I'm trying to teach myself some of the content from 'Rocket Propulsion Elements' by George P. Sutton.

After reading over the first couple of chapters feeling like I understood everything, I came across this question and am completely stumped. I only just completed high school so I am not sure if there is some required knowledge I don't have, or if I'm just missing something.

Other than a thought that maybe the fluid weight flow rate is related to the density for dynamic pressure, I haven't got far.

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1 Answer 1


So within 2 minutes of posting this I think I have the answer, and it turned out to be incredibly simple. I guess I've just been out of it for some time :)

The exit area is constant so: The density multiplied by velocity gives us the mass flow rate. Substituting this result into the equation for dynamic pressure shows us the the dynamic pressure is equal to half the mass flow rate multiplied by the 'exhaust' velocity.

We also know the the thrust produced is the mass flow rate multiplied by exhaust velocity, though this time we don't half it, so evidently the thrust is twice as big as the dynamic pressure.

  • 2
    $\begingroup$ Happy you found your answer yourself. Might I recommend that you add the equations - it will make this answer more useful for future visitors. Thanks! $\endgroup$
    – Floris
    Commented Feb 4, 2015 at 13:11

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