- AREA OF CONCERN IS OPPOSITE FSS WHERE ICE WAS PRESENT

- ANALYSIS INDICATES THAT ENERGY ASSOCIATED WITH ICE IMPINGEMENT ON TANK NOT SUFFICIENT TO CAUSE STRUCTURAL. DAMAGE

- TESTS INDICATE THAT LEAK OF 0.0037 LBM/SEC. WOULD BE DETECTABLE

- TEST IMPINGING BURNING H2 JET ON INSTAFOAM INDICATE SIGNIFICANT QUANTITIES OF FLAME AND SMOKE

• EVALUATION OF BURNING H2 JET IMPINGING ON AN MEMBRANE OR JOINT
  - ENVIRONMENT GENERATED ASSUMING STOICHEMETRIC MIXTURE OF H2 AND AIR

  - MAXIMUM SRM TEMPERATURES WITH JET IMPINGEMENT

  • 650°F MEMBRANE
  • 360°F O-RING

  - TESTS INDICATE THAT O-RING WILL MAINTAIN SEAL AT 1000°F

W-11

FINDING

• NO EVIDENCE THAT DAMAGE TO EXTERNAL TANK INITIATED A LEAK OR THAT A LEAK WITHIN THE DETECTABLE LIMITS OF TANK INSTRUMENTATION WOULD INITIATE THE OBSERVED SRM FAILURE

W-17

FAILURE MECHANISM

• HOT GAS LEAK FROM SRM IMPINGES ON EXTERNAL TANK AND INITIATES TANK FAILURE

ASSESSMENT

• SRM HOT GAS LEAK EVIDENT FROM FLIGHT FILM AT 58.7 SECONDS
• ANALYSIS HAS ESTABLISHED THAT RESULTING HEATING RATES WOULD BURN THROUGH TANK BETWEEN TIME OF VISIBLE LEAK AND INDICATION OF TANK ULLAGE PRESSURE DECREASED RISE RATE (66.7 SECONDS)

FINDING

• PROBABLE THAT SRM HOT GAS LEAK INITIATED TANK FAILURE

W-18