Report of the PRESIDENTIAL COMMISSION
on the Space Shuttle Challenger Accident
Volume 5 Index
Hearings of the Presidential
Commission on the Space Shuttle Challenger Accident: February 26,
1986 to May 2, 1986.
MARCH 7, 1986 SESSION (part 2 of
2)
[1192] [Ref. 3/7-66 1 of
2] Failure Scenarios 2A and 2B.
FAILURE SCENARIOS 2A AND
2B
FAILURE MECHANISM:
- AN UNDETECTED FLAW OR FOREIGN OBJECT
IMPACT RESULTS IN A H2 LEAK AT
LIFT-OFF
- H2 BURNS AND
IMPINGES ON THE RH SRM
- DEGRADES SEAL PERFORMANCE (HEAT EFFECT
ON JOINT ROTATION AND SEAL MATERIAL) TO THE POINT OF FAILURE IN
APPROXIMATELY 58 SECONDS
- OVERHEATS CASE MEMBRANE TO A BURN THRU
IN APPROXIMATELY 58 SECONDS
ASSESSMENT METHOD:
- DETERMINE BY ANALYSIS THE SIZE OF HOLE IN
THE LH2 TANK THAT IS NOT DETECTABLE IN TANK PRESSURE
INSTRUMENTATION
- REVIEW TANK BUILD RECORDS AND PAD DEBRIS
POTENTIAL
- REVIEW 51-L TANK LIFT-OFF LOADS
- DETERMINE BY ANALYSIS THE HEATING ON THE
SRM JOINT
- CONDUCT TESTS TO CHARACTERIZE TANK TPS
BURNING AND SIMULATE BURNING H2 IMPINGEMENT ON
SRM
[Ref. 3/7-66 2 of 2] Failure Scenarios 2A and 2B.
(continued).
FAILURE SCENARIO 2A AND 2B
(CONT'D)
FINDINGS TO DATE:
- ANALYSIS SHOWS 4 LBM/SEC LEAK FROM
H2 TANK IS NOT DETECTABLE IN PRESSURE INSTRUMENTATION
(EQUIVALENT TO 0.81" DIA. HOLE)
- PRELIMINARY ANALYSIS OF HEATING ON
SRM
- ASSUMES COMPLETE COMBUSTION OF TOTAL
FLOW
- ADDITIONAL JOINT ROTATION AND O-RING
UNSEATING CAN OCCUR DUE TO TEMPERATURES OF APPROXIMATELY
900°F
- MEMBRANE HEATING TO APPROXIMATELY
1300°F
- BURNING TPS MAY EXPLAIN "SMOKE" AT
LIFT-OFF
- LIFT-OFF LOADS ANALYSIS FOR EXTERNAL TANK
SHOW NO ANOMOLOUS CONDITIONS FOR 51-L
- THIS FAILURE MECHANISM NOT SUPPORTED BY
REVIEW OF BUILD RECORDS TO DATE
- THIS FAILURE MECHANISM REMAINS ACTIVE
PENDING COMPLETION OF:
- HEATING ANALYSES WITH REFINED
MIXING/BURNING ASSUMPTIONS AND EFFECT ON
STRUCTURE/PROPELLANT
- TESTS TO SIMULATE BURNING
H2 IGNITION SOURCES
- ASSESSMENT/ANALYSIS OF DEBRIS
POTENTIAL
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