1、Lessons Learned Entry: 1858Lesson Info:a71 Lesson Number: 1858a71 Lesson Date: 2008-05-6a71 Submitting Organization: JPLa71 Submitted by: David Oberhettingera71 POC Name: Eric J. Suh, Paul B. Willisa71 POC Email: Jong-Ook.Suhjpl.nasa.gov, Paul.B.Willisjpl.nasa.gova71 POC Phone: 818-354-4574, 818-354
2、-6998Subject: Maintain a Materials Properties Database that Covers Environmental Extremes Abstract: Vendor-supplied materials data sheets that cannot be relied upon, or do not cover materials properties throughout the ranges of extreme environmental conditions found in spaceflight, are a continuing
3、challenge facing spacecraft designers. Even where application-specific materials data has been accumulated by the institution over decades of use, it may not be readily available to design engineers. Maintain and use a Spacecraft Materials Database that defines the properties of spacecraft materials
4、 that have been observed during characterization and test under spaceflight-like conditions.Description of Driving Event: A continuing challenge facing spacecraft designers is that vendor-supplied materials data sheets often cannot be relied upon and do not cover materials properties throughout the
5、ranges of extreme environmental conditions found in spaceflight. Even when the acceptable environmental range is clearly defined in the supplied document, poor information on the boundary conditions and margins around the qualified limits may result in material failure. When the susceptibility of se
6、lected materials to temperature, radiation, vacuum, etc. is subsequently detected during testing, the required redesign and retest can significantly impact project cost and schedule. This issue has arisen on recent NASA/Caltech Jet Propulsion Laboratory (JPL) spaceflight projects. For example: a71 T
7、he major design problem that befell the CloudSat project over its development history was Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the mission-critical failure of its high voltage power supply during thermal-vacuum test (Reference (1). A value
8、 for the thermal conductivity of a potting compound (in watts/meter-Kelvin), obtained verbally from a vendor, was found to be inaccurate by an order of magnitude. a71 The thermal conductivity of two silver-filled conductive epoxies used in the Mars Science Laboratory (MSL) landing radar was specifie
9、d in the material data sheet as 7-10 watts/meter-Kelvin (W/m-K) range whereas when tested in the MSL application the epoxies were found to have a conductivity of only approximately 1 W/m-K. Over many years, JPL has retained extensive amounts of materials data obtained during characterization, testin
10、g, and flight, but it has resided mainly in the personal files of individuals and has not been available for institution-wide use. When a search for data on a material measured at JPL has not been fruitful, time and money has been spent performing duplicate measurements. To improve the availability
11、of historical materials data and mitigate the risk of using incorrect data, JPL has developed an online Spacecraft Materials Database (Reference (2). The database presently holds 168 datasets on 88 materials in the following formats: a71 Both raw and plotted materials data measured at JPL, including
12、 data from Differential Scanning Calorimetry (DSC), Thermal Mechanical Analysis (TMA), Dynamic Mechanical Analysis (DMA), Thermogravimetric Analysis (TGA), etc. a71 Data measured by manufacturers or vendors a71 Material safety data sheets (MSDSs) a71 Technical papers in journals, etc. a71 Vendor dat
13、asheets (including data that may not be applicable for spaceflight use) Of 17 polymeric materials listed in Reference (3), for example, the online database has glass transition temperature (Tg) and coefficient of thermal expansion (CTE) data on 8 of these measured by JPL using DSC and TMA, and JPL p
14、lans to characterize the remainder. Users are invited to archive their materials property data so it can be shared across the institution. Along with new data that is automatically forwarded by the JPL analytic chemistry laboratory, this uploaded data is then organized by a materials database librar
15、ian. A governing board is being formed to establish official JPL materials property parameter values. A planned upgrade to the system will permit engineers to automatically generate Materials Identification and Usage Lists (MIULs) from the materials database. References: (1) Thermal Vacuum Run #, HP
16、A 102-Diode Thermal Runaway, Problem/Failure Report No. Z82336, Jet Propulsion Laboratory, November 3, 2003. (2) JPL Spacecraft Materials Database, http:/matdb.jpl.nasa.gov. (3) JPL Standard for Spacecraft Electronic Packaging/Cabling Design and Fabrication, Rev. K Provided by IHSNot for ResaleNo re
17、production or networking permitted without license from IHS-,-,-JPL Document No. DocID 35120, December 27, 2007. Lesson(s) Learned: The limited information on a typical, vendor-supplied, material data sheet may mislead an engineer into concluding that the properties of a material are suited to the s
18、paceflight environment. The more application-specific data accumulated by the institution over many decades has not been readily available to spacecraft designers.Recommendation(s): 1. Maintain and contribute to a Spacecraft Materials Database that defines the properties of spacecraft materials that
19、 have been observed during characterization and test under spaceflight-like conditions. 2. Design engineers should check the Spacecraft Materials Database for new or updated materials properties data prior to material selection. 3. Material testing is recommended for critical spaceflight application
20、s that are not clearly covered by the Spacecraft Materials Database, and the test results should be included in the database. Evidence of Recurrence Control Effectiveness: JPL has referenced this lesson learned as additional rationale and guidance supporting Paragraph 6.10 (“Engineering Practices: M
21、aterials, Processes, and Contamination Control“) in the Jet Propulsion Laboratory standard “Flight Project Practices, Rev. 6,? JPL DocID 58032, March 6, 2006.Documents Related to Lesson: N/AMission Directorate(s): a71 Space Operationsa71 Sciencea71 Exploration Systemsa71 Aeronautics ResearchAddition
22、al Key Phrase(s): a71 Program Management.Configuration and data managementa71 Systems Engineering and Analysis.Engineering design and project processes and standardsProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Engineering Design (Phase C/D).Sp
23、acecraft and Spacecraft Instrumentsa71 Mission Operations and Ground Support Systems.Ground support systemsa71 Mission Operations and Ground Support Systems.Launch support systemsa71 Safety and Mission Assurance.Reliabilitya71 Additional Categories.Flight Equipmenta71 Additional Categories.Ground Eq
24、uipmenta71 Additional Categories.Hardwarea71 Additional Categories.Parts, Materials, & Processesa71 Additional Categories.Payloadsa71 Additional Categories.Safety & Mission Assurancea71 Additional Categories.SpacecraftAdditional Info: a71 Project: variousApproval Info: a71 Approval Date: 2008-07-14a71 Approval Name: mbella71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
