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GENERAL DYNAMICS CONCLUDES LAUNCH INVESTIGATION

 SAN DIEGO, June 8 /PRNewswire/ -- General Dynamics Space Systems Division has concluded its investigation into the major anomaly that occurred during the Atlas I launch on March 25, 1993. The vehicle, designated AC-74, carried the first in the series of Hughes-built UHF Follow-on satellites for the U.S. Navy.
 At 24 seconds into flight, the Atlas booster engine thrust started to decay and by 103 seconds had decayed to 66 percent of its nominal value. Although the Centaur upper stage tried to make up for the Atlas booster engine shortfall, the final orbit achieved was lower than required. The U.S. Navy determined that the satellite was operationally unusable.
 The General Dynamics team, which included the booster engine manufacturer Rocketdyne, concluded that the thrust decay on AC-74 was because of failure of a precision regulator in the Atlas booster engine power control subsystem. The output pressure of this regulator controls the flow of liquid oxygen to the booster gas generator that would normally provide constant booster power throughout the boost phase of flight.
 The regulator failed when an internal stem screw rotated out of adjustment, causing the regulator output pressure to decay. The stem screw rotated under normal flight environment because a set screw that prevents the stem from rotating was not adequately torqued. Instrumentation in the Atlas propulsion system provided data that allowed the team to identify early the exact component that failed. Using a rigorous "fishbone" cause and effect methodology, the team closed out all possible causes of the regulator failure. Engine analytical simulations and a hot fire test with a loose stem screw duplicated the AC-74 anomaly.
 An independent review board chaired by Lt. Gen. Forrest McCartney (USAF, retired) concurred with the findings of the investigation as well as the corrective actions that are being incorporated before Atlas returns to flight. These include a redesigned precision regulator stem screw and extensive quality confidence actions.
 Since the loose set screw was most likely caused by inadequate torquing or inadvertent loosening during a rework of the regulator, the team did an exhaustive review of quality processes at Rocketdyne, Space Systems and other key suppliers. That review de?d that existing quality systems are consistent with contemporary aerospace industry practices and that no systemic deficiencies exist. However, enhancements have been identified and are being implemented. A joint GD/Air Force team will review all hardware for the upcoming Air Force Atlas II launch, designated AC-104. A joint GD/Hughes team will do the same for next UHF launch, designated AC-75.
 General Dynamics believes, and the independent oversight review board concurs, that it has taken a conservative and prudent approach to the corrective action needed to return Atlas to flight. AC-104, which will launch the third mission in the USAF MLV II program, is undergoing launch processing on Pad A at Complex 36. AC-75 is being readied on Pad B.
 -0- 6/8/93
 /CONTACT: Julie C. Andrews of General Dynamics, 619-974-3600/


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

MS -- SD005 -- 4400 06/08/93 12:44 EDT
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Date:Jun 8, 1993
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