Influence of nozzle exhaust angle on supersonic retro propulsion

Abstract

Over the past few decades, humanity has been working to land astronauts on Martiansoil. Several candidate technologies and ideas are being developed around the world to counter the challenges posed by the Entry Descent Landing procedure. SRP (Supersonic Retro Propulsion) is one such idea with great potential but a very limited understanding of its working. This thesis explores the sensitivity of SRP shock geometry and standoff distance to the divergence angle of the nozzle. Four divergence angles in the range between 4 deg and 16 deg were studied. When fitted against the momentum ratio parameter ((Ie/I∞)1/2), the data points of the shock standoff distance acquired from different nozzles collapsed on lines with different slopes. For the highest pressure ratio case (Pe/P02 = 1.7), a difference of 8.1% in standoff distance was observed between the highest and lowest angle. A linear trend in slope variation was revealed when plotted against the cone exit angle. The variation in the numerical value of the slope, between the lowest and highest angle, was found to be 11.48% 5.5. At high thrusts, the flow also begins to become self-similar with respect to standoff distance normalized radius of curvature. This is shown with a collapse in the data points of the R/H plot. A 2” x 2” supersonic wind tunnel was also built and assembled during the duration of this research. The design requirements necessary for optimal working conditions of SRP were explored for this wind tunnel.