pelaez AlvarezI. Carreras Calvo2018-12-14T12:26:05Z2019-03-05T10:27:32Zhttp://oa.upm.es/id/eprint/53260This item is in the repository with the URL: http://oa.upm.es/id/eprint/532602018-12-14T12:26:05ZA minor mission to ice giant NeptuneBroad missions Cassini, at Saturn, and Galileo and now Juno, at Jupiter, provided deep overall knowledge about the Gas Giants. For minor missions involving specific visits, like exploring moon Europa at Jupiter, or maybe Enceladus in the Saturn case, electrodynamic tethers, which are thermodynamic in character and can provide free propulsion and power for capture by a planet, followed by free maneuvering for exploration, could make for more than ‘orbiter’ missions.Juan Ramón Sanmartín LosadaJesus Pelaez Alvarez2018-12-14T09:17:29Z2018-12-14T09:17:29Zhttp://oa.upm.es/id/eprint/53258This item is in the repository with the URL: http://oa.upm.es/id/eprint/532582018-12-14T09:17:29ZOn aluminum tapes treated for missions at JupiterElectrodynamic tethers are effective at Jupiter because of its high magnetic field, the length-averaged tether current lying well below its high short-circuit bound for dimensions of interest. With aluminium tethers having thermal emissivity as low as 0.03 at a temperature of 300 K, over the entire spectrum, they present inadequate heat dissipation in the termal infrared region. A nanostructured coating with high thermal-emissivity and high conductivity, as compared to Al and Al2O3 respectively, is being developed in the present work for tethers exposed to the hard conditions at Jovian operation.Isabel MonteroJuan Ramón Sanmartín Losada2017-04-03T11:20:49Z2017-05-12T10:39:10Zhttp://oa.upm.es/id/eprint/45402This item is in the repository with the URL: http://oa.upm.es/id/eprint/454022017-04-03T11:20:49ZA review of macroscopic motion in thermodynamic equilibriumA principle on the macroscopic motion of systems in thermodynamic equilibrium, rarely discussed in texts, is reviewed: Very small but still macroscopic parts of a fully isolated system in thermal equilibrium move as if points of a rigid body, macroscopic energy being dissipated to increase internal energy, and increase entropy along. It appears particularly important in Space physics, when dissipation involves long-range fields at Electromagnetism and Gravitation, rather than short-range contact forces. It is shown how new physics, Special Relativity as regards Electromagnetism, first Newtonian theory then General Relativity as regards Gravitation, determine different dissipative processes involved in the approach to that equilibrium.Juan Ramón Sanmartín Losada2017-03-27T12:35:56Z2017-03-27T12:36:55Zhttp://oa.upm.es/id/eprint/45320This item is in the repository with the URL: http://oa.upm.es/id/eprint/453202017-03-27T12:35:56ZAnalysis of thermionic bare tether operation regimes in passive modeA thermionic bare tether (TBT) is a long conductor coated with a low work-function material. In
drag mode, a tether segment extending from anodic end A to a zero-bias point B, with the standard
Orbital-motion-limited current collection, is followed by a complex cathodic segment. In general,
as bias becomes more negative in moving from B to cathodic end C, one first finds space-chargelimited
(SCL) emission covering up to some intermediate point B*, then full Richardson-Dushman
(RD) emission reaching from B* to end C. An approximate analytical study, which combines the
current and voltage profile equations with results from asymptotic studies of the Vlasov-Poisson system for emissive probes, is carried out to determine the parameter domain covering two limit regimes, which are effectively controlled by just two dimensionless parameters involving ambient plasma and TBT material properties. In one such limit regime, no point B* is reached and thus no segment full RD emission develops. In an opposite regime, SCL segment BB* is too short to contribute significantly to the current balance.Juan Ramón Sanmartín LosadaXin ChenGonzalo Sánchez Arriaga2016-12-13T09:17:41Z2019-06-05T10:10:17Zhttp://oa.upm.es/id/eprint/44157This item is in the repository with the URL: http://oa.upm.es/id/eprint/441572016-12-13T09:17:41ZComparison of technologies for deorbiting spacecraft from
Low-Earth-Orbit at end of missionAn analytical comparison of four technologies for deorbiting spacecraft from Low-Earth-Orbit at end of mission is presented. Basic formulas based on simple physical models of key figures of merit for each device are found. Active devices - rockets and electrical thrusters - and passive technologies - drag augmentation devices and electrodynamic tethers - are considered. A basic figure of merit is the deorbit device-to-spacecraft mass ratio, which is, in general, a function of environmental variables, technology development parameters and deorbit time. For typical state-of-the-art values, equal deorbit time, middle inclination and initial altitude of 850 km, the analysis indicates that tethers are about one and two orders of magnitude lighter than active technologies and drag augmentation devices, respectively; a tether needs a few percent mass-ratio for a deorbit time of a couple of weeks. For high inclination, the performance drop of the tether system is moderate: mass ratio and deorbit time increase by factors of 2 and 4, respectively. Besides collision risk with other spacecraft and system mass considerations, such as main driving factors for deorbit space technologies, the analysis addresses other important constraints, like deorbit time, system scalability, manoeuver capability, reliability, simplicity, attitude control requirement, and re-entry and multi-mission capability (deorbit and re-boost) issues. The requirements and constraints are used to make a critical assessment of the four technologies as functions of spacecraft mass and initial orbit (altitude and inclination). Emphasis is placed on electrodynamic tethers, including the latest advances attained in the FP7/Space project BETs. The superiority of tape tethers as compared to round and multi-line tethers in terms of deorbit mission performance is highlighted, as well as the importance of an optimal geometry selection, i.e. tape length, width, and thickness, as function of spacecraft mass and initial orbit. Tether system configuration, deployment and dynamical issues, including a simple passive way to mitigate the well-known dynamical instability of electrodynamic tethers, are also discussed.Gonzalo Sánchez ArriagaJuan Ramón Sanmartín LosadaEnrico C. Lorenzini2016-10-24T07:07:33Z2016-10-24T07:07:33Zhttp://oa.upm.es/id/eprint/43736This item is in the repository with the URL: http://oa.upm.es/id/eprint/437362016-10-24T07:07:33ZA comparison between analytical and numerical solutions
of the Vlasov equationJuan Ramón Sanmartín Losada2016-10-18T11:37:46Z2018-01-01T23:30:10Zhttp://oa.upm.es/id/eprint/43606This item is in the repository with the URL: http://oa.upm.es/id/eprint/436062016-10-18T11:37:46ZAnalysis of tether-mission concept for multiple flybys of moon EuropaAll four giant planets, far from the Earth and sun and having deep gravitational wells, present propulsion and
power mission issues, but they also have an ambient plasma and magnetic field that allows for a common mission
concept. Electrodynamic tethers can provide propellantless drag for planetary capture and operation down the
gravitational well, and they can generate power to use along with or be stored for inverting tether current. The design for an alternative to NASA’s proposed Europa mission is presented here. The operation requires the spacecraft to
pass repeatedly near Jupiter, for greater plasma density and magnetic field, raising a radiation-dose issue that past
analyses did take into account; tape tethers tens of kilometers long and tens of micrometers thick, for greater
operation efficiency, are considered. This might result, however, in attracted electrons reaching the tape with a
penetration range that exceeds tape thickness, thereby escaping collection. The mission design requires keeping the
range below thickness throughout, resulting in an orbit perijove only hundreds of kilometers above Jupiter and tapes
a few kilometers long. A somewhat similar mission design might apply to other giant outer planets.Juan Ramón Sanmartín LosadaMario CharroHenry B. GarretGonzalo Sánchez ArriagaAntonio Sánchez Torres2016-09-26T08:11:43Z2019-03-15T18:17:50Zhttp://oa.upm.es/id/eprint/43360This item is in the repository with the URL: http://oa.upm.es/id/eprint/433602016-09-26T08:11:43ZSurvivability analysis of tape-tether against two concurring impacts with debrisIt has recently been shown that a thin-tape tether, as opposite to a round one, has a high probability of survival to single impacts by space debris, under a broad range of de-orbit operation conditions. The purpose of the present work is to extend that analysis to survival to multiple impacts by smaller, but more abundant, debris. The method used here consist, essentially, in separating the particles into “large” and “small” ones. The large ones are so rare that the probability of them concurring on the same spot can be neglected. The small ones are a sort of background, and it is shown that the probability of them impinging close enough to a large particle crater to cause malfunction of the tape is negligible. A particular mission is considered, de-orbiting a 3000 kg spacecraft from 800 km altitude at 90°90° inclination by means of an aluminium tape of dimensions 10,000 m × 0.06 m × (5 × 10−5) m. It is shown that the probability that this mission survives to multiple impacts is at least 0.978. The application of this method to missions of different parameters is also discussRicardo Ángel García-Pelayo NovoShaker Bayajid KhanJuan Ramón Sanmartín Losada2016-09-22T11:50:56Z2016-09-22T11:50:56Zhttp://oa.upm.es/id/eprint/43361This item is in the repository with the URL: http://oa.upm.es/id/eprint/433612016-09-22T11:50:56ZAnalysis of thermionic bare tether operation regimes in passive modeA Thermionic Bare Tether (TBT) is a long conductor coated with a low work function material. Under drag mode, a tether segment extending from anodic end A to a zero-bias point B, with standard Orbital-motion-limited current collection and ohmic effects, is followed by a complex cathodic segment. In general, as bias becomes more negative in moving from B to cathodic end C, one first finds space-charge-limited emission covering up to some intermediate point B*, then full Richardson-Dushman emission reaching from B* to end C. An approximate analytical study, which combines current and voltage profile equations with results from asymptotic studies of the Vlasov-Poisson system for emissive probes. is carried out to determine the parameter domain covering two limit regimes. In one such regime no point B* is reached and thus no full R-D emission develops. In an opposite limit regime, segment BB* is too short to contribute significantly to current balance.Juan Ramón Sanmartín LosadaXin ChenGonzalo Sánchez Arriaga2016-09-22T11:50:24Z2016-09-22T11:50:24Zhttp://oa.upm.es/id/eprint/43367This item is in the repository with the URL: http://oa.upm.es/id/eprint/433672016-09-22T11:50:24ZOverrall review of thin-tape bare tethers operation as just thermodynamics processJuan Ramón Sanmartín Losada2016-09-22T11:43:31Z2016-09-22T11:43:31Zhttp://oa.upm.es/id/eprint/43368This item is in the repository with the URL: http://oa.upm.es/id/eprint/433682016-09-22T11:43:31ZComparison of technologies for de-orbiting spacecraft from low-earth-orbit at end of missionGonzalo Sánchez ArriagaJuan Ramón Sanmartín LosadaEnrico C. Lorenzini2016-02-10T14:00:38Z2016-04-14T10:35:58Zhttp://oa.upm.es/id/eprint/39306This item is in the repository with the URL: http://oa.upm.es/id/eprint/393062016-02-10T14:00:38ZTether-mission design for multiple flybys of moon EuropaElectrodynamic tape-tethers are shown to allow a cheap, light, fast mission to Jupiter for multiple flybys of moon Europa and close exploration of the Jovian interior. As regards flybys, this mission is similar to the Clipper mission presently considered by NASA, the basic difference (periapsis location) arising from mission-challenge metrics.Juan Ramón Sanmartín LosadaMario CharroGonzalo Sánchez-ArriagaAntonio Sánchez-Torres2016-02-09T11:11:16Z2016-02-09T11:11:16Zhttp://oa.upm.es/id/eprint/39288This item is in the repository with the URL: http://oa.upm.es/id/eprint/392882016-02-09T11:11:16ZOutreach Testing of Ancient AstronomyThis work is an outreach approach to an ubiquitous
recent problem in secondary-school education: how to
face back the decreasing interest in natural sciences
shown by students under ‘pressure’ of convenient
resources in digital devices/applications. The approach
rests on two features. First, empowering of teen-age
students to understand regular natural events around, as
very few educated people they meet could do. Secondly,
an understanding that rests on personal capability to test
and verify experimental results from the oldest science,
astronomy, with simple instruments as used from
antiquity down to the Renaissance (a capability
restricted to just solar and lunar motions).
Because lengths in astronomy and daily life are so
disparate, astronomy basically involved observing and
registering values of angles (along with times),
measurements being of two types, of angles on the
ground and of angles in space, from the ground. First,
the gnomon, a simple vertical stick introduced in
Babylonia and Egypt, and then in Greece, is used to
understand solar motion. The gnomon shadow turns around during any given day, varying in length and thus
angle between solar ray and vertical as it turns, going
through a minimum (noon time, at a meridian direction)
while sweeping some angular range from sunrise to
sunset. Further, the shadow minimum length varies
through the year, with times when shortest and sun
closest to vertical, at summer solstice, and times when
longest, at winter solstice six months later. The extreme
directions at sunset and sunrise correspond to the
solstices, swept angular range greatest at summer, over
180 degrees, and the opposite at winter, with less
daytime hours; in between, spring and fall equinoxes
occur, marked by collinear shadow directions at sunrise
and sunset.
The gnomon allows students to determine, in
addition to latitude (about 40.4° North at Madrid, say),
the inclination of earth equator to plane of its orbit
around the sun (ecliptic), this fundamental quantity
being given by half the difference between solar
distances to vertical at winter and summer solstices,
with value about 23.5°. Day and year periods greatly
differing by about 2 ½ orders of magnitude, 1 day
against 365 days, helps students to correctly visualize
and interpret the experimental measurements.
Since the gnomon serves to observe at night the moon
shadow too, students can also determine the inclination
of the lunar orbital plane, as about 5 degrees away from
the ecliptic, thus explaining why eclipses are infrequent.
Independently, earth taking longer between spring and
fall equinoxes than from fall to spring (the solar
anomaly), as again verified by the students, was
explained in ancient Greek science, which posited orbits
universally as circles or their combination, by
introducing the eccentric circle, with earth placed some
distance away from the orbital centre when considering
the relative motion of the sun, which would be closer to
the earth in winter. In a sense, this can be seen as hint
and approximation of the elliptic orbit proposed by
Kepler many centuries later.Juan Ramón Sanmartín LosadaMiguel Blanco-Marcos2016-02-09T10:28:06Z2016-02-09T11:11:35Zhttp://oa.upm.es/id/eprint/39287This item is in the repository with the URL: http://oa.upm.es/id/eprint/392872016-02-09T10:28:06ZPropellantless deorbiting of space debris by bare
electrodynamic tethers : final reportA Space tether is a thin, multi-kilometers long conductive wire, joining a satellite and some opposite end mass, and keeping vertical in orbit by the gravity-gradient. The ambient plasma, being highly conductive, is equipotential in its own co-moving frame. In the tether frame, in relative
motion however, there is in the plasma a motional electric field of order of 100 V/km, product of (near) orbital velocity and geomagnetic field. The electromotive force established over the tether length allows plasma contactor devices to collect electrons at one polarized-positive (anodic) end and eject electrons at the opposite end, setting up a current along a standard, fully insulated tether. The Lorentz force exerted on the current by the geomagnetic field itself is always drag; this relies on just
thermodynamics, like air drag.
The bare tether concept, introduced in 1992 at the Universidad Politécnica de Madrid (UPM), takes away the insulation and has electrons collected over the tether segment coming out polarized positive; the concept rests on 2D (Langmuir probe) current-collection in plasmas being greatly more efficient than 3D collection. A Plasma Contactor ejects electrons at the cathodic end. A bare tether with a thin-tape cross section has much greater perimeter and de-orbits much faster than a (corresponding) round bare tether of equal length and mass. Further, tethers being long and thin, they are prone to cuts by abundant small space debris, but BETs has shown that the tape has a probability of being cut per unit time smaller by more than one order of magnitude than the corresponding round tether (debris comparable to its width are much less abundant than debris comparable to the radius of
the corresponding round tether). Also, the tape collects much more current, and de-orbits much faster, than a corresponding multi-line “tape” made of thin round wires cross-connected to survive debris cuts.
Tethers use a dissipative mechanism quite different from air drag and can de-orbit in just a few months; also, tape tethers are much lighter than round tethers of equal length and perimeter, which can capture equal current. The 3 disparate tape dimensions allow easily scalable design. Switching the cathodic Contactor off-on allows maneuvering to avoid catastrophic collisions with big tracked
debris. Lorentz braking is as reliable as air drag. Tethers are still reasonably effective at high inclinations, where the motional field is small, because the geomagnetic field is not just a dipole along the Earth polar axis.
BETs is the EC FP7/Space Project 262972, financed in about 1.8 million euros, from 1 November 2010 to 31 January 2014, and carrying out RTD work on de-orbiting space debris.
Coordinated by UPM, it has partners Università di Padova, ONERA-Toulouse, Colorado State University, SME Emxys, DLR–Bremen, and Fundación Tecnalia. BETs work involves 1) Designing, building, and ground-testing basic hardware subsystems Cathodic Plasma Contactor, Tether Deployment Mechanism, Power Control Module, and Tape with crosswise and lengthwise structure.
2) Testing current collection and verifying tether dynamical stability. 3) Preliminary design of tape
dimensions for a generic mission, conducive to low system-to-satellite mass ratio and probability of cut by small debris, and ohmic-effects regime of tether current for fast de-orbiting. Reaching TRL 4-5, BETs appears ready for in-orbit demostration.Juan Ramón Sanmartín Losada2016-02-09T09:20:01Z2019-06-04T14:01:54Zhttp://oa.upm.es/id/eprint/39246This item is in the repository with the URL: http://oa.upm.es/id/eprint/392462016-02-09T09:20:01ZOptimum sizing of bare-tape tethers for de-orbiting satellites at end of missionDe-orbiting satellites at end of mission would prevent generation of new space debris. A proposed de-orbit technology involves a bare conductive tape-tether, which uses neither propellant nor power supply while generating power for on-board use during de-orbiting. The present work shows how to select tape dimensions for a generic mission so as to satisfy requirements of very small tether-to-satellite mass ratio mt/MS and probability Nf of tether cut by small debris, while keeping de-orbit time tf short and product tf ×× tether length low to reduce maneuvers in avoiding collisions with large debris. Design is here discussed for particular missions (initial orbit of 720 km altitude and 63° and 92° inclinations, and 3 disparate MS values, 37.5, 375, and 3750 kg), proving it scalable. At mid-inclination and a mass-ratio of a few percent, de-orbit time takes about 2 weeks and Nf is a small fraction of 1%, with tape dimensions ranging from 1 to 6 cm, 10 to 54 μμm, and 2.8 to 8.6 km. Performance drop from middle to high inclination proved moderate: if allowing for twice as large mt/MS, increases are reduced to a factor of 4 in tf and a slight one in Nf, except for multi-ton satellites, somewhat more requiring because efficient orbital-motion-limited electron collection restricts tape-width values, resulting in tape length (slightly) increasing too.Juan Ramón Sanmartín LosadaAntonio Sánchez-TorresShaker Bayajid KhanGonzalo Sánchez-ArriagaMario Charro2016-02-04T14:01:40Z2016-12-01T08:15:24Zhttp://oa.upm.es/id/eprint/39212This item is in the repository with the URL: http://oa.upm.es/id/eprint/392122016-02-04T14:01:40ZLow work-function thermionic emission and orbital-motion-limited ion collection at bare-tether cathodic contactWith a thin coating of low-work-function material, thermionic emission in the cathodic segment of bare tethers might be much greater than orbital-motion-limited (OML) ion collection current. The space charge of the emitted electrons decreases the electric field that accelerates them outwards, and could even reverse it for high enough emission, producing a potential hollow. In this work, at the conditions of high bias and relatively low emission that make the potential monotonic, an asymptotic analysis is carried out, extending the OML ion-collection analysis to investigate the probe response due to electrons emitted by the negatively biased cylindrical probe. At given emission, the space charge effect from emitted electrons increases with decreasing magnitude of negative probe bias. Although emitted electrons present negligible space charge far away from the probe, their effect cannot be neglected in the global analysis for the sheath structure and two thin layers in between sheath and the quasineutral region. The space-charge-limited condition is located. It is found that thermionic emission increases the range of probe radius for OML validity and is greatly more effective than ion collection for cathodic contact of tethers.Xin ChenJuan Ramón Sanmartín Losada2014-10-13T13:12:41Z2014-10-13T13:12:41Zhttp://oa.upm.es/id/eprint/32308This item is in the repository with the URL: http://oa.upm.es/id/eprint/323082014-10-13T13:12:41ZThin as a rail, strong as a rockSatellite de-orbiting and re-entry is essential to halting the continuous increase in orbital space debris. The BETS project, which ends this month, is making waves with a new tether solution that is faster and more resistant to damage than any other existing technology.Juan Ramón Sanmartín Losada2014-10-11T11:06:55Z2016-12-01T13:13:03Zhttp://oa.upm.es/id/eprint/32281This item is in the repository with the URL: http://oa.upm.es/id/eprint/322812014-10-11T11:06:55ZIntegración numérica de la ecuación DNLSInteracciones no lineales de ondas de Alfven existen tanto para plasmas en el espacio como en laboratorios. En ingeniería aeroespacial amarras electrodinámicas espaciales ("tethers") generan emisión de ondas de Alfven en estructuras denominadas "Alas de Alfven". La ecuación Derivada no lineal de Schrödinger (DNLS) posee la capacidad de describir la propagation de ondas de Alfven de
amplitud finita circularmente polarizadas tanto para plasmas fríos como calientes. En esta investigación, dicha ecuacion es solucionada numéricamente por medio de tecnicas espectrales para las derivadas espaciales y un esquema de Runge-Kutta de 4to orden para evaluar el avance en el
tiempo. Se considera la ecuacion DNLS sin efectos difusivos, sin embargo se mantienen el termino lineal y
lineal y el dispersivos. Se ha trabajado con dos condiciones iniciales: 1 - Una onda, 2 - Tres ondas cerca de resonancia (k1 = k2 + k3), la primera onda (correspondiente a k1) está excitada y las otras dos
amortiguadas. En el caso de una única onda los resultados numéricos verifican las condiciones analíticas de estabilidad modular, adems se ha encontrado que el tiempo en el que se produce la inestabilidad y la forma en que evoluciona el sistema depende, para un mismo número de onda, de la amplitud inicial. Con tres ondas se realiza un estudio numérico tanto para plasmas frios como calientes
encontrándose que aparece redistribución de energía en un gran número de nodos tanto para ondas polarizadas hacia la izquierda como hacia la derecha.Sergio ElaskarGonzalo Sánchez ArriagaJuan Ramón Sanmartín Losada2014-10-10T08:20:18Z2014-10-10T08:20:18Zhttp://oa.upm.es/id/eprint/32238This item is in the repository with the URL: http://oa.upm.es/id/eprint/322382014-10-10T08:20:18ZA review of electrodynamic tethers for science applicationsA bare electrodynamic tether (EDT) is a conductive thin wire or tape tens of kilometres long, which is kept taut in space by gravity gradient or spinning, and is left bare of insulation to collect (and carry) current as a cylindrical Langmuir probe in an ambient magnetized plasma. An EDT is a probe in mesothermal flow at highly positive (or negative) bias, with a large or extremely large 2D sheath, which may show effects from the magnetic self-field of its current and have electrons adiabatically trapped in its ram front. Beyond technical applications ranging from propellantless propulsion to power generation in orbit, EDTs allow broad scientific uses such as generating electron beams and artificial auroras; exciting Alfven waves and whistlers; odifying the radiation belts; and exploring interplanetary space and the Jovian magnetosphere. Asymptotic analysis, numerical simulations, laboratory tests, and planned missions on EDTs are reviewedJuan Ramón Sanmartín Losada2014-10-09T08:19:46Z2015-10-19T07:40:41Zhttp://oa.upm.es/id/eprint/32172This item is in the repository with the URL: http://oa.upm.es/id/eprint/321722014-10-09T08:19:46ZChaos in non lineal Alfven waves using the DNLS equationsThe electro-dynamical tethers emit waves in structured denominated Alfven wings. The Derivative Nonlineal
Schrödinger Equation (DNLS) possesses the capacity to
describe the propagation of circularly polarized Alfven waves of finite amplitude in cold plasmas. The DNLS equation is truncated to explore the coherent, weakly nonlinear, cubic coupling of three waves near resonance, one wave being linearly unstable and the other waves damped. In this article is presented a theoretical and numerical analysis when the growth rate of the unstable wave is next to zero considering two damping models: Landau and resistive. The DNLS equation presents a chaotic dynamics when is consider only three wave truncation. The evolution to chaos possesses three routes: hard transition, period-doubling and intermittence of type I.Sergio ElaskarGonzalo Sánchez ArriagaJuan Ramón Sanmartín Losada2014-10-03T12:59:55Z2014-10-03T12:59:55Zhttp://oa.upm.es/id/eprint/31235This item is in the repository with the URL: http://oa.upm.es/id/eprint/312352014-10-03T12:59:55ZSaturn power generation with electrodynamic tethers in polar orbitA power generation scheme based on bare electrodynamic tethers (EDT), working in passive mode is investigated for the purpose of supplying power to scientific missions at Saturn. The system employs a spinning EDT on a lowaltitude
polar orbit which permits to efficiently convert plasmasphere energy into useful power. After optimizing the tether design for power generation we compute the supplied power along the orbit and the impact of the Lorentz force
on the orbital elements as function of the tether and orbit characteristics.
Although uncertainties in the current ionosphere density modeling strongly affect the performance of the system the peak power density of the EDT appears be greater than conventional power systems.Claudio BombardelliEnrico C. LorenziniJuan Ramón Sanmartín Losada2014-10-03T12:28:19Z2014-10-03T12:28:19Zhttp://oa.upm.es/id/eprint/31234This item is in the repository with the URL: http://oa.upm.es/id/eprint/312342014-10-03T12:28:19ZElectrodynamic tethers for spacecraft propulsionRelatively short electrodynamic tethers can use solar power to "push" against a planetary magnetic field to achieve propul sion without expenditure of propellant. The groundwork has been laid for this type of propulsion.
