1、 Public Lessons Learned Entry: 2918Lesson Info:a71 Lesson Number: 2918 a71 Lesson Date: 2010-05-20 a71 Submitting Organization: KSC a71 Submitted by: Annette Pitt Subject: Start Transient Leak Detection System (STLDS) Abstract: Cryogenic propulsion systems use extremely cold propellants and high pre
2、ssures to achieve the thrust-to-weight ratios required for space vehicles. Leakage from these systems during operation can cause changes in pressure within an enclosed fuselage (such as the Space Shuttle vehicle SSV) that are significant enough to be recognized as the initiation of a potentially cat
3、astrophic leak. Monitoring for these unexpected changes in pressure can allow detection of a leak in time to abort a launch and possibly prevent damage to or loss of the vehicle. Description of Driving Event: The Space Shuttle Main Propulsion System (MPS) and Main Engine (SSME) power heads are enclo
4、sed within the aft fuselage of the Orbiter vehicle. There is no way to detect the initiation of significant and potentially catastrophic MPS/SSME system leakage within the aft fuselage during SSME thrust buildup (6.6 seconds to T-0). During SSME test firing at the Main Propulsion Test Article (MPTA)
5、 (SF6-01), a high-pressure hydrogen leak developed after ignition that resulted in an overpressure of the aft fuselage severe enough to blow off the heat shield simulators. Lesson(s) Learned: a71 Integrity of the SSV MPS/SSME following SSME start must be derived as acceptable based on historical dat
6、a and satisfaction of prestart requirements. a71 Because there is no real-time leak detection following SSME start, it is possible to allow lift-off with a significant leak occurring. Recommendation(s): Dedicate real-time onboard monitoring of the aft fuselage environment, using delta pressure and p
7、ossibly delta temperature measurements to confirm the stability of the MPS/SSME postignition/preliftoff. Implement monitoring with enough redundancy (three of four) to allow an abort decision if conditions warrant. The following is an SSV-specific example: 1. Determine the minimum amount of LO2, GO2
8、 LH2, or GH2 leakage required to affect the aft fuselage pressure, temperature, density, or vapor distribution/optics (or a combination of these parameters) enough to be detectable by available technology. To be of use, candidate technology would have to provide high-sample-rate data to allow recog
9、nition of, and reaction to, a hazard developing between 6.6 seconds and T-0. 2. Then, determine if this amount of leakage is sufficiently below a level that would affect SSME ignition “confirm“ or initial main stage “verification.“ If derived leakage values are determined to be low enough not to res
10、ult in a shutdown caused by degraded performance, implementation may be warranted. The Propulsion System Integration Group (PSIG) started an evaluation of this approach for Space Shuttle Program implementation in April 2004 (Discussion Item 040407-D05, attached). Initial analysis was promising, but
11、the effort was overcome by other events and was never completed. Note that high-sample-rate delta pressure measurements are a candidate for this task. Evidence of Recurrence Control Effectiveness: N/A Documents Related to Lesson: Propulsion Systems Integration Group Discussion Item 040407-D05 Click
12、here to download communication document. Mission Directorate(s): a71 Aeronautics Research Additional Key Phrase(s): a71 1.Cryogenic Systems a71 1.Level II/III requirements definition a71 1.Vehicle concepts a71 1.Risk management a71 0.Launch support systems a71 1.Reliability a71 1.Propulsion Addition
13、al Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Project: Space Shuttle Program Approval Info: a71 Approval Date: 2010-09-29 a71 Approval Name: mbell a71 Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
