Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_4/V15NO473.TXT

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Date: Mon, 30 Nov 92 05:01:24
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #473
To: Space Digest Readers
Precedence: bulk


Space Digest                Mon, 30 Nov 92       Volume 15 : Issue 473

Today's Topics:
                    (!) Shuttle Computer Problems
                          Breasts in zero-g
             Chicago DC-10 (Was Re: Shuttle replacement)
         DoE Experts Endorse Electrostatic Confinement Fusion
            Flying Platforms (Was Re: Shuttle replacement)
                FREE-ENERGY TECHNOLOGY For Spacecraft
                     Hubbles's mirror (good spin)
          Imaging Galileo as it flys past Earth on Dec. 8th
       Military History (Was Re: Shuttle replacement) (2 msgs)
                     Shuttle replacement (9 msgs)

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

Date: 29 Nov 92 23:29:50 GMT
From: Colby Kraybill <[e-mail]>
Subject: (!) Shuttle Computer Problems
Newsgroups: sci.space,comp.arch,comp.arch.storage

In article <[e-mail]> [e-mail] (Michael F. Santangelo) writes:
>I'm finding this a wee-bit hard to take that someone at KSC is posting
>to usenet with what seems like a critical design problem of the
>shuttle's computer systems and asking for suggestions on how to fix.
>Well, for what it is worth, I will re-post it to a couple more
>relavent groups to see what people think.  This JUST appeared in our
>nn database (~3:55PM EST) in group sci.space.shuttle.
>-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>Michael F. Santangelo                 + Internet: [e-mail]
>Computer & Network Systems Director   +           [e-mail]
>UMCEES / CBL (Solomons Island)        + BITNET:   MIKE@UMUC
>University of Maryland                + Voice:    [phone] (direct)
>                                      +           [phone] x237
>


Whoa!  DOWN boy!  This is the INTERnet, the mission of the internet is to
connect scientists and to further research.  It seems to me that the KSC
person's post was right up the internet's alley.



--
Colby Kraybill
Space and Planetary Image Facility
University of New Mexico
[e-mail]

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

Date: 29 Nov 92 23:17:18 GMT
From: Magnus Olsson <[e-mail]>
Subject: Breasts in zero-g
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Brian Tao) writes:
>In article <roelle.722116771@uars_mag> roelle@uars_mag.jhuapl.edu (Curtis Roelle) writes:
>>
>>The use of a brazier is
>>still required, although the flight version differs from the
>>terrestrial standard in that instead of lifting the breasts upward it
>>pulls them downward, keeping them out of the face.

I recall reading somewhere (I think it was in the Omni Space Almanac)
that NASA was completely unisex: the only difference between the
clothing of male and female astronauts was that the women wear bras to
keep their breasts in place.

One would think there'd be some more or less official NASA policy on
this, and that they would have put some effort into research on this
topic before sending women into space (I wouldn't be too surprised if
there really were a special "flight version" as mentioned above).
Would anybody at NASA care to comment?

>Speaking of spaceflight attire, don't the jumpsuits have some
>sort of built-in "support"?  I know they are supposed to be form-fitting
>so no baggy ends can accidentally snag a control switch or get caught
>on a corner.  With a properly designed jumpsuit, would a bra be
>superfluous in zero g?

Probably, if it were really form-fitting, like the uniforms in Star
Trek... But don't the astronauts wear trousers and short-sleeved
shirts most of the time nowadays? A guess would be that a shirt made
to such specifications would be so revealing that NASA's image would
be jeopardized :-)

              Magnus Olsson                | \e+      /_
    Department of Theoretical Physics      |  \  Z   / q
        University of Lund, Sweden         |   >----<
 [e-mail], [e-mail]  |  /      \===== g
PGP key available via finger or on request | /e-      \q

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

Date: 29 Nov 92 11:09:16 GMT
From: "John D. Boggs" <erato!jdb>
Subject: Chicago DC-10 (Was Re: Shuttle replacement)
Newsgroups: sci.space

Just a pointer for those who might be interested:

     There's discussion of the Chicago (and other) DC-10 crash(es)
right now in sci.aeronautics.airliners.