Recent important milestones include retrieval of a tether
in space (TSS-1, 1992), successful deployment of a 20-km-long tether in space (SEDS-1, 1993), and operation of an electrodynamic tether with tether current driven in both directions (PMG, 1993). The planned Propulsive Small Expendable Deployer System (ProSEDS) experiment will use the flight-proven Small Expendable Deployer System (SEDS) to deploy a 5-km bare copper tether from a Delta II upper stage to achieve -0,4 N drag thrust, thus deorbiting the stage, The experiment will use a predominantly "bare" tether for current collection in lieu of the endmass collector and insulated tether approach used on previous missions, Theory and ground-based plasma chamber testing indicate that the bare tether is a highly efficient current collector. The flight experiment is a precursor to utilization of the technology on the International Space tation (JSS) for reboost and the electrodynamic tether pper stage demonstration misión which will be capable of orbit raising, lowering, and inclination changes—all using electrodynamic thrust. In addition, the use of this type of propulsion may be attractive for future missions to Jupiter.L. JohnsonRobert D. EstesEnrico C. LorenziniManuel Martínez-SánchezJuan Ramón Sanmartín LosadaI.E. Vas2014-10-02T13:54:11Z2014-10-02T13:54:11Zhttp://oa.upm.es/id/eprint/31020This item is in the repository with the URL: http://oa.upm.es/id/eprint/310202014-10-02T13:54:11ZCollection effects on close pararell bare tethersWe review previously published results, and present new results, on the way current to a cylindrical probe drops below the orbital-motion-limited (OML) value for probe cross-sections too large or concave. Results on size and shape effects arise from unrelated behavior in the near and far potential field, and apply to a general cross-section,
which can be characterised by radius Req and perimeter peij of equivalent circles. These results are used to discuss collection interference among two or more parallel bare tethers when brought from far away to contact.Juan Ramón Sanmartín LosadaRobert D. Estes2014-10-01T13:23:22Z2014-10-01T13:23:22Zhttp://oa.upm.es/id/eprint/31146This item is in the repository with the URL: http://oa.upm.es/id/eprint/311462014-10-01T13:23:22ZTrade-off study on deorbiting S/C in near polar orbitUsual long, flexible, ED tethers kept vertical by the gravity gradient might be less efficient for deorbiting S/C in near-polar orbits than conventional (Hall, Ion) electrical thrusters. A trade-off study on this application is here presented for tethers kept horizontal and perpendicular to the orbital plane. A tether thus oriented must be rigid and short for structural reasons, requiring a non-convex cross section and a power supply as in the case of electrical thrusters. Very recent developments on bare-tether collection theory allow predicting the current
collected by an arbitrary cross section. For the horizontal tether, structural considerations on length play the role of ohmic effects in vertical tethers, in determining the optimal contribution of tether mass to the overall deorbiting system. For a given deorbiting-mission impulse, tether-system mass is minimal at some optimal length that increases weakly with the impulse. The horizontal-tether system may beat both the vertical tether and the electrical thruster as regards mass requirements for a narrow length range centered at about 100 m, allowing, however, for a
broad mission-impulse range.Juan Ramón Sanmartín LosadaEduardo Ahedo Galilea2014-09-17T08:20:38Z2016-04-22T01:11:56Zhttp://oa.upm.es/id/eprint/30957This item is in the repository with the URL: http://oa.upm.es/id/eprint/309572014-09-17T08:20:38ZPIC computation of electron current collection to a moving bare tether in the mesothermal conditionIn tethered satellite technology, it is important to estimate how many electrons a spacecraft can collect from its ambient plasma by a bare electrodynamic tether. The analysis is however very difficult because of the small but significant Geo-magnetic field and the spacecraft’s relative motion to both ions and electrons. The object of our work is the development of a numerical method, for this purpose. Particle-In-Cell (PIC) method, for the calculation of electron current to a positive bare tether moving at orbital velocity in the ionosphere, i.e. in a flowing magnetized plasma under Maxwellian collisionless conditions. In a PIC code, a number of particles are distributed in phase space and the computational domain has a grid on which Poisson equation is solved for field quantities. The code uses the quasi-neutrality condition to solve for the local potential at points in the plasma which coincide with the computational outside boundary. The quasi-neutrality condition imposes ne - ni on the boundary. The Poisson equation is solved in such a way that the presheath region can be captured in the computation. Results show that the collected current is higher than the Orbital Motion Limit (OML) theory. The OML current is the upper limit of current collection under steady collisionless unmagnetized conditions. In this work, we focus on the flowing effects of plasma as a possible cause of the current enhancement. A deficit electron density due to the
flowing effects has been worked and removed by introducing adiabatic electron trapping into our model.Tatsuo OnishiManuel Martínez-SánchezDavid L. CookeJuan Ramón Sanmartín Losada2014-09-17T07:33:52Z2016-04-22T01:11:43Zhttp://oa.upm.es/id/eprint/30953This item is in the repository with the URL: http://oa.upm.es/id/eprint/309532014-09-17T07:33:52ZA review of electrodynamic tethers for space applicationsSpace applications of electrodynamic tethers, and basic issues and constraints on their operation are reviewed. The status of the bare-tether solution to the problem of effective electron collection from a rarefied magnetized plasma is revisited. Basic modes of tether operation are analyzed; design parameters and parametric domains where a bare electrodynamic tether is most efficient in deorbiting, rebooking, or power generation, are determined. Use of bare tethers for Radiation Belt Remediation and generation of electron beams for ionospheric research is considered. Teiher heating, arcing, and bowing or breaking, as well deployment strategies are discussed.Juan Ramón Sanmartín LosadaEnrico C. LorenziniManuel Martínez Sánchez2014-08-06T16:55:33Z2014-10-01T10:52:06Zhttp://oa.upm.es/id/eprint/30696This item is in the repository with the URL: http://oa.upm.es/id/eprint/306962014-08-06T16:55:33ZEffect of magnetic field on current colection on bare tether in LEOAn eiectrodynamic Tether is a long thin conductive string deployed from a spacecraft. A part of the ED tether near one end, which is rendered positive by the Electromotive force (EMF)along the tether, collects electrons from the ambient plasma. In the frame of reference moving with theter, ions flow toward the tether, get deflected near the
tether by its high positive potential and create a wake. Due
to the asymmetry of plasma distribution and the weak but significant Geomagnetic field, the conventional probe theory becomes almost inapplicable. Computational work for the prediction of current collection is thus necessiated.. In this paper, we analyze effects of magnetic field on velocity distribution funtion at a point that is far from the tether, and discuss a new way to treat electrons at computational boundary. Three cases with different magnetic field are simulated and compiled so as to provide a part of
the pre-flight prediction of the space experiment by NASA ProSEDS, which is planned September 2002.Tatsuo OnishiManuel Martínez-SánchezD.L. CookeJuan Ramón Sanmartín Losada2014-07-23T05:16:31Z2014-10-01T13:59:39Zhttp://oa.upm.es/id/eprint/30475This item is in the repository with the URL: http://oa.upm.es/id/eprint/304752014-07-23T05:16:31ZSpace demostration of bare electrodynamic tape-tether technology on the sounding rocket S520-25A spaceflight validation of bare electro dynamic tape tether technology was conducted. A S520-25 sounding rocket was launched successfully at 05:00am on 31 August 2010 and
successfully deployed 132.6m of tape tether over 120 seconds in a ballistic flight. The electrodynamic performance of the bare tape tether employed as an atmospheric probe was measured. Flight results are introduced through the present progressive report of the
demonstration and the results of flight experiment are examined as the premier report of the international cooperation between Japan, Europe, USA and Australia. Future plans for maturing space tether technology, which will play an important role for future space activities, are also discussed.Hironori FujiiTakeo WatanabeHironori SaharaHirohisa KojimaShoichiro TakeharaYoshiki YamagiwaSusumu SasakiTakumi AbeKoji TanakaKhoichiro OyamaLes JhonsonV. KhazanovJuan Ramón Sanmartín LosadaMario CharroMichiel KruijffErik J. Van der HeideBinyamin RubinFrancisco García de QuirósPavel M. TrivailoPaul Williams2014-07-08T08:46:02Z2014-09-30T12:27:46Zhttp://oa.upm.es/id/eprint/30375This item is in the repository with the URL: http://oa.upm.es/id/eprint/303752014-07-08T08:46:02ZConductive-tether design for de-orbiting from given altitude and inclinationA bare tether with thin-tape cross section is both i) the most effective electrodinamic tether for given length and
mass, and ii) capable of effective design for an arbitrary mission through its three disparate dimensions. It handily beats the fully insulated tether that exchanges current at both ends, a result resting in advantages of 2D current collection as against 3D collection; it has much greater perimeter than the round bare tether and much lower fatal debris-impact rate, leading to greatly faster de-orbiting and greatly higher probability of survival; and it only allows multi-line tethers reaching a few hundred lines to stand competitive. In selecting the disparate values of length L, width w, and thickness h for a de-orbit mission, performance involves three criteria: a) tether-tospacecraft
mass ratio must be small; b) probability of survival against the debris environment must be high; and c) de-orbiting must be fast to reduce manoeuvres for avoiding catastrophic collisions with big active/passive satellites around. Beyond determining tether mass through the product Lwh, main dimension parameters affecting performance are L/h2li characterizing ohmic effects, and w determining electron collection. An algorithm for optimal selection of tape dimensions is elaborated.Juan Ramón Sanmartín LosadaSaker B. Khan2014-07-08T08:46:01Z2016-09-21T10:04:44Zhttp://oa.upm.es/id/eprint/30376This item is in the repository with the URL: http://oa.upm.es/id/eprint/303762014-07-08T08:46:01ZSurvivability analysis of tape-tether against multiple impact with tiny debrisWe show that for a tether at 800 km altitude, which is 5 km long, 2 cm wide and 0.05 mm thick, the risk of substantial damage during a 3 month period due to multiple impacts with debris or micrometeoroids is low, of about 1.4%. By substantial damage we mean that if the tape is divided in 2 cm2 cm squares, then in some square the damaged area by
bombardment with debris or micrometeoroids exceeds 11% of
the area of the square. Furthermore, we show that the danger
posed by the micrometeoroids is negligible compared to the risk posed by the debris.Ricardo Ángel García-Pelayo NovoShaker Bayajid KhanJuan Ramón Sanmartín Losada2014-07-08T08:43:22Z2014-09-26T12:23:14Zhttp://oa.upm.es/id/eprint/30378This item is in the repository with the URL: http://oa.upm.es/id/eprint/303782014-07-08T08:43:22ZElectrodynamic tethers in spaceEnrico C. LorenziniJuan Ramón Sanmartín Losada2014-07-08T07:14:40Z2014-09-22T11:49:15Zhttp://oa.upm.es/id/eprint/30386This item is in the repository with the URL: http://oa.upm.es/id/eprint/303862014-07-08T07:14:40ZLa physique de l'encensoirDepuis sept siècles, un mécanisme ingénieux fait osciller un encensoir géant dans la cathédrale de Saint-Jacques-de-Compostelle. Ce dispositif témoigne des connaissances empiriques des mécaniciens du Moyen Age.Juan Ramón Sanmartín Losada2014-07-08T07:14:06Z2016-04-22T00:38:27Zhttp://oa.upm.es/id/eprint/30387This item is in the repository with the URL: http://oa.upm.es/id/eprint/303872014-07-08T07:14:06ZFísica del botafumeiroHace siete siglos se instaló un mecanismo destinado al culto en la catedral de Santiago de Compostela, que introduce efectos dinámicos refinados. Pudo haber originado las primeras experiencias sobre caos determinista.Juan Ramón Sanmartín Losada2014-07-08T06:37:12Z2016-04-22T00:37:30Zhttp://oa.upm.es/id/eprint/30371This item is in the repository with the URL: http://oa.upm.es/id/eprint/303712014-07-08T06:37:12ZFloating Bare Tether as Upper Atmosphere ProbeUse of a (bare) conductive tape electrically floating in LEO as an effective e-beam source that produces artificial auroras, and is free of problems that have marred standard beams, is considered. Ambient ions impacting the tape with KeV energies over most of its length liberate secondary electrons, which race down the magnetic field and excite neutrals in the E-layer, resulting in auroral emissions. The tether would operate at night-time with both a power supply and a plasma contactor off; power and contactor would be on at daytime for reboost. The optimal tape thickness yielding a minimum mass for an autonomous system is determined; the alternative use of an electric thruster for day reboost, depending on mission duration, is discussed. Measurements of emission brightness from the spacecraft could allow
determination of the (neutral) density vertical profile in the critical E-layer; the flux and energy in the beam, varying along the tether, allow imaging line-of-sight integrated emissions that mix effects with altitude-dependent neutral density and lead to a brightness
peak in the beam footprint at the E-layer. Difficulties in tomographic inversion, to determine the density profile, result from beam broadening, due to elastic collisions, which flattens the peak, and to the highly nonlinear functional dependency of line-of-sight brightness. Some
dynamical issues are discussed.Juan Ramón Sanmartín LosadaMario CharroJ. PeláezI. TinaoSergio ElaskarA. Hilgers2014-07-08T06:35:18Z2016-04-22T00:37:32Zhttp://oa.upm.es/id/eprint/30372This item is in the repository with the URL: http://oa.upm.es/id/eprint/303722014-07-08T06:35:18ZPropellantless de orbiting of space debris by bare electrodynamic tethersJuan Ramón Sanmartín Losada2014-07-08T06:34:45Z2016-04-22T00:37:27Zhttp://oa.upm.es/id/eprint/30370This item is in the repository with the URL: http://oa.upm.es/id/eprint/303702014-07-08T06:34:45ZA proposed bare-tether experiment on board a sounding
rocketA mission on board a sounding rocket to carry out two bare-tether experiments is proposed: a test of orbital-motion-limited (OML) collection and the proof-of-flight of a
technique to determine the (neutral) density vertical profile in the critical E-layer. Since full bias from the motional field will be small (~ 20V), corresponding to a tape 1 km long and V rocket <8 km/s, a power source with a range of supply voltages of few kV would be used. First, the negative terminal of the supply would be connected to the tape, and the positive terminal to a round, conductive boom of length 10 - 20 m; electrons collected by the boom
cross the supply into the tape, where they leak out at the rate of ion impact plus secondary emission. Determination of the density profile from measurements of auroral emissions
observed from the rocket, as secondaries racing down the magnetic field reach an E-layer footprint, are discussed. Next the positive terminal of the voltage supply is connected to the tape, and the negative terminal to a Hollow Cathode (HC); electrons now collected by the tape cross the supply, and are ejected at the HC. The opposite connections, with current collection operated by tape and boom, and operating on electrons and ions, and through partial switching in the supply, allow testing OML collection in almost all respects it depends on.H.A. FujiH. TakegaharaK. OyamaS. SasakiY. YamagiwaM. KruijffE.J. Van der HeideJuan Ramón Sanmartín LosadaMario Charro2014-07-01T21:32:04Z2016-04-22T00:35:38Zhttp://oa.upm.es/id/eprint/30337This item is in the repository with the URL: http://oa.upm.es/id/eprint/303372014-07-01T21:32:04ZElectrodynamic tether for scientific mission in low Jovian orbitAn electrodynamic bare tether is shown to allow carrying out scientific observations very close to Jupiter, for exploration of its surface and subsurface, and ionospheric and atmospheric in-situ measurements. Starting at a circular equatorial orbit of radius about 1.3/1.4 times the Jovian radius, continuous propellantless Lorentz drag on a thin-tape tether in the 1-5 km length range would make
a spacecraft many times as heavy as the tape slowly spiral in, over a period of many months, while generating power at a load plugged in the tether circuit for powering instruments in science data acquisition and transmission. Lying under the Jovian radiation belts, the tape would avoid the most severe problem facing tethers in Jupiter, which are capable of producing both power and propulsion
but, operating slowly, could otherwise accumulate too high a radiation dose . The tether would be made to spin in its orbit to keep taut; how to balance the Lorentz torque is discussed. Constraints on heating and bowing are also discussed, comparing conditions for prograde versus retrograde orbits. The system adapts well to the moderate changes in plasma density and motional electric field through the limited radial range in their steep gradients near Jupiter.Juan Ramón Sanmartín LosadaClaudio BombardelliMario CharroEnrico C. Lorenzini2014-07-01T21:32:02Z2016-04-22T00:35:26Zhttp://oa.upm.es/id/eprint/30333This item is in the repository with the URL: http://oa.upm.es/id/eprint/303332014-07-01T21:32:02ZCathodic plasma / bare-tether contact through
low work function coatingXin ChenJuan Ramón Sanmartín Losada2014-07-01T21:19:10Z2016-04-22T00:35:41Zhttp://oa.upm.es/id/eprint/30338This item is in the repository with the URL: http://oa.upm.es/id/eprint/303382014-07-01T21:19:10ZBare-tether cathodic contact through thermionic emission by low-W materialsXin ChenJuan Ramón Sanmartín Losada2014-06-30T21:25:15Z2016-04-22T00:35:13Zhttp://oa.upm.es/id/eprint/30328This item is in the repository with the URL: http://oa.upm.es/id/eprint/303282014-06-30T21:25:15ZLaudatio leíada por Juan Ramón Sanmartín Losada en el homenaje al profesor Amable Liñán Martínez celebrado en la ETSI Aeronáuticos de la Universidad Politécnica de Madrid el 18 de febrero de 2010Juan Ramón Sanmartín Losada2014-06-28T05:16:17Z2014-09-24T17:25:06Zhttp://oa.upm.es/id/eprint/30313This item is in the repository with the URL: http://oa.upm.es/id/eprint/303132014-06-28T05:16:17ZAn universal system to de-orbit satellites at end of lifeA 3-year Project financed by the European Commission is aimed at developing a universal system to de-orbit satellites at their end of life, as a fundamental contribution to limit the increase of debris in the Space environment. The operational system involves a conductive tapetether left bare to establish anodic contact with the ambient plasma as a giant Langmuir probe. The Project will size the three disparate dimensions of a tape for a selected de-orbit mission and determine scaling laws to allow system design for a general mission. Starting at the second year, mission selection is carried out while developing numerical codes to implement control laws on tether dynamics in/off the orbital plane; performing numerical simulations and plasma chamber measurements on tether-plasma interaction; and completing design of subsystems: electronejecting plasma contactor, power module, interface elements, deployment mechanism, and tether-tape/end-mass. This will be followed by subsystems manufacturing and by currentcollection, free-fall, and hypervelocity impact tests.Juan Ramón Sanmartín LosadaMario CharroXin ChenEnrico C. LorenziniGiacomo ColombattiDenis ZanuttoJean-Françoise RouseePierre SarrailhJohn D. WilliamsKhan XieGarret E. MetzJose A. CarrascoFrancisco García de QuirósOlaf KroemerRoland RostaTim van ZoestJoseba LasaJesús Marcos2014-06-26T09:47:58Z2014-11-03T12:39:54Zhttp://oa.upm.es/id/eprint/30305This item is in the repository with the URL: http://oa.upm.es/id/eprint/303052014-06-26T09:47:58ZDrifting plasma collection by a positive biased tether wire in LEO-like plasma conditions: current measurement and plasma diagnosticBETs is a three-year project financed by the Space Program of the European Commission, aimed at developing an efficient deorbit system that could be carried on board any future satellite launched into Low Earth Orbit (LEO). The operational system involves a conductive tape-tether left bare to establish anodic contact with the ambient plasma as a giant Langmuir probe. As a part of this project, we are carrying out both numerical and experimental approaches to estimate the collected current by the positive part of the tether. This paper deals with experimental measurements performed in the IONospheric Atmosphere Simulator (JONAS) plasma chamber of the Onera-Space Environment Department. The JONAS facility is a 9- m3 vacuum chamber equipped with a plasma source providing drifting plasma simulating LEO conditions in terms of density and temperature. A thin metallic cylinder, simulating the tether, is set inside the chamber and polarized up to 1000 V. The Earth's magnetic field is neutralized inside the chamber. In a first time, tether collected current versus tether polarization is measured for different plasma source energies and densities. In complement, several types of Langmuir probes are used at the same location to allow the extraction of both ion densities and electron parameters by computer modeling (classical Langmuir probe characteristics are not accurate enough in the present situation). These two measurements permit estimation of the discrepancies between the theoretical collection laws, orbital motion limited law in particular, and the experimental data in LEO-like conditions without magnetic fields. In a second time, the spatial variations and the time evolutions of the plasma properties around the tether are investigated. Spherical and emissive Langmuir probes are also used for a more extensive characterization of the plasma in space and time dependent analysis. Results show the ion depletion because of the wake effect and the accumulation of- ions upstream of the tether. In some regimes (at large positive potential), oscillations are observed on the tether collected current and on Langmuir probe collected current in specific sites.Jean-Michel SiguierPierre SarrailhJean-François RousselVirgine InguimbertGaël MuratJuan Ramón Sanmartín Losada2014-06-26T05:37:56Z2016-09-23T10:32:51Zhttp://oa.upm.es/id/eprint/30299This item is in the repository with the URL: http://oa.upm.es/id/eprint/302992014-06-26T05:37:56ZAnalysis of tape tether survival in LEO against orbital debrisThe low earth orbit (LEO) environment contains a large number of artificial debris, of which a significant portion is due to dead satellites and fragments of satellites resulted from explosions and in-orbit collisions. Deorbiting defunct satellites at the end of their life can
be achieved by a successful operation of an Electrodynamic Tether (EDT) system. The effectiveness of an EDT greatly depends on the survivability of the tether, which can become debris itself if cut by debris particles; a tether can be completely cut by debris having some minimal diameter. The objective of this paper is to develop an accurate model using power laws for debris-size ranges, in both ORDEM2000 and MASTER2009 debris flux models, to calculate tape tether survivability. The analytical model, which depends on tape dimensions (width, thickness) and orbital parameters (inclinations, altitudes) is then verified with fully numerical results to compare for
different orbit inclinations, altitudes and tape width for both ORDEM2000 and MASTER2009 flux data.Shaker Bayajid KhanJuan Ramón Sanmartín Losada2014-06-25T08:22:58Z2014-09-22T11:43:44Zhttp://oa.upm.es/id/eprint/28967This item is in the repository with the URL: http://oa.upm.es/id/eprint/289672014-06-25T08:22:58ZLaudatio leída por Juan Ramón Sanmartín Losada en el acto de investidura de Manuel Martínez Sánchez como Doctor Honoris Causa por la Universidad Poltécnica de MadridJuan Ramón Sanmartín Losada2014-05-30T08:16:22Z2014-09-22T11:43:07Zhttp://oa.upm.es/id/eprint/26830This item is in the repository with the URL: http://oa.upm.es/id/eprint/268302014-05-30T08:16:22ZLa singular física del botafumeiroJuan Ramón Sanmartín Losada2014-05-29T13:45:39Z2014-09-22T11:43:06Zhttp://oa.upm.es/id/eprint/26827This item is in the repository with the URL: http://oa.upm.es/id/eprint/268272014-05-29T13:45:39ZSurvival probability of round and tape tethers against debris impactThe current space environment, consisting of manmade debris and micrometeoroids, poses a risk to safe operations in space, and the situation is continuously deteriorating due to in-orbit debris collisions and to new satellite launches. Bare electrodynamic tethers can provide an efficient mechanism for rapid deorbiting of satellites from low Earth orbit at end of life. Because of its particular geometry (length very much larger than cross-sectional dimensions), a tether may have a relatively high risk of being severed by the single impact of small debris. The rates of fatal impact of orbital debris on round and tape tethers of equal length and mass, evaluated with an analytical approximation to debris flux modeled by NASA’s ORDEM2000, shows much higher survival probability for tapes. A comparative numerical analysis using debris flux model ORDEM2000 and ESA’s MASTER2005 validates the analytical result and shows that, for a given time in orbit, a tape has a probability of survival of about one and a half orders of magnitude higher than a round tether of equal mass and length. Because deorbiting from a given altitude is much faster for the tape due to its larger perimeter, its probability of survival in a practical sense is quite high.Shaker Bayajid KhanJuan Ramón Sanmartín Losada2014-05-29T07:31:19Z2016-09-23T10:46:49Zhttp://oa.upm.es/id/eprint/26741This item is in the repository with the URL: http://oa.upm.es/id/eprint/267412014-05-29T07:31:19ZElectrodynamic tether applications and constraintsPropulsion and power generation by bare electrodynamic tethers are revisited in a unified way and issues and
constraints are addressed. In comparing electrodynamic tethers, which do not use propellant, with other propellantconsuming systems, mission duration is a discriminator that defines crossover points for systems with equal initial masses. Bare tethers operating in low Earth orbit can be more competitive than optimum ion thrusters in missions exceeding two-three days for orbital deboost and three weeks for boosting operations. If the tether produces useful onboard power during deboost, the crossover point reaches to about 10 days. Power generation by means of a bare electrodynamic tether in combination with chemical propulsion to maintain orbital altitude of the system is more efficient than use of the same chemicals (liquid hydrogen and liquid oxygen) in a fuel cell to produce power for missions longer than one week. Issues associated with tether temperature, bowing, deployment, and arcing are also discussed.
