Is C* Just a Name or Does It Hold Physical Significance in Rocketry?

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In summary, "Critical Velocity" or "C*" is a term used in rocketry to refer to the characteristic velocity, which is a way to measure engine performance independently of the exhaust nozzle. It is calculated using the area of the throat, chamber pressure, and mass flow of the propellant. It is also a function of gamma, molecular mass, and flame temperature.
  • #1
Xishan
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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?
 
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  • #2
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:

[tex]c*=\frac{A_t * p_0}{dm/dt}[/tex]

where
At is the area of the throat,
p0 is the chamber pressure
dm/dt is the mass flow of the propellant.
 
  • #3
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
yes ofcourse! I meant 'characteristic velocity' rather than 'critical velocity' and thanks for the brief but still good explanation
 

1. What exactly is critical velocity?

Critical velocity is the minimum speed at which an object must travel in order to overcome the force of gravity and maintain a constant height.

2. How is critical velocity different from escape velocity?

Critical velocity is specific to a particular planet or object, whereas escape velocity is a universal value that applies to any object in the universe.

3. What factors affect the value of critical velocity?

The main factors that affect critical velocity are the mass and radius of the planet or object, as well as its distance from the center of gravity.

4. Can critical velocity be exceeded?

Yes, critical velocity is the minimum speed required to maintain a constant height. An object can travel at a higher velocity and still maintain a constant height, but it cannot go below the critical velocity without falling back to the surface.

5. How is critical velocity important in space exploration?

Critical velocity is crucial to spacecraft entering and exiting the Earth's atmosphere. For example, during launch, a spacecraft must reach and exceed the critical velocity to enter orbit, and during re-entry, it must slow down to below the critical velocity to avoid burning up in the atmosphere.

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