1、Lessons Learned Entry: 1797Lesson Info:a71 Lesson Number: 1797a71 Lesson Date: 2007-05-8a71 Submitting Organization: JPLa71 Submitted by: David Oberhettingera71 POC Name: Robert Manninga71 POC Email: Robert.M.Manningjpl.nasa.gova71 POC Phone: (818) 393-7815Subject: Mars Exploration Rover Project: St
2、ealing Success From the Jaws of Failure Abstract: A September 23, 2005 video presentation in which the Chief Engineer for the JPL Mars Program discusses some of the hard systems engineering lessons learned from developing the Mars Exploration Rovers under severe schedule and technical constraints.De
3、scription of Driving Event: Click Here to download the Windows Media Player version of the video. Click Here to download the Quicktime version of the video. References: (1) “Design, Verification/Validation and Operations Principles for Flight Systems (JPL Design Principles),” JPL Document D-17868, R
4、ev. 3, December 11, 2006. (2) “If You Dont Understand an Environment, Provide Well-Margined Capabilities to Encompass the Worst Case,” NASA Lesson Learned No. 1712, NASA Engineering Network, December 16, 2005. Lesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or networking permitted wi
5、thout license from IHS-,-,-Mars Exploration Rover (MER) development encountered many unexpected problems that were overcome only by strong NASA and Jet Propulsion Laboratory (JPL) support for the project. This video recording of a September 23, 2005 presentation explains how JPL was able to call upo
6、n engineering expertise as needed, and how established and effective JPL engineering processes (Reference (1) supported their efforts. Rob Manning provides examples of these challenges that were overcome by the MER project, including: a71 Few believed that a new Mars rover could be designed and test
7、ed in only the 3 years available to the project. Hence, the plans called for 50 percent of the launched dry mass of MER to derive from detailed designs inherited from the 1997 Mars Pathfinder design. However, design studies showed this to be impractical, and only 2 percent of the MER dry mass was ac
8、tually derived from inherited designs. a71 A typical 4-year development cycle was compressed into 3 years for a very complex and volume-constrained spacecraft. This period encompassed repetitive redesign and test cycles for the parachutes and airbags, and the addition only 18 months before launch of
9、 a capability to directly sense horizontal motion across the Martian surface (Reference (2). a71 A non-essential fuse blown during a test pyrotechnic firing only two months before MER launch produced an unexpected circuit condition. Consequently, it appeared that mission-critical sneak circuit paths
10、 could result from the mission sequence in which a cable-cutter severs spacecraft power bus return wires that are not electrically isolated (deadfaced). One month of intensive circuit analysis by a group of very senior engineers proved that MER could safely launch. a71 Only 48 hours before the MER l
11、anding, an analysis of testbed data suggested an apparent timing problem with the pyrotechnic system electronics that trigger the landing events. Around-the-clock analysis over the next day confirmed a mission-critical hardware design flaw, and JPL made a risky decision to manually enable the firing
12、 of the pyros that may have saved the mission.Recommendation(s): Assure that key NASA projects have sufficient NASA and field center support to ensure that design problems are worked expeditiously. There is more time to solve problems than you think, but there is less time to identify problems than
13、you think. Once they realize what the technical problem is, experienced engineers can make significant progress in a short time.Evidence of Recurrence Control Effectiveness: JPL has referenced this lesson learned as additional rationale and guidance supporting Paragraph 5.12 (Project Staffing and De
14、staffing) in the Jet Propulsion Laboratory standard Flight Project Practices, Rev. 6, JPL DocID 58032, March 6, 2006, and supporting Paragraph 2.0 (Introduction) in Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the JPL standard Design, Verification
15、/ Validation and Operations Principles for Flight Systems (Design Principles), JPL Document D-17868, Rev. 3, December 11, 2006.Documents Related to Lesson: NASA NPR 7123.1A, NASA System Engineering Processes & RequirementsMission Directorate(s): a71 Space Operationsa71 Sciencea71 Exploration SystemsAdditional Key Phrase(s): N/A Additional Info: a71 Project: Mars Exploration Rover (MER)Approval Info: a71 Approval Date: 2007-10-30a71 Approval Name: ghendersona71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
