Figure 1: Space Shuttle Main Engine (SSME)^[89]

Space Shuttle Main Engine Computational Model

At its most fundamental level, the Space Shuttle Main Engine (SSME) can be thought of as a large water nozzle. It is governed by a single chemical reaction:

$$2H_2+O_2⟹2H_{2}O$$

The engine produces thrust by converting the chemical energy contained in cryogenic hydrogen and oxygen to kinetic energy in the form of high-velocity water vapor. This website establishes a computational model to trace the thermodynamic properties of these propellants as they flow through the components of the SSME. The overall results of this analysis are presented in Section 1. Section 2 contains all of the mathematical background required to predict the thermodynamic states of liquid hydrogen, liquid oxygen, and their associated high-temperature combustion products without relying on expensive commercial software like NIST RefProp. Section 3 provides all of the resources necessary to code an $H_2/O_2$ combustion model that produces results very comparable to NASA’s Chemical Equilibrium With Applications (CEA) program. Section 4 builds upon these results to predict the mass flow rates and power required to drive the SSME’s network of turbomachinery. Sections 5 and 6 describe a procedure for conducting a coupled heat transfer analysis in the SSME regenerative cooling circuit, similar to NASA’s Rocket Thermal Evaluation (RTE)^[87] and Two Dimensional Kinetics (TDK)^[88] codes.

The results of the model developed here predict the SSME’s specific impulse, thrust, and maximum hot-wall temperatures to within 2% of values reported by Boeing and Rocketdyne. This model does not rely on any commercial Computational Fluid Dynamics (CFD) software, and converges to a solution on a modest single-core processor in approximately 30 seconds.

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