Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_9/V16NO934.TXT

Text File | 1993-08-03 | 31KB | 703 lines

Space Digest                Wed, 28 Jul 93       Volume 16 : Issue 934

Today's Topics:
                         11 planets (2 msgs)
                          3-man Shuttle EVAs
                            Budget figures
                      Cats in zero gee (2 msgs)
     Cold Fusion and its possible uses (if it is proven to exist)
                            DC-X (2 msgs)
            DC-X Prophets and associated problems (2 msgs)
                   Found your own dark-sky nation?
              Low Tech Alternatives, Info Post it here!
                         Musicians and space
                      Needed: SS-Freedom update
                             Odds on ACTS
                         Passenger lotteries
                     Why I hate the space shuttle

        Welcome to the Space Digest!!  Please send your messages to
        "[e-mail]", and (un)subscription requests of the form
        "Subscribe Space <your name>" to one of these addresses: listserv@uga
        (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle
        (THENET), or [e-mail] (Internet).
----------------------------------------------------------------------

Date: 27 Jul 1993 22:38:22 GMT
From: Claudio Egalon <[e-mail]>
Subject: 11 planets
Newsgroups: sci.space

> How come we don't send up a couple satellites to
> investigate these two??

Because there are not any...

Claudio Oliveira Egalon
[e-mail]

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

Date: Tue, 27 Jul 1993 23:40:41 GMT
From: Henry Spencer <[e-mail]>
Subject: 11 planets
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>I keep wondering.  Seems to me I've read there is a planet
>closer to the sun than Mercury.  One which has an orbit which
>most of the time we earthlings can't see...

Time to go do some more reading.  There was some suspicion of such a
thing at one time, but there definitely isn't anything significant there.
There is no "orbit which most of the time we Earthlings can't see"; we'd
have seen it.  There were a couple of reported sightings when the idea
was fresh, but those are now tentatively ascribed to either human error
or Sun-approaching asteroids like Icarus.

>Also seems I
>remember there is a planet the other side of Pluto...

A couple of little iceballs have been found out beyond Pluto, but nothing
worthy of being called a planet.  There remains some speculation that
there might be another planet out there, although various recent results
have weakened that theory considerably.
--
Altruism is a fine motive, but if you   | Henry Spencer @ U of Toronto Zoology
want results, greed works much better.  |  [e-mail]  utzoo!henry

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

Date: 27 Jul 1993 22:40:10 GMT
From: Dave Akin <[e-mail]>
Subject: 3-man Shuttle EVAs
Newsgroups: sci.space,sci.space.shuttle

In article <[e-mail]> Kennelmeister,
[e-mail] writes:
>Why do the umbilicals points all have to be in the airlock?
>
>Is there any reason why a 3rd or 4th umbilical point couldn't be
>rigged within the orbiter, with EV3 (4?) using that inside a sealed
>suit, and ducking into the lock just before EV1 & 2 egress,
>or following them out later.
>
>In some instances, would there be an advantage having EV3
>come out later and possibly doing turnabout with EV1 or 2?
>(Is the airlock closed up and repressurised after EVs leave the craft?
> Can it be?)
Well, the simplest reason for not adding another EMU servicing
port outside the airlock is that it would cost many $M. The
necessary plumbing is in the airlock anyway, and the middeck
space is already saturated with the demands of locker experiments,
food preparation, exercise, etc. There is also a very simple flight
rule used for EVAs:
WHEN THERE IS A CREW MEMBER OUTSIDE, YOU
NEVER, NEVER, NEVER CLOSE THE (OUTSIDE) HATCH
FOR ANY REASON WHATSOEVER!
While there has never been a problem, the potential for thermal
distortion, failure of the depress or repressurization system, etc.,
presents the potential for someone stuck outside with no way in.
That is not a happy picture, and not one NASA is willing to
consider for any reason whatsoever. (Gotta say I agree with them
on that point.)

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

Date: Tue, 27 Jul 1993 21:19:42 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Budget figures
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:

>Allen is getting old folks and his memory is going so I will post again that
>according to Business week (First week of May 93) That the only way that
>the 5 billion dollar investment that GM made in Saturn would be termed a
>profit is if GM were to "write off" the development costs.

Sure. Of what relevance is that? NASA didn't write off the Shuttle
development funds, they simply pretend they don't exist. Someday Dennis
when you graduate and begin working in the real world you will learn the
difference between the two.

