Thermal Performance of the “MERS” Recoverable Micro Satellite in Orbit

In this paper we examine the on-orbit thermal performance of a 50kg class micro satellite which has been designed to be recoverable on ground after performing a ballistic atmospheric re-entry. What makes “MERS” – the Microgravity Experiment Recoverable Satellite – unique is that it essentially a small re-entry vehicle which must function as a LEO satellite for most of its mission. Following a period spent in Low Earth Orbit conducting microgravity experiments, the entire spacecraft re-enters the Earth’s atmosphere and completes a hard-landing on the ground. The external shape of the spacecraft and its need for a heat shield are driven by the very demanding aerothermal requirements of the final, re-entry portion of the mission. In addition, a novel internal structure is needed to enable the payload modules to survive the hard-landing. These three factors heavily influence the on-orbit thermal design, which is the main focus of this paper. The highly insulating (ablative) heat shield makes the thermal performance on orbit challenging, as heat must be rejected at various times during the mission. Initial assessments of the system were presented at ICES in 2015. Now a more detailed analysis of the on-orbit scenario is presented, based on recent test data and evolution in the design of the internal, impact-absorbing structure. One of the key design challenges for the thermal subsystem was previously identified to be the leeward heat shield, which must - counter-intuitively - be able to function as a radiator while the satellite is in orbit. Results of the extensive thermal analysis and bread-board testing will be presented.