Analysis of the operation of vehicles in space naturally involves nonequilibrium processes due to the very low density of the atmosphere. Such high Knudsen number conditions give rise to important nonequilibrium effects affecting vehicle aerothermodynamics and rocket plume structure. The NGPDL projects in this area have some overlap with the projects in Hypersonics and Electric Propulsion but the role of the rarefied atmosphere is the key phenomenon in the research described here.