One important difference: if GM continues to do this for all it's
projects, it will very soon cease to exist. NASA, simply promotes
the people who screwed up and gets more money. One is working under
a control system which encourages effieicnt activity, the other isn't.
This is why, according to a recent NASA study, NASA spends six times on
the average what a private company would for a development project.

>Additionally,
>the article stated that only when production reached the 300,000 unit per
>year rate, which has recently happened, would GM make a profit on a per
>unit rate.

I think I missed something. You seem to be saying that I believe that
all coprorations are always profitable. No, this isn't the case. In
general, they need to be or, unlike government buracracies, they cease
to exist.

>According to an Earlier Space News article, using the 500 million per launch
>figure is only correct when you add the infrastrucure costs incurred by
>the TDRSS system and the worldwide ground support for that system.

Dennis, Space News said that if you include all that, the costs goes to
something like $1.5 billion per flight. But let's forget the article and
look at the budget. According to the 1994 budget Shuttle costs are $4.193
billion which comes out to $524 million per flight assuming you use the
optimistic rate of 8 flights per year. If we add a pro-rated share of
NASA overhead, we get a cost of roughly $575M per flight.

Now, if you look at the budget, you will see this figure does not include
the $300M for ELV launches or the $820 million cost associated with TDRSS
and ground support (the Space & Ground Networks, Communications, & Data
Systems line item).

Look at the numbers Dennis. A Shuttle flight DOES cost well over half a
billion $$ and well over three times what the commercial launches cost.
If you like, I will fax you a copy of the numbers on condition that you
agree to not bring it up again.

>Which by the way DC will have to pay for as well.

Some, I'm sure. However, DC is designed to need minimal ground support
so I don't think they will need as much as you think.

>So your tired old argument about people being thrown in Jail for these
>accounting methods is as false now as it ever was.

This will come as a real suprise to the officers of RCA who where
jailed in '85 for juggling costs like NASA does. Ditto for the
officers who where fired from GD the same year.

   Allen
--
+---------------------------------------------------------------------------+
| Lady Astor:   "Sir, if you were my husband I would poison your coffee!"   |
| W. Churchill: "Madam, if you were my wife, I would drink it."             |
+----------------------89 DAYS TO FIRST FLIGHT OF DCX-----------------------+

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

Date: Tue, 27 Jul 1993 22:38:41 GMT
From: [e-mail]
Subject: Cats in zero gee
Newsgroups: sci.space

: In article <22vsl4$[e-mail]>, [e-mail] (Josh Hopkins) writes:
: > Not a cat you like certainly.  And by the way, cats do not take well to
: > microgravity--it's been tried.

Keith Mancus ([e-mail]) wrote:
:   Could you give me a reference to this?  I wasn't aware it had ever been
: tried.

I heard an anecdote, second hand, from a guy who worked at the Air
Force's zero-gravity training aircraft (similar to NASA's Vomit Comet
KC-135, but a different aircraft).  It seems that the guys on the
flight line thought they'd grab the cat who hung around the hangars and
see what happened when they took it up on a few dozen parabolas.  It
was not a pretty sight.  By the end of the flight, the cat was spewing
bodily fluids from every orifice it had and was fighting mad.  Nobody
dared to get near the poor thing -- it eventually dragged itself out of
its corner and slunk unsteadilly off the airplane.  It took them weeks
to get the smell out of the padding.

DON'T try this at home.  (But if you do, please post the results.)
(Or maybe write it up in a scientific journal -- they'd love it.)

-- Ken Jenks, NASA/JSC/DE44, Mission Operations, Space Station Systems
      [e-mail]  [phone]

                  "HERE MEN FROM THE PLANET EARTH
                    FIRST SET FOOT UPON THE MOON
                           JULY 1969, A.D.
                  WE CAME IN PEACE FOR ALL MANKIND."

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

Date: 27 Jul 1993 23:51:22 GMT
From: "Thomas A. Baker" <[e-mail]>
Subject: Cats in zero gee
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>: In article <22vsl4$[e-mail]>, [e-mail] (Josh Hopkins) writes:
>: > Not a cat you like certainly.  And by the way, cats do not take well to
>: > microgravity--it's been tried.

What was the original question here?