John D. Boggs     uunet!erato!jdb

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

Date: 29 Nov 92 18:54:16 GMT
From: Jim Bowery <[e-mail]>
Subject: DoE Experts Endorse Electrostatic Confinement Fusion
Newsgroups: sci.physics.fusion,sci.physics,sci.space,sci.energy

A panel of DoE funded experts in fusion technology have
recommended that electrostatic confinement fusion technology
be developed due to its superior potential for achieving
the  commercial goals of the EPRI (Electric Power Research
 Institute).

The specific technologies they evaluated were Energy Matter Conversion
Corporation's patented Ion Acceleration (IXL) and Electron Acceleration
(EXL).

The EPRI commissioned report was delivered on November 4, 1992.

--
INTERNET:  [e-mail] (Jim Bowery)
UUCP:   ...!ryptyde!netlink!jim
NetLink Online Communications * Public Access in San Diego, CA [phone]

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

Date: 30 Nov 92 02:08:00 GMT
From: [e-mail]
Subject: Flying Platforms (Was Re: Shuttle replacement)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Bruce Dunn) writes...
>Regarding the difficulties of vertical landings, Gary Coffman writes:
>

>For those who think that all this is too difficult, remember that it was done
>6 times for moon landings, and probably thousands of times in the various
>"flying platform" gadgets that the military used to fool with (devices that
>flew and hovered by thrust alone).
>

Just for the record, the Lunar Landings were very tough, especially the
first one that nearly ran out of fuel.  Also the flying platforms you
speak of were abandoned by the military BECAUSE they were extremely
dangerous. Neil Armstrong was nearly killed in the LM flying platform
just a few months before the launch of Apollo 11.

I do not mean this as an attack on DC series, but as a reminder that this
technology didn't work real well back then but I do have every confidence
in the ability of SSTO to land where they say they will. There WILL be
problems somewhere somehow, but if the supporters will be realistic and
admit that then when one falls down and goes boom the program will not
be canceled. That would be a shame.

Dennis, Univversity of Alabama in Huntsville

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

Date: 28 Nov 92 16:04:03 GMT
From: Brian Tao <[e-mail]>
Subject: FREE-ENERGY TECHNOLOGY For Spacecraft
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Ed Beshore) writes:
>There are a couple of fascinating things about Mr. McElwaine's postings.
>
[...]
>
>2. Another thing that is interesting is everyone else's reactions to him.
>   of considering him an amusing three sigma kind of character, people use much
>   more net capacity trying to figure out how to silence him or flaming his
>   posts.  I propose someone post a small chunk of code to filter an author
>   from a notes file.  If you don't want to read someones posts, then you
>   can let your coomputer do the clipping.
>
>   Otherwise, consider him a colorful amusement...

    He would probably be an entertaining distraction if only he came up with
something *new* once in a while.  I've seen this FREE ENERGY TECHNOLOGY
article about five times now and another one on changing the direction of
gravity once in (I think it was) sci.med.  I sent him a nasty rebuttal the
third time I read about "free energy" and he replied in the same haughty,
sensationalist style (with many capitalized words!) which characterizes his
public bulletins.  I keep telling him to post on sci.skeptic, but he ignores
me.  :)
--
-- Real name: Brian Tao (Dept. of Exobiology, University of Toronto)
-- Preferred: [e-mail] (checked daily)
-- Alternate: [e-mail] (no mail over 15K, please!)
--                                   """""""""""""""""""""""""

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

Date: Sun, 29 Nov 92 08:01:02 GMT
From: Greg Wilkins <[e-mail]>
Subject: Hubbles's mirror (good spin)
Newsgroups: sci.astro,sci.space

Just to put a good spin on the failure to detect the flawed main mirror:

What are the chances that hubble would have flown if the flaw in the mirror
was detected? It was already decades late, budgets are really tight and
Fred in on its way.  Maybe the extra delay would have killed hubble, (it
would have made a great display in the smithsonian :-)

If there was a chance that hubble would have been grounded, maybe it is
better that it went up half blind (but fixable).  The science learned from
fixing it in orbit must also be worth something -> probably will save an
extra flight practising for Fred.