Heating/cooling rates reach about 4 K/s for a 0.05-mm-thick tape and a fraction of Kelvin/second for the ProSEDS
(0.6-mm-radius) wire; under dominant ohmic effects, temperatures areover200K (night) and 380 K (day) for the tape and 320 and 415 K for that wire. Tether applications other than propulsion and power are briefly discussed.Juan Ramón Sanmartín LosadaEnrico C. LorenziniM. Martínez-Sánchez2014-05-28T09:52:25Z2015-05-25T13:49:25Zhttp://oa.upm.es/id/eprint/26738This item is in the repository with the URL: http://oa.upm.es/id/eprint/267382014-05-28T09:52:25ZJupiter power generation with electrodynamic tethers at constant orbital energyAn electrodynamic tether system for power generation at Jupiter is presented that allows extracting energy from
Jupiter's corotating plasmasphere while leaving the system orbital energy unaltered to first order. The spacecraft is
placed in a polar orbit with the tether spinning in the orbital plane so that the resulting Lorentz force, neglecting Jupiter's magnetic dipole tilt, is orthogonal to the instantaneous velocity vector and orbital radius, hence affecting orbital inclination rather than orbital energy. In addition, the electrodynamic tether subsystem, which consists of two radial tether arms deployed from the main central spacecraft, is designed in such a way as to extract maximum power while keeping the resulting Lorentz torque constantly null. The power-generation performance of the system and the effect on the orbit inclination is evaluated analytically for different orbital conditions and verified numerically. Finally, a thruster-based inclination-compensation maneuver at apoapsis is added, resulting in an efficient scheme to extract energy from the plasmasphere of the planet with minimum propellant consumption and no inclination change. A tradeoff analysis is conducted showing that, depending on tether size and orbit characteristics, the system performance can be considerably higher than conventional power-generation methods.Claudio BombardelliEnrico C. LorenziniJuan Ramón Sanmartín Losada2014-05-27T13:20:23Z2014-09-22T11:42:22Zhttp://oa.upm.es/id/eprint/26671This item is in the repository with the URL: http://oa.upm.es/id/eprint/266712014-05-27T13:20:23ZPerformance of electrodynamic tethers and ion thrusters against hybrid systemsJuan Ramón Sanmartín LosadaMario Charro2014-05-27T13:15:56Z2014-09-22T11:42:22Zhttp://oa.upm.es/id/eprint/26672This item is in the repository with the URL: http://oa.upm.es/id/eprint/266722014-05-27T13:15:56ZEfficiency of electrodynamic tether thrustersThe performance efficiency of electrodynamic bare tethers acting as thrusters in low Earth orbit, as gauged by
the ratio of the system mass dedicated to thrust over mission impulse, is analyzed and compared to the performance
efficiency of electrical thrusters. Tether systems are much lighter for times beyond six months in space-tug operations, where there is a dedicated solar array, and beyond one month for reboost of the International Space
Station, where the solar array is already in place. Bare-tether propulsive efficiency itself, with the tether considered as part of the power plant, is higher for space tugs. Tether optimization shows that thin tapes have greater propulsive efficiency and are less sensitive to plasma density variations in orbit than cylindrical tethers. The efficiency increases with tape length if some segment next to the power supply at the top is insulated to make the tether potential bias vanish at the lower end; multitape tethers must be used to keep the efficiency high at high thrust levels. The efficiency has a maximum for tether-hardware mass equal to the fraction of power-subsystem mass going into ohmic power, though the maximum is very flat. For space tugs, effects of induced-bias changes in orbit might need to be reduced by choosing a moderately large power-subsystem to tether-hardware mass ratio or by tracking the current-voltage characteristic of the solar array.Juan Ramón Sanmartín LosadaRobert D. EstesEnrico C. LorenziniSergio Elaskar2014-05-27T13:14:28Z2014-09-22T11:42:23Zhttp://oa.upm.es/id/eprint/26674This item is in the repository with the URL: http://oa.upm.es/id/eprint/266742014-05-27T13:14:28ZRole of superconducting shields in electrodynamic propulsionAn electrodynamic tether can propel a spacecraft through a planetary magnetized plasma without using propellant. In the classical embodiment of an electrodynamic tether, the ambient magnetic fleld exerts a Lorentz force on the current along the tether, the ambient plasma providing circuit closure for the current A suggested propulsion scheme would hypothetically eliminate tether performance dependence on the plasma density by using a full wire loop to close the current circuit, and a superconductor to shield a loop segment from the external uniform magnetic fleld and cancel the Lorentz force on that segment. Here, we use basic electromagnetic laws to explain how such a scheme cannot produce a net force. Because there is no net current in the superconducting shield, the circulation of the magnetic field along a closed line outside the full cross section, in its plane, is just due to the current
flowing in the loop segment. The presence of the superconducting shield simply moves the Lorentz force from the shielded loop segment to the shield itself and, as a result, the total magnetic force, acting on full loop plus shield, remains zero.Juan Ramón Sanmartín LosadaEnrico C. Lorenzini2014-05-27T10:14:50Z2014-09-22T11:42:19Zhttp://oa.upm.es/id/eprint/26665This item is in the repository with the URL: http://oa.upm.es/id/eprint/266652014-05-27T10:14:50ZAnalysis of bare-tether systems for deorbiting low-earth-orbit satellitesPerformances, design criteria, and system mass of bare tethers for satellite deorbiting missions are analyzed.
Orbital conditions and tether cross section define a tether length, such that 1) shorter tethers are electron collecting
practically in their whole extension and 2) longer tethers collect practically the short-circuit current in a fixed
segment length. Long tethers have a higher drag efficiency (defined as the drag force vs the tether mass) and are
better adapted to adverse plasma densities. Dragging efficiency and mission-related costs are used to define design criteria for tether geometry. A comparative analysis with electric thrusters shows that bare tethers have much
lower costs for low- and midinclination orbits and remain an attractive option up to 70 deg.Eduardo Ahedo GalileaJuan Ramón Sanmartín Losada2014-05-27T10:14:49Z2015-05-25T13:49:03Zhttp://oa.upm.es/id/eprint/26666This item is in the repository with the URL: http://oa.upm.es/id/eprint/266662014-05-27T10:14:49ZExploration of outer planets using tethers for power and propulsionJuan Ramón Sanmartín LosadaEnrico C. Lorenzini2014-05-26T08:33:37Z2014-09-22T11:42:05Zhttp://oa.upm.es/id/eprint/26613This item is in the repository with the URL: http://oa.upm.es/id/eprint/266132014-05-26T08:33:37ZPerformance of bare-tether systems under varying magnetic and plasma conditionsElectrodynamic tethered systems, in which an exposed portion of the conducting tether itself collects electrons
from the ionosphere, promise to attain currents of 10 A or more in low Earth orbit. For the first time, another
desirable feature of such bare-tether systems is reported and analyzed in detail: Collection by a bare tether is
relatively insensitive to variations in electron density that are regularly encountered on each revolution of an orbit. This self-adjusting property of bare-tether systems occurs because the electron-collecting area on the tether is
not fixed, but extends along its positively biased portion, and because the current varies as collecting length to a
power greater than unity. How this adjustment to density variations follows from the basic collection law of thin
cylinders is shown. The effect of variations in the motionally induced tether voltage is also analyzed. Both power and thruster modes are considered. The performance of bare-tether systems to tethered systems is compared using
passive spherical collectors of fixed area, taking into consideration recent experimental results. Calculations taking into account motional voltage and plasma density around a realistic orbit for bare-tether systems suitable for space station applications are also presented.Robert D. EstesJuan Ramón Sanmartín LosadaM. Martínez-Sánchez2014-05-25T06:49:31Z2014-09-22T11:41:35Zhttp://oa.upm.es/id/eprint/26489This item is in the repository with the URL: http://oa.upm.es/id/eprint/264892014-05-25T06:49:31ZBare Tethers for Electrodynamic Spacecraft PropulsionElectrodynamic tether thrusters can use the power provided by solar panels to drive a current in the tether and then the Lorentz force to push against the Earth's magnetic field, thereby achieving propulsion without the expenditure of onboard energy sources or propellant. Practical tether propulsion depends critically on being able to extract multiamp electron currents from the ionosphere with relatively short tethers (10 km or less) and reasonably
low power. We describe a new anodic design that uses an uninsulated portion of the metallic tether itself to collect
electrons. Because of the efficient collection of this type of anode, electrodynamic thrusters for reboost of the International Space Station and for an upper stage capable of orbit raising, lowering, and inclination changes appear to be feasible. Specifically, a 10-km-long bare tether, utilizing 10 kW of the space station power could save
most of the propellant required for the station reboost over its 10-year lifetime. The propulsive small expendable
deployer system experiment is planned to test the bare-tether design in space in the year 2000 by deploying a 5-km bare aluminum tether from a Delta II upper stage to achieve up to 0.5-N drag thrust, thus deorbiting the stage.Robert D. EstesEnrico C. LorenziniJuan Ramón Sanmartín LosadaJesús Peláez ÁlvarezManuel Martínez SánchezC.L. JhonsonI.E. Vas2014-05-22T13:37:54Z2015-05-25T13:51:30Zhttp://oa.upm.es/id/eprint/26393This item is in the repository with the URL: http://oa.upm.es/id/eprint/263932014-05-22T13:37:54ZPropulsive small expendable deployer system experimentRelatively short electrodynamic tethers can extract orbital energy to "push" against a planetary magnetic field to achieve propulsion without the expenditure of propellant. The Propulsive Small Expendable Deployer System experiment will use the flight-proven Small Expendable Deployer System to deploy a 5-km bare aluminum tether from a Delta II upper stage to achieve ~0.4-N drag thrust, thus lowering the altitude of the stage. The experiment will use a predominantly bare tether for current collection in lieu of the endmass collector and insulated tether used on previous missions. The flight experiment is a precursor to a more ambitious electrodynamic tether upper-stage demonstration mission that will be capable of orbit-raising,lowering, and inclination changes, all using electrodynamic thrust. The expected performance of the tether propulsion system during the experiment is described.Les JhonsonRobert D. EstesEnrico C. LorenziniManuel Martínez-SánchezJuan Ramón Sanmartín Losada2014-05-22T09:56:14Z2014-09-22T11:40:53Zhttp://oa.upm.es/id/eprint/26329This item is in the repository with the URL: http://oa.upm.es/id/eprint/263292014-05-22T09:56:14ZBare wire anodes for electrodynamic tethersThe collection of electrons from the ionosphere is the major problem facing high-power electrodynamic tethers.
This article discusses a simple electron-collection concept which is free of most of the physical uncertainties
associated with plasma contactors in the rarefied, magnetized environment of an orbiting tether. The idea is to
leave exposed a fraction of the tether length near its anodic end, such that, when a positive bias develops locally
with respect to the ambient plasma, and for a tether radius small compared with both thermal gyroradius and Debye length, electrons are collected in an orbital-motion-limited regime. It is shown that large currents can
be drawn in this way with only moderate voltage drops. The concept is illustrated through a discussion of performance characteristics for generators and thrusters.Juan Ramón Sanmartín LosadaManuel Martínez-SánchezEduardo Ahedo Galilea2014-05-21T12:47:17Z2014-09-22T11:40:53Zhttp://oa.upm.es/id/eprint/26327This item is in the repository with the URL: http://oa.upm.es/id/eprint/263272014-05-21T12:47:17ZSeguridad espacial : una solución práctica para el problema de los residuos espaciales en órbitaJuan Ramón Sanmartín LosadaGonzalo Sánchez Arriaga2014-05-21T07:06:07Z2014-09-29T18:20:12Zhttp://oa.upm.es/id/eprint/26270This item is in the repository with the URL: http://oa.upm.es/id/eprint/262702014-05-21T07:06:07ZBETs: Propellant less de orbiting of space debris by bare electrodynamic tethersAs a fundamental contribution to limiting the increase of debris in the Space environment, a three-year project
started on 1 November 2010 financed by the European Commission under the FP-7 Space Programme. It aims at developing a universal system to be carried on board future satellites launched into low Earth orbit (LEO), to allow de-orbiting at end of life. The operational system involves a conductive tape-tether left bare of insulation to establish anodic contact with the ambient plasma as a giant Langmuir probe. The project will size the three disparate
dimensions of a tape for a selected de-orbit mission and determine scaling laws to allow system design for a general
mission. It will implement control laws to restrain tether dynamics in/off the orbital plane; and will carry out
plasma chamber measurements and numerical simulations of tether-plasma interaction. The project also involves
the design and manufacturing of subsystems: electron-ejecting plasma contactors, an electric control and power
module, interface elements, tether and deployment mechanisms, tether tape/end-mass as well as current collection plus free-fall, and hypervelocity impact tests.Juan Ramón Sanmartín LosadaMario CharroEnrico C. LorenziniGiacomo ColombattiJean-François RousselPierre SerrathJohn D. WilliamsKan XieFrancisco García de QuirósJosé A. CarrascoRoland RostaTim van ZoestJoseba LasaJesús Marcos2014-05-21T05:51:04Z2014-09-22T11:40:34Zhttp://oa.upm.es/id/eprint/26267This item is in the repository with the URL: http://oa.upm.es/id/eprint/262672014-05-21T05:51:04ZActive charging control and tethersJuan Ramón Sanmartín Losada2014-05-20T11:11:59Z2014-09-22T11:40:24Zhttp://oa.upm.es/id/eprint/26230This item is in the repository with the URL: http://oa.upm.es/id/eprint/262302014-05-20T11:11:59ZShort tethers for electrodynamic thrustThe operational advantages of electrodynamic tethers of moderate length are becoming evident from studies
of collision avoidance. Although long tethers (of order of 10 kilometers) provide high efficiency and good adaptability to varying plasma conditions, boosting tethers of moderate length (- 1 kilometer) and suitable design might still operate at acceptable efficiencies and adequate adaptability to a changing environment. In this paper we carry out a parametric analysis of the performance of 1-km long boosting tethers, to maximize their efficiency. We also discuss the possible use of multiple, parallel such tethers for keeping thrust high when length is decreased. We then estimate the survivability of short tethers to micrometeoroids and orbital debris. Finally, a few considerations are made on the dynamic stability of
electrodynamic tether systems versus length.Robert D. EstesEnrico C. LorenziniJuan Ramón Sanmartín Losada2014-05-20T07:32:56Z2014-09-22T11:40:22Zhttp://oa.upm.es/id/eprint/26225This item is in the repository with the URL: http://oa.upm.es/id/eprint/262252014-05-20T07:32:56ZEfficiency of different types of ED-tether thrustersThe efficiencies of electrodynamic-tether (EDT) thrusters made of single bare tethers with different types of cross sections, several parallel bare tethers, or a fully insulated tether with a three-dimensional passive end-collector, are discussed. Current collection, mass, and ohmic resistance considerations are balanced against each other in discussing efficiencies. Use is made of recent results on the validity domain of orbital-motion-limited (OML) collection, the current law beyond that domain, and interference effects between parallel bare tethers; and on current adjustment to variations in electron density encountered in orbit. Comparisons between EDT thrusters and electrical thrusters in terms of the ratio of dedicated mass to the total mission impulse show EDT to be superior for mission times over 50-100 days.Juan Ramón Sanmartín LosadaRobert D. EstesEnrico C. Lorenzini2014-05-20T06:48:45Z2014-09-22T11:40:04Zhttp://oa.upm.es/id/eprint/26152This item is in the repository with the URL: http://oa.upm.es/id/eprint/261522014-05-20T06:48:45ZElectron heat conduction in ICF targetsJuan Ramón Sanmartín Losada2014-05-19T06:19:25Z2014-09-22T11:39:39Zhttp://oa.upm.es/id/eprint/26067This item is in the repository with the URL: http://oa.upm.es/id/eprint/260672014-05-19T06:19:25ZCurrent-voltage response of a spherical plasma contactorA theoretical model for a contactor, collecting electrons from an ambient, unmagnetized plasma and emitting a current Iiis discussed. The relation between Ii and the potential
bias of the contactor is found to be crucial for the formation of a quasineutral core around the anode and, consequently, for the current colleted. Approximate analytical
laws and charts for the current-voltage response are provided.Eduardo Ahedo GalileaJuan Ramón Sanmartín LosadaM. Martínez-Sánchez2014-05-18T08:33:52Z2014-10-01T13:58:57Zhttp://oa.upm.es/id/eprint/26064This item is in the repository with the URL: http://oa.upm.es/id/eprint/260642014-05-18T08:33:52ZPropellantless de orbiting of space debris by bare electrodynamic tethersA 3-year Project started on November 1 2010, financed by the European Commision within the FP-7 Space Program, and aimed at developing an efficient de-orbit system that could be carried on board by future spacecraft launched into LEO, will be presented. The operational system will deploy a thin uninsulated tape-tether to collect electrons as a giant Langmuir probe, using no propellant/no power supply, and generating power on board. This project will involve free-fall tests, and laboratory hypervelocity-impact and tether-current tests, and design/Manufacturing of subsystems: interface elements, electric control and driving module, electron-ejecting plasma contactor, tether-deployment mechanism/end-mass, and tape samples. Preliminary results to be presented involve: i) devising criteria for sizing the three disparate tape dimensions, affecting mass, resistance, current-collection, magnetic self-field, and survivability against debris itself; ii) assessing the dynamical relevance of tether parameters in implementing control laws to limit oscillations in /off the orbital plane, where passive stability may be marginal; iii) deriving a law for bare-tape current from numerical simulations and chamber tests, taking into account ambient magnetic field, ion ram motion, and adiabatic electron trapping; iv) determining requirements on a year-dormant hollow cathode under long times/broad emission-range operation, and trading-off against use of electron thermal emission; v) determining requirements on magnetic components and power semiconductors for a control module that faces high voltage/power operation under mass/volume limitations; vi) assessing strategies to passively deploy a wide conductive tape that needs no retrieval, while avoiding jamming and ending at minimum libration; vii) evaluating the tape structure as regards conductive and dielectric materials, both lengthwise and in its cross-section, in particular to prevent arcing in triple-point junctions.Juan Ramón Sanmartín LosadaSaker B. KahnClaudio BombardelliEnrico C. LorenziniGiacomo ColombattiDenis ZanuttoJean-François RousselPierre SarrailhJohn D. WilliamsGarret E. MetzJames K. ThomasJosé A. CarrascoFrancisco García de QuirósOlaf KroemerRoland RostaTim van ZoestJoseba LasaJesús Marcos2014-05-18T08:32:13Z2016-11-24T11:46:39Zhttp://oa.upm.es/id/eprint/26072This item is in the repository with the URL: http://oa.upm.es/id/eprint/260722014-05-18T08:32:13ZAn anodeless tether generatorA new simple concept for electron collection by an electrodynamic tether is presented. No anodic contactor Is needed, the tether itself, left bare, drawing a current with neither shielding nor magnetic effects. Application to a generator is discussed.Juan Ramón Sanmartín LosadaEduardo Ahedo GalileaM. Martínez-Sánchez2014-05-16T17:12:23Z2014-09-22T11:39:39Zhttp://oa.upm.es/id/eprint/26066This item is in the repository with the URL: http://oa.upm.es/id/eprint/260662014-05-16T17:12:23ZTape-tether design for de-orbiting from given altitude and inclinationThe product of the tether-to-satellite mass ratio and the
probability of tether cuts by small debris must be small
to make electrodynamic bare tethers a competitive and
useful de-orbiting technology. In the case of a circular
orbit and assuming a model for the debris population, the
product can be written as a function that just depends
on the initial orbit parameters (altitude and inclination)
and the tether geometry. This formula, which does not
contain the time explicitly and ignores the details of the
tether dynamics during the de-orbiting, is used to find design rules for the tape dimensions and the orbit parameter
ranges where tethers dominate other de-orbiting technologies
like rockets, electrical propulsion, and sails.Juan Ramón Sanmartín LosadaAntonio Sánchez-TorresS. B. KhanGonzalo Sánchez ArriagaMario Charro2014-05-13T05:30:43Z2014-09-26T11:46:46Zhttp://oa.upm.es/id/eprint/25886This item is in the repository with the URL: http://oa.upm.es/id/eprint/258862014-05-13T05:30:43ZThe ESA "Plasma Laboratory in Space" studyThe European Space Agency has initiated, in the context of its General Studies Programme, a study of the
possible use of space for studies in pure and applied plasma physics, in areas not traditionally covered by “space plasma physics”. A team of experts has been set-up to review a broad range of area including industrial
plasma physics and pure plasma physics, astrophysical and solar-terrestrial areas. A set of experiments have been identified that can potentially provide access to new phenomena and to allow advances in several fields
of plasma science. These experiments concern phenomena on spatial scale (102 to104 m) intermediate between what is achievable on ground experiment and usual solar system plasma observations.B. AnnaratoneD. BrunoM. CapitelliF. CeccheriniE. DalyO. de PascaleA. HilgersK. LacknerS. LongoS. MarcuccioT. MendoncaV. NagnibedaF. PegoraroJuan Ramón Sanmartín Losada2014-05-12T11:57:04Z2016-04-21T12:32:00Zhttp://oa.upm.es/id/eprint/21785This item is in the repository with the URL: http://oa.upm.es/id/eprint/217852014-05-12T11:57:04ZOn the charged particle drag acting on LAGEOSA recent study by the authors points to Charged Particle Drag (CPD) as a contributor to revisit in the LAGEOS non-gravitational perturbations problem. Such perturbations must account for dynamical contributions in the order of pms−2 . The simulated effect takes into account: (i) spatial and temporal variations of the plasmatic parameters
(temperature and concentration of the species), (ii) spacecraft potential variations caused by both the eclipse passages and variations in the parameters mentioned above, and (iii) solar and geomagnetic conditions. Furthermore, recent theoretical improvements concerning scattering drag overcome previous limitations allowing for a complete
formulation of this effect. For each satellite the lifetime CPD instantaneous acceleration is computed. The plasmatic parameters have been obtained fromthe Sheffield Coupled Thermosphere-Ionosphere-Plasmasphere (SCTIP) semi-empirical
model (up to the polar region), as well as alytical/empirical approximations based on spacecraft measurements for the auroral and polar regions. Results show that maximum amplitudes for LAGEOSI are larger than those for LAGEOS-II: −85 pms−2 and −70 pms−2 respectively. This is due to the almost (magnetically) polar orbit configuration of the first, producing larger combinations of plasmatic parameter values. High solar activity has a huge impact in the resulting LAGEOS accelerations: it yields a perfect modulation of the resulting
acceleration with maximum amplitudes up to a factor of 10 when comparing low and high activity periods. On the other hand, the impact of the geomagnetic activity results into a reduction of the effect itself, probably due to a decrease in the hydrogen concentration for high energy input periods. The acceleration results will be used in a
refined orbit computation in a subsequent investigation.J.I. AndrésJuan Ramón Sanmartín LosadaR. Noomen2014-05-12T10:03:16Z2014-09-22T11:38:46Zhttp://oa.upm.es/id/eprint/25883This item is in the repository with the URL: http://oa.upm.es/id/eprint/258832014-05-12T10:03:16ZElectrodynamic tether at Jupiter 2. Tour missions after captureThree separate scenarios of an electrodynamic tether mission at Jupiter following capture of a spacecraft (SC) into an equatorial, highly elliptical orbit around the planet, with perijove at about 1.5 times the Jovian radius,
are discussed. Repeated application of Lorentz drag on the spinning tether, at the perijove vicinity, can progressively lower the apojove. One mission involves the tethered-SC rapidly and frequently visiting Galilean moons;
elliptical orbits with apojove down at the Ganymede, Europa, and Io orbits are in 2:5, 4:9, and 1:2 resonances with the respective moons. About 20 slow flybys of Io would take place before the accumulated radiation dose exceeds 3 Mrad (Si) at 10 mm Al shield thickness, with a total duration of 5 months after capture (4 months for lowering the apojove to Io and one month for the flybys). The respective number of flybys for Ganymede would be 10 with a total duration of about 9 months. An alternative mission would have the SC acquire a low circular orbit around Jupiter, below the radiation belts, and manoeuvre to get an optimal altitude, with no major radiation effects, in less than 5 months after capture. In a third mission, repeated thrusting at the apojove vicinity, once down at the Io
torus, would raise the perijove itself to the torus to acquire a low circular orbit around Io in about 4 months, for a total of 8 months after capture; this corresponds, however, to over 100 apojove passes with an accumulated
dose, of about 8.5 Mrad (Si), that poses a critical issue.Juan Ramón Sanmartín LosadaMario CharroEnrico C. LorenziniHenry B. GarretCristina BramantiClaudio Bombardelli2014-05-12T09:53:29Z2014-09-22T11:38:10Zhttp://oa.upm.es/id/eprint/25758This item is in the repository with the URL: http://oa.upm.es/id/eprint/257582014-05-12T09:53:29ZA theory of electron collection by a grid sphereUse of a spherical grid as electron collector at the anodic end of a tether, as recently proposed, is considered. The standard analysis of space-charge limited current to a solid sphere (with neither magnetic nor plasma-motion
effects), which has been shown to best fit TSS1R in-orbit results at very high bias, is used to determine effects from grid transparency on current collected; the analysis is first reformulated in the formalism recently
introduced in the two-dimensional analysis of bare-tethers. A discussion of the electric potential created by a spherical grid in vacuum is then carried out; it is shown that each grid-wire collects current well below its
maximum OML current, the effective grid transparency being close to its optical value. Formulae for the current to a spherical grid, showing the effects of grid transparency, is determined. A fully consistent analysis of electric potential and electron density, outside and inside the grid, is completed.Juan Ramón Sanmartín LosadaÓscar López-Rebollal2014-05-07T09:59:51Z2014-09-22T11:38:06Zhttp://oa.upm.es/id/eprint/25746This item is in the repository with the URL: http://oa.upm.es/id/eprint/257462014-05-07T09:59:51ZPerformance of coupled ED-tether/ion thrsuter systemUse of propulsion systems that couple electyrodynamic tethers to ion thrusters, as suggested in the literature, is
discussed. The system establishes electrical contact with the ionospheric plasma, at the anodic end of the tether, by
ejecting ions instead of collecting electrons; also, the ion thruster adds its thrust to the Lorentz force on the tether. In this paper, we analyze the performance of this coupled system, as measured by the ratio of mission impulse (thrust times mission duration) to the overall system mass, which includes the power subsystem mass, the tether subsystem mass, and the propellant mass consumed in the ion thruster. It is shown that a tether acting by itself, collecting electrons at its anodic end, substantially outperforms the coupled system for times longer than a characteristic time of the ion thruster, for which propellant mass equals the power subsystem mass; for shorter times performances are shown to be similar.Juan Ramón Sanmartín LosadaMario Charro2014-05-07T09:59:10Z2014-09-30T12:24:16Zhttp://oa.upm.es/id/eprint/25745This item is in the repository with the URL: http://oa.upm.es/id/eprint/257452014-05-07T09:59:10ZSpherical collectors versus bare tethers for drag, thrust, and power generationPerformances of ED-tethers using either spherical collectors or bare tethers for drag, thrust, or power generation, are compared. The standard Parker-Murphy model of current to a full sphere, with neither space-charge nor plasmamotion effects considered, but modified to best fit TSS1R results, is used (the Lam, Al'pert/Gurevich space-charge limited model will be used elsewhere) In the analysis, the spherical collector is assumed to collect current well beyond its random-current value (thick-heath). Both average current in the bare-tether and current to the sphere are normalized with the short-circuit current in the absence of applied power, allowing a comparison of performances for all three applications in terms of characteristic dimensionless numbers. The sphere is always substantially outperformed by the bare-tether if ohmic effects are weak, though its performance improves as such effects increase.Juan Ramón Sanmartín LosadaMario CharroEnrico C. Lorenzini2014-05-07T09:58:19Z2014-09-22T11:38:06Zhttp://oa.upm.es/id/eprint/25747This item is in the repository with the URL: http://oa.upm.es/id/eprint/257472014-05-07T09:58:19ZA proposed bare tether experiment on board a sounding rocketA sounding rocket experiment is proposed to carry out two experiments by the conductive bare-tether; 1) the test of the OML (Orbital-Motion-Limited) theory to collect electron, and II) the test of techniques to determine (neutral) density profile in critical E-layer. The main driver of the mission is provide a space tether technology experiment in low-Earth-Orbit (LEO) deploying a long tape tether in space and verify the performance of the bare electrodynamic tape tether. The sounding rocket experiment will show no danger to other satellites as the tether missions YES1, SEDSAT, and ProCEDS, which is cancelled just for afraid of collision with the ISS orbit. Also, the sounding rocket mission is possible to demonstrate the bare tether technology in low cost, simple mission concept, fast realization for space structures. The present sounding rocket experiment is expected to be the first conductive bare tether experiment.Hironori FujiiKohichiro OyamaSusumu SasakiYoshiki YamagiwaMengu ChoJuan Ramón Sanmartín LosadaMario CharroErik J. van der HeideMichiel KruijffJean-Pierre LebretonAlain Hilgers2014-05-06T11:45:10Z2014-09-22T11:38:02Zhttp://oa.upm.es/id/eprint/25729This item is in the repository with the URL: http://oa.upm.es/id/eprint/257292014-05-06T11:45:10ZA "Free-Lunch" tour of the Jovian SystemAn ED-tether mission to Jupiter is presented. A bare tether carrying cathodic devices at both ends but no power supply, and using no propellant, could move 'freely' among Jupiter's
4 great moons. The tour scheme would have current naturally driven throughout by the motional electric field, the Lorentz force switching direction with current around a 'drag' radius of 160,00 kms, where the speed of the jovian ionosphere equals the speed of a spacecraft in circular orbit. With plasma density and magnetic field decreasing rapidly with distance from Jupiter, drag/thrust would only be operated in the inner plasmasphere, current being near shut off conveniently in orbit by disconnecting cathodes or plugging in a very large resistance; the tether could serve as its own power supply by plugging in an electric