>Keith Mancus ([e-mail]) wrote:
>:   Could you give me a reference to this?  I wasn't aware it had ever been
>: tried.
>
>I heard an anecdote, second hand, from a guy who worked at the Air
[description of folklore about a cat on the Vomit Comet]

I'll confirm at least the part about cats on a plane.  There was a picture
in a book, decades ago, taken on one.  A guy in the plane had a kitten
hanging in the air next to his head.  The cat's kind legs were up past
its ears, and it had a very confused look on its face.

But, I want to add, I think "not liking the Vomit Comet" is not the same
thing as not liking zero gee.  That plane supplies a two hour roller
coaster type of thing, alternating between double gravity and zero gravity.
I think a constant, gentle zero-gee would be much more enjoyable.

Tom

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

Date: Tue, 27 Jul 1993 18:25:36 CDT
From: [e-mail]
Subject: Cold Fusion and its possible uses (if it is proven to exist)
Newsgroups: sci.physics,sci.space

In article <[e-mail]>, [e-mail] (SCOTT I
CHASE) says:
>This problem, and it's hypothetical solution, is supposed to have been
>a motivating factor in P&F's early experiments.  But P&F claimed to
>have stumbled upon an effect far larger than anyone expected.  That's
>where the reasonable science starts to end and the pathology seems to
>start.
Actually Steven Jones was motivated by this problem. He had measured a much  '
smaller rate and no heat. I had never heard that P&F were motivated by it.
--------------------------------------------------
Thaddeus Olczyk, University of Illinois at Chicago

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

Date: Tue, 27 Jul 1993 22:34:25 GMT
From: fred j mccall 575-3539 <[e-mail]>
Subject: DC-X
Newsgroups: sci.space

In <233j4p$[e-mail]> [e-mail] (Michael C. Jensen) writes:

>Pat ([e-mail]) wrote:
>:   Who needs Doors?  just idle the thrusters,  and they should put out
>: a gas stream that will keep the re-entry barrier off the nozzles.

>: pat

>Intersting theory.. anybody know if this would actually be possible?
>(and it brings up a concern, if one jet fails, how bad a heat-leak
>would it cause?) Allen? This stuff all seems right up your alley..

This was one of the reentry options looked at (rather than the
'pitch-up' manuever).  Instead of entering nose first, enter base
first with the engines idled.  They may still try it that way, if the
pitch-up from nose first entry proves too dicey.

--
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
[e-mail] - I don't speak for others and they don't speak for me.

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

Date: Tue, 27 Jul 93 22:39:08 GMT
From: [e-mail]
Subject: DC-X
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Allen W. Sherzer) writes:
> +---------------------------------------------------------------------------+
> | Lady Astor:   "Sir, if you were my husband I would poison your coffee!"   |
> | W. Churchill: "Madam, if you were my wife, I would drink it."             |
> +----------------------90 DAYS TO FIRST FLIGHT OF DCX-----------------------+
                         ^^

Hey Allen,

Whats the deal?   Has the schedual changed radicaly?

Matt Sexton

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

Date: Tue, 27 Jul 1993 23:05:16 GMT
From: Tommy Nordgren <[e-mail]>
Subject: DC-X Prophets and associated problems
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Paul Dietz) writes:
|> In article <[e-mail]> [e-mail] (Tommy Nordgren) writes:
|>
|> >|> In article <[e-mail]> [e-mail] (Paul Dietz) writes:
|>
|>  >|> >What is most galling about all this is that cheaper, simpler
|>  >|> >alternatives that could have reduced launch costs considerably were
|>  >|> >under development in the 1960s.
|>
|>  >   Not only that, but except that the designs suggested in the sixties
|>  > almost always used disposable tanks for hydrogene, they were basically very
|>  > similar to the DC-X design.
|>
|> No, you are very confused.  The designs I am talking about were about
|> as different from DC as they could be.  Different design philosophy,
|> different fuels, different materials, different engine type.  These
|> would *not* have been SSTOs; some were to be completely expendable.
|>
|> The DC-series is based on the idea of making an expensive vehicle and
|> reusing it to amortize the cost over many launches.  The Big Dumb
|> Booster idea was to make a very cheap expendable rocket from low tech
|> materials, like steel, sacrificing some Isp for lower complexity and
|> cost (for example, using ablatively cooled engines rather than complex
|> regeneratively cooled engines, and using pressure-feed instead of
|> turbopump-feed).
|>
|>      Paul F. Dietz
|>      [e-mail]
|>
|>      "Absolute stupidity of the worst sort"
|>         -- Freeman Dyson commenting on the space shuttle.
        I was referring specifically to the following suggestions:
        Pegasus,ROMBUS,Hyperion, which were all suggestions very similar
to the DC-X design
--
-------------------------------------------------------------------------
Tommy Nordgren                     "What is a woman that you forsake her
Royal Institute of Technology       and the hearth fire,
Stockholm                           and the home acre,
[e-mail]                 to go with the old grey widow maker."
--------------------------------------------------------------------------

