Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_9/V16NO997.TXT

Text File | 1993-08-13 | 30KB | 754 lines

Space Digest                Sat,  7 Aug 93       Volume 16 : Issue 997

Today's Topics:
                      engine failures and safety
                       Exploding Heads (2 msgs)
   Fractional Millikans (was Re: Cold Fusion and its possible uses)
                         Happy Birthday, NASA
                           LMF and Energiya
                 Magellan Update - 08/05/93 (2 msgs)
                     Mars Observer's First Photo
                   Mars Observer Update - 08/02/93
                            Milt Thompson
            Planned BMDO test in Utah/New Mexico? (2 msgs)
               Quick guide to propellant usage (2 msgs)
                         Support the Shuttle
            The Inquisition (The Usenet edition) (2 msgs)

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----------------------------------------------------------------------

Date: 6 Aug 1993 14:44:27 GMT
From: Steve Derry <[e-mail]>
Subject: engine failures and safety
Newsgroups: sci.space

George William Herbert ([e-mail]) wrote:
: In <[e-mail]> [e-mail] (Henry Spencer) writes:
: >
: >Note, though, a more general point:  when an airliner loses *all* its
: >engines, it better get at least one of them relit, or it's going to
: >crash unless the gods are really smiling.  When you're out over the
: >Pacific at night and run into a Pinatubo ash cloud, the engines are
: >at least as important as the wings -- without engines, wings just
: >postpone the inevitable briefly.

: True.  However, all-engine failures are pretty rare in both planes
: and rockets.  Offhand, I remember that one 747 in the ash cloud,
: (very nearly) the DC-10 with the oil leaks in all 3 engines, the
: (727?) from columbia that ran out of fuel and crashed in NY, and the
: Canadair 767 which suffered from metric-conversion induced fuel
: starvation but lucked out and landed intact on a racetrack. 8-)

There was also a Boeing 737 that lost both engines in a hailstorm at 16,000
feet while approaching New Orleans (I believe it was 1987).  After several
unsuccessful restart attempts, the crew prepared to ditch in the Intracoastal
Waterway.  At that point the crew noticed an abandoned grass landing strip
and successfully landed there, without casualties to the passengers or the
aircraft.

: >Sure, in particularly favorable conditions -- nearby long hard-surface
: >runway, pilot who flies gliders as a hobby -- an airliner can survive
: >an unpowered landing.  And in particularly unfavorable conditions, even
: >having two or three surviving engines won't help enough.  But in the
: >average situation, one engine out is okay and all engines out is lethal,
: >wings or no wings.

But having wings can give you more flexibility in working the conditions to
your advantage, as in the case above.  Of course, rocket engines would not
have been vulnerable to hail ingestion.

--
Steve Derry
<[e-mail]>

------------------------------

Date: Fri, 6 Aug 1993 21:06:35 GMT
From: Dillon Pyron <[e-mail]>
Subject: Exploding Heads
Newsgroups: sci.space

In article <23u41r$[e-mail]>, [e-mail] (Keith Nicewarner) writes:
>OK, could someone please back me up on this:
>
>A person's head will *not* explode in the vacuum of space, nor will
>the rest of his/her body, nor will the eyes pop out of their sockets.
>There is simply not enough pressure behind the eye sockets to push
>them out (in spite of Hollywood's attempts to keep the public as
>ignorant and as gullible as they are...).  A person would most likely
>die of an extreme case of the bends (from rapid decompression).
>
>I'm tired of arguing with my naive friends, and am lacking any hard
>evidence/numbers.  For instance, I would imagine that the pressure
>differential between 1 atmosphere and empty space is about the same as
>that experienced by a diver under 32 ft of water (if I recall
>correctly), right?  I've never seen a diver's head explode when he
>surfaced.
>
>Any hard evidence would be appreciated; for instance, has anyone
>thrown an animal out the airlock of the Space Shuttle (or something
>along those lines...)?  (I'm sure the animal lovers would have a fit
>if they did... especially if it was a cute furry animal.)

Do monkeys qualify as cute furries?  Several tests have shown that monkeys not
only didn't boil or explode, but that they survived.  At thirty thousand feet,
an airliner is a long way towards that vaccum level, so, if say a baggage door
failed and caused explosive decompression, most of the passengers would
experience short term distress (but nothing like the distress of thinking the
plane would crash).

