LR91

LR91-11
Titan IV-B aft with a LR91-AJ-11.
Country of origin United States
First flight1 September 1964 (1964-09-01)
Last flight19 October 2005 (2005-10-19)
DesignerAerojet
ManufacturerAerojet
ApplicationUpper stage[1]
Associated LVTitan[1]
PredecessorLR91-9[1]
StatusRetired
Liquid-fuel engine
PropellantN2O4 / Aerozine 50
Mixture ratio1.86
CycleGas-generator[1]
Configuration
Chamber1[1]
Nozzle ratio49.2[1]
Performance
Thrust, vacuum467 kN (105,000 lbf)
Thrust, sea-level232.7 kN (52,300 lbf)
Thrust-to-weight ratio80.85[1]
Chamber pressure5.93 MPa (860 psi)[1]
Specific impulse, vacuum316 s (3.10 km/s)
Specific impulse, sea-level160 s (1.6 km/s)
Burn time247 seconds
Dimensions
Length2.81 m (9 ft 3 in)
Diameter1.63 m (5 ft 4 in)
Dry mass589 kg (1,299 lb)
Used in
Titan III and Titan IV[1]
References
References[1]

The LR91 was an American liquid-propellant rocket engine, which was used on the second stages of Titan intercontinental ballistic missiles and launch vehicles. While the original version - the LR91-3 - ran on RP-1/LOX (as did the companion LR87-3) on the Titan I, the models that propelled the Titan II and later were switched to Aerozine 50/N2O4.[1]

This engine was vacuum optimized and ran the gas-generator cycle. The thrust chamber used fuel for regenerative cooling, with separate ablative skirt.[1] The LR87, which was used for the Titan first stage, was used as a template for the LR91.

Early LR91 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.[2]

  1. ^ a b c d e f g h i j k l Cite error: The named reference ea-lr9111 was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference hr-lr91 was invoked but never defined (see the help page).