load where convenient, with just some reduction in thrust or drag. The periapsis of the spacecraft in a heliocentric transfer orbit from Earth would lie inside the drag sphere; with tether deployed and current on around periapsis, magnetic drag allows Jupiter to capture the spacecraft into an elliptic orbit of high eccentricity. Current would be on at succesive perijove passes and off elsewhere, reducing the eccentricity by lowering the apoapsis progressively to
allow visits of the giant moons. In a second phase, current is on around apoapsis outside the drag sphere, rising the periapsis until the full orbit lies outside that sphere. In a third phase, current is on at periapsis, increasing the eccentricity until a last push makes the orbit hyperbolic to escape Jupiter. Dynamical issues such as low gravity-gradient at Jupiter and tether orientation in elliptic orbits of high eccentricity are discussed.Juan Ramón Sanmartín LosadaEnrico C. Lorenzini2014-05-06T11:22:01Z2014-09-22T11:38:00Zhttp://oa.upm.es/id/eprint/25725This item is in the repository with the URL: http://oa.upm.es/id/eprint/257252014-05-06T11:22:01ZAnalysis of Proseds bare-tether performanceNASA's tether experiment ProSEDS will be placed in orbit on board a Delta-II rocket in early 2003. ProSEDS will test bare-tether electron collection, deorbiting of the rocket second stage, and the system dynamic stability. ProSEDS performance will vary both because ambient conditions change along the orbit and because tether-circuit parameters follow a step by step sequence in the current operating cycle. In this work we discuss how measurements of tether current and bias, plasma density, and deorbiting rate can be used to check the OML law for current collection. We review circuit bulk elements; characteristic lengths and energies that determine collection (tether radius, electron thermal gyroradius and Debye length, particle temperatures, tether bias, ion ram energy); and lengths determining current and bias profiles along the tether (extent of magnetic self-field, a length gauging ohmic versus collection impedances, tether length). The
analysis serves the purpose of estimating ProSEDS behavior in orbit and fostering our ability for extrapolating ProSEDS flight data to different tether and environmental conditions.Juan Ramón Sanmartín LosadaEnrico C. LorenziniM.L. CosmoRobert D. Estes2014-04-25T10:30:26Z2014-09-30T11:49:24Zhttp://oa.upm.es/id/eprint/25611This item is in the repository with the URL: http://oa.upm.es/id/eprint/256112014-04-25T10:30:26ZShort electrodynamic tethersED bare theters are best systems to deorbit S/C at end of service. For near polar orbits, usual tethers kept vertical by the gravity gradient, yield too weak magnetic drag. Here we propose keeping tethers perpendicular to the orbital plane. they mus be rigid and short for structural reasons, requiring power supply like Ion thrusters. terher tube-booms that can be rolled up on a drum would lie on each side of the S/C. One boom, carying in idle Hollow Cathode, collects electrons; the opposite boom's HC ejects electrons.Juan Ramón Sanmartín LosadaEduardo Ahedo GalileaLuis Conde LópezJesús Peláez ÁlvarezM. RuizM. WeinbergerA. Hilgers2014-04-25T10:00:59Z2014-09-22T11:37:24Zhttp://oa.upm.es/id/eprint/25610This item is in the repository with the URL: http://oa.upm.es/id/eprint/256102014-04-25T10:00:59ZMagnetic self-field effects on bare-tether current collectionIt has been recently suggested that the magnetic field
created by the current in a bare tether could sensibly
reduce its electron collection capability in the magnetised ionosphere, a region of closed magnetic surfaces disconnecting the cylinder from infinity. In this paper, the ohmic voltage drop along the tether is taken into account in considering self-field effects. Separate analyses are carried out for the thrust and power generation and drag modes of operation, which are affected in different ways. In the power generation and drag modes, bias decreases as current increases along the tether, starting at the anodic, positively-biased end (upper end in the usual, eastward-flying spacecraft); in the thrust mode of operation, bias increases as current increases along the tether, starting at the lower end. When the ohmic voltage drop is considered, self-field effects are shown to be weak, in all cases, for tape tethers, and for circular cross-section tethers just conductive in a thin outer layer. Self-field effects might become important, in the drag case only, for tethers with fully conductive cross sections that are unrealistically heavy.Juan Ramón Sanmartín LosadaRobert D. Estes2014-04-25T09:59:52Z2014-09-22T11:37:24Zhttp://oa.upm.es/id/eprint/25609This item is in the repository with the URL: http://oa.upm.es/id/eprint/256092014-04-25T09:59:52ZAn upper atmospheric probe for auroral effectsAn electrically floating bare tether in LEO orbit may
serve as upper atmospheric probe. Ambient ions bombard the negatively biased tether and liberate secondary electrons, which accelerate through the same voltage to form a magnetically guided planar e-beam resulting in auroral effects at the E-layer. This beam is free from the S/C charging and plasma interaction problems of standard e-beams. The energy flux is weak but varies accross the large beam cross section, allowing continuous observation from the S/C. A brightness scan of line-integrated emissions, that mix emitting altitudes and tether points originating the electrons, is analysed. The tether is magnetically dragged at nighttime operation, when power supply and plasma contactor at the S/C are off for electrical floating; power and contactor are on at daytime for partial current reversal, resulting in thrust. System requirements for keeping average orbital height are discussed.Juan Ramón Sanmartín LosadaEduardo Ahedo GalileaM. Martínez Sánchez2014-04-25T09:05:33Z2014-09-22T11:37:22Zhttp://oa.upm.es/id/eprint/25605This item is in the repository with the URL: http://oa.upm.es/id/eprint/256052014-04-25T09:05:33ZProbe current in a magnetized,collisional plasma revisitedAn old analysis of probe current in a strongly magnetized plasma is reconsidered. It is shown that, in the collisional limit, the plasma beyond the sheath heats up in the collection process at positive probe bias enough. The modified current is compared to the current collected in the
case of collection due to Bohm diffusion.Mario CharroJuan Ramón Sanmartín Losada2014-04-25T06:33:11Z2016-04-21T23:19:19Zhttp://oa.upm.es/id/eprint/23490This item is in the repository with the URL: http://oa.upm.es/id/eprint/234902014-04-25T06:33:11ZNew results on bare-tether currentRecent results on the validity of the orbital-motion-limited (OML) regime of cylindrical Langmuir probes, which are essential for bare-tether applications, are extended to show how the current lags behind the OML value beyond the OML regime, and the possible effects of motion of the probe relative to the plasma.Robert D. EstesJuan Ramón Sanmartín Losada2014-04-12T17:22:22Z2016-04-21T23:19:15Zhttp://oa.upm.es/id/eprint/23489This item is in the repository with the URL: http://oa.upm.es/id/eprint/234892014-04-12T17:22:22ZA correction to Whipple's law for ion-trap CurrentWe have analyzed a phenomenon heretofore ignored in the analyses of ion traps, which are used to determine ion temperature, among other plasma parameters, in planetary ionospheres: ions that are rejected by the trap perturb the plasma well ahead of the Debye sheath at the front of the trap.The determination of the perturbed plasma flow is found to depend on the fact that the ionospheric plasma be stable to quasineutral, ion-acoustic perturbations.Juan Ramón Sanmartín LosadaÓscar López-Rebollal2014-04-11T08:38:04Z2014-09-29T08:11:15Zhttp://oa.upm.es/id/eprint/23477This item is in the repository with the URL: http://oa.upm.es/id/eprint/234772014-04-11T08:38:04ZTechnology of bare tether current collectionThe outstanding problem for useful applications of electrodynamic tethers is obtaining sufficient electron current from the ionospheric plasma. Bare tether collectors, in which the conducting tether itself, left uninsulated over kilometers of its length, acts as the collecting anode, promise to attain currents of 10 A or more from reasonably sized systems. Current collection by a bare tether is also relatively insensitive to drops in electron density, which are regularly encountered on each revolution of an orbit. This makes nighttime operation feasible. We show how the bare tether's high efficiency of current collection and ability to adjust to density variations follow from the orbital motion limited collection law of thin cylinders. We consider both upwardly deployed (power generation mode) and downwardly deployed (reboost mode) tethers, and present results that indicate how bare tether systems would perform as their magnetic and plasma environment varies in low earth orbit.Robert D. EstesJuan Ramón Sanmartín LosadaManuel Martínez-Sánchez2014-04-11T08:21:31Z2016-04-21T23:17:19Zhttp://oa.upm.es/id/eprint/23478This item is in the repository with the URL: http://oa.upm.es/id/eprint/234782014-04-11T08:21:31ZValidity of the orbital-motion-limited regime of cylindrical probesJuan Ramón Sanmartín LosadaRobert D. Estes2014-04-10T07:46:57Z2014-09-30T12:32:02Zhttp://oa.upm.es/id/eprint/23460This item is in the repository with the URL: http://oa.upm.es/id/eprint/234602014-04-10T07:46:57ZTwo-temperature model of the coronal irradiated pelletsA two electron-temperature, quasi-steady model of the corona of a laser-ablated pellet is considered. Ablation pressure, critical radius and mass flow rate are determined. Results are close to those obtained with heat flux saturation well below the free-streaming limit.Juan Ramón Sanmartín LosadaJosé Luis Montañés GarcíaRafael Ramis AbrilJ. Sanz2014-04-10T07:42:00Z2014-09-30T12:05:12Zhttp://oa.upm.es/id/eprint/23441This item is in the repository with the URL: http://oa.upm.es/id/eprint/234412014-04-10T07:42:00ZAn anodeless (bare) tether experimentNETT (New Electrodynamic Tether Technology) is an experiment proposed to ESA in 1991 as part of the Columbus Precursor Flights. It was originally intended to fly as
an exposed payload in the Shuttle cargo bay. The main purpose was to demonstrate the electrodynamical capabilities of the innovative "bare tether" concept. The proposed conceptual design was recommended by a Scientific Panel of ESA, meeting in Heidelberg in March 1992. Unfortunately, the Precursor Flights have all but been scuttled, particularly as far as exposed payloads are concerned. The experiment, horever, is being considered
in accomodation studies (APLSS, PIERS) for the European modulus of the future Space Station. Additionally, it might be possible to fly the bare tether in a Russian spacecraft.Juan Ramón Sanmartín LosadaEduardo Ahedo GalileaLuis Conde LópezF. IbáñezJesús Peláez Álvarez2014-04-10T07:41:46Z2016-04-21T23:09:40Zhttp://oa.upm.es/id/eprint/23443This item is in the repository with the URL: http://oa.upm.es/id/eprint/234432014-04-10T07:41:46ZTether wave emissionJuan Ramón Sanmartín LosadaManuel Martínez-Sánchez2014-04-10T07:37:08Z2016-04-21T23:12:11Zhttp://oa.upm.es/id/eprint/23455This item is in the repository with the URL: http://oa.upm.es/id/eprint/234552014-04-10T07:37:08ZNon local heat flux in weakly collisional plasmasJuan Ramón Sanmartín Losada2014-04-10T07:35:55Z2016-04-21T23:12:19Zhttp://oa.upm.es/id/eprint/23456This item is in the repository with the URL: http://oa.upm.es/id/eprint/234562014-04-10T07:35:55ZExpectations from EMET and OESEE ground listening of possible EM events generated by the TSS 1ROn 22nd February '96, the space mission STS 75 started ,from the NASA facilities at Cape Canaveral. Such a mission consists in the launch of the shuttle Columbia in order to carry out two experiments in the space: the TSS 1R (Tethered Satellite Sistem 1 Refliight) and the USMP (United States
Microgravity Payload). The TSS 1R is a replica of a similar mission TSS 1 '92. The TSS space programme is a bilateral scientific cooperation between the USA space agency NASA (National Aeronautics and Space Agency) and the ASI (Italian Space Agency. The TSS 1R system consists on the shuttle
Columbia which deploys, up-ward, by means a conducting tether 20 km long, a spherical satellite (1.5 mt diameter) containing scientific instrumentation. This system, orbiting at about 300 km from the Earth's surface, represents,
presently, the largest experimental space structure, Due to its dimensions, flexibility and conducting properties of the tether, the system interacts, in a quite complex manner,
wih the earth magnetic field and the ionospheric plasma, in a way that the total system behaves as an electromagnetic radiating antenna as well as an electric power generator.
Twelve scientific experiments have been assessed by US and Italian scientists in order to study the electro dynamic behaviour of the structure orbiting in the ionos phere. Two
experiments have been prepared in the attempt to receive on the Earth's surface possible electromagnetic events radiated by the TSS 1R. The project EMET (Electro Magnetic Emissions from Tether),USA and the project OESEE (Observations on the Earth Surface of Electromagnetic Emissions) Italy, consist in a coordinated programme of passive detection of such possible EM emissions. This detection will supply the verification of some thoretical hypotheses on the electrodynamic interactions between the orbiting system, the
Earth's magnetic field and the ionospheric plasma with two principal aims as the technological assesment of the system concept as well as a deeper knowledge of the ionosphere properties for future space applications. A theoretical model that keeps the peculiarities of tether emissionsis being developed for signal prediction at constant tether current. As a step previous to the calculation of the expected ground signal , the Alfven-wave signature left by the tether far back in the ionosphere has been determined.
The scientific expectations from the combined effort to measure the entity of those perturbations will be outlined taking in to account the used ground track sensor systems.Robert D. EstesJuan Ramón Sanmartín LosadaGiorgio Tacconi2014-04-09T13:20:30Z2014-09-30T11:39:57Zhttp://oa.upm.es/id/eprint/23444This item is in the repository with the URL: http://oa.upm.es/id/eprint/234442014-04-09T13:20:30ZLight pressure effects on ion spectra in two-ion laser plasmaJosé Luis Montañés GarcíaJuan Ramón Sanmartín Losada2014-04-09T13:18:52Z2014-09-29T08:00:19Zhttp://oa.upm.es/id/eprint/23446This item is in the repository with the URL: http://oa.upm.es/id/eprint/234462014-04-09T13:18:52ZAlfven wave signature from constant-current tethersRobert D. EstesJuan Ramón Sanmartín Losada2014-04-09T13:18:31Z2014-09-30T11:37:52Zhttp://oa.upm.es/id/eprint/23447This item is in the repository with the URL: http://oa.upm.es/id/eprint/234472014-04-09T13:18:31ZAn extended electron beam for auroral studiesAn electrically floating metallic bare tether in a low Earth orbit would be highly negative with respect to the ambient plasma over most of its length, and would be bombarded by ambient ions. This would liberate secondary
electrons, which, after acceleration through the same voltage, would form a magnetically guided two-sided planar e-beam. Upon impact on the atmospheric E-layer, at about 120-140 Km altitude auroral effects (ionization and light emission) can be expected. This paper examines in a preliminary way the feasibility of using this effect as an upper atmospheric probe. It is concluded that significant perturbations can be produced along the illuminated planar sheet of the atmosphere, with ionization rates of several
thousand cm-3 sec1. Observation of the induced optical emission is made difficult by the narrowness and high moving speed of the illuminated zone, but it is shown that vertical resolution of single spectral lines is possible, as is wider spectral coverage with no vertical resolution.Manuel Martínez-SánchezJuan Ramón Sanmartín Losada2014-04-09T08:40:42Z2017-05-10T11:14:24Zhttp://oa.upm.es/id/eprint/23411This item is in the repository with the URL: http://oa.upm.es/id/eprint/234112014-04-09T08:40:42ZScience with an electrodynamic tetherIonospheric interaction experiments using a conductive, fully bare tether
are discussed. With an optimal design, requiring 1.15 mm diameter and 7.5 km full length for a collected current of 0.87 A at day conditions, the tether radiates 0.33 watts as Fast Magnetosonic waves and 0.16 watts as Alfven waves. Secondary keV electrons are produced over a 6.5 km length, giving raise to noticeable auroral effects in the D-layer, at low geomagnetic latitudes. A preliminary design of the experiment, to be implemented on either a satellite or a Station, has been carried out. An ejector gives an initial velocity to an end mass, a free spool of tether unwinding from that mass during a first stage of deployment; other phases are monitored through the tether velocity, driving a reel with an unwinding device.Juan Ramón Sanmartín LosadaM. HayardM. Soudet2014-04-09T08:38:08Z2016-12-01T13:29:16Zhttp://oa.upm.es/id/eprint/23434This item is in the repository with the URL: http://oa.upm.es/id/eprint/234342014-04-09T08:38:08ZMagnetantrieb für RaumfahrzeugeEinfache Metallseile könnten Raumfahrzeuge mit billigem
Strom versorgen, zu Antrieb und Steuerung beitragen und der Besatzung die Annehmlichkeiten künstlicher Schwerkraft verschaffen. Dahinterstecken elementare Naturgesetze aus Mechanik und ElektrodynamikEnrico C. LorenziniJuan Ramón Sanmartín Losada2014-04-09T08:37:32Z2014-09-29T07:50:06Zhttp://oa.upm.es/id/eprint/23407This item is in the repository with the URL: http://oa.upm.es/id/eprint/234072014-04-09T08:37:32ZNew electrodynamic tether technologyNew Electrodynarnic Tether Technology (NETT) is
an experiment we proposed to ESA as part of the Columbus
Precursor Flights. It was designed to fly as an exposed
payload in the Spacelab carrier. Its primary objective
is performance testing for the innovative bare tether
concept. The experiment also includes two scientific objectives, specific for uninsulated tethers: i) detection of artificial auroral effects produced by secondary electron
emission, and ii) detection of VLF wave emission. Additional
objectives of the project are space performance of an electron-emitting hollow cathode and engineering verification of an open-loop deployment strategy.Eduardo Ahedo GalileaLuis Conde LópezJesús Peláez ÁlvarezJuan Ramón Sanmartín Losada2014-04-09T08:35:56Z2014-09-30T11:42:18Zhttp://oa.upm.es/id/eprint/23404This item is in the repository with the URL: http://oa.upm.es/id/eprint/234042014-04-09T08:35:56ZInverse bremsstrahlung effects in the corona of laser-irradiated pellets and slabsJosé A. NicolásJuan Ramón Sanmartín Losada2014-04-09T07:40:39Z2016-04-21T23:04:47Zhttp://oa.upm.es/id/eprint/23412This item is in the repository with the URL: http://oa.upm.es/id/eprint/234122014-04-09T07:40:39ZShort, high current electrodynamic tetherAn electrodynamic tether experiment, to be carried out in the Russian spacecraft Almaz, is proposed. A 10 km tether would be deployed downwards; the lower 8 km would be nonconductive, the upper 2 km would be conductive, bare,
and 2.2 mm in diameter, and would act as a thruster, with power supply at the top. This hybrid arrangement allows for other, onelectrodynamic experiments,reducing costs; it also limits the induced electromotive force, reducing the power to be handled. The current-voltage characteristic of contactors would be measured. With the anode switched off, the wire itself should collect a current over 5 A at day conditions, providing a thrust of 0.11 N at a 0.77 kW
power.N.A. SavichJuan Ramón Sanmartín Losada2014-04-09T06:24:55Z2016-04-21T22:54:38Zhttp://oa.upm.es/id/eprint/23361This item is in the repository with the URL: http://oa.upm.es/id/eprint/233612014-04-09T06:24:55ZSelf-similar deflagration in laser half-plasmasThe self-similar motion of a half-space plasma, generated
by a linear pulse of laser radiation absorbed anomalously
at the critical density, has been studied. The resulting
plasma structure has been completely determined for [pulse duration (critical density)maximum irradiation] large enoughJuan Ramón Sanmartín LosadaA. Barrero2014-04-08T18:11:42Z2016-12-01T08:25:57Zhttp://oa.upm.es/id/eprint/15556This item is in the repository with the URL: http://oa.upm.es/id/eprint/155562014-04-08T18:11:42ZRelativistic current collection by a cylindrical Langmuir probeThe current I to a cylindrical Langmuir probe with a bias Φp satisfying β≡eΦp/mec2∼O(1) is discussed. The probe is considered at rest in an unmagnetized plasma composed of electrons and ions with temperatureskTe∼kTi≪mec2. For small enough radius, the probe collects the relativistic orbital-motion-limited (OML) current I OML , which is shown to be larger than the non-relativistic result; the OML current is proportional to β1/2 and β3/2 in the limits β≪1 and β≫1, respectively. Unlike the non-relativistic case, the electron density can exceed the unperturbed density value. An asymptotic theory allowed to compute the maximum radius of the probe to collect OML current, the sheath radius for probe radius well below maximum and how the ratio I/I OML drops below unity when the maximum radius is exceeded. A numerical algorithm that solves the Vlasov-Poisson system was implemented and density and potential profiles presented. The results and their implications in a possible mission to Jupiter with electrodynamic bare tethers are discussed density value. An asymptotic theory allowed to compute the maximum radius of the probe to collect OML current, the sheath radius for probe radius well below maximum and how the ratio I/IOML drops below unity when the maximum radius is exceeded. A numerical algorithm that solves the Vlasov-Poisson system was implemented and density and potential profiles presented. The results and their implications in a possible mission to Jupiter with electrodynamic bare tethers are discussed.Gonzalo Sánchez ArriagaJuan Ramón Sanmartín Losada2014-04-08T11:37:56Z2016-04-21T23:02:00Zhttp://oa.upm.es/id/eprint/23405This item is in the repository with the URL: http://oa.upm.es/id/eprint/234052014-04-08T11:37:56ZA steady solution of the Vlasov equationsJuan Ramón Sanmartín Losada2014-04-05T11:20:30Z2016-04-21T22:59:38Zhttp://oa.upm.es/id/eprint/23384This item is in the repository with the URL: http://oa.upm.es/id/eprint/233842014-04-05T11:20:30ZHidrodinámica de la fusión por laserJuan Ramón Sanmartín Losada2014-04-03T11:26:49Z2016-04-21T22:53:47Zhttp://oa.upm.es/id/eprint/23358This item is in the repository with the URL: http://oa.upm.es/id/eprint/233582014-04-03T11:26:49ZOn the formation of nitrogen oxides in the combustion processes of hydrogen in airA research programme is being carried out at the Institute
Nacional de Tecnica Aeroespacial of Spain, on several aspects of the formation of nitrogen oxides in continuous flow combustion systems, considering hydrogen and hydrocarbons as fuels. The research programme is fundamentally oriented on the basic aspects of the problem, although it also includes the study of the influence on the formation process of several operational and design variables of the combusters, such as type of fuels, fuel/air ratio, degree of mixing in premixed type flames,
existence of droplets as compared with homogeneous combustion.This problem of nitrogen oxides formation is receiving lately great attention, specially in connection with automobile reciprocating engines and aircraft gas turbines. This is due to the fact of the increasing frequency and intensity of photochemical hazes or smog, typical of urban areas submitted to strong solar radiation, which are originated by the action on organic compounds of the oxidants resulting from the photochemical decomposition of nitrogen dioxide N02. In the combustion process almost all nitrogen oxides are in form of NO. This nitric oxide reacts with the oxygen of the air and forms N02, this reaction only taking place in or near the exhaust of tne motors, since the N0-02 reaction becomes frozen for the concentration existing in the atmosphere.Carlos Sánchez-TarifaJuan Ramón Sanmartín LosadaEnrique Fraga2014-03-27T13:56:28Z2016-12-02T11:26:41Zhttp://oa.upm.es/id/eprint/23248This item is in the repository with the URL: http://oa.upm.es/id/eprint/232482014-03-27T13:56:28ZT-REX: Bare electro-dynamic tape-tether technology experimetn on sounding rocket S520The project to verify the performance of space tether technology was successfully demonstrated by the launch of the sounding rocket S520 the 25tu. The project is the
space demonstration of science and engineering technologies of a bare tape electrodynamic tether (EDT) in the international campaign between Japan, USA, Europe and Australia. Method of "Inverse ORIGAMI (Tape tether folding)" was employed in order to deploy the bare tape EDT in a short period time of the suborbital flight. The deployment of tape tether was tested in a various experimental schemes on ground to show high reliability of tape tether deployment. The rocket was launched on the summer of 2010 and deployed a bare electro-dynamic tape tether with length 132.6 m, which is the world record of the length deployment of tape tether. The verification of
tether technology has found a variety kind of science and technology results as the first in the humankind and will lead a large number of applications of space tether technologiesTakeo WatanabeHironori FujiiTairo KusagayaHironori SaharaHirohisa KojimaShoichiro TakeharaYoshiki YamagiwaSusumu SasakiTakumi AbeKoji TanakaKhoichiro OyamaTakuji EbinumaLes JohsonGeorge KhazanovJuan Ramón Sanmartín LosadaMario CharroMichiel KruijffErik J. van der HeideBinyamin RubinFrancisco G. García de QuirósPavel M. TrivailoPaul Williams2014-03-26T12:53:38Z2016-12-05T07:59:21Zhttp://oa.upm.es/id/eprint/23245This item is in the repository with the URL: http://oa.upm.es/id/eprint/232452014-03-26T12:53:38ZTether radiation in Juno-type and circular-equatorial
Jovian orbitsWave radiation by a conductor carrying a steady current in both a polar, highly eccentric, low perijove orbit, as in NASA's planned Juno mission, and an equatorial low
Jovian orbit (LJO) mission below the intense radiation belts, is considered. Both missions will need electric power generation for scientific instruments and
communication systems. Tethers generate power more efficiently than solar panels or radioisotope power systems (RPS). The radiation impedance is required to determine the
current in the overall tether circuit. In a cold plasma model, radiation occurs mainly in the Alfven and fast magnetosonic modes, exhibiting a large refraction index. The
radiation impedance of insulated tethers is determined for both modes and either mission. Unlike the Earth ionospheric case, the low-density, highly magnetized Jovian plasma makes the electron gyrofrequency much larger than the plasma frequency; this substantially modifies the power spectrum for either mode by increasing the Alfven velocity. Finally, an estimation of the radiation impedance of bare tethers is considered. In LJO, a spacecraft orbiting in a slow downward spiral under the radiation belts would
allow determining magnetic field structure and atmospheric composition for understanding the formation, evolution, and structure of Jupiter. Additionally, if the cathodic contactor is switched off, a tether floats electrically, allowing e-beam emission that generate auroras. On/off switching produces bias/current pulses and signal emission,
which might be used for Jovian plasma diagnostics.Antonio Sánchez-TorresJuan Ramón Sanmartín Losada2014-03-25T14:18:40Z2016-04-21T22:16:41Zhttp://oa.upm.es/id/eprint/23242This item is in the repository with the URL: http://oa.upm.es/id/eprint/232422014-03-25T14:18:40ZThe radiation impedance of electrodynamics tethers in a polar Jovian orbitJuno, the second mission in the NASA New Frontiers Program, will both be a polar Jovian orbiter, and use solar arrays for power, moving away from previous use of radioisotope power systems (RPSs) in spite of the weak solar light reaching Jupiter. The power generation at Jupiter is critical, and a conductive tether could be an alternative source of power. A current-carrying tether orbiting in a magnetized ionosphere/plasmasphere will radiate waves. A magnitude of interest for both power generation and signal emission is the wave impedance. Jupiter has the strongest magnetic field in the Solar Planetary System and its plasma density is low everywhere. This leads to an electron plasma frequency smaller than the electron cyclotron frequency, and a high Alfven velocity. Unlike the low Earth orbit
(LEO) case, the electron skin depth and the characteristic size of plasma contactors affect the Alfven impedance.Antonio Sánchez-TorresJuan Ramón Sanmartín LosadaJose Manuel Donoso VargasMario Charro2014-03-25T12:47:00Z2016-12-01T12:53:28Zhttp://oa.upm.es/id/eprint/23230This item is in the repository with the URL: http://oa.upm.es/id/eprint/232302014-03-25T12:47:00ZMagnetic pumping of whistler waves by tether current modulationMagnetic excitation of whistlers by a square array of electrodynamic tethers is discussed. The array is made of perpendicular rows of tethers that carry equal, uniform,
and time-modulated currents at equal frequency with a 90° phase shift. The array would fly vertical in the orbital equatorial plane, which is perpendicular to the geomagnetic field B0 when its tilt is ignored. The array radiates a whistler wave along B0. A parametric instability due to pumping by the background magnetic field through the radiated wave gives rise to two unstable coupled whistler perturbations. The growth rate is maximum for perturbations with wave vector at angles 38.36° and 75.93° from B0. For an experiment involving a wavefront that moves with the orbiting array, which might serve to study nonlinear wave interactions and turbulence in space plasmas, characteristic values of growth rate and parameters, such as the number of tethers and their dimensions and distances in the array, are discussed for low Earth orbit ambient conditions.Gonzalo Sánchez ArriagaJuan Ramón Sanmartín Losada2014-03-24T12:58:50Z2016-04-21T21:58:31Zhttp://oa.upm.es/id/eprint/23194This item is in the repository with the URL: http://oa.upm.es/id/eprint/231942014-03-24T12:58:50ZShort electrodinamic tethers. ESTEC Contract nº 13395/98/NL/MV. Final Report for Work Packages 100 and 300.Juan Ramón Sanmartín LosadaEduardo Ahedo GalileaLuis Conde LópezJesús Peláez ÁlvarezManuel Ruiz Delgado2014-03-24T12:58:13Z2016-04-21T22:07:40Zhttp://oa.upm.es/id/eprint/23218This item is in the repository with the URL: http://oa.upm.es/id/eprint/232182014-03-24T12:58:13ZFloating bare tether as upper-atmosphere probe. Final Report for ESTEC Contract No. 17384/03/NL/LvH/bjJuan Ramón Sanmartín LosadaMario CharroSergio ElaskarJesús Peláez ÁlvarezIgnacio Tinao2014-03-24T12:57:59Z2015-05-25T13:51:49Zhttp://oa.upm.es/id/eprint/23219This item is in the repository with the URL: http://oa.upm.es/id/eprint/232192014-03-24T12:57:59ZElectrodynamics tether microsats at the giant planets. Final Reports. Ariadna study 05/3023Juan Ramón Sanmartín LosadaMario CharroCristina BramantiClaudio BombardelliEnrico C. LorenziniH. Garret2014-03-24T12:56:44Z2016-04-21T22:08:41Zhttp://oa.upm.es/id/eprint/23221This item is in the repository with the URL: http://oa.upm.es/id/eprint/232212014-03-24T12:56:44ZThe determination of ionospheric charged particle temperatures from in situ measurementsThe recently noticed disagreement between ionospheric charged-particle temperature values obtained from ground-based (incoherent backscatter) and in situ (Langmuir probe type) measurements is considered; it is suggested that a main cause of disagreement lies in the poor theoretical basis of present in situ measurements. It is pointed out that the usually neglected geomagnetic field influence may result in too high an electron temperature. It is also shown that the theory used at present to interpret data from ion retarding potential analyzers has serious pitfalls, and that these devices greatly disturb the surrounding plasma when measuring ion temperature. Finally, it is shown how the ion temperature can be accurately obtained from the characteristic of a cylindrical Langmuir probe in a rarefied plasma flow.Juan Ramón Sanmartín Losada2014-03-24T12:54:47Z2016-04-21T21:56:30Zhttp://oa.upm.es/id/eprint/23189This item is in the repository with the URL: http://oa.upm.es/id/eprint/231892014-03-24T12:54:47ZElectrostatic plasma instabilities excited by a
high-frequency electric field. AT(30-1)-1238-MATT-669An analysis of the electrostatic plasma instabilities excited by the application of a strong, uniform, alternating
electric field is made on the basis of the Vlasov equation.