DCI is more of a long term disorder, it takes hours to kill.  The various lung
expansion injuries and arterial gas emboli are more likely to do a quick kill.
In a healthy, breathing individual, neither of these problems is likely (but
anything CAN happen).  The 1ATM ascent (30 ft in saltwater, 33 ft in fresh)
takes me about a minute, so this hardly qualifies as explosive decompression.

--
Dillon Pyron                      | The opinions expressed are those of the
TI/DSEG Lewisville VAX Support    | sender unless otherwise stated.
[phone] (when I'm here)     |
[phone] (when I'm home)     |Please send mail to [e-mail]
[e-mail]                 |since skndiv is going away.  Thanks
PADI AI-54909                     |

------------------------------

Date: Sat, 7 Aug 1993 00:39:47 GMT
From: Bruce Dunn <[e-mail]>
Subject: Exploding Heads
Newsgroups: sci.space

> with regard to the danges of vacuum exposure Dillon Pyron writes:
> Do monkeys qualify as cute furries?  Several tests have shown that monkeys
> not
> only didn't boil or explode, but that they survived.  At thirty thousand
> feet,
> an airliner is a long way towards that vaccum level, so, if say a baggage
> door
> failed and caused explosive decompression, most of the passengers would
> experience short term distress (but nothing like the distress of thinking
> the
> plane would crash).


        And don't forget that the summit of Mount Everest is at 29,000 feet,
and that the mountain has been climbed ***without*** supplemental oxygen.


--
Bruce Dunn    Vancouver, Canada   [e-mail]

------------------------------

Date: Fri, 6 Aug 1993 22:19:41 GMT
From: "Phil G. Fraering" <[e-mail]>
Subject: Fractional Millikans (was Re: Cold Fusion and its possible uses)
Newsgroups: sci.physics,sci.space

Leigh Palmer <[e-mail]> writes:

>In article <[e-mail]> Phil G. Fraering,
>[e-mail] writes:
>>Or that a couple of careful professionals could devise an improved
>>apparatus that would have less noise.

>In the same Physics 110C lab at Cal where I did my conventional oil-drop
>measurements there was an apparatus using a horizontal E-field and a strobe
>light, taking data photographically. I didn't know anyone who ever got that
>crossed-field apparatus to work.

>Leigh

Mail it out here and I'll try ;-)

(Be glad to. For free.)
--
+-----------------------+
|"Standard disclaimer"  |Clever quote will be back next week!
|[e-mail] |
+-----------------------+

------------------------------

Date: Fri, 6 Aug 1993 22:21:50 GMT
From: "Phil G. Fraering" <[e-mail]>
Subject: Happy Birthday, NASA
Newsgroups: sci.space,sci.math

[e-mail] (Dave Michelson) writes:

>In article <[e-mail]> [e-mail] (Phil G. Fraering) writes:
>>
>>In Greek myth there is but one Apollo. He is sometimes associated with
>>Helios, god of the Sun. In _Chinese_ myth there is a legend of multiple
>>suns. All but one were destroyed.

>Correct.  Because all those extra suns made the earth unbearably hot,
>one fellow decided to shoot all but one of them down.  Since this made
>life bearable, he was given several rewards including a potion that would
>make him immortal.  He was to drink the potion after brewing it for a
>month but when the time came, his wife accidently drunk the potion instead.
>She became the moon goddess and the Chinese pay tribute to her every fall
>during the eighth month of the Chinese lunar calendar...

And if you look closely, you can see in the moon the outline of
her and her immortal rabbit (although the particulars of who is
who sometimes vary).

--
+-----------------------+
|"Standard disclaimer"  |Clever quote will be back next week!
|[e-mail] |
+-----------------------+

------------------------------

Date: Fri, 6 Aug 1993 21:50:46 GMT
From: Lauren Massa-Lochridge <[e-mail]>
Subject: LMF and Energiya
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>In article <[e-mail]> [e-mail] writes:
>>I just finished a term paper on automation, and I came across a very
>>interesting idea about using robots to do mining on the moon.  I came
>>across this idea of a Lunar Manufacturing Facility (LMF) in a book on
>>robots by Philip Croix. The very interesting thing about this LMF is that
... some deleted to save net bandwidth ...
>
>If such a LMF were feasible, then the same system would be easier and
>cheaper to operate on Earth. But we don't see any, so that seems to say
>that it isn't feasible. One of the many technical problems with this
>scheme is that tolerances stack. In a 2^N system, each copy is less
>precise than the one that produced it. Pretty soon you're churning out
>worthless junk. This is the machinist nightmare. There are ways around
>this, see biological systems, but we haven't mastered them. One of the
>many *economic* problems with this scheme is that higher grade ores exist.
>So mining dirt isn't economical.
>
>Gary
>--
>Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
>Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
>534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
>Lawrenceville, GA 30244     |                     |

