Distributed Guidance for Flexible Spacecraft Landing on Asteroid

For the microgravity asteroid, even small residual impact energy may cause the spacecraft to bounce and overturn, triggering unexpected events. To suppress the rebound and overturn, a flexible spacecraft concept has been proposed. Nevertheless, a strong coupling exists between the rotational and translational dynamics of the flexible spacecraft. In this paper, a distributed guidance law is developed to control the overall flexible spacecraft's orbit and attitude motion simultaneously through the coordination of the motion of mass blocks. The composite motion of mass blocks can approximate the overall motion of the flexible spacecraft, and the relative height difference of mass blocks can also reflect the attitude of the flexible spacecraft. Therefore, the working principle of the integrated translation and rotation distributed guidance scheme is that each localized controller cooperates to adjust the relative height difference and composite motion of mass blocks. To qualitatively characterize the effort required to adjust the relative altitude difference, a pseudo-attitude control effort index is derived, which is a function of the relative altitude difference. By weighting the attitude control effort index into the minimum orbit control efficiency index, an analytical distributed guidance law is obtained, which guarantees the near-fuel optimality. Monte Carlo simulations show that the attitude requirement of the flexible spacecraft can be realized during landing.