Path: utzoo!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!valid!caber!lou From: lou@caber.valid.com (Louis K. Scheffer) Newsgroups: sci.space.shuttle Subject: Re: New Shuttle Computers Message-ID: <240@valid.valid.com> Date: 13 Mar 91 05:12:21 GMT References: <1991Mar7.010752.10632@agate.berkeley.edu> <1991Mar9.044834.27802@cimage.com> <1991Mar10.164459.5216@rodan.acs.syr.edu>, <00945749.54A05580@KING.ENG.UMD.EDU> Sender: news@valid.com Lines: 19 A hard disk drive would probably work OK on the shuttle, although perhaps not during launch. Hard disk drives are surprisingly rugged while running. When operating, the air bearing is quite stiff, and keeps the head off the surface very easily. The bearings are quite strong, so the most likely limiting factor would be the servos that keep the head on track. These servos have a few hundred hertz of bandwidth and about 10 Gs of acceleration, so they can handle many Gs at low frequencies. Maneuvers are probably OK, but the vibrations of launch probably would not be. NASA used to use standard commercial disc drives (from HP) in the Kuiper(?) observatory, which is the plane they fly with the infrared telescope. The drives had to cope with vibration, reduced atmospheric pressure (a problem for most hard disks), gyroscopic effects, temperature variations, etc. These were about 1975 vintage drives, though, which had large disk-to-head clearances, and these drives also retracted the heads when not in use. I don't know what they use now. Optical drives should be better still, since the head to disc spacing can be so large (1 mm) and does not depend on air bearings.