Collected Reports of the Panel on Technical Evaluation of NASA's Redesign of the Space Shuttle Solid Rocket Booster (1988) / Chapter Skim
Currently Skimming:
6 Interim Report #6: March 17, 1988
6 Interim Report #6: March 17, 1988
Pages 37-46
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From page 37... ...
Since our last report, the Panel has conducted three meetings and some of our members have attended the DM-9 Test Readiness Review, one run of the Assembly Test Article, three meetings of the Outer Boot Ring Anomaly investigation team, and the SRM Critical Design Review Level ITI preboard and board meetings. I also presented a testimony on the progress of the redesign effort to the Senate Subcommittee on Science, Technology, and Space on February 16th.
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From page 38... ...
Even though the carbon cloth pheno~ic materials used in the two outer boot ring designs are ostensibly the same based on coupon tests and chemistry, the performance of the parts depends strongly on their internal geometrical configurations and fabrication procedures. The results of future full-scale tests of the outer boot ring should be assessed from a sound and adequate base of data from laboratory tests and in-process inspections.
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From page 39... ...
system in the DM-9 test has been suggested as a potential contributing factor to failure of the outer boot ring in that test. We believe that the TIC duty cycles used in static motor tests should be realistic but should be significantly more severe than those experienced in flight to demonstrate the margins in the design.
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From page 40... ...
We agree with the viewpoint, expressed by some within the program, that the success criteria for these tests, including the PVM, need not be the same as those for tests of the flight design since the test hardware must be significantly modified from the flight design in the pressureassuring tests. We conclude that an appropriate success criterion in the later tests might allow some erosion of the seal under test but should prohibit leakage past it.
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From page 41... ...
The masking effect may, in fact, be beneficial; other rocket motor systems intentionally rely on liberal applications of grease to assist in the sealing function. In view of the clear benefit of corrosion protection, potential benefit of assisting in the sealing function, and uncertain arguments concerning the detection of small leaks, we conclude that in resolving the conflicting implications of the requirements for the design, priority should be given to assuring that liberal amounts of grease are applied to the O-rings.
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From page 42... ...
For large debonds, a procedure has been specified for repair. We suggest that NASA qualify the procedure using realistic laboratory specimens to be sure that the technique for repairing defects does not inadvertently weaken the bonds.
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From page 43... ...
We believe that it is essential that NASA have in place an appropriately staffed and funded program for planning and implementing a continuing development program, including provision for the requisite ground tests and determination of flight performance; the means to analyze results, upgrade and evaluate designs; and provision to introduce risk-reducing improvements into flight hardware and operations. An important result of a continuing development and product improvement program wit ~ be an increased understanding of the capabilities of the SRB, leading in turn perhaps to lower operational costs.
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From page 44... ...
In those instances in which the element under consideration affects safety, it is essential that the program incorporate a plan for certification and adoption of modified designs, materials, or processes on a timely basis. Critical Design Review As we understand it, the Critical Design Review (CDR)
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From page 45... ...
_ 9 _ In our second interim report, we commented on the lack of a clear separation of organizational responsibility for defining requirements, making design choices, and conducting design reviews. Based on the observations of members of the Panel who attended the recent Level III SRM CDR preboard and board meetings, we could not distinguish the differences between the roles of NASA Level III and those of its contractor in the preboard meeting nor was it clear that the participation of NASA Level II in either the preboard or board meetings thus far has assured an independent review.
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