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

Date: Tue, 27 Jul 1993 23:51:05 GMT
From: Keith Mancus <[e-mail]>
Subject: DC-X Prophets and associated problems
Newsgroups: sci.space

[e-mail] (Michael C. Jensen) writes:
> and personally I believe that people get more excitement and pride out of
> our manned missions than our unmanned missions, justified or not..

  That's the fundamental difference, you see.  I am not interested in
"excitement and pride"; I am interested in living and working in space
myself someday.  If I can't, then my children.  I am NOT NOT *NOT*
interested in anything which does not move us toward that goal.
  I suspect this is the real reason that many people are pushing for
more commercial spaceflight today.  It's not that they are fanatical
libertarians; they are just tired of seeing space as a big PR/glory campaign,
and figure that some hard-headed businessmen are more likely to move
spaceflight towards maturity.
  I approve of Henry Spencer's criteria.  He said something like "my
support is reserved for vehicles I have a hope of riding someday".  Amen.

--
 Keith Mancus    <[e-mail]>                                  |
 N5WVR           <[e-mail]>                                |
 "Black powder and alcohol, when your states and cities fall,          |
  when your back's against the wall...." -Leslie Fish                  |

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

Date: Tue, 27 Jul 1993 23:08:08 GMT
From: Leigh Palmer <[e-mail]>
Subject: Found your own dark-sky nation?
Newsgroups: sci.astro,sci.geo.geology,sci.space

In article <233ni7$[e-mail]> Robert Bunge, [e-mail]
writes:
>So was using a 6-inch f/5 reflector from a ship on the equator
>in the middle of the Indian Ocean (during the winter).

OK, Bob, let us in on how one defines winter on the equator.

Leigh

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

Date: Tue, 27 Jul 1993 23:23:23 GMT
From: Keith Mancus <[e-mail]>
Subject: Low Tech Alternatives, Info Post it here!
Newsgroups: sci.space

In article <231kn3$[e-mail]>, [e-mail] (George William Herbert) writes:
> The only problem with this is that Space isn't inherently a small-business
> environment.  The business plan for Retro for example, at the _lowest_
> expected flight rate, is making ten million dollars a year in 1995 or 96,
> and the high end of the possible growth curve has us in the half-billion
> range by 1998.  So do I become a bad guy once I start making serious
> money?

  Personally, I define a small business in terms of number of people
employed rather than $$$ earned.  The reason for this is that bureaucracy,
the enemy of creativity, correlates well with the number of employees.
So no, earn as much as you can, just don't turn into an empire.

--
| Keith Mancus    <[e-mail]>                                  |
| N5WVR           <[e-mail]>                                |
| "Black powder and alcohol, when your states and cities fall,          |
|  when your back's against the wall...." -Leslie Fish                  |

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

Date: Tue, 27 Jul 1993 22:47:52 GMT
From: [e-mail]
Subject: Musicians and space
Newsgroups: sci.space

[e-mail] wrote:

: Lots of people straddle
: music and science. Weir of the Grateful Dead was one of the original
: L5 members. Astronaut McNair was a jazz musician, and one of his
: friends did a video that was on MTV as a remembrance.

: Look at all the rock bands that used space themes in their music and
: in their videos. ZZ Top "Rough Boy" comes to mind, as do many others.

: I won't put myself in anywhere near the same category, but I did get
: my (albiet small) PRS check this month :-) (That's the UK/Ireland
: equivalent of ASCAP and BMI, only better ;-)

You probably won't find them on any major labels, but the NASA
Astronaut Office sports its own band, Max Q.  These are astronauts
(mostly) who play at selected official and (mostly) unofficial
functions.  They're not bad at all, but I don't think they've ever
gotten a video produced a la MTV.

