相似則に基づいた火星衛星探査機の着陸挙動における模型実験

抄録

The Martian Moons eXploration (MMX) mission to be launched on 2024 by JAXA aims to send a spacecraft towards the Martian moon and to land it on the surface of the Phobos. One of the most critical phase on the mission is the landing phase of the spacecraft since an impact force at the landing may damage the spacecraft. This paper describes a landing dynamics analysis of a Martian moon lander. The analysis exploits a similarity rule to correlate a lander dynamics with a model experiment. Since the gravitational acceleration of the Martian moon is much smaller than that of the earth, the gravity term in the similarity rule is explicitly considered when model experiments are carried out to estimate the impact force. The drop experiment apparatus developed in this work has a 1.8-meter-long linear motion guide placed vertically, and the model of the spacecraft freely falls along with the guide. The velocity of the model can be arbitrarily given by putting the model at an appropriate initial height which satisfies a basic physics of the free-fall equation. A laser displacement sensor measures the vertical displacement of the model, and therefore, an impact acceleration of the model at the landing phase can be estimated as a 2nd-order time derivative of the displacement. An impact force applied to the real spacecraft is then estimated from the impact force of the model experiment based on the similarity rule. The drop test were performed with varied model velocity and model mass. The experimental result clarifies that the impact force and landing velocity has a positive correlation one another.