Dust, a risk for LUNAR and Asteroid surface operations: how sticky is the reality?

Kurzfassung

The Moon and small asteroids are the targets for a multitude of landed missions in the near future. The fine, very rough and abrasive lunar dust was an issue in the Apollo lunar missions, while limited data exist for asteroid landing craft. Small, regolith-covered bodies (our example is Phobos, the target of the MMX mission with rover IDEFIX provided by DLRCNES) have so low surface gravity that the granular Bond number, the ratio of adhesion force to weight could become >>1 even for large pebbles. We reviewed the conventional, notionally physics-based models of dry adhesion of granular media and found them not applicable to rough, irregular, polydisperse particles that make up real regolith on planetary bodies, moons and asteroids. We use a new theory of the co-/adhesion a of granular media consisting of rough, irregular grains [1] and apply it to common problems, e.g. which particles stick on a vertical, horizontal plate, which acceleration (e.g. by vibration) can remove sticking particles from said surfaces, and how to calculate the trajectories of particles catapulted from, say, a regolith-covered shutter which is opened by a spring mechanism. The regolith grains can be mechanical polycrystalline or amorphous aggregates of constituent pure silicate minerals and from technical surfaces only the surface material and the surface roughness is needed. Practical operation planning, e.g. the sequence of opening camera shutters or the solar arrays, or maximum driving speed, depend on answers to these questions: a contamination of optical surfaces, radiators, solar array surfaces or critical system sensors (sun sensor!)