Greg Wilkins @ Highland Logic
       Snail : Suite 1, 348 Argyle St., MossVale, NSW, 2577, Australia
       Email : [e-mail]
       Phone : [phone]  or direct: ([phone]
       Fax   : [phone]

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

Date: 30 Nov 92 01:23:23 GMT
From: Gerald Cecil <[e-mail]>
Subject: Imaging Galileo as it flys past Earth on Dec. 8th
Newsgroups: sci.space,sci.astro

We have a CCD on our campus 24" telescope.  I recognize that Dec 8 is close to
full moon (too bad it wasn't a day later, during the lunar eclipse!), but I'd
like to try to image Galileo in I-band as it streaks by.  Does anyone
(Ron Baalke?) have access to an ephemeris for a given long,lat & altitude?
--
Gerald Cecil [e-mail]  919-962-7169
Physics & Astronomy, U of North Carolina, Chapel Hill, NC 27599-3255 USA

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

Date: 29 Nov 92 21:18:26 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Military History (Was Re: Shuttle replacement)
Newsgroups: sci.space

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

>>Those gliders only flew during
>>very good weather. As it is, they only saw very limited use because they
>>where judged too dangerous.

>The Gliders flown in the Normandy Invasion saw limited use because the utility
>of gliders in warfare is very limited.

It is limited because they are so unreliable and dangerous.

>The high casualty rate of the glider
>force was mainly due to their being deployed in the dark and the landing
>field consisting of cow pastures.

As for landing in cow pastures, that's all you get. As for laning in the
dark, that turns out not to have important. Gliders used during operation
Market-Garden suffered similar fates.

They where dropped because they where simply too dangerous.

  Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------146 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: 30 Nov 92 01:30:18 GMT
From: Joseph Askew <[e-mail]>
Subject: Military History (Was Re: Shuttle replacement)
Newsgroups: sci.space

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

>In article <[e-mail]>, [e-mail] (Allen W. Sherzer) writes...

>>In article <[e-mail]> [e-mail] (Gary Coffman) writes:

>>Those gliders only flew during
>>very good weather. As it is, they only saw very limited use because they
>>where judged too dangerous.

>The Gliders flown in the Normandy Invasion saw limited use because the utility
>of gliders in warfare is very limited. The high casualty rate of the glider
>force was mainly due to their being deployed in the dark and the landing
>field consisting of cow pastures.

Also because (it has been rumoured) the pilots of the planes they were
attached to had a decided lack of interest in getting anywhere *near*
the beach. This meant lots fell into the sea.

>This was the only time gliders were used in mass in WWII or at any other
>time in warfare. Before WWII it was not feasable and after WWII the Helicopter
>had replaced it.

Actually no - depending on what you mean by 'mass'. The Germans used them
during the invasion of France. The US used them in the invasion of Scilly
(where a considerable number were shot down by the US Navy, you would think
that they could see that gliders heading inland weren't bombers but no!)
And of course there was Arnhem - you haven't been watching enough trash
midday TV :-)

Gliders were and are too exposed to AAA and a simply incredible number
have been shot down by their own side! Not much of a fun job really.

Note the direction of the Follow up


Joseph Askew


--
Joseph Askew, Gauche and Proud  Barbarian horns draw out the northern wind;
[e-mail]  Paler than water lies the Thistle Pass;
Disclaimer? Sue, see if I care  Sky swallows up the road to Kokonor;
One China One Korea One Eire32  Moonlight, a thousand miles along the Wall.

