Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V08/V8_239.TXT

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From ota Tue May 31 03:08:31 1988
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Subject: SPACE Digest V8 #239

SPACE Digest                                      Volume 8 : Issue 239

Today's Topics:
     Re: A high volume Earth to high orbit launch system
              Re: Bombs on Mars
             Re: Small comets & The Moon
              Re: Bombs on Mars
             Re: Small comets & The Moon
                 Space suits
               Re: Space suits
               Re: Space suits
               Re: Space suits
               Re: Space suits
               Re: Space suits
----------------------------------------------------------------------

Date: 17 May 88 19:48:27 GMT
From: mcvax!unido!ecrcvax![e-mail]  (John Gregor)
Subject: Re: A high volume Earth to high orbit launch system

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>>[Re: Launch loop]
>it has a couple of modest practical flaws shared by most of the (so to
>speak) mechanical Earth-to-orbit schemes:
>
>1. It works much better on a large scale than on a small one, so it's
>    impractical to start with a little one and use its revenues to
>    bootstrap up.  All the money has to be raised up front.

True.  But the US space program never was one for a slow, well
established bootstraping process.

There is another use for the same basic technology as the launch loop:
storage of energy.  Calculate the amount of energy stored in that
ribbon.  Increase the mass of the ribbon, decrease the speed a bit,
remove the hardware needed for space launching, mount the whole thing
horizontally, and you now have a very usefull means of staring LARGE
amounts of energy.  I think this could be used to 1. act as a proof of
concept demonstration for many of the basic ideas, 2. raise research
money, 3. act as a testbed for further development, 4. generate revenue,
and 5. even be usefull.  A giant Q-Tip (TM) brand cotton swab shaped
loop is probably the best:
    1) Linear sections are easier than curved ones.
    2) It reduces the likelyhood that a failure would send roughly a
       billion MJ (amount of energy stored in a loop of the size in the
       paper, knock off 3 orders of magnitude for power storage) in an
       inhabited direction.

>2. It's big enough and fragile enough to be very vulnerable to attack
>    by clever terrorists.

Fortunately, the terrorists of the world haven't been very clever.
Friends and I have thought of many truly destructive things that can be
accomplished with very low technology.  Maybe they are clever, but the
NSA/CIA combo is more effective and useful than we realize.  I don't
know which is scarier.  But I digress...

Keith has been somewhat cavalier about the terrorist threat for several
reasons:
    1) The majority of the beast is 80km up, not easy for many people
       (including us right now) to get to.
    2) The target is only 5 to 10 cm wide for 99.9% of it's length.  How
       many SAMs have that kind of accuracy?
    3) The loop would be a MAJOR resource to the planet.  The
       governments using it's services would definitely have incentive
       to keep the surrounding waters well patrolled.  Hopefully, one
       nation wouldn't try to monopolize it's use.
    4) Once the industry has been set up to produce the ~500,000
       identical pieces of track, producing more shouldn't be very
       difficult.
     A) The track sections are pretty low tech.
     B) Most of the original track would be recovered.  Only the
        ribbon (2.6 million pieces of transformaer iron -- lot's
        cheaper than a shuttle) would be a write off.
       So yes, a terrorist attack would be painful, but not shattering.
       The loop would be out of commision for at most a month or three.
       After a once or twice, the novelty would wear off (hopefully).  I
       guess the best analogy I can come up with would be the blowing up
       of high tension power lines: It's annoying, it stops the whole
       system for a while, but it really doesn't change things in the
       long run.

>These are not insuperable obstacles, but they do present problems.  He
>may have addressed them since.

The control theory and dynamics of the structure are some of the biggest
headaches.  Gurus comfortable with higher order differential equations,
should make themselves known.  Sensor technology was another problem
Keith mentioned.

Keith -- are you still out there?  I saw your vote for the
     nanotechnology group, so I know you still read a few things.
     How about an update?

If this discussion has piqued anybody's curiosity, I STRONGLY urge you
to order the paper.  It is also probably in many university libraries.
If somebody else want to put a full description on the net, be my guest.
But, I'd really like to see more people go out and get references for a
change.