A very general dispersion relation is obtained and discussed. Under the assumption W 2 O » C 2 pi. (where wO is the applied frequency and wpi the ion plasma frequency) a detailed analysis is given for wavelengths of the order of or large compared with the Debye length. It is found that there are two types of instabilities: resonant (or parametric) and nonresonant.
The second is caused by the relative streaming of ions and electrons, generated by the field; it seems to exist only if wO is less than the electron plasma frequency wpe. The instability only appears if the field exceeds a certain threshold, which is found.Juan Ramón Sanmartín Losada2014-03-24T12:54:12Z2016-04-21T21:58:00Zhttp://oa.upm.es/id/eprint/23193This item is in the repository with the URL: http://oa.upm.es/id/eprint/231932014-03-24T12:54:12ZZero-G Gauging systems. CONTRACT No 17/8/4Various systems for measuring propellant content in spacecrafts under weightlessness conditions are reviewed. The cavity resonator method is found to be the most suitable measurement; technique. This method is analyzed in detail. A determination of errors intrinsec to the method is carried out.Juan Ramón Sanmartín LosadaEnrique FragaA. Muñoz2014-03-24T12:53:15Z2016-04-21T21:57:35Zhttp://oa.upm.es/id/eprint/23192This item is in the repository with the URL: http://oa.upm.es/id/eprint/231922014-03-24T12:53:15ZIon-Ion correlations effect on nonlinear high-frequency plasma conductivity. AT(30-1)-1238-MATT-675On the basis of the BBGKY hierarchy of equations an expression is derived for the response of a fully ionized
plasma to a strong, high-frequency electric field in the limit of infinite ion mass. It is found that even in this limit the ionion correlation function is substantially affected by the field. The corrections to earlier nonlinear results for the current density appear to be quite ssential. The validity of the model introduced by Dawson and Oberman to study the response to a vanishingly small field is confirmed for larger values of the field when the eorrect expression for the ion-ion correlations i s introduced; the model by itself does not yield such an expression. The results have interest for the heating of the plasma and for the propagation of a strong electromagnetic wave through the plasma. The theory seems to be valid for any field intensity for which the plasma is stable.Juan Ramón Sanmartín Losada2014-03-17T07:32:19Z2014-10-09T08:12:52Zhttp://oa.upm.es/id/eprint/23081This item is in the repository with the URL: http://oa.upm.es/id/eprint/230812014-03-17T07:32:19ZThe theory of electrostatic probes in strong magnetic fields : Thesis submitted to the Faculty of The Graduate School of the University of Colorado for the Degree Doctor of Philosophy Department of Aerospace Engineering ScienceA theory is developed of an electrostatic probe in a fully-ionized plasma in the presence of a strong magnetic field.
The ratio of electron Larmor radius to probe transverse dimension is assumed to be small. Poisson's equation, together with kinetic equations for ions and electrons are considered. An asymptotic perturbation method of multiple scales is used by considering the characteristic lengths appearing in the problem. The leading behavior of the solution is found. The results obtained appear to apply to weaker fields also, agreeing with the solutions known in the limit of no magnetic field. The range of potentials for wich results are presented is limited.
The basic effects produced by the field are a depletion of the plasma near the probe and a non-monotonic potential surrounding the probe. The ion saturation current is not changed but changes appear in both the floating potential Vf and the slope of the current-voltage diagram at Vf. The transition region extends beyond the space potential Vs,at wich point the current is largely reduced.
The diagram does not have an exponential form in this region as commonly assumed. There exists saturation in electron collection. The extent to which the plasma is disturbed is determined. A cylindrical probe has no solution because of a logarithmic singularity at infinity. Extensions of the theory are considered.Juan Ramón Sanmartín Losada2014-03-17T07:31:47Z2016-04-21T20:50:46Zhttp://oa.upm.es/id/eprint/22901This item is in the repository with the URL: http://oa.upm.es/id/eprint/229012014-03-17T07:31:47ZEfecto de extremo en la respuesta de una sonda cilíndrica de LangmuirTanto en plasmas de laboratorio como en la ionosfera, se ha observado recientemente un fenómeno nuevo en la respuesta de una sonda cilindrica de Langmuir que se mueve en un plasma rarificado. Bajo condiciones tales que: a) el potencial de la sonda respecto al plasma sea muy negativo; b)su velocidad sea mucho mayor que la velocidad de las ondas iono-acústicas del plasma; y c) la longitud de Debye sea grande comparada con el radio de la sonda pero pequeña con respecto a su longitud, la corriente eléctrica registrada por aquella muestra un máximo muy agudo cuando el ángulo entre la dirección del movimiento y el eje de la sonda pasa por cero. En la presente tesis se desarrolla una teoría de este fenómeno, la cual conduce a una expresión analítica para la corriente eléctrica recogida por la sonda; se obtienen fórmuías sencillas para la altura y semiancliura del máximo de la corriente y resultados gráficos universales para la estructura de dicho máximo. La teoría está en muy buen acuerdo con los datos experimentales existentes.Se muestra cómo puede hacerse uso del efecto en la corriente para medir las variables de estado en los plasmas, y en particular para la medida de la temperatura iónica.Juan Ramón Sanmartín Losada2014-03-14T11:06:55Z2016-02-09T09:20:57Zhttp://oa.upm.es/id/eprint/23090This item is in the repository with the URL: http://oa.upm.es/id/eprint/230902014-03-14T11:06:55ZTheory of a Probe in a Strong Magnetic Field. AT(30-1)-1238-MATT 599A kinetic approach is used to develop a theory of electrostatic probes in a fully ionized plasma in the presence of a magnetic field. A consistent asymptotic expansion is obtained assuming that the electron Larmor radius is small compared to the radius of the probe. The order of magnitude of neglected terms is given. It is found that the electric potential within the tube of force defined by the cross section of the probe decays non-mono tonic ally from the probe; this bump disappears at a certain probe voltage and the theory is valid up to this voltage. The transition region, which extends beyond plasma potential, is not exponential. The possible saturation of the electron current is discussed. Restricted numerical results are given; they seem to be useful for weaker magnetic fields down to the zero-field limit. Extensions
of the theory a r e considered.Juan Ramón Sanmartín Losada2014-03-11T13:19:18Z2016-04-21T20:22:38Zhttp://oa.upm.es/id/eprint/22781This item is in the repository with the URL: http://oa.upm.es/id/eprint/227812014-03-11T13:19:18ZOveral reaction rate and stoichiometry for thermal decomposition of hydrazineAn asymptotic analysîs of the Eberstein-Glassman kinetic
mechanlsm for the thermal décomposition of hydrazine is carried out. It is shown that at températures near 800°K and near 1000°K,and for hydrazine molar fractions of the order of unity, 10-2 the entire kinetics reduces to a single, overall reaction.
Characteristic times for the chemical relaxation of ail
active, intermediate species produced in the décomposition, and for the overall reaction, are obtained. Explicit expressions for the overall reaction rate and stoichiometry are given as functions of température, total molar concentration (or pressure)and hydrazine molar fraction. Approximate, patched expressions can then be obtained for values of température and hydrazine molar fraction between 750 and 1000°K, and 1 and 10-3 respectively.Juan Ramón Sanmartín Losada2014-03-05T07:48:00Z2016-12-05T08:34:43Zhttp://oa.upm.es/id/eprint/22708This item is in the repository with the URL: http://oa.upm.es/id/eprint/227082014-03-05T07:48:00ZFloating bare tether as upper atmosphere probeUse of a conductive bare tape electrically floating in low Earth orbit as an effective electron beam source to produce artificial auroral effects, free of problems that mard tandard beams, is considered. Ambient ions impacting the tape with keV energies over most of its length liberate secondary electrons that race down the magnetic field, excite neutrals in the E layer, and result in auroral emissions. The tether would operate with both a power supply and a plasma contactor off at nighttime; power and contactor would be on at daytime for reboost. Tomographic analysis of auroral emissions from the footprint
of the beam, as observed from the spacecraft, can provide density profiles of dominant neutral species in the E layer. A characteristic tether system, at altitude 300 km and moderate orbital inclination, would involve an aluminum tape with a length of 20 km, a width of 15 mm, and a thickness of 0.2 mm for a full-system mass around 1200 kg,
with two thirds going into the power subsystem.Juan Ramón Sanmartín LosadaMario CharroJesús Peláez ÁlvarezI. TinaoSergio ElaskarA. HilgersManuel Martínez-Sánchez2014-02-20T14:23:32Z2016-12-01T08:53:19Zhttp://oa.upm.es/id/eprint/22482This item is in the repository with the URL: http://oa.upm.es/id/eprint/224822014-02-20T14:23:32ZFast magnetosonic wave excitation by an array of wires with
time-modulated currentsThe excitation of Fast Magnetosonic (FMS)waves by a cylindrical array of parallel tethers carrying timemodulated
current is discussed. The tethers would fly vertical
in the equatorial plane, which is perpendicular to the
geomagnetic field when its tilt is ignored, and would be stabilized by the gravity gradient. The tether array would radiate a single FMS wave. In the time-dependent background
made of geomagnetic field plus radiated wave, plasma FMS
perturbations are excited in the array vicinity through a parametric instability. The growth rate is estimated by truncating the evolution equation for FMS perturbations to the two azimuthal modes of lowest order. Design parameters such as tether length and number, required power and mass are discussed for Low Earth Orbit conditions. The array-attached wave structure would have the radiated wave controlled by the intensity and modulation frequency of the currents, making an active experiment on non-linear low frequency waves possible in real space plasma conditions.Gonzalo Sánchez ArriagaJuan Ramón Sanmartín Losada2014-02-18T07:42:01Z2016-04-21T14:33:33Zhttp://oa.upm.es/id/eprint/22437This item is in the repository with the URL: http://oa.upm.es/id/eprint/224372014-02-18T07:42:01ZElectron cooling in probe collection from magnetized plasmas with anomalous transportThe electron-retarding range of the current-voltage characteristic of a flat Langmuir probe perpendicular to a strong magnetic field in a fully ionized plasma is analysed allowing for anomalous (Bohm) cross-field transport and
temperature changes in the collection process. With probe size and ion thermal gyroradius comparable, and smaller than the electron mean free path, there is an outer quasineutral region with ion viscosity determinant in allowing nonambipolar parallel and cross flow. A potential overshoot lying either at the base or inside the quasineutral region both makes ions follow Boltzmann's
law at negative bias and extends the electron-retarding range to probe bias e(j)p ~ +2Too. Electron heating and cooling occur roughly at positive and negative bias, with a re-minimum around efa ~ - 2 7 ^ ; far from the probe
heat conduction cools and heats electrons at and radially away from the probe axis, respectively. The potential overshoot with no thermal effects would reduce the electron current Ie, making the In Ie versus 4>p graph downwards-concave,but cooling further reduces Ie substantially, and may tilt the slope upwards past the temperature minimum. The domain of strict validity of our analysis is narrow in case of low ion mass (deuterium), breaking down with the ion Boltzmann law.Mario CharroJuan Ramón Sanmartín Losada2014-01-24T09:18:04Z2016-10-26T11:22:12Zhttp://oa.upm.es/id/eprint/22192This item is in the repository with the URL: http://oa.upm.es/id/eprint/221922014-01-24T09:18:04ZMagnetic self-field effects on current collection by an ionospheric bare tetherIt was recently suggested that the magnetic field created by the current of a bare tether strongly reduces its own electron-collection capability when a magnetic separatrix
disconnecting ambient magnetized plasma from tether extends beyond its electric sheath. It is here shown that current reduction by the self-field depends on the ratio meterizing bias and current profiles along the tether (Lt tether length, characteristic length gauging ohmic effects) and on a new dimensionless number Ks involving ambient and tether parameters. Current reduction is weaker the lower Ks and L*/
Lt, which depend critically on the type of cross section: Ks varies as R5/3, h2/3R, and h2/3 1/4 width for wires, round tethers conductive only in a thin layer, and thin tapes, respectively; L* varies as R2/3 for wires and as h2/3 for tapes and round tethers conductive
in a layer (R radius, h thickness). Self-field effects are fully negligible for the last two types of cross sections whatever the mode of operation. In practical efficient tether systems having L*/Lt low, maximum current reduction in case of wires is again negligible for power generation; for deorbiting, reduction is <1% for a 10 km tether and 15% for a 20 km tether. In the reboost mode there are no effects for Ks below some threshold; moderate effects may occur in practical but heavy reboost-wire systems that need no dedicated solar power.Juan Ramón Sanmartín LosadaRobert D. Estes2014-01-23T16:41:03Z2016-04-21T13:54:48Zhttp://oa.upm.es/id/eprint/22173This item is in the repository with the URL: http://oa.upm.es/id/eprint/221732014-01-23T16:41:03ZSudden transition to chaos in plasma wave interactionsThe coherent three-wave interaction, with linear growth in the higher frequency wave and damping in the two other waves, is reconsidered; for equal dampings, the resulting three-dimensional (3-D) flow of a relative phase and just two amplitudes behaved chaotically, no matter how small the
growth of the unstable wave. The general case of different dampings is studied here to test whether, and how, that hard scenario for chaos is preserved in passing from 3-D to four-dimensional flows. It is found that the wave with higher damping is partially slaved to the other damped wave; this retains a feature of the original problem an invariant surface that meets an unstable fixed point, at
zero growth rate! that gave rise to the chaotic attractor and determined its structure, and suggests that the sudden transition to chaos should appear in more complex wave interactions.Óscar López RebollalJuan Ramón Sanmartín LosadaE. del Río2014-01-22T21:50:13Z2016-04-21T13:54:43Zhttp://oa.upm.es/id/eprint/22172This item is in the repository with the URL: http://oa.upm.es/id/eprint/221722014-01-22T21:50:13ZNonuniform irradiation of laser targetsSmoothing of plasma ablated from a laser target under weakly nonuniform irradiation is discussed. Conduction is assumed restricted to a quasisteady layer enclosing the critical surface (large pellet or focal spot, and long, low-intensity, short-wavelength pulse). Light refraction can make the ablated plasma unstable.Juan Ramón Sanmartín LosadaJosé A. Nicolás2014-01-20T18:25:15Z2016-04-21T13:45:30Zhttp://oa.upm.es/id/eprint/22079This item is in the repository with the URL: http://oa.upm.es/id/eprint/220792014-01-20T18:25:15ZSelf-similar motion of laser half-space plasmas. II Thermal wave and intermediate regimes.Juan Ramón Sanmartín LosadaA. Barrero2014-01-20T18:18:24Z2016-04-21T13:50:18Zhttp://oa.upm.es/id/eprint/22130This item is in the repository with the URL: http://oa.upm.es/id/eprint/221302014-01-20T18:18:24ZNonlocal electron heat-fluxElectron thermal conduction in a not quite collisional
unmagnetlzed plasma is analysed. The failure of classical
results for temperature scale-length up to 100 times larger than thermal mean-free-path for electron scattering, and large ion-charge number Z , is discussed. Recent results from a nonlocal model of conduction at large Z are reviewed.
Closed form expressions for Braginskii's coefficients a ,/3 , y for Z =0(1) are derived. An extension of the nonlocal model for Z =0(1) is discussed.Juan Ramón Sanmartín Losada2014-01-20T18:17:53Z2016-04-21T13:45:36Zhttp://oa.upm.es/id/eprint/22080This item is in the repository with the URL: http://oa.upm.es/id/eprint/220802014-01-20T18:17:53ZTransition from isentropic to isothermal expansion in laser produced plasmasA. BarreroJuan Ramón Sanmartín Losada2014-01-20T18:17:33Z2016-04-21T13:45:42Zhttp://oa.upm.es/id/eprint/22081This item is in the repository with the URL: http://oa.upm.es/id/eprint/220812014-01-20T18:17:33ZRevolución educativa, investigación estratégica : lección magistral pronunciada por el profesor Juan Ramón Sanmartín Losada en el acto académico de fin de curso de 2000Juan Ramón Sanmartín Losada2014-01-20T18:16:09Z2016-04-21T13:51:18Zhttp://oa.upm.es/id/eprint/22145This item is in the repository with the URL: http://oa.upm.es/id/eprint/221452014-01-20T18:16:09Z1971-1980. Diez años de maduraciónJuan Ramón Sanmartín Losada2014-01-17T14:31:46Z2016-04-21T13:50:32Zhttp://oa.upm.es/id/eprint/22133This item is in the repository with the URL: http://oa.upm.es/id/eprint/221332014-01-17T14:31:46ZPhysics and applications of electrodynamic space tethersBasic effects and dynamical and electrical contact issues in the physics of (electrodynamic space) bare tethers are discussed. Scientific experiments and powerpropulsion
applications, including a paradoxical use of bare tethers in outer-planet exploration,are considered.Juan Ramón Sanmartín Losada2014-01-17T09:40:44Z2016-04-21T13:48:03Zhttp://oa.upm.es/id/eprint/22107This item is in the repository with the URL: http://oa.upm.es/id/eprint/221072014-01-17T09:40:44ZFísica del botafumeiroJuan Ramón Sanmartín Losada2014-01-14T16:54:54Z2016-04-21T13:47:15Zhttp://oa.upm.es/id/eprint/22098This item is in the repository with the URL: http://oa.upm.es/id/eprint/220982014-01-14T16:54:54ZCoherent excitation of nonlinear oscillatorsCoherently driven, dissipative nonlinear oscillators,(driving kept permanently in phase with the oscillators
response) are proposed as systems with interesting dynamics.
