1、Lessons Learned Entry: 0913Lesson Info:a71 Lesson Number: 0913a71 Lesson Date: 2000-08-17a71 Submitting Organization: JPLa71 Submitted by: J. Newell, D. OberhettingerSubject: Space Mechanisms Reliability (2000) Abstract: Studies have shown that mechanical failures are more frequent and more likely t
2、o significantly affect mission success than are electronic failures. Spaceflight mechanisms are usually unique designs that lack the years of testing and usage common to electrical devices and in general cannot be designed with the same level of block of functional redundancy, or graceful degradatio
3、n, common with electronic circuit design. The lesson provides a recommended checklist that contains 92 measures for enhancing the reliability, ease of fabrication, testability, maintainability, and robustness of mechanical designs. Description of Driving Event: JPL reliability studies of NASA roboti
4、c spacecraft have shown that mechanical hardware/ mechanism failures are more frequent and more likely to significantly affect mission success than are electronic failures. Spaceflight mechanisms are usually unique designs that lack the years of testing and usage common to electrical devices. They a
5、lso generally cannot be designed with the same level of block or functional redundancy, or graceful degradation, common with electronic circuit design. Mechanisms, such as deployables, intended for use after a prolonged or severe exposure to space environments provide a special challenge to designer
6、s.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-refer to D descriptionD 60-meter SRTM mast is an example of increasingly large and mechanically complex space mechanisms. Two resources are available to assist in the design and qualification of fligh
7、t mechanisms:1. A NASA Space Mechanisms Lessons Learned Study (Reference 1) identifies common mechanical failure modes and suggests preventive measures. The study, which employed an industry survey and a literature search, covers three major categories of mechanisms- deployable appendages, rotating
8、systems (gears, motors, bearings, reaction wheels, etc.), and oscillating systems (i.e., gimbal bearings).2. JPL has prepared a Checklist for Reliable Mechanism Usage. This checklist is provided in the Recommendations. Reference 2 also provides a link to the latest version of this checklist. It prov
9、ides a list of key measures that can be taken to avoid design and test oversights. Some of these items may appear obvious to the experienced mechanical engineer, but may be overlooked under deadline pressure. The Space Mechanisms Lessons Learned Study is used by JPL as a primary design reference, an
10、d the Checklist has recently been used to identify high probability/major impact failure modes subject to risk management.Reference(s):1. Space Mechanisms Lessons Learned Study, NASA Technical Memorandum 107046, Mechanical Technology Inc., November 1994, at http:/www-rel.jpl.nasa.gov/reltec/mechpart
11、/mti95tr4.pdf2. Checklist for Reliable Mechanism Usage, James Newell, Jet Propulsion Laboratory, May 2000, at http:/www-rel.jpl.nasa.gov/reltec/mechpart/ mechlist.htmLesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Overall reliabili
12、ty, ease of fabrication, testability, maintainability, and robustness of mechanical designs can all be enhanced by early and continuous application of the following checklist.Parts, Materials avoid compounds, springs or star type lock washers) Structurea71 Load, stress, fatigue and fracture analyses
13、 completeda71 Material properties from MIL-HDBK-5 and MIL-HDBK-17a71 Pressurized components designed per MIL-STD-1522 Generala71 Launch and operating environments defined; tests and analyses conducteda71 Clearances checked over temperature and load conditionsa71 Failure Mode and Effects Criticality
14、Analysis conducteda71 Minimum integrity check: benchtop performance, followed by vibe and thermalSeveral of the referenced standards have been withdrawn but still represent an excellent source of guidelines.Additional Key Words: failure mechanism, mechanical faults, design analysis, design margin, m
15、echanical anomaly, gyros, mechanism designRecommendation(s): (see lessons learned)Evidence of Recurrence Control Effectiveness: A JPL Corrective Action Notice will be assigned and practices will be modified as appropriate.Documents Related to Lesson: N/AMission Directorate(s): a71 Exploration System
16、sa71 Sciencea71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Flight Equipmenta71 Ground Operationsa71 Hardwarea71 Parts Materials & Processesa71 Payloadsa71 Spacecrafta71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 2000-10-20a71 Approval Name: Eric Raynora71 Approval Organization: QSa71 Approval Phone Number: 202-358-4738Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
