1、Lessons Learned Entry: 0191Lesson Info:a71 Lesson Number: 0191a71 Lesson Date: 1992-11-04a71 Submitting Organization: KSCa71 Submitted by: David PenningtonSubject: Preintegrated Truss (PIT) Sections for Space Station Freedom Description of Driving Event: The use of truss segments, which are preinteg
2、rated with distributed systems and verified on the ground instead of erected on-orbit, has reduced technical risk and made the space station a more viable program. The preintegrated truss members (PIT) must be heavier than the original truss elements per running foot because the entire mass of the P
3、IT is subjected to launch loads.PIT members are aluminum I-beams bolted together instead of the more flexible graphite composite elements that previously were part of the design. The heavier construction allows orbit replaceable units (ORUS) to be located in their optimum positions for accessibility
4、One benefit of the restructured design is that EVA time has been reduced considerably so that EVA targets are now feasible. This has been accomplished by reducing the demand for EVAs and increasing the efficiency of those that must be performed.In the assembly of the PIT sections on-orbit, a captur
5、e latch provides final alignment by engaging guide pins after the sections are brought into proximity by the space shuttle remote manipulator arm. Motorized bolts then make the final latch-up. There is a chance that these sections may not line up correctly; therefore, damage may occur to the guide p
6、ins and bolts when the motorized bolts engage. Because the PIT sections will be assembled on the ground, the opportunity exists to test the alignment and mating procedures prior to flight.Lesson(s) Learned: The capture latch guide pins and motorized bolts used to couple the assemblies are not always
7、 in proper alignment. This could damage guide pins.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Recommendation(s): Develop a hardware test encompassing the full range of misalignments, tolerances, and impacts that might reasonably be expected to o
8、ccur.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Space Operationsa71 Exploration SystemsAdditional Key Phrase(s): N/AAdditional Info: Approval Info: a71 Approval Date: 1994-06-06a71 Approval Name: James G. Klinea71 Approval Organization: KSC/HEIa71 Approval Phone Number: 407-867-7614Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
