First Results of Testing the Re-entry Thermal Design of the “MERS” Recoverable Micro Satellite

This paper presents a more detailed look at the thermal performance during re-entry of the “MERS” recoverable micro satellite, whose preliminary thermal design was reported at previous ICES conferences in 2014 and 2015. “MERS” – the Microgravity Experiment Recoverable Satellite - is a very unique LEO spacecraft which, following a period spent conducting microgravity experiments in Low Earth Orbit, must re-enter the Earth’s atmosphere and complete a safe landing on the ground. Because the entire spacecraft undergoes re-entry, the very demanding aerothermal requirements of this portion of the mission strongly drive its external shape. Thus, MERS is essentially a small re-entry vehicle which must function as a LEO satellite and this brings some unusual thermal design challenges. This paper presents the results of arc tunnel testing which was carried out in September 2015 at the JAXA facility in Tokyo on representative MERS heat shield models using a new, light-weight ablation material, known as “LATS”. The subsequent analysis of these results allows greater confidence in the prediction of the internal temperatures which will be reached inside the MERS satellite during and after it has re-entered the Earth’s atmosphere and returned its scientific payload. In addition, a qualitative examination of the behaviour of solar cells mounted within the heat shield was made in the arc tunnel and these results will be presented in the paper. Not only is a knowledge of the heat shield performance essential for the re-entry, but both its mass (thickness) and thermal insulating performance have important impacts on the system design and the thermal behaviour on-orbit since, as has been presented in previous papers, the spacecraft relies on utilising the leeward heat shield as a thermal radiator during nominal on-orbit operations.