1、Lessons Learned Entry: 0578Lesson Info:a71 Lesson Number: 0578a71 Lesson Date: 1997-12-11a71 Submitting Organization: JPLa71 Submitted by: D. Oberhettinger/D. LordSubject: Cassini-Huygens Probe On-Pad Cooling Incident (1997) Abstract: After Cassini was mated to the launch vehicle, excessively high v
2、elocity cooling airflow blew insulation particles into the Descent Module. The responsibility for supplying cooling to the probe on the launch pad had been informally transferred from ESA to JPL without adequate control of the on-pad interface.Require that program decisions affecting interfaces auto
3、matically trigger a review of the need to change the IRD or ICD. Ensure that the verification methodology is thorough and considers responsibilities as well as requirements. Description of Driving Event: On August 28, 1997, after the Cassini spacecraft was initially positioned on the launch pad and
4、mated to the Titan IVB/Centaur launch vehicle, a cooling incident occurred which affected the Huygens Probe. During ground operations, cool air is injected into the probe to prevent internal heat build-up and damage to probe hardware. Prior to movement to the launch pad, cooling was provided without
5、 incident by a JPL cart. At the launch pad, cooling air was provided by the facility and routed to the probe through a diverter box provided by JPL, as shown in Figure 1. After mating Cassini to the launch vehicle, cooling air was supplied to the probe at approximately 0.26 kg/s (35 lbs/min). This a
6、ir was routed to the descent module via the European Space Agency (ESA)-furnished ducting whose configuration and effects were not fully communicated. This produced a high-velocity airflow in the vicinity of internal probe insulation. It was later determined that the desired flow in that configurati
7、on was 0.04 kg/sec, and the air flow was adjusted accordingly.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-refer to D description D Figure 1. Worst Case On-Pad Configuration To assess potential damage from the high airflow, a borescope was used to
8、 inspect the area inside the Descent Module (DM) in the vicinity of the air inlet. A tear approximately 5 cm long was seen on a Kapton blanket, along with evidence of foam insulation particles. The spacecraft was removed from the launch pad and returned to the Payload Hazardous Servicing Facility (P
9、HSF) for removal and more detailed inspection of the probe. The probe was cleaned, repaired, re-verified, reinstalled on the spacecraft, and transported back to the launch pad. These unplanned activities resulted in a delay of seven days in the scheduled launch of the Cassini-Huygens mission. A fail
10、ure review board concluded that, although ESA originally had responsibility for providing cooling air to the probe, the responsibility for supplying cooling to the probe on the launch pad was informally transferred from ESA to JPL without adequately defining and documenting nor implementing the resu
11、lting new interface requirement. Thus, no unambiguous assignment of responsibility for interface control existed. In addition, the internal probe cooling configuration at the launch pad, prior to backshell close-out, was changed without adequate review and coordination. These two factors resulted in
12、 excessive cooling air velocity within the DM, which caused the damage.Additional Keyword(s): Test & Launch Operations, Requirements DocumentationReference(s):Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. JPL Problem/Failure Report No. Z440982.
13、“Cassini-Huygens Probe On-Pad Cooling Incident: Report of Formal Review Board,“ JPL Document D-15158, October 24, 19973. Probe Interface Requirements Document (IRD) PD-699-080Lesson(s) Learned: The Cassini-Huygens Probe review board identified a solution to each of two Interface Requirements Documen
14、t (IRD)-related problems:1. The probe IRD was not updated when the responsibility for probe cooling was split between organizations.2. The specification compliance matrix failed to identify an inconsistency across the interface.End-to-end responsibility for elements within a given interface should r
15、eside within a single organization. Specifically, one single individual should be assigned responsibility for on-pad cooling (purge source, to purge outlet, to thermally controlled elements).Recommendation(s): 1. Require that program decisions affecting interfaces, whether made at the working group
16、level or at program reviews, automatically trigger a review of the need to change the IRD or Interface Control Drawing (ICD).2. Ensure that the verification methodology is thorough and considers responsibility statements as well as requirements.Evidence of Recurrence Control Effectiveness: N/ADocume
17、nts Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Administration/OrganizationProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Configuration Managementa71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 1997-12-16a71 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-,-,-
