# Aerospace Critical Velocity?

1. Apr 22, 2004

### Xishan

Critical Velocity???

I've often come up with the term C* also called 'Critical Velocity' in rocketry. Is there any physical significance attached to this term or its just a name given to a combination of some constant terms?

2. Apr 22, 2004

### enigma

Staff Emeritus
It's the characteristic velocity, not the critical velocity

The characteristic velocity is a way to measure engine performance independant of the exhaust nozzle.

It is defined as:

$$c*=\frac{A_t * p_0}{dm/dt}$$

where
At is the area of the throat,
p0 is the chamber pressure
dm/dt is the mass flow of the propellant.

3. Apr 23, 2004

### enigma

Staff Emeritus
Just wanted to add:

With a lot of re-arranging, it is a (complicated) function of gamma, the molecular mass of the combustion products, and the flame temperature.

4. Apr 23, 2004

### Xishan

yes ofcourse! I meant 'characteristic velocity' rather than 'critical velocity' and thanks for the brief but still good explanation