Flame spreading over solid fuels at microgravity conditions. Results obtained in the minitexus rocket and future programmes

Abstract

The problem of fires in spacecraft is briefly commented, pointing out that they still are a high safety risk in long endurance manned missions. It is pointed out that the basic process of a fire is the combustión of a solid fuel in an 02 N2 mixture, and that this basic process is not yet well understood. The research programme presented in this paper is a contribution in this field. Experimental results obtained on fíame spreading in the MiniTexus rocket are shown. These experimental programmes have been sponsored by the European Space Agency (ESA). Ignition and fíame spreading over hollow PMMA cylinders in O2 N2 mixtures against a forced flow with velocities ranging from zero up to 20 cm/s at zero and at 45 * incidence angle are presented and discussed. Special attention is given to the región of very small flow velocities (0-5 cm/s), in which the fíame extinguishes or becomes non visible in the optical range if the fuel is thick or the oxygen concentration is not high. The existence of these flames for a relatively long time have been clearly detected in the MiniTexus experiments. The observations of these flames and their theoretical treatment present special difficulties, which are discussed in the paper. Future programmes to be carried out in the MiniTexus, already approved by ESA are shown, as well as the possible extensión of these research programmes, with the possibility of being carried out in space laboratories.