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.
FEBRUARY 26, 1986 SESSION (part 1 of
2)
[903] [Ref. 2/26-4 7 of
14] STS-51C (SRM-15) STS-20 O-RING EROSION SCENARIO.
STS-51C (SRM-15) STS-20 DURING EROSION
SCENARIO
- A NO EROSION UNTIL SONIC FLOW ESTABLISHED
IN FIELD JOINT AREA (0 - 50 PSI)
- B PRIMARY O-RING SEATING PHASE (50 - 200
PSI)
- LOW TEMPERATURE SHRINKS O-RING AND
INCREASES DUROMETER
- GAS JET THROUGH PUTTY IMPINGES ON
PRIMARY O-RING
- INITIAL EROSION OF PRIMARY O-RING
OCCURS (<10 MILS)
- GAS FLOW PAST PRIMARY O-RING
OCCURS
- O-RING PRODUCTS FOUND IN SOOT
- PUTTY PRODUCTS FOUND IN SOOT
- GAS FLOW DEPOSITS SOOT AND LOSES HEAT
(Delta T = 5265°F) IN CIRCUMFERENTIAL EXPANSION BETWEEN
O-RINGS, Delta T = 570°F BETWEEN O-RINGS
- NO DAMAGE TO SECONDARY O-RING
[904] [Ref. 2/26-4 8 of
14] STS-51C (SRM-15) STS-20 O-RING EROSION SCENARIO
(continued).
- C PRIMARY O-RING SEALS AND CONTINUES TO
ERODE
- PRIMARY O-RING SEATS BY THE TIME
PRESSURE REACHES 200 PSI
- FREE VOLUME INCREASES 10X FROM POINT
"A" TO POINT "C"
- DUE TO MOTOR PRESSURIZATION AND JOINT
EXPANSION
- MAJORITY OF O-RING EROSION OCCURS
DURING THIS PHASE UNTIL
- PRESSURE EQUILIBRATION OCCURS AT
APPROXIMATELY 330MS
- DEPTH OF EROSION IS A FUNCTION OF GAS
JET SIZE I.E. SMALLER SIZE HIGHER EROSION
- A67 (L.H.) GAS PATH 2.2 INCHES NEAR
O-RING COMPARED TO 1.0 INCH ON A68 (R.H.) I.E. AREA RATIO =
4.8, EROSION DEPTH RATIO = 3.8, ASSUMING FINAL AREA SAME.RATIO
AS INITIAL
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