Its true there are still many problems to overcome in total automation,
but this would become much more feasible if a combination of teleoperation
with automation were used. In addition, some external checks and corrections
could also be automated rather than carried out by human telepresence.
There is a lot of interesting work going on in the prediction of faults
statisics based adaptive control for processing that could also be
applied so that a desired level of operation may be possible to maintain
by prediction of failures. Degradation of performance through wear etc.
in a system can be characterised and ameliorated as part of routine
maintenance.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
  Lauren Massa-Lochridge
  [e-mail]           Systems Integration Lab IEOR
  [e-mail]           CIM/BCAM (Comp. Automated Manu.)EECS
                University of California at Berkeley
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

------------------------------

Date: 7 Aug 1993 00:20:20 +0100
From: Mr PJ Mahon <[e-mail]>
Subject: Magellan Update - 08/05/93
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]>,
    [e-mail] (Ron Baalke) writes:
>Forwarded from Doug Griffith, Magellan Project Manager
>
>                          MAGELLAN STATUS REPORT
>                              August 5, 1993
>
>1.  EOTMs 3, 4 and 5 (Exit Orbit Trim Maneuvers) to further raise Magellan's
>periapsis will be performed today on three consecutive orbits beginning at
>about 11AM PDT.  Each EOTM will raise the periapsis by 14 km with a final
>level at 205 km.
>
>3.  The Magellan Transition Experiment demonstrates a significent new maneuver
>technology by achieving a major orbit change with minimal propellant and
>enabling new scientific observations near the poles of Venus.
>
>4.  Circular orbit operations will begin August 16th with a command sequence
>
>5.  As of next Tuesday, August 10, the 3rd anniversary of Magellan's arrival

        Well, I don't know about anyone else, but as a bystanding Limey,
I'd just like to say " Well Done!!!" to everyone at JPL. Regardless of what's
happenning on sci.space, it's nice to know that someone's still going for
it!!! Well done JPL!
***************************************************************************
*       Pat Mahon                  _           [e-mail]    *
*       Dept. Of Physics          / \          Work: [phone]        *
*       Warwick University       /  |          Home: [phone]        *
*       Coventry UK.            /   /       I'd rather be hang gliding... *
*                              /   (                                      *
******************************<    (***************************************
                               \   (
                                \   \
                                 \  |
                                  \_/

------------------------------

Date: 6 Aug 1993 20:24:46 -0400
From: Pat <[e-mail]>
Subject: Magellan Update - 08/05/93
Newsgroups: sci.space,sci.astro,alt.sci.planetary

 Excellent.
--
I don't care if it's true.  If it sounds good, I will
publish it.  Frank Bates Publisher  Frank Magazine.

------------------------------

Date: Fri, 6 Aug 1993 21:12:03 GMT
From: Dave Michelson <[e-mail]>
Subject: Mars Observer's First Photo
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]> [e-mail] (Eric H Seale) writes:
>
>>The images from JPL images are generally stored in VICAR format, which is
>>the format developed by the Image Processing Lab at JPL.  The images are not
>>compressed....
>
>and later,
>
>>I can't speak for the other NASA centers, but the Public Information Office
>>at JPL purchased a color scanner last year specifically to scan in the
>>public released photos and convert them to GIF images....
>
>
>Has any thought been given to doing a direct (digital) VICAR=>GIF
>conversion and skipping the Print-Scan process?

You missed the point.  The original images are held back for a year until
the science teams have a chance to complete their work and make their
submissions to archival journals.  The "publicly released" photos are
intended only for use by the media and their resolution is intentionally
degraded...

If you're willing to wait for a year, you'll find all sorts of original
images in their original format available on CD-ROM from various sources.

--
Dave Michelson  --  [e-mail]  --  University of British Columbia

------------------------------

Date: Fri, 06 Aug 1993 19:50:48 GMT
From: Innocent Bystander <[e-mail]>
Subject: Mars Observer Update - 08/02/93
Newsgroups: sci.space,sci.astro,alt.sci.planetary

[e-mail] (Dave Michelson) Pontificated:
>
>Anyone have any bright ideas for an appropriate name?  Maybe it's not
>too late....   :-)
>

Barsoom?



