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Reaction Motors XLR11 Rocket

DAYTON, Ohio -- Reaction Motors XLR99 rocket engine at the National Museum of the United States Air Force. (U.S. Air Force photo)

DAYTON, Ohio -- Reaction Motors XLR99 rocket engine at the National Museum of the United States Air Force. (U.S. Air Force photo)

The XLR11 was the first liquid-fuel rocket engine developed in the United States for use on airplanes, and it had a long career powering important research aircraft. An XLR11 engine powered the first airplane to break the speed of sound, the Bell X-1, in 1947, and also powered other X-1 models. XLR11s also flew in the X-24A and X-24B lifting bodies and other vehicles including the record-breaking X-15s, which used two XLR11 engines mounted together during their early flights.

The XLR11, also known early in its career as the LR11, delivered a total of 5,900 pounds of thrust. It featured the ability to stop and restart its four individual chambers, but the engine was only “on-off” and not throttleable like the later XLR99 on display nearby. The engine’s propellants were liquid oxygen and a mix of water and ethyl alcohol. A pressurized system delivered propellants to the engine in early versions; later versions used turbopumps. Like later engines, the XLR11 circulated fuel around its thrust chambers to cool them before the fuel was burned.

5,900 lbs. (1,475 lbs. in each of four chambers)
Propellants: Ethyl alcohol and water fuel and liquid oxygen oxidizer
Weight: 345 lbs. including turbopump

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Bell X-1B
Republic XF-91 Thunderceptor
North American X-15A-2
Reaction Motors XLR99 Rocket Engine
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