Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!wuarchive!psuvax1!rutgers!rochester!uhura.cc.rochester.edu!ub!image.soe.clarkson.edu!rpi!skeeve
From: skeeve@pawl.rpi.edu (Sean C. Cox)
Newsgroups: comp.arch
Subject: Re: Why not evacuate Disk drives.
Message-ID: <_66$^Q&@rpi.edu>
Date: 2 Aug 90 00:49:54 GMT
References: <V%6$_&|@rpi.edu> <7592@amelia.nas.nasa.gov> <0093A806.2A4E2160@KING.ENG.UMD.EDU> <10064@pt.cs.cmu.edu>
Organization: Rensselaer Polytechnic Institute, Troy NY
Lines: 23

lindsay@MATHOM.GANDALF.CS.CMU.EDU (Donald Lindsay) writes:

>In article <0093A806.2A4E2160@KING.ENG.UMD.EDU> sysmgr@KING.ENG.UMD.EDU 
>	(Doug Mohney) writes:
>>Why helium? That's pretty expensive, I'd think. Why not something "common" 
>>like nitrogen?

>The speed of sound is higher in helium.  Actually, hydrogen is even
>faster, but it's not chemically inert.

       The speed of sound?? I thought that the lower viscosity would be the
  primary reason, lower viscosity=lower drag on the surface of the disk,
  as well as a smaller boundary layer (the layer of fluid the heads "float"
  on to avoid contact with the surface of the disk). The lesser drag helping
  rotation, but the smaller boundary layer being making it more difficult to
  "float" the heads.

                                          -Sean

-- 
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
| Sean_Cox@mts.rpi.edu  |  userGDQT@RPITSMTS.BITNET  |  skeeve@pawl.rpi.edu |
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-