Analysis of tether-mission concept for multiple flybys of moon Europa

Abstract

All 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.