AIAA-85-1368
The Launch Loop: A Low Cost Earth-To-High-Orbit Launch System
K. H. Lofstrom, Launch Loop, Portland, OR
AIAA/SAE/ASME/ASEE 21st Joint Propulsion Conference
July 8-10, 1985 Monterey, California

American Institute of Aeronautics and Astronautics
1633 Broadway, New York, NY 10019

John Gregor  -  [e-mail]

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

Date: 5 May 88 10:07:30 GMT
From: mcvax!ukc!strath-cs!glasgow![e-mail]  (Mr Jack Campin)
Subject: Re: Bombs on Mars

[e-mail] (ERCF02 Adam Hamilton) writes:

>Since I wouldn't mind seeing [a nuke] used on an asteroid, perhaps its
>time to draw up some sensible guidelines.  How about nothing over 15 km
>long.

I assume you are thinking of fending off something like the Alvarez
meteorite.  I have occasionally wondered about that. Would the world's
present sky surveying activity give us any warning at all of a
continent-smasher on its way? Would our present interplanetary launcher
and bomb technology be adequate to deal with it? I would assume the best
that could be done would be an Energeia with an American warhead (I
believe they're a lot more reliable) on top of it - which leaves an
interesting political problem; what chance would there be of persuading
Reagan to ship a state-of-the-art nuclear warhead to Baikonur in the few
weeks, at most, we'd have?

ARPA: [e-mail]       USENET: [e-mail]

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

Date: Tue, 10 May 88 10:04:23 PST
From: Peter Scott <[e-mail]>
Subject: Re: Small comets & The Moon
X-Vms-Mail-To: EXOS%"[e-mail]"

[e-mail] (Allen C. Kistler) writes:
>> From: spar![e-mail]  (Jay Freeman)

>> If that were so, then there should be at least hundreds of thousands
>> of new craters on the MOON each year, each caused by the impact of a
>> small comet.  I think we have enough high-resolution lunar
>> photography, over a sufficient time base, so that any such phenomenon
>> would be pretty obvious....

>The thing you have to get out of your head is that these are rocks.
>You admit they're snowballs, but you're still thinking of them as
>rocks.  The heat of impact vaporizes them before they make a crater.
>The most they do is stir up the surface.  There are photographs of
>small vapor plumes on the moon.

Well, hold on a moment.  Using the authors' figures of 12m diameter and
0.1 g/cm**3 density, such a snowball travelling at 6 km/sec impacts with
1.5 *10**12 joules, a yield of about a quarter of a kiloton.  It's not
the mass of the object that causes a crater, it's kinetic energy.  If
someone can explain how such an impact could not leave a crater at least
10m in diameter, I'd like to hear from them.  By my calculations, at
most one-fifth of the energy would be used in vaporizing the snowball.

Peter Scott ([e-mail])

("Could we get this newsletter mailed out a little more rapidly so us
guys in Internet land aren't two weeks behind on the articles?")

[Yes, I'm trying... -Ed]

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

Date: 9 May 88 17:16:15 GMT
From: attcan!lsuc!spectrix!tmsoft!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Bombs on Mars

> ... Would the world's present sky surveying activity give us any
> warning at all of a continent-smasher on its way?

Only by chance.  There is no systematic watch kept, and the smaller
asteroids are not easy to see unless you know where to look.

> Would our present interplanetary launcher and bomb technology be
> adequate to deal with it? I would assume the best that could be done
> would be an Energeia with an American warhead...

This is plausible, although one would have to wonder about whether
Energia could support a high launch rate.  The MIT student study in the
late 60s concluded that the odds were much better with multiple attacks;
they postulated four Saturn Vs each carrying a 100-MT bomb.  This
required a third launch pad at KSC and massive industrial effort.
Nothing much smaller than the Saturn V has the lift capability, so it
would have to be Energia.  A problem would be the lack of a suitable
cruise-maneuvering stage; the MIT study used modified Apollo service
modules, but we don't have those on hand any more.  Another problem
might be bomb design: the MIT folks (with some expert advice) concluded
that 100 MT was the biggest that could be built on short notice with
reasonable assurance that it would work, but that was twenty years ago,
before the general trend toward smaller bombs really took hold.

