Rocket Engine Combustion Chamber Equations

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Discussion Overview

The discussion revolves around the equations and design considerations for rocket engine combustion chambers and De Laval nozzles. Participants explore the complexities involved in the design process, including dimensions and specific parameters related to combustion efficiency.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks equations for designing combustion chambers and nozzles but notes difficulty in finding specific dimensional guidelines.
  • Another participant expresses skepticism about the simplicity of using equations for design purposes, suggesting that the process may be more complex.
  • A third participant provides a link to an article on nozzle design and mentions NASA's use of a program called RAMP for analyzing nozzle designs, implying that proprietary codes may also be in use by other organizations.
  • One participant asserts that there are established equations for combustion chamber design, emphasizing the relationship between the chamber's length and diameter and the nozzle.
  • A participant shares specific parameters for the Space Shuttle Main Engine (SSME), including area ratio, chamber pressure, engine mixture ratio, and dimensions, suggesting these could serve as a reference for design considerations.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the simplicity of the design process. While some assert that equations exist for proper design, others question the feasibility of relying solely on these equations without considering additional complexities.

Contextual Notes

Participants mention specific parameters and references related to the SSME, but the discussion does not resolve how these parameters should be applied or whether they are universally applicable to all rocket engine designs.

Who May Find This Useful

Individuals interested in rocket propulsion design, engineering students, and professionals in aerospace engineering may find this discussion relevant.

FiggyOO
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Good evening all,

I was wondering if anyone would be able to point me in the right direction to equations in regards to designing a proper combustion chamber for a rocket engine, as well as for the throat/De Laval nozzle as well. I've looked around and I can't seem to find anything that covers the actual dimensions of the chamber.
 
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I don't think things are just as easy as using equations & feeding numbers for designing purpose.
 
This might be useful.

http://www.pwrengineering.com/articles/nozzledesign.htm


NASA Marshall used a program called RAMP to analyze nozzle designs. I would expect Rocketdyne (now part of United Technologies/Pratt & Whitney) used their own proprietary code.

Search Google or other search engine with "SSME","nozzle"

The SSME uses an H2-rich mixture.

AIAA has a number of books on propulsion, including some description of combustion chambers, throats, and nozzles.
 
Last edited by a moderator:
Thanks, I know there are equations to make a proper combustion chamber though. I know that the chamber needs to be a certain length and diameter in relation to the nozzle.
 
One could take a cross-section and simply plot diameter or radius of nozzle as a function of distance from throat.

For SSME -
Area Ratio: 69:1
Chamber Pressure: 2,994 psia
Engine Mixture Ratio: 6.0 (IIRC, mass O2/mass H2)

Dimensions
Length: 168 in.
Diameter: 96 in.

http://www.enginehistory.org/SSME/SSME1.pdf
 
Last edited by a moderator:

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