binding/jamming/seizing within the NEA release mechanism. Because the NEA is a simple, reliable  mechanism that has been used successfully in many other applications – including numerous space  applications, an internal design flaw leading to this failure was considered unlikely. The most probable  cause was considered a defect in manufacturing due to the test article being a development unit.  Description of Qualification Test Failure  The second CCLR failure occurred during qualification testing of the capture latch assembly. Similar to the  development test, the qualification secondary release test occurred toward the end of the qualification  program, to be followed only by the ultimate load test. However, for the qualification testing, the mechanism  was tested under the thermal vacuum (cold) conditions. Like the  development test, the unit had already been subjected to all other  environmental tests, including random vibration. Additionally, the test  load was lowered based on updated structural analysis of the worst  case undocking conditions. The test setup for the qualification test  was identical to flight except that a camera was added inside the  thermal vacuum chamber to allow direct viewing of the NEA, and an  oscilloscope was used to obtain high speed current data for the  performance of the NEA. The test setup is shown in Figure 7.  During the  secondary release  test when current  was applied, there  was no evidence  the release  mechanism moved. Additionally, the position sensor and  the camera showed no discernable movement. It was then  decided that an inspection, including both visual and x-ray  of the test hardware must be performed, so the chamber  was returned to ambient conditions, which took  approximately 24 hours. During the visual inspection, no  signs of debris or jamming were observed. However,  during the setup for the x-ray imaging, the load released  prior to any direct imaging being performed.  Qualification Test Failure Investigation Summary  After the test failure and then inadvertent release, a Failure Investigation Team was convened to investigate  and resolve the test failure. The initial goals of the team were to review the development test failure, collect  all data relating to the qualification failure, development of a fault tree, and establishing a troubleshooting  plan. After reviewing all data and developing the fault tree, the team determined that the first investigation  step should be the teardown and inspection of the secondary release mechanism. The most significant  finding of the teardown was the identification of wear marks potentially consistent with galling found on the  load washer inside the NEA. The load washer is part of the NEA Cover and has the surface that reacts the  load from tension applied to the NEA shaft. Figure 8 shows the load washer and Figure 11 item B shows  the approximate position of the load washer in the mechanism. The apparent galling is evident in the silver  area on the otherwise black surface of the load washer, as noted as item A in Figure 8.  Corresponding wear marks were also observed on the spool half that was located against this surface. Both  parts were examined using a laser profilometer, light microscopy, and a scanning electron microscope to  determine whether galling of the wear surfaces had occurred. As shown in Figure 9, the profilometry  analysis showed that material on the load washer was displaced and removed. The light microscopy  measurement confirmed the presence of fretting and galling, as shown in Figure 10. From these results,  the investigation team concluded that the most likely cause of the failure to release was galling of the load  washer to the spool inside the NEA. The team’s next task was to determine the cause of the galling. Figure 9. Load Washer Profile Figure 8. NEA Load Washer  NASA/CP—2018-219887 494