Results for simple, preliminary examples, which do not show chaotic behavior, are briefly discussed.Juan Ramón Sanmartín Losada2013-12-05T09:17:01Z2016-04-21T12:39:26Zhttp://oa.upm.es/id/eprint/21860This item is in the repository with the URL: http://oa.upm.es/id/eprint/218602013-12-05T09:17:01ZSpherical thermal waves in laser plasmaJuan Ramón Sanmartín LosadaJosé Luis Montañés García2013-12-05T09:14:11Z2016-04-21T12:39:20Zhttp://oa.upm.es/id/eprint/21859This item is in the repository with the URL: http://oa.upm.es/id/eprint/218592013-12-05T09:14:11ZSelf-similar motion of laser half-space plasmas. I Deflagration regimeJuan Ramón Sanmartín LosadaA. Barrero2013-12-04T13:58:46Z2016-04-21T12:39:16Zhttp://oa.upm.es/id/eprint/21858This item is in the repository with the URL: http://oa.upm.es/id/eprint/218582013-12-04T13:58:46ZInfluencia de los parámetros básicos del laser sobre la hidrodinámica de plasmas para microfusión (I)Juan Ramón Sanmartín LosadaA. Barrero2013-11-28T11:02:54Z2016-12-01T13:11:30Zhttp://oa.upm.es/id/eprint/21768This item is in the repository with the URL: http://oa.upm.es/id/eprint/217682013-11-28T11:02:54ZElectrodynamic Tether at Jupiter I: Capture operation and constraintsTethered spacecraft missions to the Jovian system suit the use of electrodynamic tethers because: 1) magnetic stresses are 100 times greater than at the Earth; 2) the stationary orbit is one-third the relative distance for Earth; and 3) moon Io is a nearby giant plasma source. The (bare) tether is a reinforced aluminum foil with tens of kilometer length L and a fraction of millimeter thickness h, which collects electrons as an efficient Langmuir probe and can tap Jupiter’s rotational energy for both propulsion and power. In this paper, the critical capture operation is explicitly formulated in terms of orbit geometry and established
magnetic and thermal plasma models. The design parameters
L and h and capture perijove radius rp face opposite criteria independent of tape width. Efficient capture requires a low rp and a high L 3/2/h ratio. However, combined bounds on tether bowing and tether tensile stress, arising from a spin made necessary by the low Jovian gravity gradient, require a high rp and a low L 5/2/h
ratio. Bounds on tether temperature again require a high rp and a low L 3/8/(tether emissivity)1/4 ratio. Optimal design values are discussed.Juan Ramón Sanmartín LosadaMario CharroEnrico C. LorenziniHenry B. GarretClaudio BombardelliCristina Bramanti2013-11-28T10:06:51Z2014-11-03T12:51:19Zhttp://oa.upm.es/id/eprint/21772This item is in the repository with the URL: http://oa.upm.es/id/eprint/217722013-11-28T10:06:51ZLow work-function coating for an entirely propellantless bare electrodynamic tetherWe present the possibility of a low work-function material, calcium aluminate electride, being used for a coating
on a bare electrodynamic tether system. Analyses suggest that the coating would eliminate the need for an active cathodic device like a hollow cathode and, consequently, eliminate the need for an expellant to the hollow cathode, thus resulting in an electrodynamic tether system that requires no consumables. Applications include on-orbit power generation and deorbiting debris from low Earth
orbit in a simple and trouble-free manner.John D. WilliamsJuan Ramón Sanmartín LosadaLauren P. Rand2013-11-26T15:33:47Z2016-04-21T12:29:33Zhttp://oa.upm.es/id/eprint/21760This item is in the repository with the URL: http://oa.upm.es/id/eprint/217602013-11-26T15:33:47ZBare-tether sheath and current: comparison of asymptotic theory and kinetic simulations in stationary plasmaAnalytical expressions for current to a cylindrical Langmuir probe at rest in unmagnetized plasma are compared
with results from both steady-state Vlasov and particle-in-cell simulations. Probe bias potentials that are much greater than plasma temperature (assumed equal for ions and electrons), as of interest for bare conductive tethers, are considered. At a very high bias, both the electric potential and the attracted-species density exhibit complex radial profiles; in particular, the density exhibits a minimum well within the plasma sheath and a maximum closer
to the probe. Excellent agreement is found between analytical and numerical results for values of the probe radiusR close to the maximum radius Rmax for orbital-motion-limited (OML) collection at a particular bias in the following number of profile features: the values and positions of density minimum and maximum, position of sheath boundary, and value of a radius characterizing the
no-space-charge behavior of a potential near the high-bias probe. Good agreement between the theory and simulations is also found for parametric laws jointly covering the following three characteristic R ranges: sheath radius versus probe radius and bias for Rmax; density minimum versus probe bias for Rmax; and (weakly bias-dependent) current drop below the OML value versus the probe radius for R > Rmax.Juan Ramón Sanmartín LosadaEric ChoinièreBrian E. GilchristJean-Benoit FerryManuel Martínez-Sánchez2013-11-26T11:03:48Z2016-12-02T12:29:00Zhttp://oa.upm.es/id/eprint/21773This item is in the repository with the URL: http://oa.upm.es/id/eprint/217732013-11-26T11:03:48ZSounding rocket experiment of bare electrodynamic tether systemAn overview of asounding rocket S-520-25th, project on space tether technology experiment is presented.The project
is prepared by an international research group consisting of Japanese,European,American,andAustralianresearchers.The
sounding rocket will be assembled by the ISAS/JAXA and will be launched in the summer of 2009.Hironori FujiiTakeo WatanabeHirohisa KojimaKoh-Ichiro OyamaTairo KusagayaYoshiki YamagiwaHirotaka OhtsuMengu ChoSusumu SasakiKoji TanakaJohn WilliamsBinyamin RubinCharles Les JhonsonGeorge KhazanovJuan Ramón Sanmartín LosadaJean-Pierre LebretonMichiel KuijffFabio de PascalPavel M. Trivailo2013-11-25T12:38:29Z2014-09-26T11:36:29Zhttp://oa.upm.es/id/eprint/21770This item is in the repository with the URL: http://oa.upm.es/id/eprint/217702013-11-25T12:38:29ZA proposed two-stage two-tether scientific mission at JupiterA two-stage mission to place a spacecraft (SC) below
the Jovian radiation belts, using a spinning bare tether with plasma contactors at both ends to provide propulsion and power,is proposed. Capture by Lorentz drag on the tether, at the periapsis of a barely hyperbolic equatorial orbit, is followed by a sequence of orbits at near-constant periapsis, drag finally bringing the SC down to a circular orbit below the halo ring. Although increasing both tether heating and bowing, retrograde motion can substantially reduce accumulated dose as compared with prograde
motion, at equal tether-to-SC mass ratio. In the second stage,the tether is cut to a segment one order of magnitude smaller, with a single plasma contactor, making the SC to slowly spiral inward over severalmonths while generating large onboard power, which would allow multiple scientific applications, including in situ study of Jovian grains, auroral sounding of upper atmosphere, and space- and time-resolved observations of surface and subsurface.Mario CharroJuan Ramón Sanmartín LosadaClaudio BombardelliAntonio Sánchez-TorresEnrico C. LorenziniHenry B. GarretRobin W. Evans2013-11-25T11:13:27Z2014-09-26T12:33:51Zhttp://oa.upm.es/id/eprint/21769This item is in the repository with the URL: http://oa.upm.es/id/eprint/217692013-11-25T11:13:27ZElectrodynamic tether at Jupiter II:Fast moon tour after captureAn electrodynamic bare-tether mission to Jupiter,following the capture of a spacecraft (SC) into an equatorial
highly elliptical orbit with perijove at about 1.3 times the Jovian radius, is discussed. Repeated applications of the propellantless Lorentz drag on a spinning tether, at the perijove vicinity, can progressively lower the apojove at constant perijove, for a tour of Galilean moons. Electrical energy is generated and stored as the SC moves from an orbit at 1 : 1 resonance with a moon, down
to resonance with the next moon; switching tether current off, stored power is then used as the SC makes a number of flybys of each moon. Radiation dose is calculated throughout the mission,during capture, flybys and moves between moons. The tour mission is limited by both power needs and accumulated dose. The three-stage apojove lowering down to Ganymede, Io, and Europa resonances would total less than 14 weeks, while 4 Ganymede, 20 Europa, and 16 Io flybys would add up to 18 weeks, with the entire mission taking just over seven months and the accumulated
radiation dose keeping under 3 Mrad (Si) at 10-mm Al shield
thickness.Juan Ramón Sanmartín LosadaMario CharroEnrico C. LorenziniHenry B. GarretClaudio BombardelliCristina Bramanti2013-11-25T09:40:38Z2016-12-01T13:14:47Zhttp://oa.upm.es/id/eprint/21759This item is in the repository with the URL: http://oa.upm.es/id/eprint/217592013-11-25T09:40:38ZPlasma kinetics issues in an ESA study for a plasma
laboratory in spaceA study supported by the European Space Agency (ESA), in the context of its General Studies Programme, performed an investigation of the possible use of space for studies in pure and applied plasma physics, in areas not traditionally
covered by ‘space plasma physics’. A set of experiments have been identified that can potentially provide access to new phenomena and to allow advances in several fields of plasma science. These experiments concern phenomena on a
spatial scale (101–104 m) intermediate between what is achievable on the ground and the usual solar system plasma observations. Detailed feasibility studies have been performed for three experiments: active magnetic experiments, largescale discharges and long tether–plasma interactions. The perspectives opened by these experiments are discussed for magnetic reconnection, instabilities,
MHD turbulence, atomic excited states kinetics, weakly ionized plasmas,plasma diagnostics, artificial auroras and atmospheric studies. The discussion is also supported by results of numerical simulations and estimates.B. AnnaratoneA. BiancaliniD. BrunoM. CapitelliF. CeccheriniE. DalyO. PascaleP. DiomedeG.D. D'AmmandoA. HilgersS. LongoS. MarcuccioJ.T. MendocaV. NagnibedaF. PegoraroJuan Ramón Sanmartín Losada2013-11-22T10:56:42Z2016-04-21T12:28:17Zhttp://oa.upm.es/id/eprint/21740This item is in the repository with the URL: http://oa.upm.es/id/eprint/217402013-11-22T10:56:42ZSpherical collectors versus bare tethers for drag,
thrust, and power generationDeorbit, power generation, and thrusting performances
of a bare thin-tape tether and an insulated tether with a
spherical electron collector are compared for typical conditions in low-Earth orbit and common values of length L = 4−20 km and cross-sectional area of the tether A = 1−5 mm2. The relative performance of moderately large spheres, as compared with bare tapes, improves but still lags as one moves from deorbiting to power generation and to thrusting: Maximum drag in deorbiting requires maximum current and, thus, fully reflects on anodic collection capability, whereas extracting power at a load or using a supply to push current against the motional field requires
reduced currents. The relative performance also improves
as one moves to smaller A, which makes the sphere approach
the limiting short-circuit current, and at greater L, with the higher bias only affecting moderately the already large bare-tape current. For a 4-m-diameter sphere, relative performances range from 0.09 sphere-to-bare tether drag ratio for L = 4 km and A = 5 mm2 to 0.82 thrust–efficiency ratio for L = 20 km and A = 1 mm2. Extremely large spheres collecting the short-circuit current at zero bias at daytime (diameters being about 14 m for A = 1 mm2 and 31 m for A = 5 mm2) barely outperform the bare tape for L = 4 km and are still outperformed by the bare tape for L = 20 km in both deorbiting and power generation; these large spheres perform like the bare tape in thrusting. In no
case was sphere or sphere-related hardware taken into account in evaluating system mass, which would have reduced the sphere performances even further.Juan Ramón Sanmartín LosadaEnrico C. Lorenzini2013-11-22T10:56:41Z2016-10-26T11:33:01Zhttp://oa.upm.es/id/eprint/21739This item is in the repository with the URL: http://oa.upm.es/id/eprint/217392013-11-22T10:56:41ZElectrodynamic tethers for exploration of Jupiter and its
icy moonsUse of electrodynamic bare tethers in exploring the Jovian system by tapping its rotational energy for power and propulsion is studied. The position of perijove and apojove in elliptical orbits, relative to the synchronous orbit at 2.24 times Jupiter’s radius, is exploited to conveniently make the induced Lorentz force to be drag or thrust, while generating power, and navigating the system. Capture and evolution to a low elliptical orbit near Jupiter, and capture into low circular orbits at moons Io and Europa are discussed.Juan Ramón Sanmartín Losada2013-11-22T07:23:31Z2016-04-21T12:24:39Zhttp://oa.upm.es/id/eprint/21683This item is in the repository with the URL: http://oa.upm.es/id/eprint/216832013-11-22T07:23:31ZMacroscopic motion and gravitation in thermodynamicsA series of examples rarely presented to students is discussed to illustrate a property of thermodynamic
equilibrium: small parts of a fully isolated system move as if points of a rigid body, so as to minimize the macroscopic
(kinetic) energy EM. Most examples lie in the fields of
astronomy and astrophysics, EM then including the
gravitational energy. The paradoxical behaviour of
gravitation, in particular in the extreme case of black holes,is discussed.Juan Ramón Sanmartín Losada2013-11-21T15:56:29Z2016-10-26T11:23:30Zhttp://oa.upm.es/id/eprint/21671This item is in the repository with the URL: http://oa.upm.es/id/eprint/216712013-11-21T15:56:29ZReduced three-wave model to study the hard transition to chaotic dynamics in Alfven wave-frontsThe derivative nonlinear Schrödinger (DNLS) equation, describing propagation of circularly polarized Alfven waves of finite amplitude in a cold plasma, is truncated to explore the coherent, weakly nonlinear, cubic coupling of three waves near resonance, one wave being linearly unstable and the other waves damped. In a reduced three-wave model (equal damping of daughter waves, three-dimensional flow for two wave amplitudes and one relative
phase), no matter how small the growth rate of the unstable wave there exists a parametric domain with the flow exhibiting chaotic dynamics that is absent for zero growth-rate. This hard transition in phase-space behavior occurs for left-hand (LH) polarized waves, paralelling the known fact that only LH time-harmonic solutions of the DNLS equation are modulationally unstable.Sergio ElaskarJuan Ramón Sanmartín Losada2013-11-21T15:56:28Z2016-04-21T12:23:31Zhttp://oa.upm.es/id/eprint/21670This item is in the repository with the URL: http://oa.upm.es/id/eprint/216702013-11-21T15:56:28ZE-beam propagation and interaction with atmosphereThis study purports to investigate whether a conductive tether left uninsulated and electrically floating in LEO could serve as an effective e-beam source to produce artificial auroras. An electrically floating tether comes out biased highly negative over most of its length. Ambient ions impacting it with KeV energies liberate secondary electrons, which are locally accelerated through the 2D tether voltage-bias, race down magnetic lines, and result
in peak auroral emissions at about 120-160 km altitude. Since no current flows at either tether end, a bare-tether e-beam is fully free of spacecraft charging problems. Beam
propagation and beam-atmosphere interactions need be modelled in a simple but quantitative way so as to allow a satisfactory discussion of observational options and their feasibility. The evolution in the energy spectrum of secondary electrons, their pitch distribution, and beam
broadening due to collisions with neutrals, which would result in a broader but weaker tether footprint in the E-layer, need be modelled. Relations between particle/energy flux values, and ionization and accompanying emission rates, are considered.Juan Ramón Sanmartín LosadaSergio Elaskar2013-11-21T15:56:27Z2015-10-19T07:40:26Zhttp://oa.upm.es/id/eprint/21672This item is in the repository with the URL: http://oa.upm.es/id/eprint/216722013-11-21T15:56:27ZFully 3-wave model to study the hard transition to chaotic dynamics in alfven wave-frontsThe derivative nonlinear Schrödinger (DNLS) equation, describing propagation of circularly polarized Alfven waves of finite amplitude in a cold plasma, is truncated to explore the coherent, weakly nonlinear coupling of three waves near resonance, one wave being linearly unstable and the other waves damped. No matter how small the growth rate of the unstable wave, the four-dimensional flow for the three wave amplitudes and a relative phase, with both resistive damping and linear Landau damping, exhibits chaotic relaxation oscillations that are absent for zero growth-rate. This hard transition in phase-space behavior occurs for left-hand (LH) polarized waves, paralleling the known fact that only LH time-harmonic solutions of the DNLS equation are modulationally unstable. The parameter domain developing chaos is much broader than the corresponding domain in a reduced 3-wave model that assumes equal dampings
of the daughter wavesSergio ElaskarGonzalo Sánchez ArriagaJuan Ramón Sanmartín Losada2013-11-21T15:56:25Z2015-10-19T07:40:11Zhttp://oa.upm.es/id/eprint/21674This item is in the repository with the URL: http://oa.upm.es/id/eprint/216742013-11-21T15:56:25ZCaos en evolución no lineal de ondas de Alfven usando un modelo resistivoInteracciones no lineales de ondas de Alfvén existen tanto para plasmas en el espacio como en laboratorios, con efectos que van desde calentamiento hasta conducción de
corriente. Un ejemplo de emisión de ondas de Alfvén en ingeniería aeroespacial aparece en amarras espaciales. Estos dispositivos emiten ondas en estructuras denominadas “Alas de Alfvén”. La ecuación derivada no lineal de Schrödinger (DNLS) posee la capacidad de
describir la propagación de ondas de Alfvén de amplitud finita circularmente polarizadas en un plasma frío. En esta investigación, dicha ecuación es truncada con el objetivo de explorar el acoplamiento coherente, débilmente no lineal y cúbico de tres ondas cerca de resonancia.
De las tres ondas, una es linealmente inestable y las otras dos son amortiguadas. Por medio de la utilización de este modelo se genera un flujo 4D formado por tres amplitudes y una fase relativa. En trabajos anteriores se analizó la transición dura hacia caos en flujos 3D.2005). Se presenta en este artículo un análisis teórico y numérico del comportamiento del
sistema cuando la tasa de crecimiento de la onda inestable es muy próxima a cero y
considerando amortiguamiento resistivo, es decir se satisface una relación cuadrática entre
amortiguamientos y números de onda. Al igual que en los trabajos anteriores, se ha
encontrado que sin importar cuan pequeña es la tasa de crecimiento de la onda inestable
existe un dominio paramétrico, en el espacio de fase, donde aparecen oscilaciones caóticas
que están ausentes para una tasa de crecimiento nula. Sin embargo diagramas de bifurcación
y dominios de estabilidad presentan diferencias con respecto a lo estudiado anteriormente.Sergio ElaskarGonzalo Sánchez ArriagaJuan Ramón Sanmartín Losada2013-11-21T14:58:54Z2016-04-21T12:24:27Zhttp://oa.upm.es/id/eprint/21681This item is in the repository with the URL: http://oa.upm.es/id/eprint/216812013-11-21T14:58:54ZNon-periodic driving of coupled oscillators:a spherical swingNonlinearly coupled, damped oscillators at 1:1 frequency ratio, one oscillator being driven coherently for efficient
excitation, are exemplified by a spherical swing with some phase-mismatch between drive and response. For certain
damping range, excitation is found to succeed if it lags behind, but to produce a chaotic attractor if it leads the response. Although a period-doubhng sequence, for damping increasing, leads to the attractor, this is actually born as a hard (as regards amplitude) bifurcation at a zero growth-rate parametric line; as damping decreases, an unstable fixed point crosses an invariant plane to enter as saddle-focus a phase-space domain of physical solutions. A second hard bifurcation occurs at the zero mismatch line, the saddle-focus leaving that domain. Times on the attractor diverge when approaching either fine,
leading to exactly one-dimensional and noninvertible limit maps, which are analytically determined.Juan Ramón Sanmartín LosadaÓscar López-RebollalN. de Paola2013-11-21T14:58:13Z2016-04-21T12:24:02Zhttp://oa.upm.es/id/eprint/21676This item is in the repository with the URL: http://oa.upm.es/id/eprint/216762013-11-21T14:58:13ZAcoplamiento coherente de cuatro ondas de AlfvenInteracciones no lineales de ondas de Alfvén existen tanto para plasmas en el espacio como en laboratorios, con efectos que van desde calentamiento hasta conducción de corriente. Un ejemplo de emisión de ondas de Alfvén en ingeniería aparece en amarras espaciales. Estos dispositivos emiten ondas en estructuras denominadas “Alas de Alfvén”. La ecuación Derivada no lineal de Schrödinger
(DNLS) posee la capacidad de describir la propagación de ondas de Alfvén de amplitud finita circularmente polarizadas tanto para plasmas fríos como calientes. En esta investigación, dicha ecuación es truncada con el objetivo de explorar el acoplamiento coherente, débilmente no lineal y cúbico de cuatro ondas cerca de resonancia (k1 + k2 = k3 + k4). La onda 1 que corresponde al vector de
onda k1 puede ser linealmente inestable y las tres restantes ondas 2, 3 y 4, correspondientes a k2, k3 y k4
respectivamente, son amortiguadas. Por medio de la utilización de este modelo se genera un flujo 5D
formado por cuatro amplitudes y una fase relativa. En una serie de trabajos previos se ha analizado la transición dura hacia caos en flujos 3D (Sanmartín et al., 2004) y 4D (Elaskar et al., 2005; Elaskar et al., 2006; Sánchez-Arriaga et al., 2007). Se presenta en este artículo un análisis teórico-numérico del comportamiento del sistema cuando la tasa de crecimiento de la onda inestable es nula.Sergio ElaskarJuan Ramón Sanmartín Losada2013-11-21T09:07:25Z2016-12-01T13:22:53Zhttp://oa.upm.es/id/eprint/21662This item is in the repository with the URL: http://oa.upm.es/id/eprint/216622013-11-21T09:07:25ZDamping models in the truncated derivative nonlinear Schrödinger equationFour-dimensional flow in the phase space of three amplitudes of circularly polarized Alfven waves and one relative phase, resulting from a resonant three-wave truncation of the derivative nonlinear Schrödinger equation, has been analyzed; wave 1 is linearly unstable with growth rate , and waves 2 and 3 are stable with damping 2 and 3, respectively. The dependence of gross dynamical features on the damping model as characterized by the relation between damping and wave-vector ratios, 2 /3, k2 /k3, and the polarization of the waves, is discussed; two damping models, Landau k and resistive k2, are studied in depth. Very complex dynamics, such as multiple blue sky
catastrophes and chaotic attractors arising from Feigenbaum sequences, and explosive bifurcations involving Intermittency-I chaos, are shown to be associated with the existence and loss of stability of certain fixed point P of the flow. Independently of the damping model, P may only exist as against flow contraction just requiring.In the case of right-hand RH polarization, point P may exist for all models other than Landau damping; for the resistive
model, P may exist for RH polarization only if 2+3/2.Gonzalo Sánchez ArriagaJuan Ramón Sanmartín LosadaSergio Elaskar2013-11-21T09:07:22Z2016-12-01T08:21:14Zhttp://oa.upm.es/id/eprint/21665This item is in the repository with the URL: http://oa.upm.es/id/eprint/216652013-11-21T09:07:22ZBare-tether cathodic contact through thermoionic emission by low work-function materialsA new material, C12A7 : electride, which might present a work function as low as 0.6 eV and moderately high temperature stability, was recently proposed as coating for floating bare tethers. Arising from heating under space operation, current is emitted by thermionic emission along a thus coated cathodic segment. A preliminary study on the space-charge-limited (SCL) double layer in front of the cathodic segment is presented using Langmuir’s SCL electron current between cylindrical electrodes and orbital-motion-limited ion-collection sheath. A detailed calculation of
current and bias profiles along the entire tether length is carried out with ohmic effects and the transition from SCL to full Richardson-Dushman emission included. Analysis shows that in the simplest drag mode, under typical orbital and tether conditions, thermionic emission leads to a short
cathodic section and may eliminate the need for an active cathodic device and its corresponding gas feed requirements and power subsystem, which results in a truly “propellant-less” tether system for such basic applications as de-orbiting low earth orbit satellites.Xin ChenJuan Ramón Sanmartín Losada2013-11-20T12:17:05Z2016-04-21T12:10:52Zhttp://oa.upm.es/id/eprint/21534This item is in the repository with the URL: http://oa.upm.es/id/eprint/215342013-11-20T12:17:05ZHard transition to chaotic dynamics in Alfven wave frontsThe derivative nonlinear Schrodinger DNLS equation, describing propagation of circularly polarized Alfven waves of finite amplitude in a cold plasma, is truncated to explore the coherent, weakly nonlinear, cubic coupling of three waves near resonance, one wave being linearly unstable
and the other waves damped. In a reduced three-wave model equal dampings of daughter waves, three-dimensional flow for two wave amplitudes and one relative phase, no matter how small the growth rate of the unstable wave there exists a parametric domain with the flow exhibiting chaotic
relaxation oscillations that are absent for zero growth rate. This hard transition in phase-space behavior occurs for left-hand LH polarized waves, paralleling the known fact that only LH time-harmonic solutions of the DNLS equation are modulationally unstable, with damping less than
about unstable wave frequency 2/4 x ion cyclotron frequency. The structural stability of the transition was explored by going into a fully 3-wave model different dampings of daughter waves,four-dimensional flow; both models differ in significant phase-space features but keep common features essential for the transition.Juan Ramón Sanmartín LosadaÓscar López-RebollalE. del RíoSergio Elaskar2013-11-20T11:53:18Z2016-12-01T13:37:03Zhttp://oa.upm.es/id/eprint/20420This item is in the repository with the URL: http://oa.upm.es/id/eprint/204202013-11-20T11:53:18ZInterference of parallel cylindrical Langmuir probesCurrent to a cylindrical probe of arbitrary cross section is discussed. Previous results for circular cylinders at the high bias and moderate radius R of interest for electrodynamic bare tethers, for which space charge may be ignored over a large neighborhood of the probe, depend in separate ways on both R and perimeter p. These results are extended to a general convex cross section by introducing certain equivalent radius Req. For any concave cross section, results use a proper equivalent perimeter peq , in addition to Req. Finally, for the joint cross section of separate parallel probes, certain effective perimeter peff replaces peq. Rules to determine Req. peq. and peff are used
to discuss collection interference among two or more parallel cylinders when brought from far away to contactJuan Ramón Sanmartín LosadaRobert D. Estes2013-11-20T10:16:12Z2016-04-21T12:22:13Zhttp://oa.upm.es/id/eprint/21653This item is in the repository with the URL: http://oa.upm.es/id/eprint/216532013-11-20T10:16:12ZA new basic effect in retarding potential analyzersThe Retarding Potential Analyzer (RPA) is the standard instrument for in situ measurement of ion temperature and other ionospheric parameters. The fraction of incoming ions rejected by a RPA produces perturbations that reach well ahead of a thin Debye sheath, a feature common to all
collisionless, hypersonic flows past ion-rejecting bodies. This phenomenon is here found to result in a correction to Whipple’s classical law for the current characteristic of an ideal RPA sheath thin; inverse ram ion Mach number M-1, and ram angle of RPA aperture u, small or moderately small.Juan Ramón Sanmartín LosadaÓscar López-Rebollal2013-11-20T09:32:50Z2016-04-21T12:22:07Zhttp://oa.upm.es/id/eprint/21652This item is in the repository with the URL: http://oa.upm.es/id/eprint/216522013-11-20T09:32:50ZCylindrical Langmuir probes beyond the orbital-motion-limited regimeThe current I to a cylindrical probe at rest in an unmagnetized plasma, with probe bias highly positive, is determined. The way I lags behind the orbital-motion-limited OMLcurrent, 1 OML R, as the radius R exceeds the maximum radius for the OML regime to hold, is of interest for space-tether applications. The ratio I/I OML is roughly a decreasing function of R/lD R max /lDe , which is independent of bias, with lDe the electron Debye length and Rmax /l De roughly an increasing function of the temperature ratio, Ti /Te. The dependence of current on ion energy is used to discuss the effect of probe motion through the plasma, a case applying to tethers in low orbit.Robert D. EstesJuan Ramón Sanmartín Losada2013-11-20T09:23:21Z2016-04-21T12:21:32Zhttp://oa.upm.es/id/eprint/21648This item is in the repository with the URL: http://oa.upm.es/id/eprint/216482013-11-20T09:23:21ZElectron current to a probe in a magnetized, collisional plasmaCollisional analysis of electron collection by a probe in a strongly magnetized, fully ionized plasma is carried out. A solution to the complete set of macroscopic equations with classical transport coefficients that is wholly consistent in the domain is determined; R and le are probe radius and electron gyroradius, respectively. If R2/le 2 is large compared with mi/3me probe large compared with ion gyroradius, ion–electron energy exchange—rather than
electron heat diffusion—keeps electrons isothermal. For smaller probes at negative bias, however, electron cooling occurs in the plasma beyond the sheath, with a potential overshoot lying well away from it. The probe characteristic in the electron-retarding range may then mimic the characteristic for a two electron-temperature plasma and lead to an overestimate of electron temperature; the
validity of these results for other transport models is discussedMario CharroJuan Ramón Sanmartín Losada2013-11-19T13:51:40Z2016-04-21T12:21:28Zhttp://oa.upm.es/id/eprint/21647This item is in the repository with the URL: http://oa.upm.es/id/eprint/216472013-11-19T13:51:40ZThe orbital-motion-limited regime of cylindrical Langmuir probesAn asymptotic analysis of electron collection at high bias Fp serves to determine the domain of validity of the orbital-motion-limited regime of cylindrical Langmuir probes, which is basic for the workings of conductive bare tethers. The radius of a wire collecting OML current in an
unmagnetized plasma at rest cannot exceed a value, Rmax , which is found to exhibit a minimum as a function of Fp ; atFp values of interest, Rmax is already increasing and is larger than the electron Debye length lDe . The breakdown of the regime relates to conditions far fromthe probe, at electron energies comparable to the ion thermal energy, kTi ; Rmax is found to increase with Ti . It is also
found that ~1! the maximumwidth of a thin tape, if used instead of a wire, is 4Rmax ; ~2! the electron thermal gyroradius must be larger than both R and lDe for magnetic effects to be negligible; and ~3! conditions applying to the tether case are such that trapped-orbit effects are negligible.Juan Ramón Sanmartín LosadaRobert D. Estes2013-11-19T12:34:16Z2016-10-26T09:37:40Zhttp://oa.upm.es/id/eprint/21646This item is in the repository with the URL: http://oa.upm.es/id/eprint/216462013-11-19T12:34:16ZExperimental evidence of a hard transition to chaosA generic, sudden transition to chaos has been experimentally verified using electronic circuits.