/~~~(-: James T. Green :-)~~~~(-: [e-mail] :-)~~~\
|  I didn't do it! Nobody saw me do it! You can't prove anything!  |
|                                        <Bart Simpson>            |

------------------------------

Date: Fri, 6 Aug 1993 21:45:06 GMT
From: Mary Shafer <[e-mail]>
Subject: Milt Thompson
Newsgroups: sci.space

Milt Thompson, former X-15 pilot, died at about 12:45 today, 6 August.

Milt, who was our Chief Engineer, will be greatly missed by his Dryden
colleagues.

--
Mary Shafer  DoD #362 KotFR NASA Dryden Flight Research Facility, Edwards, CA
[e-mail]                 Of course I don't speak for NASA
 "A MiG at your six is better than no MiG at all."  Unknown US fighter pilot

------------------------------

Date: 6 Aug 93 15:14:16 CDT
From: Greg Titus <[e-mail]>
Subject: Planned BMDO test in Utah/New Mexico?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Jonathan Griffitts) writes:
>
>An unreliable source tells me the following:
>
>BMDO (formerly SDIO) is planning a test in which missles will be
>launched from the vicinity of Green River, Utah on a trajectory
>landing them in White Sands Missle Range, New Mexico.  BMDO will
>attempt to intercept/destroy them before impact at White Sands.  Spent
>boosters from the launch will be dropped into the Hatch Point, Utah
>area.

There is a proposed series of cruise missile tests that is the
likely seed from which this story grew.  The launch and landing
sites match the proposed tests.  There wouldn't be any boosters
dropped, though.  I believe I recall that the tests did involve
attempts to intercept and destroy the missiles before impact,
but *after* they had already entered WSMR airspace.  I don't
recall who the agency involved was -- most likely it was BMDO or
the Air Force.

The last I heard was that the agency had met with residents of
several affected towns, trying to reassure them that the tests

wouldn't endanger them (the flight paths pass directly over a number
of towns -- I think Farmington, NM, pop. ~50k, is one of them).  I
believe there was a push on to force the agency to do a full-up
environmental impact study.

All of the above is subject to the vagaries of human (my) memory.
AW&ST would have reported on it, sometime in the last year.

greg
--
--------------------------------------------------------------
Greg Titus ([e-mail])                   Compiler Group
Cray Research, Inc.                               Santa Fe, NM
Opinions expressed herein (such as they are) are purely my own.

------------------------------

Date: Fri, 6 Aug 1993 22:34:03 GMT
From: "Phil G. Fraering" <[e-mail]>
Subject: Planned BMDO test in Utah/New Mexico?
Newsgroups: sci.space

[e-mail] (Greg Titus) writes:

>In article <[e-mail]> [e-mail] (Jonathan Griffitts) writes:
>>
>>An unreliable source tells me the following:
>>
>>BMDO (formerly SDIO) is planning a test in which missles will be
>>launched from the vicinity of Green River, Utah on a trajectory
>>landing them in White Sands Missle Range, New Mexico.  BMDO will
>>attempt to intercept/destroy them before impact at White Sands.  Spent
>>boosters from the launch will be dropped into the Hatch Point, Utah
>>area.

>There is a proposed series of cruise missile tests that is the
>likely seed from which this story grew.  The launch and landing
>sites match the proposed tests.  There wouldn't be any boosters
>dropped, though.  I believe I recall that the tests did involve
>attempts to intercept and destroy the missiles before impact,
>but *after* they had already entered WSMR airspace.  I don't
>recall who the agency involved was -- most likely it was BMDO or
>the Air Force.

>The last I heard was that the agency had met with residents of
>several affected towns, trying to reassure them that the tests
>wouldn't endanger them (the flight paths pass directly over a number
>of towns -- I think Farmington, NM, pop. ~50k, is one of them).  I
>believe there was a push on to force the agency to do a full-up
>environmental impact study.

>All of the above is subject to the vagaries of human (my) memory.
>AW&ST would have reported on it, sometime in the last year.


