1、Lessons Learned Entry: 1041Lesson Info:a71 Lesson Number: 1041a71 Lesson Date: 2001-10-15a71 Submitting Organization: MSFCa71 Submitted by: Robert B. GossSubject: Gravity Probe-B Nitrogen Contamination Mishap Investigation Final Report Description of Driving Event: At approximately 10:30 a.m. on Aug
2、ust 26, 2001, gaseous nitrogen (GN2) was erroneously connected to the Gravity Probe-B (GP-B) guard tank vent line as the GP-B Science Payload (Figure 1) was readied for transport from Stanford University (SU) to Lockheed Martin (LM) in Palo Alto, California. At approximately 2:30 p.m. (after the GP-
3、B Science Payload arrived at LM), the error was recognized and the GN2 was disconnected. Gaseous helium (GHe) was the intended gas to be connected instead of GN2. Since the guard tank is at a much lower temperature than the freezing point of GN2, concerns arose over the possible detrimental effects
4、of frozen nitrogen (N2) in the vent line and/or the guard tank itself.The purpose of the move was to transfer the GP-B Science Payload from SU to LM for later integration with the spacecraft. The move was uneventful except for the discovery of the connection of the incorrect gas to the guard tank. T
5、he immediate cause of the incident was the inadvertent connection of the GN2 to the guard tank instead of utilizing the required GHe.A procedure to check the guard tank vent line impedance was executed on September 15, 2001. The data showed significant but not total blockage of the vent line with fr
6、ozen N2. The procedure added heat to the guard tank and flowed gas through the vent line until there was no further indication of N2 in the tank or line. There is no reason to believe that damage to the hardware had occurred since the vent line was only partially blocked. There was an impact on the
7、schedule due to the recovery time, and there will be an associated cost based on the schedule impact.Lesson(s) Learned: 1. All operations and modifications to flight hardware and its interfacing GSE should always have comprehensive and well reviewed written procedures.Provided by IHSNot for ResaleNo
8、 reproduction or networking permitted without license from IHS-,-,-2. Schedule pressure can cause even top performers to make mistakes and/or take short cuts.3. Gas K-bottles or other sources of gases should be readily identifiable in safety critical and contamination critical programs.4. Gases shou
9、ld be positively verified in safety critical and contamination critical programs.5. Gases should be segregated by species. Controls should be in place to avoid inadvertently placing a different gas in a rack or storage location designated for another species of gas.6. All personnel supervising or wr
10、iting procedures for transportation activities should be trained on DOT HAZMAT regulations.7. In addition to the need for a positive identification of gases, the traceability and accountability must be maintained to ensure that no changes have occurred.8. Lessons learned should be widely disseminate
11、d and appropriate follow-through on appropriate actions from the lessons must occur.9. It is important to maintain configuration control on GSE that interfaces with flight hardware and diligently verify its configuration and functions, especially if repairs or modifications are being incorporated.10
12、. A single integrated procedure should be used when multiple simultaneous operations are occurring in order to establish clear lines of authority. Ensure safety and minimize distractions and concerns of the participants.11. Contamination plans and control should be thorough and consider all sources
13、of contamination including using the incorrect materials and gases.12. MIPs should be utilized to ensure success in executing the procedures and not be viewed as hindrances to completing the tasks.13. All program and project offices should be familiar with the NASA Mishap Notification process and re
14、quirements, and also with initial actions necessary to preserve evidence (including independence of witness statements).Recommendation(s): The Boards principal findings and recommendations are:DOMINANT ROOT CAUSES:1. Finding: The GP-B Cryo Team (Stanford University Cryogenics Team) performed the sup
15、ply connect and disconnect operations on the flight hardware and its interfacing ground support equipment (GSE) without a written procedure or checklist. Recommendation: Train employees on the significance of documented procedures. Require the use of comprehensive and well-reviewed procedures and ch
16、ecklists.2. Finding: The work schedule pressure caused some individuals to be overworked. Recommendation: Review manpower, work schedules, and limit overtime. Ensure the project Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-schedule is reasonable.C
17、ONTRIBUTING CAUSES:1. Finding: The K-bottles of gases are not color coded for different gases. Recommendation: Develop a method of uniquely identifying K-bottles by gas species and consider using unique fittings for different types of gas systems.2. Finding: The individual connecting the GN2 K-bottl
18、e to the flight hardware exhibited complacency when he failed to look at the label on the K-bottle prior to connection and when he tagged the K-bottle for pick up earlier in the move sequence. Recommendation: Provide training to all Integration and Test (I&T) personnel to verify gas type, inspect fo
19、r cleanliness, check grade, and document the activity and results during any operation that involves the flight article.3. Finding: Department of Transportation (DOT) Hazardous Materials (HAZMAT) regulations were not met. Recommendation: Provide training for appropriate individuals on DOT HAZMAT reg
20、ulations and shipping documents.4. Finding: SU identification, traceability, and accountability of gas K-bottles are inadequate. Recommendation: Improve the identification of gases and the control and traceability by requiring appropriate identifying paperwork to accompany all fluid supplies and by
21、providing a segregated and labeled storage area for different types of gases.More detailed recommendations may be found in the complete board report which is included with this lesson learned.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): Pro
22、vided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 ScienceAdditional Key Phrase(s): a71 Administration/Organizationa71 Configuration Managementa71 Cryogenic Systemsa71 Ground Equipmenta71 Ground Operationsa71 Human Factorsa71 Mishap Reportinga71 Payloa
23、dsa71 Safety & Mission Assurancea71 Spacecrafta71 Test & Verificationa71 TransportationMishap Report References: Gravity Probe-B Nitrogen Contamination Mishap Investigation Final ReportAdditional Info: Approval Info: a71 Approval Date: 2001-12-12a71 Approval Name: Lisa Hedigera71 Approval Organization: MSFCa71 Approval Phone Number: 256-544-2544Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
