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aero_zeppelin

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## Homework Statement

A rocket nozzle is operating with a stretched out throat, (L = 50 cm and

D = 10 cm). If the inlet stagnation conditions are po1 = 1 MPa and To1 = 1500 K, determine the nozzle exit velocity and mass flow for a back pressure of 30 kPa. The diameter of the nozzle at the exit station is the same as at the inlet station: 30 cm. Treat the exhaust gases as perfect, with γ = 1.4 and R = 0.50 kJ/kg · K. Assume isentropic flow in variable-area sections and Fanno flow in constant-area sections with f = 0.22.

## The Attempt at a Solution

Before going into the actual solution, I'm getting confused with this kind of problems.

If you use the area ratio Aexit/A* = 9, then you get a Mach number at the exit of

Mexit= 3.8017 and a pressure ratio of Pexit/Po = 0.008558. If you use your actual pressures to get the pressure ratio you get Pexit/Po = 30/1000 = 0.03, which is higher than the one before.

So, does this mean that the flow is less than Mexit = 3.8017 at the exit and that there is a shockwave upstream of it?