# Calculate Exhaust Velocity

#### garyw

Moderator
Tutorial Publisher
Hi All,

Can anyone tell me how you'd get the exhaust velocity for a multistage rocket? The only thing I can see in the multistage files is the thrust in newtons so, how can I get the exhaust velocity from that?

Thanks all!

#### Linguofreak

##### Well-known member
I assume the files must have a fuel fraction somewhere. Do they have a burn time?

And when you say "multistage" I assume you mean the old multistage.dll, rather than any old rocket with more than one stage, real or simulated?

#### Urwumpe

##### Not funny anymore
Donator
You can't get it from the (vacuum) thrust alone, you also need the fuel consumption there. For example, if you know propellant mass and burn time, you can estimate the average fuel flow for that stage.

The relation is $F = w \cdot \dot{m}$ for the thrust (F). Or $w = \frac{F}{\dot{m}}$ for the exhaust velocity (w).

#### garyw

Moderator
Tutorial Publisher
And when you say "multistage" I assume you mean the old multistage.dll, rather than any old rocket with more than one stage, real or simulated?

Yes, the old multistage.dll - sorry, I should have made that clear.

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