Rocket Engine, Liquid Fuel, XLR-91, Second Stage, Titan I Missile

The LR91 was the second stage engine for the two-stage Titan I, which was a U.S. Air Force Intercontinental Ballistic Missile (ICBM). Titan I was conceived in 1954 to close the "missile gap" between the U.S. and Soviet Union. Although the Atlas ICBM was already under development, the USAF authorized Titan as a backup.

Developed by Aerojet-General, the LR91-AJ-1 engine produced 80,000 pounds of thrust and had a burn time of 160 seconds. Its propellants were liquid oxygen and RP-1, a type of kerosene. The LR91 featured a turbopump, a regeneratively-cooled thrust chamber assembly, and an asbestos-based ablative skirt. LR91 testing began in 1956.

The first successful flight of Titan I was in 1959 from Cape Canaveral. It became operational in 1962 and was deployed in five U.S. states. Because Titan II was more advanced, Titan I was deactivated in 1965.

The U.S. Air Force transferred this engine to the Smithsonian in 1969.