1、Lessons Learned Entry: 1124Lesson Info:a71 Lesson Number: 1124a71 Lesson Date: 1999-02-01a71 Submitting Organization: HQa71 Submitted by: David M. LengyelSubject: Computer Hardware-Software/Space Shuttle/General Purpose Computer (GPC) Limitations Description of Driving Event: Outmoded Design of Spac
2、e Shuttle General Purpose Computer (GPC) Limit Software and Hardware UpgradesLesson(s) Learned: Outmoded Design of Space Shuttle General Purpose Computer (GPC) Limit Software and Hardware UpgradesRecommendation(s): Outmoded Design of Space Shuttle General Purpose Computer (GPC) Limit Software and Ha
3、rdware UpgradesEvidence of Recurrence Control Effectiveness: The Space Shuttle Program is addressing the finding and recommendation identified by the ASAP.A review of the GPC and its flight software was performed in April 1998. Based on current estimates on GPC mean time between failures, the flight
4、 hardware and spares are expected to be available through at least 2016 (and likely significantly later). The flight software estimate on memory availability and usage has projected that memory capacity would be expected to reach its limit in the 2005-2006 time-frame. A software architecture strateg
5、y as part of the overall SSP avionics upgrade effort is being developed which will mitigate the memory capacity concern. This strategy will partition the critical software such as flight control and guidance from software that requires periodic change. The result of this partition would allow those
6、stable software functions like flight control to remain within the current GPCs while allowing those functions that frequently change to be Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-migrated to a newer computer technology. The offloading of the
7、 software functions such as display processing and systems management from the current GPCs should permit current GPC memory capacity to remain acceptable through at least 2020. Additionally the software subject to frequent change would be located within a system, which will be designed to be more e
8、asily reconfigurable than the existing system.In summary, a supportability concern does not exist for the current GPCs. Continued use of the existing GPCs and their established processes will maintain high levels of safety. Software partitioning involving the offloading of software functions to a mo
9、re flexible system will provide sufficient memory availability for future GPC software changes. This approach will provide an evolutionary and a migration path to full GPC upgrade if it is later required.Documents Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Aeronautics R
10、esearchAdditional Key Phrase(s): a71 Aerospace Safety Advisory Panela71 Computersa71 Policy & Planninga71 Softwarea71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 2002-02-12a71 Approval Name: Bill Loewya71 Approval Organization: HQa71 Approval Phone Number: 202-358-0528Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
