1、Public Lessons Learned Entry: 5796 Lesson Info: Lesson Number: 5796 Lesson Date: 2011-06-13 Submitting Organization: JPL Submitted by: Matthew Wallace Subject: MSL Backshell Crane Incident Abstract: In May 2011, the Mars Science Laboratory (MSL) Flight Backshell was inadvertently lifted while attach
2、ed to the Backshell Cart. The incident occurred at Kennedy Space Center (KSC) in the Payload Hazardous Servicing Facility (PHSF). The weight of the Backshell Cart imparted loads into the Backshell structure through the flight hardware ground support interfaces. The event was caused by a crane operat
3、or error in which the operator drove the crane in the up direction instead of the commanded down direction. The MSL project identified a set of actions to address the vulnerability experienced in this operation. Immediate corrective actions have been implemented, and longer-term corrective actions a
4、re in progress. Description of Driving Event: A “near miss” handling incident (Reference (1) occurred during an Aeroshell Mass Properties Test conducted at the NASA Kennedy Space Center (KSC) on the Mars Science Laboratory (MSL) spacecraft Flight Backshell. Designed and built by the NASA/Caltech Jet
5、 Propulsion Laboratory (JPL), the MSL spacecraft (Figure 1) consists of a Cruise Stage, an Entry, Descent, and Landing System that ejects the protective Backshell immediately following Parachute Descent and just prior to Powered Descent, and the Rover. Provided by IHSNot for ResaleNo reproduction or
6、 networking permitted without license from IHS-,-,- Figure 1. Major elements of the MSL spacecraft A crane was used for the installation of the Descent Stage Simulator (DSS) into the Backshell in preparation for a Backshell to Heatshield fit-check (see Figures 2 and 3). Just prior to the incident, t
7、he DSS had been secured to the Backshell, and the system test team prepared to unload the crane and remove the rigging. A “Hydra Set” load positioning system was used to lower the crane hook until the lifting slings went slack and the load cell read zero. The lift conductor then gave the “down slow“
8、 command. The “down slow“ command was repeated by the crane operator, but the crane operator commanded the crane to go “up slow.“ The team observed the tautening of the lifting slings, and the “Stop” command was immediately issued. The crane was stopped, and then lowered. It was noted that the load
9、cell peaked at 4,400 lbs., and it appeared that two of the legs (jacks) of the Backshell Cart were lifted slightly off the floor. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Figure 2. Backshell and Backshell CartThe topmost note (yellow font) in
10、the photo states, “Crane pulled in up direction (while BS was attached to cart).” The second note states, “Essentially, a large nut plate, Descent Stage Surrogate, is attached at the flight interfaces on the bottom of the BIP (Backshell Interface Plate).” The third note (red font) states, “Backshell
11、 is attached to Cart at nine (9) locations.” The bottom note states, “Red GSE fitting straddles flight interface. GSE fitting is attached into 4 inserts on bottom of BS (Backshell) on one side and to Backshell cart on the other.” Figure 3. Backshell and Descent Stage Simulator / Surrogate Suspended
12、from Spacecraft Assembly and Rotation Fixture (SCARF) The topmost note (yellow font) in the photo states, “4X size #10 inserts in Backshell Stiffening Ring used to attach the Red GSE fitting that attaches the Backshell to the Cart.” The lower note states, “Descent Stage Surrogate in action. Used to
13、attach the Backshell to our rotation fixture (SCARF) by attaching to our flight like GSE LVA (Launch Vehicle Adapter) Ring.” A loads analysis of the lift incident was performed. The area of concern was associated with the GSE fittings on the bottom of the Backshell where the structure connects to th
14、e Backshell Cart, and the area near these fittings. The structure was found to have been tested to loads that provided sufficient margin against the loads imparted during the incident. Analysis, inspections, and tap tests on the Backshell conducted by the Backshell manufacturer and JPL confirmed tha
15、t the flight structure was not damaged. An assessment of the incident and the root cause, performed by the project and mission assurance representatives, concluded that the team was operating in accordance with JPL guidelines and practices: The lift lead provided correct direction to the crane opera