I'm a little nervous about these tests running at White Sands
while the DC-X prototype is there...
--
+-----------------------+
|"Standard disclaimer"  |Clever quote will be back next week!
|[e-mail] |
+-----------------------+

------------------------------

Date: 7 Aug 93 00:59:28 GMT
From: Paul Dietz <[e-mail]>
Subject: Quick guide to propellant usage
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Bruce Dunn) writes:


 >2) A bright yellow or orange flame from a liquid propellant engine,  -
 >indicates that the propellant combination is probably kerosene and LOX
 ...
 >3) A virtually colorless flame, with no smoke.  Indicates hydrazine and
 >nitrogen tetroxide (Titan), or hydrogen and LOX (Shuttle main engines).


 >Can anyone describe the flames for:
 >
 >1)  Hydrazine and LOX (an early Soviet booster if I remember correctly)
 >
 >2)  Hydrazine and nitric acid (some tactical missiles, including probably the
 >Scud)


Both of these should be nearly colorless, with little or no smoke.
The yellow flame in LOX/kerosene rockets is emission from soot.
There is no carbon in either of these combinations, so no soot.

BTW: Titan uses aerozine-50 (50/50 hydrazine+UDMH), not hydrazine.
However, the H/C ratio is high enough that sooting is suppressed in
favor of increased hydrogen.  I'd expect a peroxide/kerosene flame to
also be less emissive than LOX/RP-1, for the same reason.

Does the Scud use hydrazine?  I had the vague impression it used
something easier to make, like gasoline or some amine.

    Paul




------------------------------

Date: Sat, 7 Aug 1993 00:36:28 GMT
From: Bruce Dunn <[e-mail]>
Subject: Quick guide to propellant usage
Newsgroups: sci.space

> Henry Spencer writes:
> Yes.  Both stages of Titan II (both the ICBM variant and the Gemini
> variant)
> used hypergolic fuels:  nitrogen tetroxide and a hydrazine mixture.



If you have a picture of a vehicle at launch or in flight, look for:

1) Truly massive clouds of smoke - indicates use of solid propellants (Scout,
Shuttle, some Ariane configurations)

2) A bright yellow or orange flame from a liquid propellant engine,  -
indicates that the propellant combination is probably kerosene and LOX
(Atlas, Saturn lower stage, Delta - although you probably won't see the flame
in modern Delta launches because of the attached solid boosters)

3) A virtually colorless flame, with no smoke.  Indicates hydrazine and
nitrogen tetroxide (Titan), or hydrogen and LOX (Shuttle main engines).


Can anyone describe the flames for:

1)  Hydrazine and LOX (an early Soviet booster if I remember correctly)

2)  Hydrazine and nitric acid (some tactical missiles, including probably the
Scud)

--
Bruce Dunn    Vancouver, Canada   [e-mail]

------------------------------

Date: Fri, 6 Aug 1993 22:31:57 GMT
From: "Phil G. Fraering" <[e-mail]>
Subject: Support the Shuttle
Newsgroups: sci.space

[e-mail] ([u]Phillip Potts) writes:




>>Please quit bashing the Shuttle.  And for Pete's sake, stop singing
>>the praises of Russian equipment.  If I hear one more comment
>>about how we should scrap our stuff and buy from them.....Anyway,
>>do a little comparison before you do


>AMEN. It's about time someone added some positive to this
>negative track.

What do you want? The shuttle wastes billions, but it's
so darn _pretty_...?

I always thought the Pinto was a good looking car, and the
flames on it were pretty too.

(See, I can look on the bright side of things!

>       /----------------------------------------------------/
>      /    Phillip M. Potts          Loral Data Systems                                       /
>     /     [e-mail]                                                                      /
>    /                                                                                                       /
>   /              LWMA SII 1898 - 1998                                                      /
>  /----------------------------------------------------/

--
+-----------------------+
|"Standard disclaimer"  |Clever quote will be back next week!
|[e-mail] |
+-----------------------+

------------------------------

Date: Fri, 6 Aug 1993 22:28:32 GMT
From: "Phil G. Fraering" <[e-mail]>
Subject: The Inquisition (The Usenet edition)
Newsgroups: sci.space

[e-mail] (R.E. Wiersbe) writes:

>In article <[e-mail]> [e-mail] (Mary Shafer) writes:
>>On Fri, 6 Aug 1993 02:01:53 GMT, [e-mail] (Phil G. Fraering) said:
>>
>>Phil> [e-mail] (Ward Paul) writes:
>>
>>>In article <[e-mail]> [e-mail] (S.H.)
>>>writes: > >What is your backgroud?  >Who do you speak for ?  > >What
>>>do you do besides writing posters ?
>>
>>>Gee, no one told me the inquisition had started again.
>>
>>Phil> Same here. I didn't expect the Spanish Inquisition.
>>
>>Nobody expects the Spanish Inquisition!
>>--
>Our weapon is Fear! Fear and Surprise!
>Our two main weapons are Fear, and Surprise, and Ruthless Efficiency!
>Our three main weapons are Fear, Surprise, Ruthless Efficiency, and an almost
>fanatical devotion to the Pope!
>Our four weapons are Fear....I'll come in again..............

