Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_2/V10_262.TXT

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Subject: SPACE Digest V10 #262

SPACE Digest                                     Volume 10 : Issue 262

Today's Topics:
            Re: More about a spacial lift
            Re: More about a spacial lift
       Re: NASA Headline News for 11/14/89 (Forwarded)
         Re: Frequently asked SPACE questions
           Re: Looking for US launcher family tree
               Re: Air launches
----------------------------------------------------------------------

Date: 18 Nov 89 17:40:45 GMT
From: cs.utexas.edu!mailrus!jarvis.csri.toronto.edu!me!radio.astro!helios.physics![e-mail]  (Christopher Neufeld)
Subject: Re: More about a spacial lift

In article <[e-mail]> [e-mail] (Bob Gray) writes:
>In article <[e-mail]> [e-mail] (Christopher Neufeld) writes:
>>   Just a minor point. You can't anchor a lunar skyhook (where do you have
>>to go for selenostationary orbit?). The proposed scheme for a lunar skyhook
>>is a sort of rolling wire. The centre of mass orbits the moon, and the
>
>It occurs to me that you don't need to go all the way out to
>selenostationary orbit to find a position to find a stable
>position to drop a skyhook to the Lunar surface.
>
>There is another way to balance the forces and maintain a
>stationary position above the lunar surface to drop a cable
>from. Use the Earth's gravitational field.
>
   You're quite right, of course. I checked the article by Moravec, which I
had only skimmed before making my earlier posting.

>A cable from the Lunar surface, passing through the L point
>between the Earth and the Moon (L2 ?) and extending into the
>Earth's gravitational field far enough to keep the cable
>taught, would only be a few thousand miles long and could be
>done with existing materials technology.
>
   Quoting Moravec's article in _The Endless Frontier_ again,
     "Pearson [Jerome, see the references in my earlier posting] calculated
     that a lunar skyhook through L1 would be twice as long, 300000km, as
     an Earth hook.... Existing substances such as Kevlar and graphite
     composites are strong enough, and result in mass ratios ... of a few
     hundred. An L2 skyhook is 550000km long, and twice as heavy as a
     similar L1 hook."
Apologies to Dr. Moravec for these quotations, reproduced again without
permission.

>A small asteriod "hung" from the Moon by cables would be
>more stable yet, and make a good base to build a shipping
>station on.
>
   Yes, this would shorten the required length of cable. The ballast would
have to lie somewhere between L1 and earth.

>It would be very easy to ship materials back from the Moon.
>Just hoist them up to the station, wait till the right bit
>of the Earth shows under your feet remembering that anything
>will take a few days to fall, put the parcel out the window,
>and let go.
>
   Not quite. There is still some orbital motion at the station, since it
completes an orbit around the centre of mass of the earth in about a month.
If the station is at the midpoint between the earth and moon (200000km),
you'd still have to cancel most of 480m/s orbital velocity in order to hit
the earth. (Note: I use the term "orbital velocity" loosely. It is not a
true orbit since the stability depends on it being tied to the moon.)

>Getting stuff from the Earth and down the cables to the
>Lunar surface would be a little awkward.
>
>Not to mention what some people would think about having a
>few million tons of rock hanging above them, held in place
>by cables which might break.
>
   Well, the ballast weight is falling away from the moon, so it won't
bother anybody there. Also, it has the same 480m/s orbital velocity
mentioned above, so it wouldn't actually fall on anybody. It would just be
another satellite of the earth.

>I call it Damocles station.
>
   Dramatic, if somewhat inaccurate.

>    Bob.

--
 Christopher Neufeld....Just a graduate student  | "Out of my way,
 [e-mail]                    | I'm a scientist!"
 [e-mail]              |  - War of the Worlds
 "Don't edit reality for the sake of simplicity" |

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

Date: 17 Nov 89 15:48:06 GMT
From: mcsun!ukc!edcastle![e-mail]  (Bob Gray)
Subject: Re: More about a spacial lift

In article <[e-mail]> [e-mail] (Christopher Neufeld) writes:
>   Just a minor point. You can't anchor a lunar skyhook (where do you have
>to go for selenostationary orbit?). The proposed scheme for a lunar skyhook
>is a sort of rolling wire. The centre of mass orbits the moon, and the

It occurs to me that you don't need to go all the way out to
selenostationary orbit to find a position to find a stable
position to drop a skyhook to the Lunar surface.

The Selenostationary orbit is needed to balance the
gravitational and centripetal forces, and achieve a
stationary orbit. Quarter of a million miles is a LONG
cable.

There is another way to balance the forces and maintain a
stationary position above the lunar surface to drop a cable
from. Use the Earth's gravitational field.

A cable from the Lunar surface, passing through the L point
between the Earth and the Moon (L2 ?) and extending into the
Earth's gravitational field far enough to keep the cable
taught, would only be a few thousand miles long and could be
done with existing materials technology.

