Experts have discovered some charring from rocket exhaust into insulation protecting all six of the O-ring joints in both 15-story solid rocket boosters used in Columbia's launch.
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The decision was prompted by the discovery that the June 20 launching of the shuttle Columbia produced unexpected exhaust that charred insulation which protects six O-ring joints.
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Launch pad repairs commenced late last week with the excavation of the rubber insulation in two of five O-ring joints in the left and right side booster nozzles.
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That decision was made after unexpected burn damage was found on the insulation protecting several O-ring joints in similar boosters used to launch the shuttle Columbia on June 20.
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The mission itself was delayed nearly seven weeks by the discovery of unexpected damage to the insulation protecting O-ring joints on the boosters used for a June 20 shuttle launching.
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NASA launched the shuttle despite dire warnings that the O-ring joints in Challenger's booster rockets were at far greater risk of failing in the icy conditions and triggering a fatal explosion.
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The flange faces are also made to standardized dimensions and are typically " flat face ", " raised face ", " ring joint " styles, although other obscure styles are possible.
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As originally designed by Thiokol, the O-ring joints in the SRBs were supposed to close more tightly due to forces generated at ignition, but a 1977 test showed that when pressurized water was used to simulate the effects of booster combustion, the metal parts bent away from each other, opening a gap through which gases could leak.