-- Ken Jenks, NASA/JSC/DE44, Mission Operations, Space Station Systems
      [e-mail]  [phone]

                ASCAN (Astronaut Candidate) 10 COMMANDMENTS

      1. Keep smiling, but not grinning

      2. Keep your humor harmless, pure and perfect.  People don't
         understand irony.

      3. Keep your weaknesses to yourself.  If you don't point them out
         to others, they will never see them.

      4. Never complain; make survival look easy.

      5. You are expected to say something nice after each flight,
         class, of simulation.

      6. If you can't say something nice, lie -- nicely.

      7. In particular, practice saying, "Thanks for pointing that out,
         sir.  I'll really work on that."

      8. Be aggressively humble and dynamically inconspicuous.  Save
         your brilliance for your friends and family.

      9. Remember -- whatever's encouraged is mandatory.  Whatever's
         discouraged is prohibited.

     10. Nothing is sometimes a good thing to do and always a clever
         thing to say.

                             REVIEW THIS LIST DAILY

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

Date: 27 Jul 1993 22:01:39 GMT
From: Tony Hamilton <[e-mail]>
Subject: Needed: SS-Freedom update
Newsgroups: sci.space

Where can I find a comprehensive update of the status of SSF today? Something
which explains what the current design is, what work has been done so far,
schedules, and so forth. Is there a document on the Internet somewhere? A
good article in a recent magazine? Ya hear things now and then on the news,
but not much (like the recent decision to lay off a thousand or so people
working on the project). Any help would be appreciated. Thanks.

Tony Hamilton
[e-mail]

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

Date: Tue, 27 Jul 93 02:23:00 BST
From: [e-mail]
Subject: Odds on ACTS

> Date: Fri, 16 Jul 93 06:32:00 -0500
> Charles Radley <[e-mail]>

Writes:

 Pa> Message-ID: <224jka$[e-mail]>
 Pa> Newsgroup: sci.space
 Pa> Organization: Express Access Online Communications, Greenbelt, MD USA

 Pa> In article <[e-mail]> [e-mail] (Henry
 Pa> Spencer) writes:
 Pa> |In article <223vf2$[e-mail]> [e-mail] (Pat)
 Pa> writes: |>But real question.  ANyone know why it's going up on the TOS?
 |>I guess the IUS is too small  and the Centaur is banned from shuttle ops.
 Pa> |
 Pa> |No, IUS is too big.  TOS is a mid-sized upper stage, for loads too
 Pa> heavy |for PAMs and too light for effective use of IUS.  Unfortunately
 Pa> for OSC, |there aren't many such shuttle payloads any more.
 Pa> |--

Excuse me for interjecting here, I am sure that all the experts, like Henry
and Pat understand all this, but I am afraid that there may be those who do
not understand the relationship between the TOS and the IUS.

The IUS is a two stage vehicle which consists of two solid rocket motors,
called, very unimaginatively, SRM-1 and SRM-2. Unlike most of the current
upperstages, it takes a payload from a low orbit and delivers it to
geostationary orbit (if that is where the customer wants to go) with out any
action by the payload, and with no spinning, jostling, or other disturbances
which some of your more discriminating payloads do not like.

In addition to the two solid stages there is also a full set of avionics,
including dual inertial navigation systems, a reaction control system, and
other payload services.  (The IUS has also been used for several planetary
missions, firing the two SRM sequentially to attain earth escape velocity,
which, as it turns out, is somewhat easier than GSO.)

As far as "size" goes, the IUS is roughly the same weight as the Shuttle
Centaur was going to be, both push the Shuttle to its max weight limits, both
are variable in propellant capacity. Obviously, the Centaur, with LO2/LH2
has somewhat more payload capacity, on paper.

At some point, NASA decided that for some missions, they didn't want
anything except the first stage, and for reasons that I won't go into (for one
reason, I am not unbiased, having been associated with the IUS program for
quite a while, and another, I don't know all the details, and couldn't talk
about them, if I did.) it was decided to buy a "new" vehicle from a different
source. However, the "loaded motor case" was identical to, and produced by
the same supplier as the IUS motor. Therefore, the TOS is exactly the same
size as the IUS SRM-1, which is a maximum of about 21,000 pounds of
propellant.

The nozzle is different, in that it does not have thrust vector control
capability, and, of course, it does not have the actuators, either.

