Aerojet LR87
The LR87 was an American liquid-propellant rocket engine used on the first stages of Titan intercontinental ballistic missiles and launch vehicles. Composed of twin motors with separate combustion chambers and turbopump machinery, it is considered a single unit and was never flown as a single combustion chamber engine or designed for this. The LR87 first flew in 1959.
XLR87 Rocket Engine | |
| Country of origin | United States |
|---|---|
| First flight | 1959 |
| Last flight | 2005 |
| Manufacturer | Aerojet |
| Application | Titan Main engine |
| Successor | D LR-91 |
| Liquid-fuel engine | |
| Propellant |
|
| Cycle | Gas-generator |
| Performance | |
| Thrust, sea-level | LR87-11: 1,900 kN |
| Chamber pressure | 40–59 bar |
| Specific impulse, vacuum | 2,840 N‑s/kg (290 s) |
| Specific impulse, sea-level | 2,510 N‑s/kg (256 s) |
| Dimensions | |
| Length |
|
| Diameter | 1.14 m |
| Dry weight | 839 kg |
The LR87 was developed in the late 1950s by Aerojet.: 82,319 It was the first production rocket engine capable (in its various models) of burning the three most common liquid rocket propellant combinations: liquid oxygen/RP-1, nitrogen tetroxide (NTO)/Aerozine 50 (a 50:50 mixture by mass of hydrazine and UDMH), and liquid oxygen/liquid hydrogen. The engine operated on an open gas-generator cycle and utilized a regeneratively cooled combustion chamber. 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. This lowered fuel use in the gas generator and improved specific impulse.: 380-385 The LR87 served as a template for the LR-91, which was used in the second stage of the Titan missile.
The LR87 was a fixed-thrust engine, which could not be throttled or restarted in flight. The LR87 delivered approximately 1,900 kilonewtons (430,000 pounds) of thrust in its hypergolic configuration. 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.
For the Titan III and IV, which were larger, more capable space launch vehicles, the LR87 was modified further. Thrust and nozzle area ratio were progressively increased, requiring heavier turbopumps, pipes, and other parts.: 384