REG NASA-LLIS-0579-1997 Lessons Learned - Avoid Inadvertent Hot Mates or Demates of Connectors (1996).pdf

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1、Lessons Learned Entry: 0579Lesson Info:a71 Lesson Number: 0579a71 Lesson Date: 1997-12-18a71 Submitting Organization: JPLa71 Submitted by: D. OberhettingerSubject: Avoid Inadvertent “Hot“ Mates or Demates of Connectors (1996) Abstract: During integration and test of Mars Global Surveyor, the mating

2、configuration for a power connector permitted a pin to short to ground. Use “scoop-proof” power connectors. Where possible, avoid mating or demating any powered connector, whether powered externally or by a spacecraft battery.Description of Driving Event: While mating two electrical power connectors

3、 during integration and test of the Mars Global Surveyor (MGS) Electrical Power Subsystem (EPS), a pin on one connector came into contact with the backshell (at spacecraft ground potential) on the other connector. Spacecraft external power was disconnected at the time, but the batteries were charged

4、. A short occurred between a solar panel power return pin and the backshell.The event caused a transient energizing of the power system. The pin was isolated from spacecraft ground by a remote power switch. The shorting of the pin to ground provided a current path around the remote power switch, all

5、owing the batteries to energize the power bus to no more than 22 volts. This short probably existed for only a few milliseconds and did not power any loads connected to the bus.The incident was attributed to the connector mating configuration-the exposed position of a corner pin during a slightly tw

6、isted entry. This event caused no damage to flight hardware due to the adequate surge rating of the blocking diodes and inductors. The corrective action was to add a test cable to the positive side of the battery allowing battery voltage to be interrupted prior to and during cable mating or demating

7、. Where use of the test cable was not feasible (e.g., during spacecraft acoustic test), the solution was to discharge the battery prior to any mate/demate which could cause a turn-on transient.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Reference

8、(s):1. MGS Problem/Failure Report No. B0RE5V2. A related lesson is recorded in Magellan Battery Fire, Lesson Learned #4-112 (NASA LLIS #386)Lesson(s) Learned: 1. Where possible, avoid mating or demating any powered connector, whether powered externally or by a spacecraft battery.2. Use scoop-proof p

9、ower connectors. “Scoop-proof“ means that the connectors long shell design prevents inadvertent cocking of the mating plug connector into the mating receptacle. Such cocking can occur in other connector designs, causing physical damage to the pins or electrical shorting. refer to D descriptionDIn th

10、e event of connector “mismates,“ scoop-proofing will also preclude the inadvertent partial electrical mating of differently keyed connectors. 3. Positively isolate the power source or follow appropriate spacecraft battery discharge procedures whenever connectors are being mated or demated.Recommenda

11、tion(s): See Lessons LearnedEvidence of Recurrence Control Effectiveness: N/AProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Documents Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Energya71 Hardwarea71 Parts Materials & ProcessesAdditional Info: Approval Info: a71 Approval Date: 1998-01-08a71 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-,-,-