 Henry Spencer @ U of Toronto Zoology
{ihnp4,decvax,uunet!mnetor}!utzoo!henry

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

Date: 11 May 88 23:48:13 GMT
From: oliveb!3comvax![e-mail]  (Michael McNeil)
Subject: Re: Small comets & The Moon

In article <[e-mail]>
[e-mail] (Peter Scott) writes:
> . . .
>can explain how such an impact could not leave a crater at least 10m in
>diameter, I'd like to hear from them.  By my calculations, at most
>one-fifth of the energy would be used in vaporizing the snowball.

I also believed that the lack of lunar craters constantly being created
was a flaw in this idea, but then one newspaper report I read implied
that what was happening was that tidal forces would break up the very
fragile snowballs well before they got near the Earth or the Moon.  If
the matter were sufficiently dispersed by the time it arrived at the
Moon, creation of a crater could be avoided.

I don't know if the idea is sound theoretically, as I haven't heard any
technical commentary on this suggestion.  Anybody know more?

Michael McNeil

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

Date: 10 May 88 04:57:03 GMT
From: ubvax!weitek!sci![e-mail]  (Dave Rickel)
Subject: Space suits

The local paper ran an article on a couple of contenders for designs for
space suits a while back.  These space suits were supposed to have a few
features to make them useful for constructing a space station--easier to
tailor for different builds, better armor for micro-meteoroid
collisions, cheaper, higher internal pressure (oxy/nitrogen atmosphere
rather than pure oxygen) etc.  So far as i could tell, all the space
suit designs under consideration were pretty much the standard
designs--two arms, two legs, etc.  Wernher von Braun (i think, the idea
might have been Bonestell's) in his Man in Space series proposed a
different space suit design--more like an ice cream cone.  Transparent
hemisphere on top (the ice cream), metal body with manipulator
appendages and rockets (the cone).  It seems to me that making a suit
along these lines would have several advantages--feet are pretty well
useless in space, you might as well get rid of them in the suit(although
you might have some sort of articulated gripper down there, so you could
either anchor the suit or grab hold of something and fly with it).  You
could stick in quite a bit better armor.  Maintenence ought to be
simpler.  Attitude control could be simpler.  The manipulator waldoes
could have specialized fittings for various jobs.  It ought to be
simpler to eat and drink inside these than inside regular suits.

As long as i'm here, i may as well mention some of the disadvantages.
These suits are obviously special-purpose--some sort of emergency suit
will be needed anyway.  These suits are essentially miniature space
ships--they would be much more massive and somewhat more complex than
traditional space suits.  I don't know what the current level of
technology is with regard to manipulator arms--it may be that the
manipulators would be too clumsy, wouldn't offer the necessary level of
tactile feedback, or may be too subject to vacuum welding or other
nastiness.  People inside might want to wear something like a space suit
anyway, so why bother?

david rickel
decwrl!sci!daver

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

Date: 13 May 88 16:23:22 GMT
From: mcvax!ukc!its63b![e-mail]  (ERCF08 Bob Gray)
Subject: Re: Space suits

In article <[e-mail]> [e-mail] (Dave Rickel) writes:
>......  These suits are essentially miniature space ships--they would
>be much more massive and somewhat more complex than traditional space
>suits.

The basic design doesn't need to use waldos. A tubular structure with a
couple of spacesuit arms sticking out the front is all that is needed.
Put an adjustable harness inside, and it will fit people of very
different sizes.  This would be a MUCH simpler design than the
conventional suit where a lot of effort goes into designing flexible leg
joints.

It would also be easier to get into and out of and it would be much more
comfortable to work in for extended periods.

The only real disadvantage I can think of at the moment, would be for
publicity purposes. People in spacesuits at least look human on the TV
screens.
    Bob.

