Modeling of the Space Shuttle solid rocket motor nozzle boot cavity pressurization process

Abstract

Pressurization of the Space Shuttle solid rocket motor (SRM) nozzle boot cavity involves compressible gas flow along a duct with friction and a pressurizing volume with heat transfer at the boundaries. Numerical simulation of the process requires a solution of the simultaneous compressible flow, boot cavity conservation, and solid-conduction equations. Basic geometry consists of circular flow path connected to a plenum-free volume that is surrounded by a solid-conduction media (i.e., the cowl vent holes, boot cavity, and cavity insulation). An existing methodology is used to compute the compressible mass-flow rates through the vent hole. Boot cavity conditions are computed by the application of a finite-difference form of the conservation equations. In the boot cavity insulation (i.e., the solid-conduction regions), the finite-difference transient diffusion equation is applied. A conjugate solution is developed whereby the coupled first-order differential equations are solved simultaneously, along with a set of algebraic equations, by fully implicit successive point iteration. A model was constructed to simulate a boot cavity pressurization test, and a comparison of model response vs test data is given. The agreement is generally good.