The LR87 was a "fixed-thrust" engine, that was first flown in 1959 and was used to launch Titan II missiles. This engine used Aerozine-50 nitrogen tetroxide fuels, which are storable at room temperature and can remain in their tanks for long periods. This gave Titan II missiles quick launch capability, an important feature when responding to a threat. The LR87 was also used to power launch vehicles for the Gemini manned spacecraft program. (Flight-Ready Artifact)