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TRW LOx/LH2 rocket engine. Development. Innovative TRW 650K Low Cost Pintle Engine, test fired at NASA's test center in October 2000.

AKA: LPCE; TR106. Status: Development. Date: 2000. Thrust: 2,892.00 kN (650,147 lbf).

The innovative TRW 650K Low Cost Pintle Engine was test fired at NASA's John C. Stennis Space Center through October 2000. The objectives of the test program were to demonstrate that the design concept could be scaled up to 300 tf from an earlier 18.2 tf test article; confirm performance; and test stability with bomb testing. The combustion chamber had an external diameter of 1.72 m. TRW scaled up the pintle injector design and provided an injector, combustion chamber and GOX/GH2 torch igniters for hot fire testing. A total of 12 performance tests and four stability tests demonstrated the ability to start the engine without any injector pre-chill, despite using LH2; and complete absence of any signs of combustion instability. A production engine was expected to be low cost compared to traditional designs through lower pressure operation and use of TRW single element coaxial pintle injection technology, notably demonstrated on the Apollo Lunar Module Descent Engine thirty years earlier.

TRW Inc. successfully completed initial static-fire testing of a low-cost booster engine based on TRW's pintle injection technology in September 2000. The 295,000 kgf thrust Low Cost Pintle Engine (LCPE), one of the largest liquid rocket engines built since Saturn F-1 engines powered Apollo program flights in the 1970s, was designed as a simple, easy-to-manufacture, low-cost engine. The LCPE had parts made from common steel alloys using standard industrial fabrication techniques, employed ablative cooling techniques instead of more expensive regenerative cooling, and featured the least complex type of rocket propellant injector -- a single element coaxial pintle injector. Al Frew, vice president and general manager, TRW Space & Technology Division stated

Most engines are designed for maximum performance and minimum weight, but we deliberately set out to develop an engine that minimizes cost while retaining excellent performance. We believe this engine will cost 50 to 75 percent less than comparable liquid hydrogen boosters. By reducing engine costs, which make up almost half of the cost of a launch vehicle, we will reduce the cost of launch vehicles and access to space for government and commercial customers.
The LCPE was subjected in the summer of 2000 to hot fire testing at 100 percent of its rated thrust as well as at a 65 percent throttle condition at NASA's John C. Stennis Space Center in Mississippi. TRW changed the pintle injector configuration three times during testing to explore the engine's performance envelope; engineers also replaced the ablative chamber once while the engine was on the test stand -- demonstrating the LCPE's ease of operation.

"The LCPE has demonstrated nominal performance and absolute combustion stability throughout its testing," said Kathy Gavitt, TRW's LCPE program manager. "This testing is an important first step in validating that a low-cost pintle engine can substantially lower the cost of future launch vehicles."

Engine testing was planned to continue throughout the year under a cooperative agreement between TRW and NASA's Marshall Space Flight Center.

The key element of the LCPE's design was its single element coaxial pintle injector, used to introduce propellants into the combustion chamber. TRW had used this design in nearly all of its bipropellant liquid rocket engines. This included the Lunar Module Descent Engine (LMDE) which safely landed 12 astronauts on the lunar surface between 1969 and 1972 and was critical in the rescue of Apollo 13.

Other notable features of the LCPE were:

  • Scalability. The LCPE was scalable over a range of thrust levels and propellant combinations. It could be readily adapted to a wide range of launch vehicles, from the Bantam Lifter class (about 90 kg to low-Earth orbit) to Heavy Weight Lifter class (about 90,000 kg to low-Earth orbit). The LCPE could power the first stage of an EELV-class, multistage launch vehicle, and scaled down versions could easily be used for the vehicle's second stage.
  • Combustion Stability. The LCPE was inherently stable over a wide range of operating conditions due to the unique injection and combustion flow fields created by the pintle injector.
  • Size. Incorporated the second largest rocket combustion chamber ever built, with an outside diameter of 1.73 m.
  • Simplicity. A complete pintle injector contained only five parts (excluding seals and attachment nuts, bolts and washers).
  • Throttling Ability. LCPE had already demonstrated its ability to operate at a 65 percent throttle condition. Moveable pintle injector attributes included deep throttle capability, such as the LMDE 10:1 throttling engine.

    TRW had tested more than 50 different pintle injector engines, using more than 25 different propellant combinations with complete combustion stability and no need for acoustic cavities or baffles. Previously, pintle injector engines were successfully tested with liquid hydrogen and liquid oxygen at thrust levels of 7,000 and 18,000 kgf. TRW had flown more than 140 engines ranging in size from the 45-kgf thrust liquid apogee engine used on NASA's Chandra X-ray Observatory to the 4500 kgf-thrust Delta and LMDE engines.

    Despite the promise the motor demonstrated, NASA cancelled further work together with the rest of the Space Launch Initiative.

    Country: USA. Propellants: Lox/LH2. Agency: TRW. More at: 7567. Bibliography: 553.

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