XPost: sci.space.shuttle   
   From: bpalmer201@optonline.net   
      
   Henry Spencer wrote:   
   > In article <5wNVb.1574$h44.295246@stones.force9.net>,   
   > Ian Stirling   wrote:   
   >   
   >>>No, actually, "gyro" means "gyro" here.  It's the high-precision sensors   
   >>>that are giving trouble.  The gyrodynes (I think) that actually produce   
   >>>torque to rotate Hubble have been reliable.   
   >>   
   >>There seems to be talk on various pages about "2 gyro mode".   
   >>How degraded is this?   
   >   
   >   
   > I don't know quite enough about Hubble's guidance to be sure, but possibly   
   > not at all, except for perhaps more headaches for the operations crew.   
   >   
   > IUE was successively operated on two gyros, one, and none at all, although   
   > that was an easy case because it was in GSO and hence in continuous contact   
   > with the ground.   
   >   
   >   
   >>Were the gyros brought down, and if so, did they all fail the same way?   
   >   
   >   
   > They certainly brought the old ones down both times.  I haven't seen a   
   > detailed report; my understanding is that the analysis of the first batch   
   > did conclude that they all died the same way and that the design has a   
   > fundamental weakness.   
      
   If they were the ones originally built by Bendix GSD then I'm not   
   surprised.  I knew a couple of people who worked on the ST project there   
   back in the late '70s that used to go on and on about the quality   
   control there.  Hearsay, I know, but IIRC they were always talking about   
   the thin line between out-of-spec and "good enough".  A drift test   
   failed?  Run it again (without tweaking anything or making any changes).   
     It's good now?  Ship it.   
      
   --   
   bp   
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