XLR

USAF Experimental Liquid Rocket Engine

XLR engines were experimental engines powered by liquid fuels. The XLR and manufacturer serials are combined into a single Air Force designation.

The Reaction Motors XLR10 (XLR-10-RM-2 / 20K) LOX/Alcohol engine powered the Viking rocket. Its XLR11 (XLR-11-RM-5) flew on the Bell X-1 rocket plane helping it to break the sound barrier. The XLR11-RM-13 was temporarily used on the North American X-15 rocket plane, before being replaced by the LOX and Ammonia fueled XLR99 (XLR-99-RM-2) which would help it cross the Kármán line.

The Curtiss-Wright XLR25 (XLR-25-W-1) powered the Bell X-2 Starbuster experimental aircraft, which was fueled by LOX and Alcohol.

The Rocketdyne XLR43 (XLR-43-NA-1 / 75K) LOX/Alcohol engine, and its XLR71 and XLR83 (240K & 405K) derivatives powered the Navaho missile, based on the V-2 engine. It would further develop into the NAA 75-110 A-series of engines for the Redstone rocket.

The Bell XLR81 was fueled by unsymmetrical dimethylhydrazine (UDMH) and red fuming nitric acid (RFNA). The XLR81 model 8084 powered the Agena-A which flew first in 1959, followed in 1960 by model 8081 on the Agena-B, with the Agena-D as the final development with the XLR81 model 8096. The XLR-81-BA-13 or model 8247 was the engine used on the Gemini-Agena Target Vehicle (GATV) and the Ascent Agena. It was further developed into the Lunar Module Ascent Engine (LMAE) for the Apollo Lunar Module.