Parametric Study of Peripheral Nozzle Configurations for Supersonic Retropropulsion

摘要

With sample-return andmannedmissions on the horizon forMars exploration, the ability to decelerate high-massnsystems to the planet’s surface has become a research priority. This paper explores the use of supersonicnretropropulsion, the application of jets facing into the freestream, as a means of achieving drag augmentation.nNumerical studies of retropropulsion flows were conducted using a Cartesian Euler solver with adjoint-drivenmeshnrefinement. After first validating this simulation tool with existing experimental data, a series of three broadnparametric studies comprising 181 total runs was conducted using tri- and quad-nozzle capsule configurations.nThese studies chronicle the effects of nozzle location, orientation, and jet strength over Mach numbers from two toneight and angles of attack ranging from u00015to10u0002n. Although many simulations in these studies actually producednnegative drag augmentation, some simulations displayed local overpressures 60%higher than that possible behind annormal shock and produced drag augmentation on the order of 20%. Examination of these cases leads to thendevelopment of an aerodynamicmodel for significant drag augmentation inwhich the retrojets are viewed as obliquenshock generators and flow approaching the capsule face is decelerated and compressed by multiple oblique shocks.nBy avoiding the massive stagnation pressure losses associated with the bow shock in typical entry systems, thisnapproach achieves significant overpressure on the capsule face and strong drag amplification.With a fundamentalnphysical mechanism for drag augmentation identified, follow-on studies are planned to exploit this feature and tonunderstand its impact on potential entry trajectories and delivered mass limits for future Mars missions.