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

Date: Sun, 29 Nov 92 16:37:24 EST
From: John Roberts <[e-mail]>
Subject: Shuttle replacement

-From: [e-mail] (Brian Stuart Thorn)
-Subject: Re: Shuttle replacement
-Date: 28 Nov 92 05:34:41 GMT
-Organization: The Portal System (TM)

-I'm sure Allen or Henry will say it momentarily... the DCX is very
-unlikely to lose all power on the way in. True enough, but this discussion
-appears to be of worst-case scenarios (at least when directed at the
-Shuttle) so I chose the worst case scenario for a DCX accident, too.

"Worst-case" scenarios are of very limited use unless you can calculate some
probabilities. If I were to launch a model rocket, it *could* frighten a
goose, which could cause it to migrate north out of schedule, which could
cause it to be at the wrong place at the wrong time, and get sucked into
an engine of a 747 over New York, which could cause the engine to fail,
which could cause it to crash into the UN building, which could just
happen to be hosting a meeting of world leaders, and the accident could
precipitate a global thermonuclear war. However, I suspect the odds of
all that happening are somewhat slim. :-)

John Roberts
[e-mail]

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

Date: 29 Nov 92 22:15:35 GMT
From: "Michael V. Kent" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space.shuttle,sci.space

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>In article <[e-mail]> [e-mail] (Michael V. Kent) writes:
>
>>I would hope this country could do more with its space program than just keep
>>its contractors profitable.  But NASA isn't a contractor -- it's a government
>>agency.  Government agencies don't earn profits, nor should they.
>
>1. The original poster said that Shuttle had the 'highest return on
>investment' of any launcher. I am simply pointing out that isn't correct
>and I am glad that you seem to agree.

The difference, I think, is our uses of the term "return on investment."  In
the commercial world, ROI has a specific meaning relating dollars earned and
dollars spent.  Since NASA is not seeking monetary profit, I consider its
income scientific knowledge, technology, and practical space-related info (eg,
how to capture a spinning satellite).  Since the types of "income" are complete-
ly different, comparing them quantitatively makes little sense.

>>They should
>>be doing things in the public interest that can't earn a profit.
>
>Since providing launch services is a profitable buisness then I am glad
>to see we agree.

Yes, and since launching payloads is profitable (for some), I think NLS is
the most expendable of the three launcher programs: NLS, NASP, and SSRT.

BTW, what are the possibilities of developing the STME as a replacement for
the SSME?

Mike

--
Michael Kent                                   [e-mail]
McDonnell Douglas                              Rensselaer Polytechnic Institute

Tute Screwed Aero Class of '92                              Apple II Forever !!

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

Date: Sun, 29 Nov 92 17:53:26 EST
From: John Roberts <[e-mail]>
Subject: Shuttle replacement

-From: [e-mail] (Gary Coffman)
-Subject: Re: Shuttle replacement
-Date: 28 Nov 92 17:05:52 GMT
-Organization: Gannett Technologies Group

-Fault tolerance is basically a way of saying multiple redundant systems.
-I get this picture of a system so complex and so heavy that it won't fly.

This model of fault tolerance is too simplistic to be useful. Fault
tolerance is much more than just bolting redundant parts together.

-The entire *zero defect* concept grew out of the need to avoid too many
-backup systems in spacecraft.

In the early days of NASA, this approach grew out of the desire to
make the launchers work *at all*. It arose after most of NASA's first
umpteen launches failed. Remember that some forms of redundancy and fault
tolerance add little or nothing to weight. Making the control computers in
the Apollo command module and lunar module identical presumably didn't hurt
payload too much, but it came in handy during the Apollo 13 mission.

-SSTO is a thin margin system compared to
-ordinary multi-stage rockets. I'd expect *less* redundancy in such a
-system. Ok, it uses multiple engines, but that's the norm for any launcher
-in current use. They still fail or blow up with disturbing regularity.
-It would seem natural to assume that a system with a higher margin would
-be more reliable than a system with a thin margin. That leads me to
-believe that the SSTO will be *less* reliable than more conventional
-approaches.

