The LR87 was an American liquid-propellant rocket engine used on the first stages of Titan intercontinental ballistic missiles and launch vehicles.

For each thrust chamber assembly, a single high-speed turbine drove the lower-speed centrifugal fuel and oxidizer pumps through gearing, a configuration designed for high turbopump efficiency.

For the Titan II, the engine was converted to use Aerozine 50 and nitrogen tetroxide, which are hypergolic and storable at room temperature.

This allowed Titan II missiles to be kept fully fueled and ready to launch on short notice.

Thrust and nozzle area ratio were progressively increased, requiring heavier turbopumps, pipes, and other parts.

[citation needed] The LR87-3 was also operated with NTO/Aerozine 50 and ground tested with LOX/H2 (with a new fuel pump), making it one of very few engines to have been run on three different propellant combinations.

[3]: 381  The engine was generally lighter and simpler than its predecessor, partly due to the use of hypergolic propellants, which do not need an independent ignition system.

The engines also had simpler controls, solid-propellant cartridges to start the turbopumps, simplified injectors, and autogenous pressurization, replacing the heavy tanks of cold helium gas.

[3]: 381  The performance was similar to the previous version, only reducing the chamber pressure and nozzle thrust to meet human-rating requirements.