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

Date: 18 May 88 06:38:43 GMT
From: attcan!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Space suits

> The basic design doesn't need to use waldos. A tubular structure with
> a couple of spacesuit arms sticking out the front is all that is
> needed...  This would be a MUCH simpler design than the conventional
> suit where a lot of effort goes into designing flexible leg joints.

Unfortunately, you have the problem backwards.  A lot of effort goes
into designing flexible *ARM* joints; the legs are a trivial issue by
comparison.  Current spacesuit arms are poor and gloves are grossly
unsatisfactory.  Fix that and there won't be any problem making good
legs to match.

> It would also be easier to get into and out of...

Compared to the NASA suits, perhaps.  The Soviets have this one licked:
the backpack hinges out away from the suit, you slide legs, arms, and
head into the suit from behind, and the backpack closes and latches.
--
NASA is to spaceflight as            |  Henry Spencer @ U of Toronto Zoology
the Post Office is to mail.          | {ihnp4,decvax,uunet!mnetor}!utzoo!henry

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

Date: 18 May 88 06:09:15 GMT
From: attcan!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Space suits

> ...feet are pretty well useless in space...

Not so, actually; staying in one place is a major hassle in free-fall,
much more so than anybody really expected.  Those pretty pictures of
non-anthropomorphic suits floating next to the space station (or
whatever) while the occupants work away look nice, but those suits would
be expending fantastic amounts of fuel holding their positions.  One can
re-invent mechanical feet as anchors, and they would have some
advantages, but it's not clear that it's worth it.

> The manipulator waldoes could have specialized fittings for various
> jobs...

The state of waldo technology can be described, charitably, as "crude".
They aren't up to being arm substitutes, not really.
--
NASA is to spaceflight as            |  Henry Spencer @ U of Toronto Zoology
the Post Office is to mail.          | {ihnp4,decvax,uunet!mnetor}!utzoo!henry

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

Date: 19 May 88 20:57:07 GMT
From: dartvax!eleazar.dartmouth.edu![e-mail]  (Joe Walker and Hal Jr.)
Subject: Re: Space suits

>> It would also be easier to get into and out of...
>
>Compared to the NASA suits, perhaps.  The Soviets have this one licked:
>the backpack hinges out away from the suit, you slide legs, arms, and
>head into the suit from behind, and the backpack closes and latches.

  I think the only advandage a "pod" type of suit is that it would not
have to be depressurized...Soft suits have a limit on interior
pressure..too high and the astronaut would not be able bend arms, legs,
or even fingers..  as it is the astronaut has to pre-breathe pure oxygen
for a while before suiting up to prevent the bends when he's in the low
pressure environment of the suit.  right now NASA is looking at designs
for "Hard suits" to be used in the space station..this simplifies the
process of going from coabin to suit...

    Hard suits...best of both worlds..

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

Date: 20 May 88 21:57:50 GMT
From: cos![e-mail]  (Steve Smith)
Subject: Re: Space suits

In article <[e-mail]> [e-mail] (Henry Spencer) writes:

> ... Current spacesuit arms are poor and gloves are grossly
> unsatisfactory.

Many years ago, I saw an idea for a "spacesuit" that solved this problem
elegantly.  It uses the fact that human skin is a very good gastight
membrane.  It simply consists of a mechanical support layer that doesn't
let the user swell up in vacuum.  Think of a *very* stiff body stocking.
A helmet finishes it off.  There are some obvious problems -- getting in
and out would not be trivial, and there are parts of the human anatomy
that would be difficult to handle (armpits, for example).

Suposedly, a large aerospace company (Avco-Everett?) built a model suit
that was comfortable, inexpensive, and *far* more efficient than NASA's
suits.  NASA rejected the idea with an excuse that translated "not
invented here".

Does anybody have any further information?

                -- Steve
([e-mail])    ({uunet sundc decuac hqda-ai hadron}!cos!smith)
"Truth is stranger than fiction because fiction has to make sense."

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

End of SPACE Digest V8 #239
*******************