There's more than one kind of "thin margin". SSTO admittedly has a thin
weight margin to get into orbit, but that should not be interpreted that
it has a thin margin to land. Another type of margin is in performance
limitations and safety limits. The SSMEs push these margins pretty hard,
which contributes to the expensive servicing requirements. DC is specifically
intended to *avoid* this type of thin margin, at least as far as the engines
are concerned. You may be convinced that the designers, possibly faced with
weight problems, will choose to push these margins, but I haven't seen
any indication that this is the case - at least so far, they appear dedicated
to either proving that it can be done with a reasonable safety margin, or
giving the whole thing up as a bad job if they can't prove it.

Goldin has mentioned possible margins in materials performance, which I
would interpret to include thermal management, but Allen hasn't responded
to my question on this, so I can't really comment on it.

Also, you have to look at your criteria for judging "reliability". If a DC
launches, but has a few engines fail and has to land, the engines can be
repaired, and the payload can be relaunched. That's hardly the same as
a non-reusable booster failing to get into orbit, and the payload being
destroyed.

If you want to criticize DC landing safety, general remarks are not
adequate - you really have to have some numbers. For instance, how many
engines is DC currently expected to have? How many are required to hover or
land with most of the fuel mass gone? Based on previous engine performance,
what are the odds of more than a "landable" number failing during a typical
flight? What are the requirements of symmetry for safe flight? What types
of events might cause the failure of multiple engines? And so on.

John Roberts
[e-mail]

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

Date: 29 Nov 92 15:05:24
From: Steinn Sigurdsson <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

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

   For a more accurate comparison with a DC-1 landing, consider that you will be
   landing on a huge flat area which has been cleared of all personnel and
   obstructions.  Furthermore consider that it doesn't matter where on the area
   you land - if there is a gust of wind which pushes the vehicle sideways, you
   will have to do some thrust vectoring to kill the sideways velocity, but
   there is no need to maneuver to regain your original touchdown point.

Now here's a question: How is the DC to be refuelled and reloaded
between missions? That is, it won't necessarily land on a pad and it
has no wheels (?) so how will the ground crew handle it? A crawler
to take it back to a payload bay or ground vehicles for fuel and
payload? In either case what is projected manpower and cost?
(remember it's a _lot_ of croygenic fuel and the sucker is quite
heavy, even when empty...) Where is the payload bay? Above the fuel
tanks right? Does it need a gantry to load heavy payloads or will a
mobile crane be used?

Allen? ;-)

|  Steinn Sigurdsson    |I saw two shooting stars last night        |
|  Lick Observatory    |I wished on them but they were only satellites    |
| [e-mail] |Is it wrong to wish on space hardware?        |
| "standard disclaimer"    |I wish, I wish, I wish you'd care - B.B. 1983    |

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

Date: 30 Nov 92 00:19:45 GMT
From: Mary Shafer <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

If the DC-X is going to be so safe, why are they testing it at White
Sands instead of, oh, say, John Wayne Airport?  And why is the test
team limited by how many people will fit in the blockhouse?

I think that Allen is the only one who doesn't think there's any risk.

--
Mary Shafer  DoD #0362 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: Mon, 30 Nov 1992 01:03:30 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (John Roberts) writes:

>Goldin has mentioned possible margins in materials performance, which I
>would interpret to include thermal management, but Allen hasn't responded
>to my question on this, so I can't really comment on it.

I'm sorry but I must have missed this question. What was it?

If the issue is material for the heat shield, that isn't a problem. If the
selected materials won't work then they can use shuttle tiles. DC re-entry
produces less heat than Shuttle.

  Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------146 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: 30 Nov 92 01:18:22 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Steinn Sigurdsson) writes:

>Now here's a question: How is the DC to be refuelled and reloaded
>between missions? That is, it won't necessarily land on a pad and it
>has no wheels (?) so how will the ground crew handle it?

I believe current plans are to put weels on it after it lands and tow it
to a hanger or the launcher. Empty weight is only 80K pounds so this isn't
hard.

If it works out as expected, it can fly a few missions with just re-rueling.
In this case it is towed to the launch pad, re-fueled, the payload is
integrated, and off it goes. The launch pad is nothing more than a simple
support structure; the landing system can't take the weight of a fully
loaded vehicle.

