Cubic rovers that traverse by hopping systems are promising in low-gravity environments. Although several analyses of the control methods and mobility of the cubic rover are available, investigations of its attitude-adjusting behavior are still limited. This study derives the dynamic equations of the two attitude-adjusting modes of the cubic rover, referred to as walking and twisting. The relationships between the speed threshold and rotation angle of the cubic rover were investigated in both rigid and regolith environments using a self-designed low-gravity testbed. Comparative studies were conducted by considering the experimental and simulated outputs. The results of this study can be interesting for roving mission planning when exploring planetary moons and small celestial bodies.

The set of the orbital angular-momentum reversal, or $H$-reversal, sailcraft trajectory was born as a type of unconventional precursor interstellar mission trajectory by using high-performance solar sails. Starting from an outline of the $H$-reversal sail trajectory, this paper mainly focuses on the 2D reversal-mode solution to the general solar-photon sail motion equations. The feasible region for $H$-reversal trajectories in fixed sail attitude angles is illustrated. Some interesting applications of the $H$-reversal trajectory are presented in detail to show its advantages. As a special case, a precursor interstellar probe can be delivered with a constant sail orientation in the $H$-reversal trajectory to be compared with the direct-motion sail flyby of the Sun. Of importance are the heliocentric periodic orbits in double $H$-reversal modes, obtained via both fixed and time-varying sail attitude angles. Two more applications involving $H$-reversal trajectories are discussed in terms of asteroid deflection and transfer trajectory to rectilinear orbits. Finally, some items of the mathematics behind the 3D motion-reversal trajectories are summarized.

Periodic orbits in irregular gravitational fields are significant for an understanding of dynamical behaviors around asteroids as well as the engineering aspect for deep space explorations. The rotating mass dipole, referred to as the Chermnykh problem, is a good alternative model to study qualitative dynamical environments near elongated asteroids, like the asteroid 1620 Geographos, 216 Kleopatra, or 25143 Itokawa. In this paper a global searching method is adopted to search for periodic orbits around the dipole model based on the concept of Poincaré section of surface. Representative families of periodic orbits are illustrated with respect to all three topological cases of the dipole model. Topological transitions of orbits during iso-energetic continuations are also presented as well as identification of new types of periodic orbits.