The LR87 was an American liquid-propellantrocket engine, which was used on the first stages of Titanintercontinental ballistic missiles and launch vehicles. Composed of twin motors with separate combustion chambers and turbopump machinery, it is considered a single unit. The LR87 first flew in 1959. The LR87 was developed in the late 1950s by Aerojet. It was the first production rocket engine capable of burning the three most common liquid rocket propellant combinations: liquid oxygen/RP-1, nitrogen tetroxide/Aerozine 50, and liquid oxygen/liquid hydrogen. The engine operated on an open gas-generator cycle and utilized a regenerative cooled nozzle and combustion chamber. Later versions had additional ablative-cooled flanges. The LR87 served as a template for the LR-91, which was used in the second stage of the Titan missile. It was a fixed-thrust engine, which could not be throttled or restarted in flight. The LR87 delivered approximately 1,900 kilonewtons of thrust. Early LR87 engines used on the Titan I burned RP-1 and liquid oxygen. Because liquid oxygen is cryogenic, it could not be stored in the missile for long periods of time, and had to be loaded before the missile could be launched. 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.
Variants
LR87-3
Used on the Titan I, the LR87-3 burned liquid oxygen and RP-1. Following the retirement of the Titan missile program, these engines saw no further use. The LR87-3 was also tested with LOX/H2 and NTO/Aerozine 50 making it one of very few engines to have been run on three different propellant combinations.
Modified to burn nitrogen tetroxide and Aerozine 50 for the Titan II. The engine was generally lighter and simpler than its predecessor, partly due to the use of hypergolic propellants, which did not need an independent ignition system.
Operating parameters
Thrust : 956.5 kN
Thrust : 1096.8 kN
Specific impulse :
Specific impulse :
Burn time: 155 seconds
Weight: 739 kg
Length: 3.13m
Diameter: 1.14m
Chambers: 2
Chamber pressure: 5.4MPa
Chamber temperature: ~3000 °C
Expansion ratio: 8:1
Fuel consumption: 750 kg/s
Ratio NO:Aerozine 50: 1.93:1
Ratio of thrust:weight: 151.34
LR87-7
Modified versions of LR87-5 adapted to the needs of the Gemini program. The performance was similar to the previous version, only reducing the chamber pressure and nozzle thrust to meet human-rating requirements. This version was only used on the Titan II GLV.
Used on Titan 24B, 34B, IIIBS, IIID, 34D, 34D7, IIIE. The LR-87-11A was used on the Titan IV A/B.
Operating parameters
Thrust : 2001.7 kN
Thrust : 2413.2
Specific impulse : 252s
Specific impulse : 304s
Burn time: 146–185 seconds
LR87 LH2
Modified to burn liquid oxygen and liquid hydrogen. The development coincided with other variants of the late 1950s. Compared to the -3, it had a number of changes associated with the use of lighter and colder liquid hydrogen. The fuel injector turbo was changed along with the fuel turbopump among other things. A total of 52 static tests were performed without serious issue. Aerojet took part in the selection process for a new engine for the second stage of the Saturn IB and Saturn V. Though LR87 LH2 was the best in 10 out of 11 criteria, NASA selected Rocketdyne's J-2. Lessons learned were used during development of the Aerojet M-1
