Microgravity experiments of sampling and landing technologies for Martian Moons eXploration(MMX) in ZARM Drop Tower

Martian Moons eXploration(MMX) is a sample return mission under study in JSEC(JAXA Space Exploration Center)/JAXA to be launched in 2020s. MMX probe will land on and stay a Martian moon surface and collect samples from it. The gravity of the Martian moons is almost two thousandth part of Earth's gravity and it relatively large as compared to the past-investigated small bodies. The development of sampling and landing systems is a critical issue for achieving MMX mission. The corer mechanism is adopted for the MMX sampler because the requirement for sample collection volume of MMX is 100 times larger than HAYABUSA 2(100mg). A cylindrical corer is ejected and stores regolith including the sub-surface. In addition to that, the landing system development for MMX is also a critical issue for preventing an anomaly landing, which readily causes an incident such as a mechanical rupture and a mission failure. Especially, microgravity influences resistive force onto footpad and liquid sloshing in the probe's fuel tank. These key technologies need to be verified on how to design and how it works under microgravity. However, it is difficult to establish an analytical solution in terms of granular or liquid material behavior which are completely different under microgravity conditions. Therefore, we conducted three experiments related to the critical issues of MMX by using ZARM drop tower. (1) The corer mechanism verification under microgravity (2) Resistive force estimation for the landing footpad design (3) Sloshing behavior observation in a propellant tank when the probe lands on the surface While the capsule in which the corer installed drops, the stuck behavior into the sand under vacuum and microgravity environment was observed with a high-speed camera. Following similar experiments, parameters for landing gear design which is based on the resistive force theory were also measured. The liquid motion in an acrylic tank which was applied motion to mimic the landing was observed and verified the numerical simulation.