327 The environments experienced by the bearing sets  appeared to be the catalyst for creating and/or  exacerbating the torque spikes . Vibration loads, bulk temperature changes, and temperature gradients  across the bearing assembly, in particular, are conditionally implicated in causing the torque spikes. Pretest  handling was exonerated because functional tests performed after assembly did not result in detectable  torque spike behavior.  

Table 7: Summary of bearing anomaly tests   Test  Index  Test Name  Test  Unit Environment  Results  1 Pre TVAC Torque  Measurement  EM Room  Average measured torque aligned with predicted, small (~0.02  Nm) periodic torque spikes observed   2 TVAC Qual 1st Cycle  Hot EM +70°C, Vacuum  Torque spike magnitude increased to ~0.05 Nm from predicted  drag torque   3 TVAC Qual 1st Cycle  Room  EM Room  Torque spike magnitude appears to be permanently increased  at the same locations   4 TVAC Qual 1st Cycle  Cold EM -45°C, Vacuum  Torque spike magnitude increased to ~0.30 Nm from predicted  drag torque   5 TVAC Qual 2nd Cycle  Hot EM +70°C, Vacuum  Torque spike magnitude appears to be permanently increased  to ~0.30 Nm from predicted   6 TVAC Qual 3rd Cycle  Hot, Offset  EM +70°C, Vacuum  Performing hot TVAC cycle with bearing set rotated 6° from  nominal position creates new sp ike location   7 TVAC Qual 3rd Cycle  Room, Offset  EM Room  Torque spike magnitude appears to be permanently created at  the new locations   8 TVAC Qual 3rd Cycle  Cold, Offset  EM -45°C, Vacuum  New torque spikes still present, no apparent increase to  magnitude (~0.05 Nm)   9 TVAC Qual 3rd Cycle  Room, Offset  EM Room  Torque spikes are permanently created following TVAC cycles,  not exacerbated at cold   10 Post Vibe Torque  Measurement  FM1 Room  Small torque spikes observed in data, on the order of 0.02 Nm  in magnitude   11 Bearing Run- in Test  (200 cycles)  EM Room  Torque spikes diminished in magnitude, from ~0.20 Nm to ~0.05  Nm, 6° spikes are no longer present   12 Pre TVAC Torque  Measurement  BB Room  Brassboard unit exhibits torque spikes with ~0.04 Nm  magnitude   13 TVAC Qual Cycle Hot  BB +70°C, Vacuum  Torque spike magnitude increased to ~0.10 Nm   14 TVAC Qual Cycle Room  BB Room  Torque spikes appear permanently increased from previous hot  cycle   15 Pre TVAC Torque  Aluminum Gear  EM Room  Torque spikes (~0.06 Nm) still present in bearings with steel  gear replaced with aluminum stand -in   16 TVAC Qual Cycle Hot  EM +70°C, Vacuum  Torque spikes increased to ~0.10 Nm with aluminum gear   17 TVAC Qual Cycle Room  EM Room  Torque spikes permanently increased, average running torque  also increased   18 TVAC Qual Cycle Cold  EM -45°C, Vacuum  Torque spikes still present, no noticeable change in magnitude   19 TVAC Qual Cycle Room  EM Room  Torque spikes still present, no noticeable change in magnitude,  running torque in -line with pre hot cycle   20 TVAC Qual Cycles  Repeat at Hot  EM Room & +70°C,  Vac Repeated tests with steel gear reinstalled at hot and room  temperature shows no significant change to torque spike  magnitude   The test program includes over 20 discrete thermal vacuum tests meant to collect data on the bearing sets’  anomalous behavior and find a root cause. The types of tests run were informed by various hypotheses  developed between Honeybee and JPL during the investigation. Table 7 summarizes the tests performed.