SSME Streamtube Evaluation Program (SSTEP)

An analytical model of the Space Shuttle Main Engine (SSME) called SSME Streamtube Evaluation Program (SSTEP) has been developed based upon the assumption that the propellant flows through the main combustion chamber can be represented by a bundle of parallel streamtubes. The motivation for the development of SSTEP lies in the desire to gain a basic understanding of the engine performance effects of several common SSME hardware modifications. Specifically, this model has been used to evaluate the changes in performance due to boundary layer coolant hole enlargement, LOX post plugging, acoustic cavity elimination, baffle removal, and main combustion chamber coolant leakage. The results show a good general agreement with the available test data suggesting at least a qualitative agreement between SSTEP modeling and actual engine performance. Through the use of several adjustment factors, which represent relaxations of the SSTEP formulation assumptions, it is shown that the test data can be very closely matched and that SSTEP can be used as a performance prediction tool.