The particular system studied involves the near resonance of two coupled oscillators at 2:1 frequency ratio when the damping of the first oscillator becomes negative. We identified in the experiment all types of orbits described by theory. We also found that a theoretical, ID limit map fits closely a map of the experimental attractor which, however, could be strongly disturbed by noise. In particular, we found noisy periodic orbits, in good agreement with noise theory.Ezequiel del Rio FernandezJuan Ramón Sanmartín LosadaÓscar López-Rebollal2013-11-19T07:41:20Z2016-10-26T09:29:26Zhttp://oa.upm.es/id/eprint/21640This item is in the repository with the URL: http://oa.upm.es/id/eprint/216402013-11-19T07:41:20ZArtificial auroral effects from a bare conducting tetherAn electrically floating metallic bare tether in a low Earth orbit would be highly negative with respect to the ambient plasma over most of its length, and would be bombarded by ambient ions.This would liberates secondary electrons which after acceleration through the same voltage, would form a magnetically guided two-sided planar e beam,and result in auroral effects(ionization and light emission)upon impacto on the atmospheric E layer, at
about 120-140 km altitude.This papere examines in a preliminary way the feasibility of using this effecet as an uppeart atmospheric probe. Ionization rate can reach up to 10 3 cm 3 S -1 if a tape, instead of a wire, is used as tether. Contrary to standard e beams,the beam from the
tether is free of spacecrafct charging and plasma interaction problems and its energy flux varies across the crosss ection,w hich is quite large;this would make possible continuous observation from the satellite, with high resolution both spectral and vertical, of the induced optical emissions. Ground observation might be possible at latitudes around 40ø , for night, magnetically quiet conditions.Manuel Martínez SánchezJuan Ramón Sanmartín Losada2013-11-18T13:10:02Z2016-04-21T12:20:49Zhttp://oa.upm.es/id/eprint/21639This item is in the repository with the URL: http://oa.upm.es/id/eprint/216392013-11-18T13:10:02ZThe radiation impedance of orbiting conductorsThe dispersion relation for waves in a cold, magnetized plasma is discussed using the potential for the longitudinal part of the electric field. This clarifies wave emission from a conductor in low Earth orbit and should be useful in considering the far field and
both hot plasma and nonlinear, near-field effects. General formulas for radiation impedance are directly obtained. For tethers a fundamental dependence on contactor size is discussed. Spherical and ellipsoidal contactors and an (anodcless) bare tether are considered. Simple arguments on nonlinear contactor effects lead to a surprisingly simple result for impedances off the Alfven branch.Juan Ramón Sanmartín LosadaManuel Martínez-Sánchez2013-11-18T12:20:36Z2016-12-05T09:04:15Zhttp://oa.upm.es/id/eprint/21585This item is in the repository with the URL: http://oa.upm.es/id/eprint/215852013-11-18T12:20:36ZAlfvén wave far field from steady-current tethersWe analyzed he Alfvén waves ignaturele ft behindi n the ionospherbe y orbiting insulatedt etherso peratinga s thrusterso r generatorws ith steadyc urrentsU. sing a recentd escription of tetherr adiationt o determineth e far field, we showt hat, at their leadinge dges,t heA lfv6n
wingsh avea n Airy functionc rosswises tructureT. he field amplitudef alls off weakly as the inversec uber oot of the distancea longt he wavef ront.T he fronti tself, whichc arriesa negligible fractiono f the powerr adiateda sA lfven waves,b roadensp roportionallyto the cuber oot of that
distanceW. e showt hatc ollisionadl ecayb ecomesim portanat t about1 03k m alongt he front.F or tethersl ongert han about2 km, the top andb ottoms tructures("wings")a re fully disjoint.Juan Ramón Sanmartín LosadaRobert D. Estes2013-11-12T07:27:43Z2016-10-26T09:21:32Zhttp://oa.upm.es/id/eprint/21581This item is in the repository with the URL: http://oa.upm.es/id/eprint/215812013-11-12T07:27:43ZSelf-similar expansion of laser plasmas with nonlocal heat fluxA previous hydrodynamic model of the expansion of a laser-produced plasma, using classical (Spitzer) heat flux, is reconsidered with a nonlocal heat flux model. The nonlocal law
is shown to be valid beyond the range of validity of the classical law, breaking down ultimately, however, in agreement with recent predictions.J. RamírezJuan Ramón Sanmartín Losada2013-11-12T07:26:25Z2014-09-26T12:41:04Zhttp://oa.upm.es/id/eprint/21577This item is in the repository with the URL: http://oa.upm.es/id/eprint/215772013-11-12T07:26:25ZNonlocal electron heat relaxation in a plasma shock at arbitrary ionization numberA recently obtained nonlocal expression for the electron heat flux valid for arbitrary ionization numbers Z is used to study the structure of a plane shock wave in a fully ionized plasma.
Nonlocal effects are only important in the foot of the electronic preheating region, where the electron temperature gradient is the steepest. The results are quantified as a function of a characteristic Knudsen number of that region. This work also generalizes to arbitrary values of Z previous results on plasma shock wave structure.J. RamírezJuan Ramón Sanmartín LosadaRafael Fernández-Feria2013-11-12T07:24:54Z2016-10-26T09:22:24Zhttp://oa.upm.es/id/eprint/21583This item is in the repository with the URL: http://oa.upm.es/id/eprint/215832013-11-12T07:24:54ZA generic, hard transition to chaosA hard-in-amplitude transition to chaos in a class of dissipative flows of broad applicability is presented. For positive
values of a parameter F, no matter how small, a fully developed chaotic attractor exists within some domain of additional
parameters, whereas no chaotic behavior exists for F < 0. As F is made positive, an unstable fixed point reaches an
invariant plane to enter a phase half-space of physical solutions; the ghosts of a line of fixed points and a rich heteroclinic
structure existing at F = 0 make the limits t --* +oc, F ~ +0 non-commuting, and allow an exact description of the chaotic
flow. The formal structure of flows that exhibit the transition is determined. A subclass of such flows (coupled oscillators
in near-resonance at any 2 : q frequency ratio, with F representing linear excitation of the first oscillator) is fully analysedÓscar López-RebollalJuan Ramón Sanmartín Losada2013-11-12T07:24:50Z2016-04-21T12:15:27Zhttp://oa.upm.es/id/eprint/21584This item is in the repository with the URL: http://oa.upm.es/id/eprint/215842013-11-12T07:24:50ZA derivation of thermodynamic principlesA detailed macroscopic description as in continuum mechanics, and just the concept of microstate,have been used to derive thermodynamics from mechanics. In opposition to statistical physics, the derivation lays emphasis on a definite prescription for macrostates (and non-equilibrium entropy), and uses basic features of the macrostate concept: complementary descriptions, involving either conservative and additive quantities or densities;scale-free character; reference to finite velocities and regions distant in space, thus introducing time indirectly. On the other hand, the derivation keeps the particle substratum (limit of number of particles N taken at fixed densities), and makes no ergodic-type considerations.Juan Ramón Sanmartín Losada2013-11-11T11:33:08Z2016-04-21T12:14:15Zhttp://oa.upm.es/id/eprint/21576This item is in the repository with the URL: http://oa.upm.es/id/eprint/215762013-11-11T11:33:08ZCurrent collection by an active spherical electrode in an unmagnetized plasmaA theoretical model for the steady-state response of anodic contactors that emit a plasma current Ii and collect electrons from a collisionless, unmagnetized plasma is
presented. The use of a (kinetic) monoenergetic population for the attracted species, well known in passive probe theory, gives both accuracy and tractability to the theory.
The monoenergetic population is proved to behave like an isentropic fluid with radial plus centripetal motion, allowing direct comparisons with ad hoc fluid models. Also, a modification of the original monoenergetic equations permits analysis of contactors operating in orbit-limited conditions. Besides that, the theory predicts that, only for plasma emissions above certain threshold current a presheath/double layer/core structure for the potential is formed (the core mode), while for emissions below that threshold, a plasma contactor behaves exactly as a positive-ion emitter with a presheath/sheath structure (the no-core mode). Ion emitters are studied as a particular case. Emphasis is placed on obtaining dimensionless charts and approximate asymptotic laws of the current-voltage characteristic.Eduardo Ahedo GalileaManuel Martínez-SánchezJuan Ramón Sanmartín Losada2013-11-09T13:02:04Z2016-04-21T12:12:18Zhttp://oa.upm.es/id/eprint/21552This item is in the repository with the URL: http://oa.upm.es/id/eprint/215522013-11-09T13:02:04ZLa electrodinámica de cables espacialesSe discuten los fundamentos que subyacen en la concepción y en las aplicaciones de un cable espacial, o tether. Si el cable es metálico y órbita en un planeta con ionosfera y campo magnético propio —la Tierra misma, o uno de los grandes planetas exteriores-, su movimiento genera una fuerza electromotriz por el mismo proceso de inducción magnética de un simple generador eléctrico, y el circuito conductor se "cierra" a través del plasma ionosférico. Se analiza el problema técnico central al que se enfrentan los
tethers electrodinámicos de potencia: cómo establecer un buen contacto eléctrico entre el cable y la rarificada ionosfera. Se discute una reciente solución al problema.Juan Ramón Sanmartín LosadaEduardo Ahedo Galilea2013-11-09T13:01:02Z2016-04-21T12:12:23Zhttp://oa.upm.es/id/eprint/21553This item is in the repository with the URL: http://oa.upm.es/id/eprint/215532013-11-09T13:01:02ZSelf-consistent, nonlocal electron heat flux at arbitrary ion charge numberA single, nonlocal expression for the electron heat flux, which closely reproduces known results at high and low ion charge number 2, and “exact” results for the local limit at all 2, is derived by solving the kinetic equation in a narrow, tail-energy range. The solution involves asymptotic expansions of Bessel functions of large argument, and (Z-dependent)order above or below it, corresponding to the possible parabolic or hyperbolic character of the kinetic equation; velocity space diffusion in self-scattering is treated similarly to isotropic thermalization of tail energies in large Z analyses. The scale length H characterizing nonlocal effects varies with Z, suggesting an equal dependence of any ad hoc flux limiter. The model is valid for all H above the mean-free path for thermal electrons.Juan Ramón Sanmartín LosadaJ. RamírezRafael Fernández-FeriaF. Minotti2013-11-08T11:47:32Z2014-09-26T12:46:53Zhttp://oa.upm.es/id/eprint/21549This item is in the repository with the URL: http://oa.upm.es/id/eprint/215492013-11-08T11:47:32ZMagnetic and electric current morphoiogy in the plasma ejected
by a laser-irradiated foilA quasisteady model for the plasma ablated from a thick foil by a laser pulse, at low $lln $ and R /A i within a low, narrow range, is given (4, is absorbed intensity, /zL wavelength, R focalspot radius). An approximate analytical solution is given for the two-dimensional plasma dynamics. At large magnetic Reynolds number Rm, the morphology of the magnetic field shows features in agreement with recent results for high intensities. Current lines are open:
electric current flows toward the spot near its axis, then turns and flows away. The efficiency of converting light energy into electric energy peaks at Rm- 1, both the validity of the model.
and accuracy of the solution are discussed, The neighborhood of the spot boundary is analyzed
in detail by extending classical Prandtl-Meyer results.Juan Ramón Sanmartín LosadaPeter Reinicke2013-11-08T11:14:55Z2016-04-21T12:11:42Zhttp://oa.upm.es/id/eprint/21545This item is in the repository with the URL: http://oa.upm.es/id/eprint/215452013-11-08T11:14:55ZNonlocal electron heat flux revisitedA known nonlocal model of electron heat flux, applying for (scale length/thermal ion-electron mean-free path) of order Z)1/2(e*/T)312, ionization number Z, large, and e*~ 6.5 T (the energy of electrons carrying most of the flux), is reconsidered. The large e*/T ratio simplifies the complete formalism. A simple flux formula, exact for both smooth and steep profiles, is given. Thermoelectric effects and other models are discussed.Juan Ramón Sanmartín LosadaJ. RamírezR. Fernández Feria2013-11-07T11:00:52Z2016-04-21T12:09:58Zhttp://oa.upm.es/id/eprint/21523This item is in the repository with the URL: http://oa.upm.es/id/eprint/215232013-11-07T11:00:52ZSelf-consistent resonance absorption with two layer profile steepeningResonance absorption of p-polarized light, incident at angle 6 on a flowing, stratified plasma, is analyzed; profile steepening within (i) a layer around the turning point, and (ii) a thinner,embedded sublayer at the critical surface is taken into account self-consistently. The entire
steepened region is taken as collisionless and isothermal. The structure of the main layer shows a variety of regimes, depending on how the flow crosses a sonic point. The structure of the sublayer is also determined; it is entirely subsonic (with no wave breaking) for a well-defined,broad parameter range. Density changes across both layer and sublayer, and fractional absorption, are given in terms of [(wavelength)2 Xintensity/temperature], and
(temperature/mec2). The flow outside the double structure is also analyzed for particular conditions.Eduardo Ahedo GalileaJuan Ramón Sanmartín Losada2013-11-07T07:34:58Z2016-04-21T12:09:49Zhttp://oa.upm.es/id/eprint/21521This item is in the repository with the URL: http://oa.upm.es/id/eprint/215212013-11-07T07:34:58ZNon uniform target illumination in deflagration regime : refractive smoothingRefractive smoothing of weak non-uniformities in the illumination of laser targets is analyzed, assuming absorption at the critical density and restricting conduction to a thin layer, and using results from thermal smoothing, which is uncoupled from the refraction. Magnetic effects are included. Non-uniformity wavelengths comparable to the thickness of the conduction layer are considered; efficient smoothing exists at both short and long wavelengths in this range. Thermal focusing could make the ablated plasma unstable.José A. NicolásJ. SanzJuan Ramón Sanmartín LosadaJ. Hilario2013-11-07T07:34:31Z2016-04-21T12:09:54Zhttp://oa.upm.es/id/eprint/21522This item is in the repository with the URL: http://oa.upm.es/id/eprint/215222013-11-07T07:34:31ZThermal self-focusing instability in the conduction layer of a laser targetRefraction is included in the stability analysis of the corona ablated from a laser target, assuming conduction restricted to a thin layer and absorption at the critical density inside it. A thermal self-focusing instability, with growth rate ~ (ion-electron collision frequency) X (electron-to-ion mass ratio), is found.Juan Ramón Sanmartín LosadaJ. SanzJosé A. Nicolás2013-11-05T15:19:11Z2016-04-21T12:09:23Zhttp://oa.upm.es/id/eprint/21515This item is in the repository with the URL: http://oa.upm.es/id/eprint/215152013-11-05T15:19:11ZCoronal fluid-dynamics in laser fusionThe fluid-dynamics of the corona ejected by laser-fusion targets in the direct-drive approach (thermal radiation and atomic physics unimportant) is discussed. A two-fluid
model involves inverse bremsstrahlung absorption, refraction, different ion and electron temperatures with energy exchange, different ion and electron velocities and
magnetic field generation, and their effect on ion-electron friction and heat flux. Four dimensionless parameters determine coronal regimes for one-dimensional flows under
uniform irradiation. One additional parameter is involved in two-dimensional problems,including the stability of one-dimensional flows, and the smoothing of nonuniform driving.Juan Ramón Sanmartín Losada2013-11-05T15:18:52Z2016-04-21T12:09:19Zhttp://oa.upm.es/id/eprint/21514This item is in the repository with the URL: http://oa.upm.es/id/eprint/215142013-11-05T15:18:52ZNon-uniform target illumination in deflagration regime : thermal smoothingThermal smoothing in the plasma ablated from a laser target under weakly nonuniform irradiation is analyzed, assuming absorption at nc and a deflagration regime (conduction
restricted to a thin quasisteady layer next to the target). Magnetic generation effects are included and found to be weak. Differences from results available in the literature are explained; the importance of the character of the underdense flow at uniform irradiation is emphasized.J. SanzJosé A.. NicolásJuan Ramón Sanmartín LosadaJ. Hilario2013-11-05T09:12:43Z2016-04-21T12:07:55Zhttp://oa.upm.es/id/eprint/21501This item is in the repository with the URL: http://oa.upm.es/id/eprint/215012013-11-05T09:12:43ZResonant absorption in a plasma step profileResonant absorption of p-polarized light shined on a plane-layered plasma with a step profile, is discussed as a function of wavelength (or critical density n,) of the light: for simplicity the incidence angle is assumed small. If n, lies within or above the step, the absorption A is given by Ginzburg’s result modified by strong reflections at the foot and top of the step. The absorption above is total for particular values of nc and U. For n, crossing the top of the density step the absorption is not monotonical: it exhibits a minimum that vanishes for zero radius of curvature U there and zero collision frequency 1’ (A - Iln VI-’). The results are applied to the profile produced by irradiating a solid target with a high-intensity pulse that steepens the plasma by radiation pressure.Eduardo Ahedo GalileaJuan Ramón Sanmartín Losada2013-11-04T11:01:41Z2016-04-21T12:07:50Zhttp://oa.upm.es/id/eprint/21500This item is in the repository with the URL: http://oa.upm.es/id/eprint/215002013-11-04T11:01:41ZOrtega sobre Relatividad : un contraejemplo.Se discuten juicios epistemológicos de Ortega sobre Relatividad, a la luz de una crítica recienteJuan Ramón Sanmartín Losada2013-11-04T11:01:26Z2016-04-21T12:05:57Zhttp://oa.upm.es/id/eprint/21482This item is in the repository with the URL: http://oa.upm.es/id/eprint/214822013-11-04T11:01:26ZInverse bremsstrahlung absorption in spherical laser targetsInverse bremsstrahlung has been incorporated into an analytical model of the expanding corona of a laser-irradiated spherical target. Absorption decreases slowly with increasing intensity, in agreement with some numerical simulations, and contrary to estimates from simple models in use up to now, which are optimistic at low values of intensity and very pessimistic at high values. Present results agree well with experimental data from many laboratories; substantial absorption is found up to moderate intensities,say below IOl5 W cm-2 for 1.06 pm light. Anomalous absorption, wher, included in the analysis, leaves practically unaffected the ablation pressure and mass ablation rate, for given absorbed intensity. Universal results are given in dimensionless fom.J.A. NicolásJuan Ramón Sanmartín Losada2013-10-31T12:48:21Z2016-04-21T12:02:55Zhttp://oa.upm.es/id/eprint/21447This item is in the repository with the URL: http://oa.upm.es/id/eprint/214472013-10-31T12:48:21ZInfluence of air drag on the optimal hand launching of a small, round projectileConditions leading to a maximum range for a small, round projectile, fired by hand, are discussed taking into account air drag and the dependence of the initial speed on the mass launched. Both the optimal angle of release for given projectile and initial speed, and the optimal radius for given density (i.e., among a bed of pebbles) are determined; an increase on the height of release is found
to always decrease the angle and increase the radius. The influence of the projectile mass on the optimal manner of launching is considered. The validity of the approximations used in the analysis is discussed. Results from very simple measurements show good agreement with theory.J.A. ZufiriaJuan Ramón Sanmartín Losada2013-10-30T11:26:18Z2016-04-21T12:05:43Zhttp://oa.upm.es/id/eprint/21480This item is in the repository with the URL: http://oa.upm.es/id/eprint/214802013-10-30T11:26:18ZO Botafumeiro: parametric pumping in the Middle AgeThe pendular motion of a giant censer (O Botafumeiro) that hangs in the transept of the cathedral of Santiago de Compostela, and is cyclically pumped by men who pull at the supporting rope, is analyzed. Maximum angular amplitude attainable, and number of cycles and time needed to
attain it, are calculated; the results agree with observed values (~ 82°, ~ 17 cycles, ~ 80 seconds) to the few percent accuracy of both the analysis and the observations and parameter measurements. The energy gain in a pumping cycle is obtained for an arbitrary pumping procedure to two orders in the small fractional change of pendular length; the relevance of the ratio (characteristic radial acceleration during pumping)/g to the gain is discussed- Effects due to rope mass, air drag on both Censer and rope, and the fact that the Censer is not a point mass, are
considered. If the pumping cycle is inverted once the maximum amplitude has been attained, the Censer could be swiftly brought to rest, avoiding the usual violent stop. Historically recorded accidents, rope shape, and the influence of relevant parameters on the motion are discussed.Juan Ramón Sanmartín Losada2013-10-30T11:25:14Z2016-04-21T12:05:18Zhttp://oa.upm.es/id/eprint/21478This item is in the repository with the URL: http://oa.upm.es/id/eprint/214782013-10-30T11:25:14ZComment on "Another look at the uniform rope sliding over the edge of a smooth table"Comment on "Another look at the uniform rope sliding over the edge of a smooth table"Juan Ramón Sanmartín LosadaM.A. Vallejo2013-10-30T07:36:19Z2016-04-21T12:04:51Zhttp://oa.upm.es/id/eprint/21473This item is in the repository with the URL: http://oa.upm.es/id/eprint/214732013-10-30T07:36:19ZIon charge number and flux saturation effects in the corona of a laser-irradiated pelletThe quasisteady structure of the corona of a laser-irradiated pellet is completely determined for arbitrary Z, (ion charge number} and re/ra (ratio of critical and ablation radii), and for heat-flux saturation factor/above approximately 0.04. The ion-to-electron temperature ratio at rc grows sensibly with Z,; all other quantities depend weakly and nonmonotonically on Z,. For rc /ra close
to unity, and all Z, of interest (Z, < 47}, the flow is subsonic at rc. For a given laser power W, flux saturation may decrease (low/) or increase (high/) the ablation pressure Pa relative to the value obtained when saturation is not considered; in some cases a decrease in/with W fixed increases Pa. For intermediate^ ~0.1), Pa cc (W/r* )2/3 p\n\pc = critical density), independently of rc/ra;
for/~0.6, Pa «s larger by a factor of about [rc/raf13. For rjra > 1.2 roughly, the mass ablation rate is C{Z,) [{m/kZ.f^Kr^Pl) l,\ independent of pc and/, and barely dependent on Z,(m, is ion mass; k, Boltzmann's constant; K, conductivity coefficient; and C, a tabulated function).J. SanzJuan Ramón Sanmartín Losada2013-10-30T07:27:54Z2016-10-24T11:00:27Zhttp://oa.upm.es/id/eprint/21475This item is in the repository with the URL: http://oa.upm.es/id/eprint/214752013-10-30T07:27:54ZElectron temperature versus laser intensity times wavelength squared: a comparison of theory and experimentsThe peak temperature in the corona of plasma ejected by a laser-irradiated slab is discussed in terms of a one-electron-temperature model. Both heat-flux saturation and pulse rise-time effects are considered;the intensity in the rising half of the pulse is approximated by a linear function of time, I(t) = Iot/r. The temperature is found to be proportional to (IQX2)273 and a function of I0X4/r. Above a certain value of I0X4/T, the plasma presents two characteristic temperatures (at saturation and at the critical surface) which can be identified with experimentally observed cold- and hot-electron temperatures. The results are compared with extensive experimental data available for both nd and CO2 lasers, I0(W'cnf2) X2 (/um) starting around 1012. The agreement is good if substantial flux inhibition is assumed (flux-limit factor f = 0.03), and fails for I0X2 above 1O1S. Results for both ablation pressure and mass ablation rate are also given.Rafael Ramis AbrilJuan Ramón Sanmartín Losada2013-10-28T09:08:13Z2016-04-21T12:01:48Zhttp://oa.upm.es/id/eprint/21441This item is in the repository with the URL: http://oa.upm.es/id/eprint/214412013-10-28T09:08:13ZFusión termonuclear por confinamiento inercialJuan Ramón Sanmartín Losada2013-10-26T13:13:25Z2016-04-21T12:01:27Zhttp://oa.upm.es/id/eprint/21436This item is in the repository with the URL: http://oa.upm.es/id/eprint/214362013-10-26T13:13:25ZTransition from isentropic to isothermal expansion in laser produced plasmaThe transition that the expansion flow of laser-produced plasmas experiences when one moves from long, low intensity pulses (temperature vanishing at the isentropic plasma-vacuum front,lying at finite distance) to short, intense ones (non-zero, uniform temperature at the plasma-vacuum
front, lying at infinity) is studied. For plznar geometry and lqge ion number Z, the transition occurs for dq5/dt=0.14(27/8)k712Z’1zn$/m4f, 12nK,,; mi, and K are laser intensity, critical density,ion mass, and Spitzer’s heat conduction coefficient. This result remains valid for finite Zit,h ough the numerical factor in d$/dt is different. Shorter wavelength lasers and higher 4 plasmas allow faster rising pulses below transition.A. BarreroJuan Ramón Sanmartín Losada2013-10-21T12:31:27Z2016-04-21T11:58:45Zhttp://oa.upm.es/id/eprint/21389This item is in the repository with the URL: http://oa.upm.es/id/eprint/213892013-10-21T12:31:27ZWidespread error in a standard problem in the dynamics of deformable bodiesJuan Ramón Sanmartín LosadaM.A. Vallejo2013-10-19T05:05:56Z2016-04-21T11:58:25Zhttp://oa.upm.es/id/eprint/21384This item is in the repository with the URL: http://oa.upm.es/id/eprint/213842013-10-19T05:05:56ZSelf-similar motion of laser half-space plasmas. I. Deflagration regimeThe one-dimensional self-similar motion of an initially cold, half-space plasma of electron density 0,produced by the (anomalous) absorption of a laser pulse of irradiation <j> = (j>0f/T(0< (< T) at the critical density nc(«c/«0=e<l), is considered. The analysis allows for electron heat conduction and ion-electron energy exchange and retains three dimensionless numbers: e, Zt (ion charge number), and a = (9/c/4m,) (T/C 2n l/4>oKe)213, where k, m, are Boltzmann's constant and the ion mass, and Ke X (electron temperature)5'2 = heat conductivity. If a >e- 4 ' 3 , a deflagration wave separates an isentropic compression
with a shock bounding the undisturbed plasma, and an isentropic expansion flow to the vacuum. The structures of these three regions are completely determined; in particular, the Chapman-Jouguet condition is proved and the density behind the deflagration is found. The deflagration-compression thickness ratio is large (small) for a^e- 5 ' 3(a>e- 5 ' 3 ) . The compression to expansion ratio for both energy and thickness is 0(e"2). For Z,- large, a deflagration exists even if a~e~413. Condition a>e~4'3 may be applied to pulses that are not linear.Juan Ramón Sanmartín LosadaA. Barrero2013-10-19T05:04:31Z2016-10-26T07:39:38Zhttp://oa.upm.es/id/eprint/21385This item is in the repository with the URL: http://oa.upm.es/id/eprint/213852013-10-19T05:04:31ZSelf-similar motion of laser half-space plasmas. II. Thermal waves and intermediate regimesThe one-dimensional self-similar motion of an initially cold, half-space plasma of electron density n,produced by the (anomalous) absorption of a laser pulse of irradiation <p ^ <p0 f /T (0< t < T) at the critical density nc, is considered; the analysis, which allows for electron heat conduction and ion-electron energy exchange, involves three dimensionless numbers: e = nc/n0 assumed small, Z, (ion charge number), and a parameter a<x(«0 2r/<j)0)2'3. For a < l , a weak discontinuity develops, separating a thermal wave (where convection is negligible) moving into the undisturbed plasma, from a much thinner isothermal flow expanding into the vacuum. For l<a<e~4'3, there is an isentropic compression flow between a shock,
bounding the undisturbed plasma, and a very thin transition layer bounding an expansion flow, much larger in extent than the compression region. In both regimes, the critical plane lies far in the expansion tail. The results break down when the density is so small that the plasma becomes collisionless. The analysis is also invalid for a too small. Using results previously found for a>€~4'3, a qualitative discussion of how plasma behavior changes with a, is given.Juan Ramón Sanmartín LosadaA. Barrero2013-10-18T19:34:04Z2016-04-21T11:54:40Zhttp://oa.upm.es/id/eprint/21353This item is in the repository with the URL: http://oa.upm.es/id/eprint/213532013-10-18T19:34:04ZSelf-similar motion of laser fusion plasmas. Absorption in
an unbounded plasmaThe one-dimensional motion generated in a cold, infinite, uniform plasma of density na by the absorption, in a certain plane, of a linear pulse of energy per unit time and area <j> = 4>0t/r, 0< t< r, is considered, the
analysis allows for thermal conduction and viscosity of ions and electrons, their energy exchange, and an electron heat flux limiter The resulting motion is self-similar and governed by a single nondimensional parameter a«(n0
2T/<f>0)2/3 Detailed asymptotic results are obtained for both a < l and a > l , the general behavior of the solution for arbitrary a is discussed The analysis can be extended to the case of a plasma initially occupying a half-space, and throws light on how to optimize the hydrodynamics of laser fusion plasmas Known approximate results corresponding to motion of a plasma submitted to constant irradiation (<()) are recovered in the present work under appropriate limiting processesA. BarreroJuan Ramón Sanmartín Losada2013-10-11T08:30:52Z2016-04-21T11:32:32Zhttp://oa.upm.es/id/eprint/21324This item is in the repository with the URL: http://oa.upm.es/id/eprint/213242013-10-11T08:30:52ZDispersion relation for electron waves propagating in an isotropic plasma containing Maxwellian and suprathermal electronsThe paper discusses the dispersion relation for longitudinal electron waves propagating in a collisionless, homogeneous isotropic plasma, which contains both Maxwellian and suprathermal electrons. I t is found that the dispersion curve, known to have two separate branches for zero suprathermal energy spread,depends sensitively on this quantity. As the energy half-width of the suprathermal
population increases, the branches approach each other until they touch at a connexion point, for a small critical value of that half-width. The topology of the dispersion curves is different for half-widths above and below critical; and this can affect the use of wave-propagation measurements as a diagnostic technique for the determination of the electron distribution function. Both the distance between the branches and spatial damping near the connexion frequency depend on the half-width, if below critical, and can be used to determine it. The theory is applied to experimental data.Juan Ramón Sanmartín Losada2013-10-11T07:21:59Z2016-04-21T11:31:15Zhttp://oa.upm.es/id/eprint/21322This item is in the repository with the URL: http://oa.upm.es/id/eprint/213222013-10-11T07:21:59ZEnd effect in Langimur probe reponse under ionospheric satellite conditionsA theory is presented for an end effect in the current response of a highly negative, cylindrical Langmuir
probe in a collisionless plasma flow. Under conditions where the ratio of probe radius to debye length is small and the ion-acoustic Mach number is large, the current exhibits a strong peak when the probe axis is brought into alignment with the flow direction. Closed formulas are given for the maximum and angular half-width of the peak, and universal graphical results are presented for the entire peak structure.
