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GENERAL DYNAMICS CONCLUDES LAUNCH FAILURE INVESTIGATION

 SAN DIEGO, Feb. 3 /PRNewswire/ -- General Dynamics Space Systems announced today that it has concluded its intensive, five-month investigation into the Aug. 22, 1992, Atlas I launch failure from Cape Canaveral, Fla.
 At about eight minutes into that flight, designated AC-71, the Centaur upper stage vehicle had to be destroyed by Air Force Range Safety when one of its engines failed to achieve full thrust and the vehicle began to tumble.
 The investigation was conducted by the General Dynamics Failure Investigation Team which reported regularly to an independent oversight board, chaired by Lt. Gen. Forrest McCartney USAF (Ret.), and assisted by other senior industry officials and customer representatives. Pratt & Whitney, builder of the Centaur engines, participated fully in the investigation.
 After extensive analysis and testing, monitored closely by the oversight board, the team concluded that the failure was caused by a check valve in the Centaur RL10 rocket engine that failed to close before liftoff, allowing air to be ingested in the engine during the Atlas boost phase. This air, predominantly nitrogen gas, immediately solidified in the first stage of the liquid hydrogen fuel pump, preventing the Centaur C-1 engine turbine from rotating.
 Corrective action includes the addition of a solenoid actuated valve to provide a redundant seal for the check valves. This valve will be closed and monitored before flight. The check valves will also undergo additional confidence testing. Additionally, ground pre-chill temperature is being increased to above the freezing point of nitrogen. This change assures that air or nitrogen from any source will not result in a frozen engine. Following the design and successful qualification of a check valve replacement, it will be phased in to flight.
 A review of the AC-70 investigation methods led the team to change its methodology for AC-71. The cause-and-effect "fishbone" methodology, expanded to a much lower level on AC-71 than the failure tree analysis on AC-70, will be implemented on all future hardware and software design changes and in the resolution of all flight anomalies.
 Because of the similarities between the failure of AC-71 and AC-70 in April 1991, the team reviewed and compared the data from both flights. They have concluded that the probable cause of the AC-70 failure was the same as AC-71. A key piece of data in this conclusion is the high correlation in both missions in the temperature of the C-1 engine's fuel pump housing, indicating the freezing of air on internal surfaces. The AC-70 temperature profile did not look "out of family" when compared to previous flights. However, when the temperature profiles from the five subsequent flights are plotted with AC-70 and AC-71, the "out of family" profile is very evident.
 During the AC-70 failure investigation, the discovery of contamination in propellant ducts indentical to those installed in AC-70 channeled that investigation toward a conclusion that solid contaminants entered the C-1 engine and caused the pump to seize. Extensive controls put in place after AC-70 and confirmed by the AC-71 failure investigation led the team to conclude that foreign object damage (FOD) was not the failure cause on AC-71 and probably not the cause on AC-70. The FOD prevention program put in place after AC-70, as well as other corrective actions, have added to the reliability and robustness of Atlas and Centaur processing.
 General Dynamics believes, and the oversight board concurs, that its conservative approach to the AC-71 failure investigation leaves no doubt that the cause of the failure was identified. The investigation was exhaustive and all cause-and-effect branches were closed out before the investigation was considered complete. The same conservative approach is being applied to all future corrective actions in order to provide our customers a reliable return to flight.
 General Dynamics Space Systems is continuing preparations to return to flight in March. Two atlas vehicles are now being processed for launch at Cape Canaveral; an Atlas I which will launch the first UHF satellite of the U.S. Navy and an Atlas II for an Air Force DSCS payload.
 -0- 2/3/93
 /CONTACT: Julie C. Andrews of General Dynamics, 619-974-3600/
 (GD)


CO: General Dynamics Space Systems ST: California IN: ARO SU:

EH -- SD003 -- 2429 02/03/93 13:04 EST
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Date:Feb 3, 1993
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