Re: Will Boeing Use Ada To Build $9 Bln Network For Teledesic?

["Marin David Condic, 561.796.8997, M/S 731-93" <condicma@PWFL.COM>]

Dale Pontius <pontius@BTV.VNET.IBM.COM> writes:
>
>Really, I suspect the 20% of weight they're talking of is, of
>course storage media, be it RAM, ROM, or tape. But what may have
>really happened here is that a threshold has been crossed. Perhaps
>the storage technique that worked with less sophisticated (or
>bloated?) software has become insufficient. Perhaps the issue is
>no longer "more of the same" storage, but a new hierarchy or new
>media.
>
    It could also be a matter of "large" software demanding more
    compute power which can demand more or bigger (physically)
    processors. Increases in clock speeds can also translate into
    energy consumption (bigger heat sinks, etc.). It might be an issue
    of increasing the size/complexity of the software causing a whole
    redesign of the computer which increases the weight.

>Is it possible to use a hard drive on a small satellite, or will
>the rotating platters foul things up. I'd expect that the shuttle
>is so big that the effect is insignificant.
>
    When rockets fire, you get *lots* of vibration. Head crash on a
    disk drive on a satelite would be *very* bad! And don't forget
    that spinning a disk platter is going to consume electricity -
    moreso than an EEPROM (unless you had a *lot* of EEPROM!). It may
    be that somebody has figured out how to use a disk drive in this
    sort of application, but it wouldn't be my first choice. I'd be
    real curious to find out about any space-based embedded computers
    that used a disk drive in an unmanned vehicle. (I wouldn't be
    suprised if there were some in the shuttle, but that gets to come
    home rather quickly and breakage there may have less critical
    impact.)

    I doubt the rotation of a disk say the size of one in a notebook
    computer would significantly impact the course or attitude of a
    satelite - even a "small" one. (Even "small" satelites are pretty
    heavy in comparison to the weight of a notebook sized disk.) And
    most satelites I know of contain some ability to adjust their
    course & attitude in flight to compensate for drift from any & all
    sources.

    MDC

Marin David Condic, Senior Computer Engineer    ATT:        561.796.8997
Pratt & Whitney, GESP                           Fax:        561.796.4669
West Palm Beach, FL                             Internet:   CONDICMA@PWFL.COM
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