The LR105 is a liquid-fuel rocket engine that served as the sustainer engine for the Atlas rocket family. Developed by Rocketdyne in 1957 as the S-4, it is called a sustainer engine because it continues firing after the LR89 booster engines have been jettisoned, providing thrust during the ascent phase.
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This article is an automated import of the Wikipedia article "LR105", available at https://en.wikipedia.org/wiki/LR105 . Text is licensed under CC BY-SA 4.0.