I'm under the impression that all hard drives made in the last 30 years are
Winchester-type units with hermetrically sealed cases. I dismantled a
crashed drive and it was very well sealed in a case that could easily
withstand a hard vacuum. I know there's a 3000 meter operations limit in
the spec's - why? Cooling? Maybe it's just an artifact from the
pre-winchester era. I know there are plenty of HDD based MP3 players used
by hang glider pilots that work fine up to 18K feet.

However, my camcorder can use SD cards instead of tape and a 2GB card will
store 6 hours of DV so maybe concerns abour HDD's are moot anyway.

Bill Daniels


"Frank Whiteley" wrote in message
oups.com...
The type of HDD used in this system has an altitude operating limit of
nominally 9840ft(3000m). A few operate just over 10K feet, but not by
much. A pressurized case will be needed to for any video system using
HDD's in the US west and many mountainous regions. At 3000m,
atmospheric pressure is about .67 of sea level. At 5000m, it's about
.50 of sea level. The air pressure is needed to float the heads above
the media. Going above the rated altitude leads to a potential head
crash into the media. Not good.

Now the question is the amount of heat dissipation needed to operate
this equipment safely. That will drive the size of the case and case
material or need for heat sinks along with the pressure differential.
Interesting problem.

Frank Whiteley