From: Stennis Space Center
Posted: Thursday, October 26, 2000
Headquarters, Washington, DC
Marshall Space Flight Center, Huntsville, AL
Stennis Space Center, MS
A detailed review of a Space Shuttle Main Engine test mishap, June 16, at NASA's Stennis Space Center, MS, has revealed that special tape was left behind inside the engine during processing, contaminating the system.
"Bob Sackheim and his team did an excellent job of getting to the root cause of this incident," said Joseph Rothenberg, NASA Associate Administrator for Space Flight. "Clearly this incident was preventable. We must be just as vigilant with our test hardware as we are with our precious flight engines. Complacency has no place in space flight."
Rothenberg appointed Robert Sackheim, Assistant Director for Space Propulsion at NASA's Marshall Space Flight Center, Huntsville, AL, to assess the main engine test mishap.
The investigation team found that nearly 24 square inches of tape, routinely used as a temporary closure or protective barrier during main engine processing and assembly, had been inadvertently dropped into the fuel system. Despite normal processing inspections, the tape went unnoticed before the engine was test fired.
The tape came to rest on the fuel and oxygen preburner injectors, with the majority of the tape in the fuel preburner. The tape blocked the multiple fuel-inlet holes causing an oxygen-rich mix, which rapidly increased temperatures beyond the engine's normal operating limits and melted some components upstream of the engine fuel pump.
"The engine controller performed as designed, shutting down the engine when it sensed a temperature that exceeded the safe limits set by engineers for this test," said Sackheim. "The purpose of these types of ground demonstration tests is to discover any issues prior to full certification that are related to manufacturing, assembly, processing, or design so that they will be prevented from occurring during flight, and that's what happened here."
The test was intended to be a "temperature margin" demonstration and was part of the developmental phase for a new, more robust Pratt and Whitney Advanced Technology High Pressure Fuel Turbopump.
About 5 seconds into a planned 200-second test, higher-than- expected temperatures caused the shuttle main engine to shut itself down using its own internal safety mechanisms. The engine being tested was not a flight configuration, but a development unit used to validate the engine's capability to operate at higher-than-normal temperature levels.
Sackheim's team found the handling of, accounting for, and inspecting for loose materials, used to process and rebuild engines during normal operations, were inadequate. In addition, his team concluded that the use of tape as a barrier against contamination provides the opportunity for material to be left in an engine.
Recommendations in the report to address the incident include:
* Verify all systems are free of foreign objects prior to hotfire, limit the opportunity for contamination by minimizing the use of tape and other potential contaminants, use permanent closures on joints when possible and keep joints closed at all times when not required to be open for work.
* Implement a better method of dealing with loose, non- serialized materials to ensure full accounting.
* Investigate the possibility of using reusable barriers for engine work, which can be controlled and accounted for.
The Space Shuttle Main Engine project and its prime contractor, the Rocketdyne Propulsion & Power business of The Boeing Company, are working on a plan to address the report's recommendations.
In addition, as part of NASA's emphasis on continued improvement and safety for the Space Shuttle Program, NASA has initiated an independent review of the Space Shuttle Main Engine Program and engine processing at Rocketdyne, as well as operations at NASA's Kennedy Space Center, FL.
All Space Shuttle Main Engines have been inspected and cleared for flight. No evidence of foreign-object damage or tape was found. The full text of the report can be found at:
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