REG NASA-LLIS-0438--1996 Lessons Learned - Voyager Photopolarimeter Subsystem (PPS) Filter& Analyzer Wheel Step Problems (~1977).pdf

1、Lessons Learned Entry: 0438Lesson Info:a71 Lesson Number: 0438a71 Lesson Date: 1996-07-19a71 Submitting Organization: JPLa71 Submitted by: J.A. RobertsSubject: Voyager Photopolarimeter Subsystem (PPS) Filter & Analyzer Wheel Step Problems (1977) Abstract: Palladium is a particularly efficient cataly

2、st for the formation of polymers. Palladium in the potentiometer wiper contacts on the Voyager Photopolarimeter Subsystem formed a frictional polymer that prevented the stepping of both the analyzer and filter wheels.Catalytic material, including palladium-containing substances, should not be utiliz

3、ed in designs for sliding wipers, relay contacts, etc. Description of Driving Event: (Relevant Historical Lesson(s) Learned)1. The Voyager Photopolarimeter Subsystem on both S/C-31 and S/C-32 has a history of analyzer and filter wheel stepping problems. The problem was discovered late in the test pr

4、ogram before launch. The problems persisted in Flight with the analyzer wheel becoming unsteppable. Filter wheel could be stepped marginally, but that was also given up. Numerous in-flight operational fixes were tried without success.2. Failure analysis by the PPS Diagnostic Working Group has traced

5、 the probable cause of this anomaly to formation of an insulating “frictional polymer“ on PPS potentiometer wiper contacts. Such a polymer can be formed by the sliding action of metals in the presence of small quantities of almost any organic molecule. This polymer formation reaction was noted as ea

6、rly as 1958 by the Bell System in researching relay failures. Palladium is a particularly efficient catalyst for this reaction - unfortunately, the PPS wipers are made of a palladium substance.Additional Keyword(s): Contamination, Electrical ContactsProvided by IHSNot for ResaleNo reproduction or ne

7、tworking permitted without license from IHS-,-,-Reference(s):ISAs 1392, 1420, 1677, 1720, 1899 (Also see PPS ISAs for VGR-2 Encounter)Lesson(s) Learned: Careful consideration must be given to material choices and system designs in spaceflight hardware.Recommendation(s): In particular, palladium-cont

8、aining substances (or other catalytic material) should not be utilized in future designs for sliding wipers, relay contacts, etc. to avoid a repetition of this problem.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s)

9、: a71 Hardwarea71 Parts Materials & ProcessesAdditional Info: Approval Info: a71 Approval Date: 1996-05-02a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-