REG NASA-LLIS-2816-1990 Lessons Learned - Software Modification Verification.pdf

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1、Public Lessons Learned Entry: 2816 Lesson Info: Lesson Number: 2816 Lesson Date: 1990-05-10 Submitting Organization: KSC Submitted by: Annette Pitt Subject: Software Modification Verification Abstract: On 24 April 1990, the launch of the Hubble Space Telescope, STS-31R, was held at T-31 seconds beca

2、use the Main Propulsion System (MPS) liquid oxygen (LOX) outboard fill and drain valve (PV9) was not closed. The command to close the valve was blocked by Prerequisite Control Logic (PCL) and therefore never issued. A plan to override the PCL was conceived and concurrence was granted by the launch t

3、eam. Once PV9 was successfully closed, the NASA Launch Director authorized resuming the countdown clock, and STS-31R was successfully launched. The PCL blocked the PV9 closed command because a deviation to the S1003 procedure required the LOX helium transfer line purge to be turned on at T-1:20. Thi

4、s change was in response to a potential Launch Processing System (LPS) power failure resulting in an emergency drain to prevent vehicle damage. The procedural change was coordinated and signed by all the proper personnel but was not run against the math model because it was thought to be well unders

5、tood. Description of Driving Event: As a result of a hardware failure in the KSC facility power system on 2 April 1990, it was realized that the potential existed for a total loss of the LPS. It was determined that a loss of LPS after T-31 seconds would result in unfavorable vehicle configuration: O

6、verboard LOX bleed valve PV19 closed. This configuration requires that the LOX drain be established within 9 minutes or a catastrophic LOX feedline geyser could occur. Because of the LPS power loss, a normal LOX system drain could not be performed via hardwire safing switches. Specifically, the heli

7、um transfer line purge could not be turned on prior to drain flow being initiated into the empty tail service mast because no hardwire safing switch for that purge existed. A plan to activate the purge at T-1:20 was agreed upon, and a procedural change was implemented to the S1003 procedure. Because

8、 of late discovery of this issue, the new procedure was not verified against the math model. Lesson(s) Learned: All procedural changes to cryogenic loading procedures must be verified against the math model. Recommendation(s): Perform procedural verifications against software models prior to executi

9、ng against hardware. Increase console teams training. Heightened awareness of software controls. Evidence of Recurrence Control Effectiveness: N/A Documents Related to Lesson: N/A Mission Directorate(s): Exploration Systems Science Space Operations Aeronautics Research Provided by IHSNot for ResaleN

10、o reproduction or networking permitted without license from IHS-,-,-Additional Key Phrase(s): 1.Ground support systems 1.Ground processing and manifesting 1.Planning of requirements verification processes 1.Launch support systems Additional Info: Project: Space Shuttle Program Approval Info: Approval Date: 2010-08-12 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-