16、tor. The lift leads command was clearly heard by the crane operator, and the crane operator properly repeated back the command. Hand signals were used as a backup due to some ambient noise in the area. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
17、The operator had appropriate line-of-sight to the floor lead. The team was using a Hydra Set in accordance with JPL standards. The team was well rested: fatigue was not a factor. The JPL crane operator received onsite training and was certified on this crane. Appropriate hardware quality assurance a
18、nd safety personnel were present and participating. This ground handling incident was attributed to the following factors: 1. The crane operator inadvertently pushed the wrong button on the crane controller (Figures 4 and 5). 2. Standard crane operation, as specified in Reference (2), does not provi
19、de any clear mechanism for avoiding hardware damage in the event of this type of operator error. Figure 4. KSC Payload Hazardous Servicing Facility (PHSF) crane control console. Unlike the standard pendant-type controls used at JPL, this console can be wheeled around the PHSF highbay. Figure 5. Clos
20、e-up detail of hoist control from Figure 4. Some possible contributing causes were identified, but were not found to be directly correlated to the event: 1. The crane controller panel does not have a physical separator between the up and down buttons. 2. The crane operator had completed the required
21、 certification and training; however, he had somewhat less experience on this particular crane than other operators. References: 1. “Backshell Crane Lift Incident,“ JPL Problem/Failure Report No. 48883, May 20, 2011. 2. “JPL Standard for Systems Safety (D-560), Rev. D,” JPL DocID 34880, September 17
22、, 2007. 3. “MSL ATLO Response to Backshell Lift Incident at KSC/PHSF,” JPL Memo IOM 352M-BLT-1013, May 25, 2011. Lesson(s) Learned: Lift operations can be vulnerable to single mistakes by crane operators. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,
23、-,-Recommendation(s): Following the incident, JPL Safety and the JPL ATLO (Assembly, Test, and Launch Operations) Mechanical Team reviewed JPL lift processes and made the following recommendations for improvement (Reference (3): 1. When releasing/disconnecting the load during a crane lift, utilize a
24、 Hydra Set to establish sufficient slack for the rigging to be disconnected, or for 3-5 seconds of movement at the highest crane speed in the wrong direction. This will provide sufficient time to execute an emergency stop. 2. When mating/raising a load, utilize a Hydra Set beyond the point where the
25、re is 3-5 seconds of movement available at the highest crane speed. This will provide sufficient time to execute an emergency stop. 3. When a Hydra Set is not available or the Hydra Set functionality is lost, the Lift Lead should use limited movements or bump commands for the activities described ab
26、ove. 4. Ensure an unencumbered individual is available to monitor the load cell during lifts. Evidence of Recurrence Control Effectiveness: JPL has referenced this lesson learned as additional rationale and guidance supporting Paragraph 6.12.5.3 (“Engineering Practices: Protection and Security of Fl
27、ight Hardware”) in the Jet Propulsion Laboratory standard “Flight Project Practices, Rev. 7,” JPL DocID 58032, September 30, 2008. Documents Related to Lesson: N/A Mission Directorate(s): Exploration Systems Aeronautics Research Science Additional Key Phrase(s): Additional Categories.Payloads Additi
28、onal Categories.Safety & Mission Assurance Additional Categories.Hardware Additional Categories.Ground Operations Additional Categories.Ground Equipment Additional Categories.Flight Equipment Safety and Mission Assurance.Quality Integration and Testing Safety and Mission Assurance.Advanced planning
29、of safety systems Safety and Mission Assurance.Product Assurance Additional Categories.Industrial Operations Additional Categories.Training Equipment Additional Categories.Test Article Additional Categories.Spacecraft Additional Info: Project: Mars Science Laboratory Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: Approval Date: 2011-09-30 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