 Pa> I sincerely hope the Manufacturing costs of a TOS are significantly
 Pa> less then both a centaur and a IUS then.

The parts of the TOS that are the same as the IUS cost exactly the same,
presumably, to produce. (There is, of course, a difference in "cost" and
"price.")

As it turns out, there has only been, I think,  one TOS launch to date. The
Mars Observer. Due to some bad luck, the TOS motor was damaged in
handling (could have happened to anyone) and it was replaced with a
"loaner" IUS motor, so in that case, I think that the cost was probably
exactly the same.

> IUS puts the payload into circular GEO.   ACTS and all commercial
> comm-sats need to go into GTO, it is cheaper to use an on-board
> apogee kick than use the IUS.

Based on the idea that it is cheaper to have a custom designed apogee motor,
avionics, and software in each payload than to have one common set for all.

A lot of people believe this, and it probably is true that almost anything
costs less than an IUS second stage and avionics package, but that does not
make it true, in general.

> IUS was designed to Air Force requirements, not commercial
 requirements.

Not only was the IUS designed to Air Force requirements, it is an Air Force
program, which means that if NASA wants one, they have to get it from the
Air Force. Having two agencies involved always seems to cause problems, it
has been alleged that there was some friction between those two
organizations over the AF having to procure launch services from NASA, and
it is possible that there could be something like that in return, who knows?

That could have had something to do with the reasons for NASA preferring
the TOS in the first place. A way to get an already developed motor directly,
without having to deal with the AF. Although it may well be that the TOS is
cheaper in the abstract, I think that it is very questionable if it did in fact
save money if there are only the two launches that are now programmed (to
my knowledge) as there were considerable "non recurring" costs associated
with it, and there are "hidden" costs, too. Someone has to do the second burn
for GSO, which the TOS does not do.And, someone has to provide the
avionics, software, integration, etc. although it may be charged against
something other than the   launch vehicle. Spacecraft managers do have a
tendency to see money spent "in their own shop" as being quite different
from that which goes "out of house."  .


Henry S. Hillbrath
    ----------------------------------------------------------
NO ONE  believes an analysis...   |  EVERYONE believes a.test...
   - except the guy who did it.   |     - except the guy who did it.

                   T. M. ("Scotty") Davidson



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

Date: 28 Jul 1993 00:02:56 GMT
From: Josh Hopkins <[e-mail]>
Subject: Passenger lotteries
Newsgroups: sci.space

[e-mail] writes:

>Now to old business, what about a lottery to ride onthe shuttle or DC-X??

The shuttle is flat out not available for tourists and the DC-X is not a
passenger vehicle.  It might be possible for a modified DC-X to carry a
passenger (Conrad volunteered and managment has threatened, but both jokingly).
However, DC-X is not a space vehicle.  It's not even supersonic if I recall
correctly.

>===
>Ghost Wheel - [e-mail]
--
Josh Hopkins                                          [e-mail]
     "Physics is like sex: sure, it may give some practical results,
                 but that's not why we do it."
                        -R. Feynman

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

Date: 27 Jul 1993 21:16:07 GMT
From: [e-mail]
Subject: Why I hate the space shuttle
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (jeff findley) writes:
|> In article <230m4i$[e-mail]>, [e-mail] (Michael C. Jensen) writes:
|>
|> |> : 7) I have a better more reliable computer system in my 2 mb amiga 500
|> |>
|> |> Perhaps a cheaper more powerful system (in SOME respects) but more
|> |> reliable?.. no..
|>
|> How about triple redundant Amiga 500's with a backup Amiga 500?  This is
|> how the shuttle's computers are reliable, aside from being radiation
|> hardened, etc.


Well, not exactly. Triple redundancy is _one_ way they are made reliable.
Another has to do with spaceflight certification. The three main shuttle
computers are IBM processors, whose main design was around in the 1960s.
(Read: VERY SIMPLE). The Amiga 500 is based on the Motorola 680x0 family,
around since the 1980s. In this case, newer is not necessarily better:
instead, it is more complex, and the more complex a computer system is,
in general, the more statistically possible it is for that system to fail.
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.
--
Glen Henshaw
HALOE Data Processing
[e-mail]

"Stop being stupid."
This advice is offered in leiu of <standard/disclaimer>.

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

End of Space Digest Volume 16 : Issue 934
------------------------------