DEFINITIONS

¶In Family: A reportable problem that was previously experienced, analyzed, and understood. Out of limits performance or discrepancies that have been previously experienced may be considered as in-family when specifically approved by the

¶Space Shuttle Program or design project.8

¶Out of Family: Operation or performance outside the expected performance range for a given parameter or which has not previously been experienced.9

¶Accepted Risk: The threat associated with a specific circumstance is known and understood, cannot be completely eliminated, and the circumstance(s) producing that threat is considered unlikely to reoccur. Hence, the circumstance is fully known and is considered a tolerable threat to the conduct of a Shuttle mission.

¶No Safety-of-Flight-Issue: The threat associated with a specific circumstance is known and understood and does not pose a threat to the crew and/or vehicle.

¶ment to experience during the re-entry phase.

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¶Flight STS-7 STS-32R STS-50 STS-52 STS-62 STS-112 STS-107

ET # 06 25 — 45

¶ET Type SWT LWT LWT

¶Orbiter Challenger Columbia Columbia

¶Inclination 28.45 deg 28.45 deg 28.45 deg

¶Launch Date 06/18/83 01/09/90 06/25/92

¶Launch Time 07:33:00 07:35:00 12:12:23 (Local) AM EDT AM EST PM EDT

¶Figure 6.1-1. There have been seven known cases where the left External Tank bipod ramp foam has come off in flight.

¶came to be treated as "in-family," 7 a reportable problem that was within the known experience base, was believed to be understood, and was not regarded as a safety-of-flight issue.

¶Bipod Ramp Foam Loss Events

¶Chunks of foam from the External Tankʼs forward bipod attachment, which connects the Orbiter to the External Tank, are some of the largest pieces of debris that have struck the Orbiter. To place the foam loss from STS-107 in a broader context, the Board examined every known instance of foam-shedding from this area. Foam loss from the left bipod ramp (called the –Y ramp in NASA parlance) has been confirmed by imagery on 7 of the 113 missions flown. However, only on 72 of these missions was available imagery of sufficient quality to determine left bipod ramp foam loss. Therefore, foam loss from the left bipod area occurred on approximately 10 percent of flights (seven events out of 72 imaged flights). On the 66 flights that imagery was available for the right bipod area, foam loss was never observed. NASA could not explain why only the left bipod experienced foam loss. (See Figure 6.1-1.)

¶Figure 6.1-2. The first known instance of bipod ramp shedding occurred on STS-7 which was launched on June 18, 1983.

55 62 115 — 93

LWT LWT SLWT LWT

¶Columbia Columbia Atlantis Columbia

¶28.45 deg 39.0 deg 51.6 deg 39.0 deg

¶10/22/92 03/04/94 10/07/02 01/16/03

¶1:09:39 08:53:00 3:46:00 10:39:00

PM EDT AM EST PM EDT AM EDT

¶The first known bipod ramp foam loss occurred during STS-7, Challengerʼs second mission (see Figure 6.1-2). Images taken after External Tank separation revealed that a 19- by 12-inch piece of the left bipod ramp was missing, and that the External Tank had some 25 shallow divots in the foam just forward of the bipod struts and another 40 divots in the foam covering the lower External Tank. After the mission was completed, the Program Requirements Control Board cited the foam loss as an In-Flight Anomaly. Citing an event as an In-Flight Anomaly means that before the next launch, a specific NASA organization must resolve the problem or prove that it does not threaten the safety of the vehicle or crew.11

¶At the Flight Readiness Review for the next mission, Orbiter Project management reported that, based on the completion of repairs to the Orbiter Thermal Protection System, the bipod ramp foam loss In-Flight Anomaly was resolved, or "closed." However, although the closure documents detailed the repairs made to the Orbiter, neither the Certificate of Flight Readiness documentation nor the Flight Readiness Review documentation referenced correcting the cause of the damage – the shedding of foam.

¶Figure 6.1-3. Only three months before the final launch of Columbia, the bipod ramp foam had come off during STS-112.

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¶impact damage was shallow, the tile loss was not a result