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Gas-generator rocket cycle. Some of the fuel and oxidizer is burned separately to power the pumps and then discarded. Most gas-generator engines use the fuel for nozzle cooling.

The gas-generator cycle, also called open cycle, is one of the most commonly used power cycles in bipropellant liquid rocket engines. Part of the unburned propellant is burned in a gas generator (or preburner) and the resulting hot gas is used to power the propellant pumps before being exhausted overboard, and lost. Because of this loss, this type of engine is termed open cycle.

The gas generator cycle exhaust products pass over the turbine first. Then they are expelled overboard. They can be expelled directly from the turbine, or are sometimes expelled into the nozzle (downstream from the throat) for a small gain in efficiency.

The main combustion chamber does not use these products. This explains the name of the open cycle. The major disadvantage is that this propellant contributes little to no thrust because they are not injected into the combustion chamber. The major advantage of the cycle is reduced engineering complexity compared to the staged combustion (closed) cycle.

Gas-generator combustion engines include:

Rocket launch systems that use gas-generator combustion engines include:

See also


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  2. ^ "SpaceX Merlin Engine". SpaceX. Archived from the original on 2011-01-03.
  3. ^ a b "Delta 4 Data Sheet".
  4. ^ Joe Stangeland. "Turbopumps for Liquid Rocket Engines". Archived from the original on 2012-10-18.
  5. ^ "J-2X Engine".
  6. ^ a b "F-1 Engine Fact Sheet" (PDF). Archived from the original (PDF) on 2016-04-13. Retrieved 2013-04-17.
  7. ^ "RD-107". Encyclopedia Astronautica. Archived from the original on 2014-02-09.
  8. ^ Asraff, A and Muthukumar, R and Ramnathan, T and Balan, C (2008). Structural Analysis of Propulsion System Components of an Indigenous Cryogenic Rocket Engine. 44TH AIAA/ASME/SAE/ASEE JOINT PROPULSION CONFERENCE & EXHIBIT. doi:10.2514/6.2008-5120.((cite conference)): CS1 maint: multiple names: authors list (link)
  9. ^ "Falcon 9 Overview". Archived from the original on 2013-05-01.
  10. ^ "Falcon Heavy Overview".
  11. ^ "Advanced Rocket Engines" (PDF). Institute of Space Propulsion, German Aerospace Center (DLR). Archived from the original (PDF) on 2012-09-04.