LR-91

LR-91

LR-91-11
Titan 4B aft with a LR91-AJ-11.
Country of origin United States
First flight 1964-09-01
Last flight 2005-10-19
Designer Aerojet
Manufacturer Aerojet
Application upper stage engine[1]
Associated L/V Titan[1]
Predecessor LR-91-9[1]
Status Retired
Liquid-fuel engine
Propellant N2O4[1] / Aerozine 50[1]
Mixture ratio 1.86[1]
Cycle Gas generator [1]
Configuration
Chamber 1[1]
Nozzle ratio 49.2[1]
Performance
Thrust (vac.) 467 kilonewtons (105,000 lbf)[1]
Thrust (SL) 232.7 kilonewtons (52,300 lbf)[1]
Thrust-to-weight ratio 80.85[1]
Chamber pressure 5.93 megapascals (860 psi)[1]
Isp (vac.) 316s[1]
Isp (SL) 160s[1]
Burn time 247s[1]
Dimensions
Length 2.81 metres (111 in)[1]
Diameter 1.63 metres (64 in)[1]
Dry weight 589 kilograms (1,299 lb)[1]
Used in
Titan III and Titan IV[1]

The LR-91 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 LR-91-3 - run on RP-1/LOX (as did the companion LR-87-3) on the Titan I, the models that propelled the Titan II and later were switched to Aerozine 50/N2O4.[1]

This engine was a vacuum optimized and run the gas generator cycle. The thrust chamber used fuel for regenerative cooling, with separate ablative skirt.[1] The LR-87, which was used for the Titan first stage, was used as a template for the LR-91.

Early LR-91 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]

Contents

  • Versions 1
  • See also 2
  • References 3
  • External links 4

Versions

Improvement and modifications required to comply with the man rating of the RD-0105 led it to have two versions:

  • LR-91-3: Titan I version. Run on RP-1/LOX.[3]
  • LR-91-5: Titan II version. Propellant was switched to Aerozine-5/N2O4.[4]
  • LR-91-7: Similar to LR-91-5, it was used on Stage 2 of Gemini Titan 2. This version was human rated.[5]
  • LR-91-9: Used in earlier versions of Titan 3 upper stage.[6]
  • LR-91-11: Version used on the Titan III and Titan IV.[1]

See also

References

  1. ^ a b c d e f g h i j k l m n o p q r s t u v w "LR91-11". Encyclopedia Astronautica. Retrieved 2015-06-15. 
  2. ^ "Titan I Second Stage Engine (LR-91)". Heroic Relics. Retrieved 2015-06-15. 
  3. ^ "LR91-3". Encyclopedia Astronautica. Retrieved 2015-06-15. 
  4. ^ "LR91-5". Encyclopedia Astronautica. Retrieved 2015-06-15. 
  5. ^ "LR91-7". Encyclopedia Astronautica. Retrieved 2015-06-15. 
  6. ^ "LR91-9". Encyclopedia Astronautica. Retrieved 2015-06-15. 

External links

  • Encyclopedia Astronautica
  • National Museum of the USAF, Ohio
  • Aerojet LR-87