The characteristic length of a engine's combustion chamber $L^*$ is defined as the ratio of the chamber volume to nozzle throat area:

$$L^*=\frac{V_{chamber}}{A_{throat}} $$

Would it be correct to say that it simply refers to the length of the combustion chamber or, should we say that it is the minimum length over which fuel and oxidizer can undergo stoichiometric combustion?

Thank you for sharing your knowledge.


1 Answer 1


From Sutton, Rocket Propulsion Elements, 4th edition, page 277:

The characteristic chamber length is defined as the length of a rocket of the same volume would have if it were a straight tube and had no converging section...

(He then shows the same equation you do in the question).

...Here the chamber is considered to include all the volume up to the throat area....Because this parameter does not consider any variables except the throat area, it is useful only for a particular propellant combination and a narrow range of mixture ratio and chamber pressure.


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