MPTA-098

The Main Propulsion Test Article (MPTA-098) was built by Rockwell International as a testbed for the definitive propulsion and fuel delivery systems for the U.S. Space Shuttle Program.

Never intended for actual spaceflight, the MPTA consisted of the internal structure of a Space Shuttle orbiter aft-fuselage, a truss structure that simulated the basic structure and shape of an orbiter mid-fuselage and a complete Space Shuttle Main Engine (SSME) assembly, including all main propulsion system plumbing and the associated electrical systems.

Later, the very different STA (Structural Test Article) was converted into a flightworthy orbiter, re-designated OV-099, and christened Challenger. Rockwell and NASA thus retroactively re-designated the MPTA as MPTA-098, though it was never christened with a name.

On June 24, 1977, MPTA-098 was delivered by Rockwell International to the National Space Technology Laboratory (NSTL), in Hancock County, Mississippi, where it was mated with the Main Propulsion Test Article External Tank (MPTA-ET), mounted in a launch orientation and used for static engine tests.

On July 2, 1979, MPTA-098 suffered major structural damage due to a fractured fuel valve on Space Shuttle Main Engine number 2002. The fracture allowed hydrogen to leak into the enclosed aft compartment, raising the pressure to beyond the structural capability of the heat shield supports, severely damaging the structure.

After extensive repairs were completed, testing resumed in September, but on November 4, a high-pressure oxidizer turbopump failed 9.7 seconds into a scheduled 510-second test. Finally, on December 17, 1979, a complete static firing was accomplished that included all three Space Shuttle Main Engines running at up to 100 percent of rated thrust for 554 seconds, exceeding the predicted maximum time that the SSMEs would burn during an operational shuttle launch.

The preliminary flight certification (PFC) program, which would clear the way for the SSMEs to be flown aboard manned vehicles, began in early 1980. A number of setbacks, including an overheating high-pressure turbopump that shut down an engine 4.6 seconds into a 544-second test on April 16, 1980, in July, the burn-through of a hydrogen preburner cancelled a 581-second test after 105 seconds and the structural failure of a flight-rated nozzle shut down a November 1980 test after 20 seconds, slowed progress dramatically. These failures led to a number of critical changes to the SSMEs and their associated systems.

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