I watched two trainers come up with a brand new failure.  They were so excited!!  They were so proud that they still yet had invented something new.  It was an APU (Auxiliary Power Unit) Power Diode Failure for EGILS (Electrical) and MMACS (Mechanical).  Just a failed short circuit that makes the APU appear ready.  Then I went down to sit with the controllers to see them work the problem.  The MMACS controller looked about 22 years old.  He was so focused.  He discussed both the problems he was working on.

The latch on the arm - which if it turned out to be the BUS and not the latch - was the same BUS that powered closing the payload doors.  And if that was bad, then the whole mission would be cut short because they never continue a mission without a backup system in place.  If you can’t close the payload bay doors, you can’t come home!  That would be a very bad day.  Then he talked about the APU problem and showed me the diagram, which charted the sequence of power through the APUs.  They had the problem figured out very quickly with the help of their MPSR (pronounced MIP-ser), what they call their back room staff.

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