Re: Mars Rover Not Responding
From: The Ghost In The Machine (ewill_at_sirius.athghost7038suus.net)
Date: 01/30/04
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Date: Fri, 30 Jan 2004 16:14:52 GMT
In sci.physics, Yoyoma_2
<Yoyoma_2@[>
wrote
on Fri, 30 Jan 2004 04:26:31 GMT
<X1lSb.333660$X%5.19364@pd7tw2no>:
> Bruce Bowen wrote:
>> Uncle Al <UncleAl0@hate.spam.net> wrote in message news:<4016A579.397B55A@hate.spam.net>...
>>
>>>There are no hard drives on Mars! With ambient air pressure being
>>>only 7 torr, there isn't nearly enough air pressure to levitate the
>>>read/write heads when the hard drive spins up. If you seal the hard
>>>drive, it overheats.
>>
>>
>> This is a trivial engineering problem to address. Encase the HD in a
>> larger sealed and presurize container, with enough surface area and/or
>> internal air circulation to keep it cool. A low power 2.5" HD
>> shouldn't take that much larger of a container. What about the flash
>> sized microdrives?
>
> From what i was tought all hard drives must be kept sealed. This is
> because dust and air pollutants could accumulate on the read head, and
> if disaster strikes, a particle of dust could get between the head and
> the disk (which are almost touching, but not quite).
At the scale of a disk drive's heads a human hair would
be the equivalent of hitting a mountain -- but with a
slightly different result; instead of simply destroying
the item hitting the platter, it would leave a very nasty
gouge in the platter -- a head crash. Therefore all drives
of this type have to be sealed.
I was under the impression that drives had to survive
10-G impulse tests (e.g., dropping a laptop on the floor
from the height of a desk). So 4G wouldn't be much of a
problem to handle.
I don't know about radiation.
Uncle Al has a point; here on Earth there's a good
(relatively speaking) connection between ambient air and
the drive's internals. At 1 kPa the thermal flow is much
more tenuous; of course, one could deploy the drive with
a large cooling panel which doubles as its power supply
(the sun powers the drive; the water circulates among
the panels, heating them and cooling the drive). A large
forced-air fan might complete the ensemble, making for a
Frankenstein's monster that looks like a cross between a
jet engine and a tail-dragging Godzilla... :-) though I
suspect the primary cooling method is radiative.
Modern computers are starting to use water-cooling, which
could get interesting if people get the bright idea of
hooking the heat exchanger into the cold-water supply as
opposed to letting it exhaust noisily into the ambient air.
Of course all that does is transfer the heat elsewhere
(and possibly waste water), probably into the sea if the
water is allowed to drain, or to one's neighbors if the
water goes back into the line (not recommended for various
reasons; in fact, backflow check valves are required for
certain equipment).
I would think, though, that, absent radiation concerns,
flash memory is a nice solution -- and the radiation
presumably can be mitigated by proper shielding.
>
>
>
>>
>> -Bruce
-- #191, ewill3@earthlink.net It's still legal to go .sigless.
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