Effect of Turbulence Modeling on Overexpansion and Flow Separation in RCS Thruster Nozzle Extensions in Typical Crew Module Configurations

EasyChair Preprint no. 11173

Abstract

This paper investigates the aerodynamics of combusted plume gases in RCS thruster nozzles with extensions in a typical crew module firing at three identified altitudes (at Za = 30km, 14km and 7km) using CFD. Two thruster configurations of different nozzle extension lengths (Le = De and 3De) are examined for flow separation and effective thrust, and inferences are drawn based on flow dynamics. Whereas nozzles with Le = De are able to generate over 95% of the expected thrust at 30 and 14km, for Le = 3De, it drops to about 92% at 30km and 90% at 14km. At 7km, the thruster with Le = De shows a thrust reduction of around 12%, and it drops by a remarkable 45% for Le = 3De. Such decrease is attributed to boundary layer separation within nozzle extensions due to overexpansion, which depends on the ratio of thruster combustion chamber pressure to ambient pressure, as well as scarfing of nozzle extensions. This paper documents the different flow features in RCS thruster nozzle extensions during their firing at different altitudes in a typical crew module configuration, and compares thrust estimates from using the k-omega SST and RNG k-epsilon turbulence models.

Keyphrases: Crew module RCS thruster, Nozzle overexpansion, Turbulence modeling of flow separation

@Booklet{EasyChair:11173,
  author = {Susheel Kumar Sekhar and Deepak Kumar Agarwal and T. John Tharakan and S. Sunil Kumar},
  title = {Effect of Turbulence Modeling on Overexpansion and Flow Separation in RCS Thruster Nozzle Extensions in Typical Crew Module Configurations},
  howpublished = {EasyChair Preprint no. 11173},

  year = {EasyChair, 2023}}