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When designing a rocket engine, what degrees of freedom do you have to get the combustion chamber to a desired pressure? I assume you have mass flow rate, type and mixture ratio of fuel and oxidizer, and geometry, but what aspects of the geometry matter?
With a given geometry, is there a way to calculate the minimum pressure to cause choked flow at the nozzle?
The combustion chamber is typically designed to ensure the combustion reaction goes to completion. This is often thought of in terms of characteristic length (L*). Where L* is equal to chamber volume / throat area. In practice, the smallest L* that will allow complete combustion can be found experimentally by measuring chamber temperature and characteristic velocity for different chamber lengths.
