Proximity Aerodynamics Analyses for Launch Abort

Analyses of drag variation with vehicle proximity are performed for two different launch abort systems for NASA’s Crew Launch Vehicle: a scaled-up Apollo tractor concept and a side-mounted rockets concept. The results are used to assess the abort capabilities of new crew escape systems. With the complex flow physics involved in the separation of the escape vehicle from the Service Module, both inviscid and viscous simulation methods, under nozzle thrust-on and thrust-off conditions, are evaluated for their ability to predict the axial forces during an ascent abort scenario. Also, the predictive capability of timeaccurate simulations involving prescribed and coupled six-degrees-of-freedom motion are investigated in this study. Comparisons are made with wind tunnel data from the Apollo program.