Well, neither the soft cushions or the comfy chair worked on me...
so they put me on sci.space.

Well, guys and gals? Should I confess?

>Bob Wiersbe    AT&T Bell Labs    [e-mail]
--
+-----------------------+
|"Standard disclaimer"  |Clever quote will be back next week!
|[e-mail] |
+-----------------------+

------------------------------

Date: 6 Aug 1993 20:31:30 -0400
From: Pat <[e-mail]>
Subject: The Inquisition (The Usenet edition)
Newsgroups: sci.space

 Bring out the Rack!

--
I don't care if it's true.  If it sounds good, I will
publish it.  Frank Bates Publisher  Frank Magazine.

------------------------------


From: [e-mail]
Mmdf-Warning:  Parse error in original version of preceding line at VACATION.VENARI.CS.CMU.EDU
Newsgroups: sci.space
Subject: Re: Why I hate the space shuttl
Date: 6 Aug 1993 13:29:13 GMT
Organization: /etc/organization
Lines: 48
Distribution: sci
Message-Id: <[e-mail]>
References: <[e-mail]>
Nntp-Posting-Host: hops.larc.nasa.gov
Sender: [e-mail]
Source-Info:  Sender is really [e-mail]

In article <[e-mail]> [e-mail] writes:
>> In fact, I have heard from some NASA people that the Intel 80486
>family will
>> probably never be spaceflight certified: it is just
>> too complex to be relied upon.
>>
>
>This is one of the problem's I have with NASA. Yesterday's Technology
>Today!
>
>I also don't really believe that anyone in their right mind at NASA
>would say such a thing. It's very much in the category of "Heavier
>than air flight will never be practical".
>
>Spcae will see 486's, Pentium's, Sextiums, Octiums, Noniums...
>possibly on the private stations if no where else. If it comes to
>that, I'm sure we could agree, for a suitable fee of course, to do a
>bit of computing for the poor cousins in the gummint station. :-)

Certainly, it is possible that someone will develop new validation
and manufacturing techniques that will allow NASA (or someone else - most
private satellites don't use 486's) to trust a fourth generation
CISC chip, as opposed to a 3rd generation CISC chip or a RISC chip. But until
that happens, there are good reasons not to use a 486/Pentium as a space-based
hardware controller.

Every CPU I've ever heard of has bugs in it. In general,
the more complex the system, the more bugs it has. And this is not a linear
increase, it's more like an exponential increase (i.e. if a CPU with 1M
transistors has four bugs, one with 2M might be expected to have 16).

In addition, even if the CPU has no bugs, a more complex CPU is statistically
much more likely to fail because of a component failure than a simpler one.
There isn't much you can do about that unless you can increase the reliability
of the individual components. In this case, you would probably have to
completely redo the 486/Pentium manufacturing process when new manufacturing
techniques become available.

** The above refers to the use of CPUs as mission critical hardware
controllers, not as data recorders or non-mission critical hardware
controllers.


--
Glen Henshaw
HALOE Data Processing
[e-mail]

------------------------------

Newsgroups: sci.space,sci.astro,alt.sci.planetary

From: Dave Michelson <[e-mail]>
Subject: Re: Mars Observer Update - 08/02/93
Message-Id: <[e-mail]>
Keywords: Mars Observer, JPL
Organization: University of BC, Electrical Engineering
References: <[e-mail]> <[e-mail]> <[e-mail]>
Date: Fri, 6 Aug 1993 21:57:41 GMT
Lines: 13
Sender: [e-mail]
Source-Info:  Sender is really [e-mail]

In article <[e-mail]> [e-mail] (Innocent Bystander) writes:
>>
>>Anyone have any bright ideas for an appropriate name?  Maybe it's not
>>too late....   :-)
>>
>
>Barsoom?

Umm, excuse my ignorance, but what is the significance of "Barsoom"?

--
Dave Michelson  --  [e-mail]  --  University of British Columbia

------------------------------

End of Space Digest Volume 16 : Issue 997
------------------------------