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

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Discussion Overview

The discussion revolves around the term C*, often referred to as 'Critical Velocity' or 'Characteristic Velocity' in the context of rocketry. Participants explore whether C* has physical significance or if it is merely a nomenclature for a combination of constants related to rocket engine performance.

Discussion Character

  • Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions the physical significance of the term C*, suggesting it may just be a name.
  • Another participant clarifies that C* is actually the characteristic velocity, which measures engine performance independent of the exhaust nozzle.
  • A further contribution indicates that C* can be expressed as a complex function involving gamma, the molecular mass of combustion products, and flame temperature.
  • A later reply acknowledges the correction from 'critical velocity' to 'characteristic velocity' and appreciates the explanation provided.

Areas of Agreement / Disagreement

Participants appear to agree on the correct terminology of 'characteristic velocity' but do not reach a consensus on the broader physical significance of C* itself.

Contextual Notes

There are unresolved aspects regarding the implications of C* in terms of its dependence on various factors such as molecular mass and flame temperature, which may affect its interpretation.

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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It's the characteristic velocity, not the critical velocity

The characteristic velocity is a way to measure engine performance independent 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.
 
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.
 
yes ofcourse! I meant 'characteristic velocity' rather than 'critical velocity' and thanks for the brief but still good explanation
 

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