>to take it back to a payload bay or ground vehicles for fuel and
>payload? In either case what is projected manpower and cost?

Total turnaround is expected to cost around $10 million. I have seen figures
for ground crew size and from memory is was on the order of 10 people.

Note that this will be better understood after the DCX flights.

>Where is the payload bay? Above the fuel tanks right?

Above the hydrogen tank and below the cockpit. (The oxygen tank is at the
very top).

>Does it need a gantry to load heavy payloads or will a
>mobile crane be used?

A mobile crane will be fine. Payload are put into a standard pallet and the
pallet has standard interfaces with the vehicle. This means that the complex
integration tasks can be done offline and payload/vehicle integration will
take a few hours at most. Max payload weight is 20K pounds so a mobile crane
is no problem.

  Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------146 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: Mon, 30 Nov 1992 01:26:23 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Mary Shafer) writes:
>If the DC-X is going to be so safe, why are they testing it at White
>Sands instead of, oh, say, John Wayne Airport?...


I think your confusing acronyms Mary. DCX isn't safe; it will fly with
destruct charges and the crew will be well protected. DCY will have destruct
charges for numanned flights but I assume manned flights will do without.
DC-Y also will not be airliner safe.

DC-1 however, WILL be airliner certified and will fly from John Wayne
Airport without destruct charges or blockhouses.

>I think that Allen is the only one who doesn't think there's any risk.

I have always said this is a moderate risk program.

  Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------146 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: 30 Nov 92 02:20:29 GMT
From: "Michael V. Kent" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

>>The companies who went with Shuttle went out of buisness long ago. They
>>paid too much for launch costs.
>>
>>   Allen

Oh, did they?  The very first commercial payload on the Shuttle was flown
by the same company that is building the DCX.  They are very much alive and
well in the space business, more than any other company in the world.  Perhaps
they know something you don't?

Dennis and his group are FLYING payloads on the Shuttle AND unmanned systems.
They don't see them as being mutually exclusive, but you do.  Perhaps they
know something you don't?

For the record, Allen, how many payloads have you flown?

Mike

--
Michael Kent                                   [e-mail]
McDonnell Douglas                              Rensselaer Polytechnic Institute

Tute Screwed Aero Class of '92                              Apple II Forever !!

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


Received: by  julius.CS.QUB.AC.UK  (NeXT-1.0 (From Sendmail 5.52)/NeXT-2.0a)
    id AA09542; Sun, 29 Nov 92 21:09:38 GMT
Date: Sun, 29 Nov 92 21:09:38 GMT
From: [e-mail]
Received: by NeXT Mailer (1.63)
To: [e-mail]
Subject: Re: Shuttle replacement

> If the Shuttle loses flight control power on the way in, it'll plow
> straight through that apartment complex.  Look out below, and about a
> mile in front.
>


If you are going to talk about worst case scenarios, then this is
certainly one to consider. The shuttle is dependant on the APU's for
hydraulics. Without hydraulics the GPC's cannot operate the elevon,
ailerons and rudder. The APU's burn N2O4 and Hydrazine (a nasty,
poisonouse mix) and are redundant. A complete APU failure is not
survivable. If all 5 GPC's went out, there would also be no control. To my
knowledge the shuttle is fly by wire controlled via the GPC's. (They
"vote" on the outputs by applying hydraulic pressure. If one GPC tries to
put the rudder hard over and the other 4 prefer a bit less of a turn, they
overpower the disenter hydraulically)

Of course, a complete APU or power failure on the Shuttle is no more
likely than a failure of all the engines on the DC-1, so maybe both points
are fairly moot.
--
=======================================================================
Give generously to the Betty Ford   Dale M. Amon, Libertarian Anarchist
Home for the Politically Correct            [e-mail]
=======================================================================

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

Date: Sun, 29 Nov 1992 13:24 PST
From: [e-mail]

add me the mailing list

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

End of Space Digest Volume 15 : Issue 473
------------------------------