1、Lessons Learned Entry: 1725Lesson Info:a71 Lesson Number: 1725a71 Lesson Date: 2006-04-14a71 Submitting Organization: JPLa71 Submitted by: David Oberhettingera71 POC Name: Ronald Welch / Richard Webstera71 POC Email: Ronald.T.Welchjpl.nasa.gova71 POC Phone: 818-354-7096Subject: Control Blow-By From
2、Pyrotechnic Devices (2006) Abstract: Significant leakage or “blow-by“ of combustion products past the seals within a pyrotechnic cable cutter was detected during pyroshock testing of Mars Exploration Rover. Optical flight instruments would likely have been contaminated had they been attached during
3、the test. Test plans and procedures that involve the firing of pyros should include several suggested measures predicated on an assumption that hazardous blow-by will occur.Description of Driving Event: After a Mars Exploration Rover (MER) landed, but before the vehicle could rove the Martian surfac
4、e, the rover had to be deployed from its compact mechanical configuration. This included the flight software-triggered firing of pyrotechnic cable cutters to sever restraints that had been placed on articulating assemblies. One such assembly was the Instrument Deployment Device (IDD), a mechanical m
5、anipulator mounted on the rover that carries the in-situ science instruments and positions them upon selected Martian terrain features. During pyrotechnic shock (pyroshock) and deployment testing of the IDD, a bright flash was observed, accompanied by a loud report (Reference (1). Examination of a h
6、igh speed video recording of the test (Figure 1) revealed flame and sparks discharged from the target aperture end of the cutter assembly. This is indicative of excessive leakage or “blow-by“ of combustion products past the seals within the pyrotechnic device (pyro). Some blow-by had been noted earl
7、ier during testing of similar cable cutters used to release the MER solar array and airbags. Following the IDD incident, all Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MER test and flight cable cutters were reworked to incorporate a JPL change t
8、o the pyro design that significantly reduced the leakage. Figure 1 is a color photo of the stowed MER IDD, a complex mechanical assembly with the RAT instrument attached to the top, on a bench within a test facility. A bright flare of light issues from beneath the test article, with many sparks shoo
9、ting in all directions from the flare. It is clear that the test article is taking the brunt of the apparent explosion, and no personnel are visible. The Figure 1 caption includes a link to a video clip from which the Figure 1 photo was extracted. The video shows the above-described test article in
10、a steady state on the bench, until the blow-by event is visible for a fraction of a secondFigure 1 - Blow-by from IDD cable cutter during 8/9/02 pyroshock test check Video Some blow-by (due to design tolerances) is typically considered inherent for pyrotechnic devices, the leakage is difficult to ch
11、aracterize or to measure, and it may be exacerbated by workmanship errors in their manufacture. Leakage is more pronounced at low temperature (Reference (2). Post-incident examination and testing revealed no damage to the flight hardware, including the Rock Abrasion Tool (RAT) instrument that had be
12、en installed on the IDD for the test, and no evidence of contamination on any of the adjacent surfaces. There was no hazard to personnel because the testing was done remotely. However, had the optical flight instruments been attached to the IDD during the pyroshock test, significant contamination mi
13、ght have occurred. References: (1) “Excessive Blowby/Leakage During Deployment consider appropriate protective measures such as moving adjacent hardware and providing barriers. 3. Pyrotechnic testing should always be done remotely so that there is never potential for personnel injury. (See Reference
14、 (2).) 4. The placement and orientation of pyro devices on flight hardware should always be done in conjunction with a venting analysis to assure that critical hardware will not be affected during initiation modes. Evidence of Recurrence Control Effectiveness: JPL opened Preventive Action Notice (PA
15、N) No. 1459 on April 14, 2006 to initiate and document appropriate Laboratory-wide action on the above recommendations.Documents Related to Lesson: NPG 8715.3, “NASA Safety Manual“Mission Directorate(s): a71 Space Operationsa71 Sciencea71 Exploration Systemsa71 Aeronautics ResearchAdditional Key Phr
16、ase(s): a71 Program Management.a71 Program Management.Risk managementa71 Engineering Design (Phase C/D).a71 Safety and Mission Assurance.a71 Safety and Mission Assurance.Product Assurancea71 Additional Categories.a71 Additional Categories.Risk Management/Assessmenta71 Additional Categories.Spacecraf
17、tProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Additional Categories.Test Articlea71 Additional Categories.Energetic Materials - Explosive/Propelland/Pyrotechnica71 Additional Categories.Flight Equipmenta71 Additional Categories.Hardwarea71 Add
18、itional Categories.Parts, Materials & Processesa71 Additional Categories.Payloadsa71 Additional Categories.Risk Management/Assessmenta71 Additional Categories.Spacecrafta71 Additional Categories.Test & Verificationa71 Engineering Design.Powera71 Safety and Mission Assurance.Advance planning of safety systemsAdditional Info: a71 Project: Mars Exploration Rovera71 Year of Occurrence: 2002Approval Info: a71 Approval Date: 2006-06-30a71 Approval Name: tmasona71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
