# How to calculate rocket thrust? [closed]

I’m trying to calculate the thrust of a theoretical rocket (for a simulator). The formula I’m using is F = pVeA . I can get the exhaust density by using the gas formed during combustion and then volume of the rocket but I’m having trouble getting the exhaust velocity.

## closed as off-topic by ACuriousMind♦Mar 22 '18 at 23:17

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• Please note that homework-like questions and check-my-work questions are generally considered off-topic here. We intend our questions to be potentially useful to a broader set of users than just the one asking, and prefer conceptual questions over those just asking for a specific computation. – ACuriousMind Mar 22 '18 at 23:17

## 1 Answer

If you know the temperature $T$ of the exhaust gases as they exit the nozzle, then you can make the following rough approximation for the exhaust velocity:

$$\frac{3}{2}k_B T = \frac{1}{2}mv_e^2$$

where $k_B$ is the Boltzmann constant, and $m$ is the mass of an individual gas molecule. This assumes that the exhaust gases are ideal and in equilibrium, both of which are pretty bad assumptions in this case, so the value you get shouldn't be taken as more than a rough guess.