Kevin R. Housen

The unusual dynamical environment of Phobos and Deimos

Abstract The nonintuitive dynamical environment of Phobos and Deimos is explored using a three-dimensional numerical model. Surface gravity, escape speeds, and ejecta impact contours are calculated, both for the satellites at their present orbit distances and for orbit distances they may have had in the past. Impact loci for Stickney ejecta are computed and compared with the observed groove locations in order to evaluate a possible secondary impact origin for the grooves on Phobos. Possible effects of the dynamical environment on shaping the satellites surfaces are discussed.

Experiments and Analysis of Orbital Debris Shock-Induced Penetration of Pressure Vessels in Space

An experimental technique developed by Schmidt et al. (1994), for simulating the response of single-bumper aluminium debris shields at impact velocities up to 18 km/s, is extended here to the case of double-bumper shields. The aluminium impactor and bumper(s) of interest are replaced with cadmium surrogates that have the same dimensions as the prototype, but have melt and vaporization specific energies an order of magnitude lower. Dimensional analysis is used to show that these lower specific phase transformation energies are the key to simulating impact velocities that are a factor of 3.1 higher than previously attained. The particular uniqueness of cadmium is that, by coincidence, its density is a factor of 3.1 greater than aluminium, thereby reproducing the initial momentum of an aluminium projectile and the impulse distribution delivered by the debris cloud to the pressure hull wall. The tests reported here investigate the behavior of a double bumper shield at both normal and 45° angles of incidence.