LR-87

The LR-87 was an American liquid-propellant rocket engine, which was used to propel the first stages of Titan intercontinental ballistic missiles and launch vehicles. Though this powerful engine used two discrete combustion chambers, it is considered a single unit. The LR-87 first flew in 1959.



The LR-87 rocket engine was developed in the late 1950s by Aerojet. It is the world's first production rocket engine capable (with modifications) of burning the three most common liquid rocket propellant combinations, liquid oxygen and RP-1, liquid oxygen and hydrogen, and nitrogen tetroxide and Aerozine 50 (mixture of 50 percent MMH and 50 percent UDMH). The engine operated on an open gas-generator cycle and utilizes a regenerative cooled nozzle and combustion chamber. Later versions had additional ablative-cooled flanges. LR-87 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 LR-87 delivered approximately 1,900 kilonewtons (430,000 pounds) of thrust. When used on the Titan I, early LR-87 engines were fuelled by RP-1 and liquid oxygen. Because the liquid oxygen was 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, it was converted to use Aerozine-50 and nitrogen tetroxide, which are hypergolic, and storable at room temperature, so they could remain in their tanks for long periods, allowing Titan II missiles to be launched quickly if a threat was detected.

LR-87-3
The first version used on the Titan I, burned liquid oxygen and RP-1. Following the retirement of the Titan missile program, these engines saw no further use.

Operating parameters Weight: 839 kg
 * Thrust (sea level): 647 kN
 * Thrust (vacuum): 733 kN
 * Specific impulse (vacuum): 2840 Ns/kg
 * Specific impulse (sea level): 2510 Ns/kg
 * Ignition time: 139 seconds
 * Length: 3.13 m
 * Diameter: 1.53 m
 * Number of chambers: 1
 * Chamber pressure: 4000 kPa
 * Temperature in the chamber: ~ 3300 °C
 * Expansion Ratio: 8:1
 * Ratio of LOX/RP-1: 1,91:1
 * Thrust / weight: 87.2

LR-87-5
A modified version for the Titan II used new propellants, nitrogen tetroxide and aerozine-50. The engine was generally lighter and simpler than its predecessor, partly due to the propellants being hypergolic (pyrophoric), which did not need an independent ignition system.

Operating parameters Weight: 739 kg
 * Thrust (sea level): 956.5 kN
 * Thrust (vacuum): 1096.8 kN
 * Specific impulse (vacuum): 2910 Ns/kg
 * Specific impulse (sea level): 2540 Ns/kg
 * Ignition time: 155 seconds
 * Length: 3.13 m
 * Diameter: 1.14 m
 * Number of chambers: 1
 * Chamber pressure: 5.4 MPa
 * Temperature in the chamber: ~ 3000 °C
 * Expansion Ratio: 8:1
 * Fuel consumption of 750 kg / s
 * Ratio N2O4/Aerozine 50: 1,93:1
 * Thrust / weight: 151.34

LR-87-7
Modified versions of LR-87-5 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 man-rating requirements. This version was only used on the Titan GLV 2.


 * LR-87-9 - the use of early versions of Titan 3
 * LR-87-11 - the later version of the Titan IIIB Titan 4

LR-87 LH2
Version burning liquid oxygen and 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 LR-87 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

The intended parameters Length: 4 m
 * Move (vacuum): 667 kN
 * Specific impulse (vacuum): 4420 Ns/kg
 * Weight: ~ 700 kg
 * Diameter: 1.13 m
 * Number of chambers: 1