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Posted by on July 21, 2006, 1:31 pm
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PLease clarify what you are saying, cause last time i checked all our
space vehicles had hard drives.
peace
zonker
http://2000ah.blogspot.com
Max Power wrote:
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> Hard drives on 'Deep Space' missions: any idea why they are never used?
> 4 x 100 Gb drives could store enough data such that it could take up to 6
> months to trickle the data back at 24,000 kbs (assuming high power downlink
> and turbo codes).
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Posted by American on July 21, 2006, 1:46 pm
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Max Power wrote:
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> Hard drives on 'Deep Space' missions: any idea why they are never used?
> 4 x 100 Gb drives could store enough data such that it could take up to 6
> months to trickle the data back at 24,000 kbs (assuming high power downlink
> and turbo codes).
My guess is that Hard Drives are too prone to magnetic turbulence both
in
the Van Allen Belt and Jupiter, therefore not a good storage/processing
medium. There are several methods for holographic storage, one
interesting
one being 3D Atomic Holographic, as seen by one Colossal Storage Corp.:
http://www.i4u.com/article481.html
While there are currently lesser technologies that are exploring
holographic
storage and processing, this technology seems to be at the cutting
edge.
My belief is that these technologies will advance in tandem to some
kind
of FTL propulsion technology, unless, of course, our currently
antiquated
types keep us earthbound.
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Posted by Cray74@gmail.com on July 26, 2006, 4:41 am
Please log in for more thread options Max Power wrote:
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> Hard drives on 'Deep Space' missions: any idea why they are never used?
Reliability. Tape drives and solid state storage have demonstrated
endurances of decades. The moving platters of hard drives do not yet
have the same reputation for reliability.
Mike Miller
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Posted by Jim Kingdon on July 26, 2006, 4:41 am
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> Hard drives on 'Deep Space' missions: any idea why they are never used?
Reliability would probably be a problem.
But more interestingly, spinning a drive would change the attitude of
the spacecraft (a la reaction wheels). I think there may have been at
least one mission which avoided this by having two drives spinning in
opposite directions. But given the alternatives to hard drives these
days, I'd be quite surprised to see this done now.
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Posted by Mark Adler on July 26, 2006, 4:42 am
Please log in for more thread options Max Power wrote:
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> Hard drives on 'Deep Space' missions: any idea why they are never used?
> 4 x 100 Gb drives could store enough data such that it could take up to 6
> months to trickle the data back at 24,000 kbs (assuming high power downlink
> and turbo codes).
Well there you go. Since you're not likely to collect 400 Gb all at
once, that means you put too much storage on board. (We tend to not do
a whole lot of flybys anymore, so there isn't one giant burst of data
collection.) So the basic reasons are:
1. The data rates from deep space are low, limiting the sustained
collection rates. You simply don't have any use for storing months
worth of collected data, so you don't really need that much storage. A
few weeks worth is plenty.
2. Qualifying (and possibly making design changes to) hard drives to
survive the launch, and in some cases landing environment, not to
mention working in a either a vacuum or a pressure vessel and working
in zero-G, would be an expensive proposition. I haven't heard of such
a qualification having been done, but it may have.
3. On the other hand, flash memory is already qualified. The higher
$/GB of flash memory is not a factor for spacecraft, and the kg/GB is
comparable or better for flash (depending on packaging).
4. The fewer critical mechanical devices on a spacecraft, the better.
Hard drives crash, flash memory doesn't.
That doesn't mean that some deep space application won't come along
that makes putting a hard drive on it worthwhile somehow. It's
conceivable, for some application with very high bursts of high rate
data. Even in that case, I still think the trade between hard drive
and flash will be a close one. It would basically come down to mass
vs. reliability. I'd bet on the flash.
mark
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> 4 x 100 Gb drives could store enough data such that it could take up to 6
> months to trickle the data back at 24,000 kbs (assuming high power downlink
> and turbo codes).