Physics-Based Model for Predicting Jet Plumes in Supersonic Retropropulsion

Supersonic retropropulsion (SRP) is an enabling technology for human missions to Mars and other planetary bodies, as existing parachute systems cannot provide sufficient deceleration for human-scale payloads. SRP is the use of rockets to decelerate a spacecraft by exhausting in the opposite direction of its descent. We present a physical model that predicts the boundary of a high-thrust and underexpanded single-jet plume in blunt penetration mode at zero angle of attack, which is then used in a control-volume analysis to predict the deceleration force caused by the impingement of the freestream flow on the spacecraft heatshield. The jet plume model is based on the axisymmetric method of characteristics and accounts for the post-bow-shock pressure and Mach disk location on the jet plume boundary. This model considers effects of stagnation pressure in the recirculation region for which we add a pressure deficit term in the force computation. Results demonstrate improved accuracy in predicting jet plume boundaries and force, under various operating conditions compared to existing analytical methods. Our method offers an improved low-order physics-based approach that aids in performing rapid analyses of SRP quantities of interest, thus adding to the engineering methods for designing entry, descent, and landing architectures.