Case Study of Meteoroid Fluence on a Mars Sample Return Mission

The Mars Sample Return Campaign must satisfy a Back Planetary Protection requirement that limits the risk of biological contamination of the Earth by Martian microbes. The Earth Re-turn Orbiter (ERO), being developed by the European Space Agency (ESA), will carry a Capture, Containment and Return System (CCRS), which is being developed by NASA to retrieve orbiting samples (OS) from Mars orbit, surround them with two containment layers to create a Contained OS (COS), and transfer the COS to the Earth Entry System (EES), which will be re-leased by ERO to carry the samples through entry, descent and landing at the Utah Test and Training Range. Micrometeoroid impact damage to the Thermal Protection System (TPS) of the EES, which may occur at any time in the ERO mission, is recognized as a potential risk driver for loss of sample containment that needs to be rigorously assessed. A Micrometeoroid Protection System (MMPS) will be implemented to limit that risk. The MMPS consists of a shield covering the TPS called the Micrometeoroid Garage (MMG) and a system of cameras to inspect the TPS. An extensive study was performed by the CCRS Project in collaboration with the NASA Engineering and Safety Center (NESC)to assess the probability of damage to the MMG and TPS by meteoroids over the entire ERO mission. This included the computation of the meteoroid fluence on the MMG and directly on the TPS after EES separation, and assessment of damage to the MMG and TPS via hypervelocity impact tests, hydrocode simulations, and empirical damage prediction and ballistic limit equations (BLEs). The focus of this paper is the meteoroid fluence on the MMG.