1、Lessons Learned Entry: 1330Lesson Info:a71 Lesson Number: 1330a71 Lesson Date: 2003-03-05a71 Submitting Organization: JPLa71 Submitted by: R. Frederickson/ D. OberhettingerSubject: Space Charging of Composite Structures Abstract: Although graphite/polymer composites were thought to be immune to spac
2、e plasma charging because the material is electrically conductive, it may actually retain a significant charge in places where the non-conductive resin pools.Use a non-contact charge measuring device when testing the materials electrical resistance, and consider spacecraft designs that can accept wo
3、rst-case electrical discharges.Description of Driving Event: Differential electrical charging of the spacecraft surface due to its interaction with charged plasma particles may present unrecognized hazards with non-conductive surface materials such as non-metallic and ceramic-metallic composites. Al
4、though graphite/polymer composites were thought to be immune to space plasma charging because the material is electrically conductive, it may actually retain a significant charge. Laboratory testing with multi-kV electron beams has found substantial charging to occur.Spacecraft structures made of gr
5、aphite/polymer composites have proven capable of significant weight savings while maintaining structural performance requirements. Their excellent thermal performance has led to applications in spacecraft solar arrays, radiator panels, space telescope structures, and mirrors. For these reasons, this
6、 material is widely used in the structural components of the Space Interferometry Mission (SIM) spacecraft.A surface resistance measurement of graphite composites made using an ohmmeter and flat probes would likely show zero resistance. The individual graphite fibers that penetrate the surface provi
7、de the conductive path between the probes. However, the non-conductive cyanate ester resin can be Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-shown to accumulate voltage potentials in excess of 2000 volts when exposed to a wide-angle electron bea
8、m. Preferential charging occurs at locations within the composite matrix where the weave permits the resin to pool.References: A flash animation of spacecraft charging and its effects may be found at http:/www.eas.asu.edu/holbert/eee460/spacecharge.htmlAdditional Key Words: spacecraft materials, bul
9、k dielectric charging, radiated electromagnetic interference, conducted electromagnetic interference, internal electrostatic discharge, IESD, conductive surfaces, dielectric materialsLesson(s) Learned: Surface resistance measurements of a non-homogeneous composite material may not accurately charact
10、erize the materials susceptibility to surface charging.Recommendation(s): Take precautions where any composite materials (such as graphite cyanate ester or epoxy resins) are used in exposed exterior spacecraft surfaces, and where flight electronics or other flight equipment is susceptible to degrada
11、tion or damage from radiated or otherwise coupled electrostatic discharge (ESD) energy:1. Use a non-contact charge measuring device when testing the materials electrical resistance under expected mission worst-case space plasma environment conditions. a. Conduct the first test as a measure of resist
12、ance in a vacuum, and use an electron beam to characterize the materials surface and in-depth ability to hold an electrical charge. b. If the charge does not bleed away, the materials resistivity is too high for analysis and the material may accumulate a potentially damaging charge in space. If, how
13、ever, the charge bleeds away in a measurably short time, the material may be characterized and the potential for damage may be analyzed.2. Results of such testing and analysis may warrant consideration of spacecraft designs that can accept worst-case electrical discharges. This may include pulse fil
14、ters, the use of alternative materials and coatings, or methods to improve the ESD bleed path on the composite surface.Evidence of Recurrence Control Effectiveness: Corrective Action Notice No. Z80116 was opened by JPL on April 7, 2003 to initiate and document appropriate Laboratory-wide corrective
15、action on the above recommendations. (A plan was prepared on September 29, 2003 to (1) Identify a funding source to perform the Reliability Engineering Office (REO) portion of the corrective action, (2) identify and address the appropriate REO procedures Provided by IHSNot for ResaleNo reproduction
16、or networking permitted without license from IHS-,-,-dealing with composite materials, and (3) train engineers on the changes.)Documents Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Sciencea71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Energya71
17、 Environmenta71 Flight Equipmenta71 Flight Operationsa71 Hardwarea71 Industrial Operationsa71 Parts Materials & Processesa71 Payloadsa71 Safety & Mission Assurancea71 Spacecrafta71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 2003-04-07a71 Approval Name: Carol Dumaina71 Approval Organization: JPLa71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