The theory shows very good agreement with experimental data. The use of the end effect for diagnostic purposes, in particular, for the determination of the ion temperature, is discussed.Juan Ramón Sanmartín Losada2013-10-10T12:33:35Z2016-04-21T11:29:39Zhttp://oa.upm.es/id/eprint/21311This item is in the repository with the URL: http://oa.upm.es/id/eprint/213112013-10-10T12:33:35ZIon-temperature-sensitive effect in transient langmuir probe responseA theory is presented for a method, recently proposed by Hester and Sonin, of determining the ion temperature in a plasma by measuring the transient current to a cylindrical Langmuir probe after applying a potential Vp{ — eVpy>KTe) under conditions where collection is collision free and the ratio of probe radius to Debye length is small. The ion component of the current does not approach its final steady-state value monotonicalfy, but exhibits a strong, ion-temperature-dependent overshoot in the first few ion-plasma
periods following the biasing of the probe. Analytical formulas are derived for the case of a Maxwellian
plasma, and convenient graphical results are presented. The possible masking of the overshoot by a transient
displacement current is discussed; it is shown how to avoid such displacement effects. For the overshoot to be sensitive to the ion temperature T the probe must be near plasma (zero) potential before applying V1,(eVp~<0.lKTe, VP~ being that initial potential); this is not a drawback of the method, but, on the contrary, it can be used to accurately determine plasma potential along with T.Juan Ramón Sanmartín Losada2013-10-10T12:33:16Z2016-04-21T11:29:33Zhttp://oa.upm.es/id/eprint/21310This item is in the repository with the URL: http://oa.upm.es/id/eprint/213102013-10-10T12:33:16ZSimilarities between ion waves in plasmas and gravity waves in incompressible fluidsSome similarities between ion waves in plasmas and gravity waves in incompressible fluids are investigated. It is shown that for zero ion temperature the ion-wave dispersion relation is similar to that of gravity waves in a stratified liquid between rigid, horizontal walls; for large wavelength the ion waves behave as the surface gravity waves of shallow-water theory. The general character of the pattern of ion waves arising in steady plasma flows is analyzed for arbitrary ion temperature, wavelength, and acoustic mach number (which is based on the ion-acoustic speed), and is compared to the pattern of surface gravity waves in steady water flows when surface tension is taken into account.S.H. LamJuan Ramón Sanmartín Losada2013-10-10T12:28:39Z2016-10-24T07:55:36Zhttp://oa.upm.es/id/eprint/21309This item is in the repository with the URL: http://oa.upm.es/id/eprint/213092013-10-10T12:28:39ZFar wake structure in rarefied plasma flows past charged bodiesThe asymptotic structure of the far-wake behind a charged body in a rarefied plasma flow is investigated under the assumption of small ion-to-electron temperature ratio and of flow speed hypersonic with respect to the ions but not with respect to the electrons. It is found that waves are excited even if the flow is subacoustic (flow velocity less than the ion-acoustic speed). For both superacoustic and
subacoustic velocities a steep wave front develops separating the weakly perturbed, quasineutral plasma ahead, from the region behind where ion waves appear. Near the axis a trailing front develops;the region between this and the axis is quasineutral for superacoustic speeds. The decay laws in all of these regions, the self-similar structure of the fronts and the general character of the waves are determined.The damping of the waves and special flow detail for bodies large and small compared with the Debye length are discussed. A nonlinear analysis of the leading wave front in superacoustic flow is carried out. A hyperacoustic equivalence principle is presented.Juan Ramón Sanmartín LosadaS.H. Lam2013-10-10T11:16:21Z2016-04-21T11:29:23Zhttp://oa.upm.es/id/eprint/21308This item is in the repository with the URL: http://oa.upm.es/id/eprint/213082013-10-10T11:16:21ZMedida de propulsantes en depósitos en condiciones de cero-gJuan Ramón Sanmartín LosadaEnrique Fraga2013-09-23T11:08:41Z2016-04-21T23:12:58Zhttp://oa.upm.es/id/eprint/20417This item is in the repository with the URL: http://oa.upm.es/id/eprint/204172013-09-23T11:08:41ZElectrostatic plasma instabilities excited by a high‐frequency electric fieldThe electrostatic plasma waves excited by a uniform, alternating electric field of arbitrary intensity are studied on the basis of the Vlasov equation; their dispersion relation, which involves the determinant of either of two infinite matrices, is derived. For ω0 ≫ ωpi (ω0 being the applied frequency and ωpi the ion plasma frequency) the waves may be classified in two groups, each satisfying a simple condition; this allows writing the dispersion relation in closed form. Both groups coalesce (resonance) if (a) ω0 ≈ ωpe/r (r any integer) and (b) the wavenumber k is small. A nonoscillatory instability is found; its distinction from the DuBois‐Goldman instability and its physical origin are discussed. Conditions for its excitation (in particular, upper limits to ω0,k, and k⋅vE,vE being the field‐induced electron velocity), and simple equations for the growth rate are given off‐resonance and at ω0 ≈ ωpi. The dependence of both threshold and maximum growth rate on various parameters is discussed, and the results are compared with those of Silin and Nishikawa. The threshold at ω0 ≈ ωpi/r,r ≠ 1, is studied.Juan Ramón Sanmartín Losada2013-09-23T10:05:08Z2016-04-21T23:10:46Zhttp://oa.upm.es/id/eprint/20398This item is in the repository with the URL: http://oa.upm.es/id/eprint/203982013-09-23T10:05:08ZIon correlations due to high-frequency electric field and their effect on the nonlinear plasma conductivityThe influence of a strong, high‐frequency electric field on the ion‐ion correlations in a fully ionized plasma is investigated in the limit of infinite ion mass, starting with the Bogoliubov‐Born‐Green‐Kirkwood‐Yvon hierarchy of equations; a significant departure from the thermal correlations is found. It is shown that the above effect may substantially modify earlier results on the nonlinear high‐frequency plasma conductivity.Juan Ramón Sanmartín Losada2013-09-23T10:05:04Z2016-04-21T23:10:19Zhttp://oa.upm.es/id/eprint/20396This item is in the repository with the URL: http://oa.upm.es/id/eprint/203962013-09-23T10:05:04ZTheory of a probe in a strong magnetic fieldAn asymptotic analysis of the Langmuir-probe problem in a quiescent, fully ionized plasma in a strong magnetic field is performed, for electron cyclotron radius and Debye length much smaller than probe radius, and this not larger than either ion cyclotron radius or mean free path. It is found that the electric potential, which is not confined to a sheath, controls the diffusion far from the probe; inside
the magnetic tube bounded by the probe cross section the potential overshoots to a large value before decaying to its value in the body of the plasma. The electron current is independent of the shape of the body along the field and increases with ion temperature; due to the overshoot in the potential, (1) the current at negative voltages does not vary exponentially, (2) its magnitude is strongly reduced by the field, and (3) the usual sharp knee at space potential, disappears. In the regions of the C-V diagram
studied the ion current is negligible or unaffected by the field. Some numerical results are presented.The theory, which fails beyond certain positive voltage, fields useful results for weak fields, too.Juan Ramón Sanmartín Losada2013-09-23T09:17:47Z2016-10-21T11:05:37Zhttp://oa.upm.es/id/eprint/20392This item is in the repository with the URL: http://oa.upm.es/id/eprint/203922013-09-23T09:17:47ZCuerpos de forma óptima en vuelo hipersónicoSe estudia la obtencion de la forma del fuselaje optimo de un vehiculo hipersonico, tipo planeador,de gran radio de accion, para el que es fundamental conseguir un valor alto de ( L / D ) inAx.Se utiliza la teoria de NEWTON-BUSEMANN para el cálculo de las caracteristicas aerodinámicas. Para la solucion del problema variacional, se consideran fijos ciertos parámetros (por ejemplo, el radio de curvatura en
el morro) que afectan directamente al calor recibido
por el cuerpo y a las caracteristicas en vuelo subsónico.
Como ejemplo, se considera la solucion de un caso particular.Juan Ramón Sanmartín Losada2011-08-22T07:48:39Z2016-04-20T17:02:21Zhttp://oa.upm.es/id/eprint/8146This item is in the repository with the URL: http://oa.upm.es/id/eprint/81462011-08-22T07:48:39ZThe radiation impedance of a current-carrying conductor in a JUNO-like Jovian orbit.The so-called electrical power generation problem for exploration of the outer planets could be solved deploying an electrodynamic tether. Wave radiation by a conductor carrying a steady current in a polar, highly eccentric, low perijove orbit, as in the planned NASA Juno mission, is considered. The high Jupiter's oblateness produces fast apsidal precession over the meridional plane. In a cold plasma model, radiation occurs in the Alfven and Fast Magnetosonic modes, exhibiting large refraction index. The radiation impedance in both modes is determined for a representative arc in the orbits. Unlike the Earth ionospheric case, the low-dense and highly-magnetized Jovian plasma makes the electron-gyrofrequency to plasma-frequency ratio large [1]; this substantially modifies the power spectrum in either mode.Antonio Sánchez TorresJuan Ramón Sanmartín Losada2011-08-19T10:35:57Z2016-12-01T08:44:50Zhttp://oa.upm.es/id/eprint/8463This item is in the repository with the URL: http://oa.upm.es/id/eprint/84632011-08-19T10:35:57ZA review of electrodynamic tethers for science applications.A bare electrodynamic tether (EDT) is a conductive thin wire or tape tens of kilometres long, which is kept taut in space by gravity gradient or spinning, and is left bare of insulation to collect (and carry) current as a cylindrical Langmuir probe in an ambient magnetized plasma. An EDT is a probe in mesothermal flow at highly positive (or negative) bias, with a large or extremely large 2D sheath, which may show effects from the magnetic self-field of its current and have electrons adiabatically trapped in its ram front. Beyond technical applications ranging from propellantless propulsion to power generation in orbit, EDTs allow broad scientific uses such as generating electron beams and artificial auroras, exciting Alfven waves and whistlers, modifying the radiation belts and exploring interplanetary space and the Jovian magnetosphere. Asymptotic analysis, numerical simulations, ground and space tests and past and planned missions on EDTs are briefly reviewed.Juan Ramón Sanmartín Losada2011-03-24T12:25:34Z2016-04-20T15:47:29Zhttp://oa.upm.es/id/eprint/6524This item is in the repository with the URL: http://oa.upm.es/id/eprint/65242011-03-24T12:25:34ZProblemas de contaminación atmosférica en la combustión de hidrocarburosSe exponen en esta Memoria los resultados de un programa de investigación patrocinado por la Fundación Juan March sobre "Combustión atmosférica originada por la combustión de hidrocarburos" . De acuerdo con la Propuesta presentada a la Fundación,se ha centrado especialmente el programa de investigación en el problema de los óxidos de nitrógeno. El programa ha comprendí do el aspecto básico del problema: cinética química, estructuras de llamas y formación de óxidos de nitrógeno en las mismas; y un programa fundamentalmente experimental sobre formación de óxidos de nitrógeno en sistemas de combustión continua: cámaras de combustión de motores de reacción y generadores de calor, comprendiendo en este último caso además de los óxidos de nitrógeno los demás contaminantes que se originan en estos sis temas. En el Capítulo I o (Introducción) se señalan los principa_ les aspectos de la contaminación atmosférica originada por la combustión de hidrocarburos, discutiéndose a continuación el problema de los óxidos de nitrógeno. Se destaca su importancia a causa de la formación de neblina fotoquímicas o "smog", que se inician con la descomposición del NO2 por la radiación solar ultravioleta. Se comenta la rápida proliferación mundial de esta contaminación fotoquímica, que se señaló por primera vez en Los Angeles en 19UU, y que se forma principalmente en grandes aglomeraciones urbanas con elevada densidad automovilíjs tica y que reciban fuerte radiación solar (Los Angeles, TokyoOsaka, Sidney, San Francisco, e t c ). Se discute en el Capítulo el mecanismo de formación del "smog" y los daños que ocasiona. Finalmente se reseña el programa de investigación, señalándose las razones que motivaron la elección de los temas. En los sucesivos Capítulos se reseña el programa de inves_ tigación realizado incluyendo los resultados y conclusiones. To dos los Capítulos comienzan con una revisión del tema tratado en el mismo y concluyen con una reseña bibliográfica. En el Capítulo 2 o se estudia la cinética química de forma ción de óxidos de nitrógeno en llamas hidrógeno-aire, discutién dose la extensión de este mecanismo al caso de hidrocarburos. El Capítulo 3 o está dedicado al estudio de estructuras y temperatura de llamas laminares premezcladas y de difusión y a la formación de óxidos de nitrógeno en ellas, con especial apli cación al caso de combustión de gotas y masas esféricas de gas. En el Capítulo ^° se expone un programa experimental de formación de óxidos de nitrógeno en cámaras de combustión de turbinas de gas, estudiándose la influencia de diversas variables operacionales y de diseño.Carlos Sánchez TarifaFelix Alvaro FernandezAntonio Crespo MartínezEnrique FragaAmable Liñán MartínezJosé Juan Salvá MonfortJuan Ramón Sanmartín Losada2011-02-28T09:36:01Z2016-04-20T15:30:27Zhttp://oa.upm.es/id/eprint/6200This item is in the repository with the URL: http://oa.upm.es/id/eprint/62002011-02-28T09:36:01ZThe hydrodynamic efficiency of laser-target accelerationThe acceleration of a thin foil using a laser pulse is studied. It is shown that the acceleration efficiency eta H is heavily dependent on the behaviour of the corona ejected by the foil: there is no universal relation eta H( Delta M/M0),M0 and Delta M being initial foil mass and ablated mass, respectively. Known results on the coronal flow are used to check the theory against experimental data available in the literature; effects due to both a non-planar corona, and the time-dependence of the laser irradiance, are considered. The agreement with experiments is substantially better than that for previous analyses. Acceleration of thin spherical shells is also discussed.Juan Ramón Sanmartín LosadaJosé Luis Montañés GarcíaJavier Sanz RecioRafael Ramis Abril2011-02-25T15:21:42Z2016-04-20T15:30:12Zhttp://oa.upm.es/id/eprint/6193This item is in the repository with the URL: http://oa.upm.es/id/eprint/61932011-02-25T15:21:42ZComment on "Steady-state planar ablative flow"In a recent paper Manheimer et al.1 attempted to proceed beyond older analyses2 on the ablative corona ejected by planar láser targets. Here we comment on some aspects of the analysis of Ref. 1, common to most previous papers on the subject.Juan Ramón Sanmartín LosadaJosé Luis Montañés GarcíaA. Barrero2011-02-25T14:59:28Z2016-04-20T15:30:09Zhttp://oa.upm.es/id/eprint/6192This item is in the repository with the URL: http://oa.upm.es/id/eprint/61922011-02-25T14:59:28ZProfile modification by light pressure in plasmas expanding with uniform, time-dependent temperature.Profile modification of laser plasmas, in the transition layer at critical density and in the flow on the overdense side, is studied. Assuming isothermal flow and low absorption within the layer, compression transitions are proved impossible and cavities possible only in subsonic flow. The overdense flow adjusts itself for a rarefaction transition in a manner (formation of plateaus, bumps, or cavities) critically dependent on how the (spatially uniform) temperature varies with time. Spherical effects and evidence for the results are considered.Juan Ramón Sanmartín LosadaJosé Luis Montañés García2011-02-25T14:46:33Z2016-04-20T15:30:06Zhttp://oa.upm.es/id/eprint/6191This item is in the repository with the URL: http://oa.upm.es/id/eprint/61912011-02-25T14:46:33ZSelf-consistent profile modification in the underdense region of laser-produced plasmasProfile modification in the underdense region of laser-plasmas with spatially uniform temperature Te, is studied. A multiple scale method is used to describe self-consistently the plasma flow and the wave field, in (i) the scale of the field wavelength, and (ii) the overall expansion scale. For Te taordinary differential equations with definite boundary conditions are obtained. For a = 0 and weak fields, we explicitly solve the equations and relate the field in the critical layer to the incident field.Juan Ramón Sanmartín LosadaJosé Luis Montañés García2011-02-25T14:32:13Z2016-04-20T15:30:04Zhttp://oa.upm.es/id/eprint/6190This item is in the repository with the URL: http://oa.upm.es/id/eprint/61902011-02-25T14:32:13ZSpherical thermal waves in laser plasmasThe thermal wave produced in a uniform plasma, when energy is absorbed on a spherical surface such that convection is negligible, is analyzed using an integral method, which is very accurate. The curvature speeds up (slightly slows down) the inner (outer) wave front and does not affect the temperature maximum.José Luis Montañés GarcíaJuan Ramón Sanmartín Losada2011-02-08T15:14:31Z2016-04-20T14:36:44Zhttp://oa.upm.es/id/eprint/5927This item is in the repository with the URL: http://oa.upm.es/id/eprint/59272011-02-08T15:14:31ZTwo-electron temperature model of a laser-driven implosionThe plasma ejected by a pellet irradiated with moderately intense laser light (Icrλ2 ∼1015 W cm−2 μm2, Icr and λ being intensity and wavelength) is analyzed. Both hot electrons caused by resonant absorption, and cold or thermal electrons are considered; no appeal is made to heat‐flux saturation. The cold (hot) population controls the overdense (underdense) plasma flow. Ingoing hot electrons at the critical surface are found to thermalize before reaching the ablation surface. Results obtained are compared with a model that assume one electron temperature, and a saturated flux; agreement requires using a range of saturation factors: 0.1≲f≲0.3. The validity of the model is discussed.Juan Ramón Sanmartín LosadaRafael Ramis AbrilJosé Luis Montañés GarcíaJavier Sanz Recio2010-02-15T13:01:50Z2016-04-20T12:02:13Zhttp://oa.upm.es/id/eprint/2284This item is in the repository with the URL: http://oa.upm.es/id/eprint/22842010-02-15T13:01:50ZDevelopment of a mathematical model of thermal decomposition of hydrazine in a engineAn overall chemical kinetics for the decomposition of
hydrazine has been found for temperatures near 800°K and
1000°K which can be used in the gas-dynamic equations of the
engine when the mechanical or residence time of the engine
is large compared with the radicals relaxation time. This
overall kinetics is used for an steady state analysis using
the approximation of perfectly stirred reactor, for times both shorter and larger than the time for wall temperature to reach a steady condition; the validity of these approximations is studied. An alternative plug flow model in which heat is conducted upstream by solid bars is analyzed. In the last chapter a review is made of the results and criteria useful for the experimentalist interested only in the application of the conclusions of this report.Juan Ramón Sanmartín LosadaEnrique FragaAmable Liñán MartínezAntonio Crespo Martínez2010-02-15T12:58:25Z2016-04-20T12:02:15Zhttp://oa.upm.es/id/eprint/2285This item is in the repository with the URL: http://oa.upm.es/id/eprint/22852010-02-15T12:58:25ZIngeniería y física de plasmas : discurso del académico electo Excmo. Sr. D. Juan Ramón Sanmartín Losada, leído en el acto de su recepción pública el día 18 de junio de 1998, y contestación del académico Excmo. Sr. D. Amable Liñán MartínezNo hay resumenJuan Ramón Sanmartín LosadaAmable Liñán Martínez2009-02-21Z2016-04-20T06:48:48Zhttp://oa.upm.es/id/eprint/1378This item is in the repository with the URL: http://oa.upm.es/id/eprint/13782009-02-21ZQuasi-steady expansion of plasma ablated from laser-irradiated pelletsThe ablative, quasi-steady expansion of the spherical coronal plasma produced by irradiating an overdense pellet by a high-intensity laser pulse, is studied for large ion charge number Z;. The entire structure of the flow and its changes as the laser power is increased, are determined. The instantaneous power W required to generate a given ablation pressure Pa and pellet radius rB at any time is determined in terms of Z,-, ion mass m,, and critical density; the mass ablation rate is also found. If the time law PB {t) and (consequently) ra {t) for a desired optimal compression of the pellet are determined independently, the results allow one to obtain the laser power history W[t) = W[Ptl\t),rtt\t),Zj,ml,ne]. For a critical radius much larger than ra, most of the energy flows outward; this seems to invalidate known simple estimates of the relation W[Pa).Javier Sanz RecioAmable Liñán MartínezManuel Rodríguez FernándezJuan Ramón Sanmartín Losada