1、Lessons Learned Entry: 0353Lesson Info:a71 Lesson Number: 0353a71 Lesson Date: 1994-12-09a71 Submitting Organization: JPLa71 Submitted by: R.F. CollinsSubject: Facility Failure During Testing of the Galileo Near Infrared Mapping Spectrometer (NIMS) Abstract: During a recalibration test of the Galile
2、o NIMS flight instrument in a subsystem vacuum chamber, a facility failure subjected it to subjected to a temperature below its qualification limits. Subsystem facilities must be critically examined for the probability of any failure modes which may subject flight hardware to out-of-specification en
3、vironments. Specification limits should be alarmed, and there should be straightforward safing procedures available to the operator.Description of Driving Event: During a recalibration test of the Galileo NIMS flight instrument in a subsystem vacuum chamber, a facility failure occurred. A liquid nit
4、rogen supply line fitting separated, causing liquid nitrogen to spray on the outside of the chamber, and filling the room with fog. After the break was repaired and in preparation to restart the test, four additional failures occurred, one of which caused the flight instrument to be subjected to a t
5、emperature below its qualification limits.These failures can be attributed to substandard liquid nitrogen plumbing, a known idiosyncrasy in a control circuit and human error.Before the flight instrument was permitted to be tested in the subsystem facility, the required safety certification process h
6、ad been accomplished and a flight projects office waiver had been requested and approved. The reason for requesting to test in a facility other than the JPL environmental test lab was so as not to introduce unknowns into the recalibration process.Additional Keyword(s): Science InstrumentsLesson(s) L
7、earned: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Environmental test chambers are subject to several hazards not familiar to most practicing engineers and technicians. Cryogenics, vacuum systems, and thermal control systems all have serious pot
8、ential safety risks if wrong materials, parts, or assembly techniques are used. Once incorporated, these improper elements may perform well for indefinite periods before bursting, leaking, or otherwise failing. They look ok, they work ok, but they arent ok.Recommendation(s): 1. Subsystem facilities
9、must be critically examined for the probability of any failure modes which may subject flight hardware to out-of-specification environments. Specification limits should be alarmed separately from control system limits. Operator response to alarms should be covered by straightforward safing procedure
10、s.2. The proposed use of nonstandard facilities for flight hardware should be very carefully weighed during the planning phase of a project or task and the following should be considered: a. Safety certification isnt a foolproof process.b. Availability of qualified operators is a greater problem for
11、 small subsystem teams than for the officially prescribed environmental test lab, particularly if long-term tests are planned.c. Upgrading facilities to meet requirements that are imposed because of the testing of flight hardware is likely to be expensive in schedule and dollars.d. Damage and subseq
12、uent repair to flight instruments or subsystems is costly in both schedule and dollars and could have severe project and mission impact.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Cryogenic Systemsa71 Envir
13、onmenta71 FacilitiesProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Test FacilityAdditional Info: Approval Info: a71 Approval Date: 1987-12-17a71 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-,-,-