A small asteriod "hung" from the Moon by cables would be
more stable yet, and make a good base to build a shipping
station on.

It would be very easy to ship materials back from the Moon.
Just hoist them up to the station, wait till the right bit
of the Earth shows under your feet remembering that anything
will take a few days to fall, put the parcel out the window,
and let go.

Getting stuff from the Earth and down the cables to the
Lunar surface would be a little awkward.

Not to mention what some people would think about having a
few million tons of rock hanging above them, held in place
by cables which might break.

I call it Damocles station.
    Bob.

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

Date: 18 Nov 89 16:50:44 GMT
From: mailrus!jarvis.csri.toronto.edu!db.toronto.edu![e-mail]  (John Hogg)
Subject: Re: NASA Headline News for 11/14/89 (Forwarded)

In article <[e-mail]> [e-mail] (Brian McClendon) writes:
>>The Washington based publication "Space News" reports that
>>scientists from Lawrence Livermore National Laboratory have
>>proposed that NASA build an inflatable space station...
>>...a series of inflatable space structures
>>whose walls would be reinforced by kevlar, a strong, lightweight
>>fiber.
>
>After reading about all the problems with space debris in orbit
>(and even in interplanetary space) how in the hell can the above
>stay "inflated"??

Most debris will miss.  Of the debris that hits, large chunks (where
``large'' starts somewhere around a large chip of paint) will go
through any rigid structure that could feasibly be flown, as well.
Bearing in mind that Kevlar is used for bulletproof vests, an
inflatable structure should be capable of dealing with small
microscopic impacts without problems.

There is certainly a class of debris that would puncture an inflatable
station, but not a rigid one, given reasonable scantlings for each.
But this doesn't make the difference between an acceptable and an
unacceptable design.  In either case, holes shouldn't appear very
often.  When they do, patches should be applied before too much air is
lost; this may actually be faster and simpler in an inflatable.  The
patches would probably be similar, but the aluminum design might have
an added problem of permanent deformation around the hole, which would
make it harder to get a good seal.

If there's nobody around with a repair kit, by the way, an inflatable
*could* still be easier to maintain.  The secret is to make the bag
double-walled, with a ``clotting agent'' between the two layers.  If it
works for military fuel tanks, it should be workable in space.  Of
course, you could apply the same idea to a rigid station, but the
mass penalty would be greater.

The serious engineering question is, ``How much does an inflatable
pressure vessel actually save you?''  You still need some sort of rigid
frame to carry equipment during launch, and probably in use, as well.
(Some items could be mounted directly to the bag after deployment, but
that also has its problems.)  It's not clear that bag-plus-frame-plus-
deployment-gear is a lot lighter than rigid-pressure-vessel-including-
frame, when they both have to go through a 3g ride.  In orbit as on
earth, inflatables give you a lot of volume at low cost.  This volume
is useful if you're covering a tennis court, but becomes less appealing
when you have to build another structure inside in order to do anything
worthwhile.

The Livermore people may have excellent numbers to answer this one
with, but the mass advantage of a bag isn't self-evident.
--
John Hogg            [e-mail]
Department of Computer Science, University of Toronto

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

Date: 17 Nov 89 21:14:21 GMT
From: gem.mps.ohio-state.edu!samsung!caesar.cs.montana.edu!ogccse!littlei!nosun![e-mail]  (David Schneider)
Subject: Re: Frequently asked SPACE questions

In article <[e-mail]> [e-mail] (Eugene Miya) writes:
>This list does change.
>
I hope so.  Eugene is always very clear, but he has evolved a very terse style.
Almost as if he had to key his answers in a "dih" and a "da" at a time,
but I know that NASA is more up to date than that.  Sorry, let's get to the
meat of the matter.

>1) What happen to Saturn V plans? What about reviving the Saturn V
>as a heavy-lift launcher?
>
>Possible but very expensive -- tools, subcontractors, plans, facilities
>are gone or converted for the shuttle, and would need rebuilding,

The other other side of the coin is that materials science has progressed
a lot since those days, and one could expect at least better processes:
NC/laser lathes for more precise engine carving, for instance; the immense
improvements in wiring harnesses.  Only once have I seen this touched on
for this thread, and that was arguing that we could revive the Saturn V
by having the Mexican subassembly contractors used for automobile manufacturing
toss off a few extra cables before the end of the shift, but the real implication
is that with the amount of re-engineering already involved -- why just duplicate
the Saturn V instead of making it what it *should* be?  If there was a 5%
improvement in motor performance because the throat was lighter material
and more precisely shaped....

                        Dave Schneider
                        Friday, Nov 17

P.S.  During my brief fling as a student naval architect (sailboats), I was going
to right all the wrongs I had encountered as a dock boy.  Run wiring through
service alleys instead of "random path" point to point, for instance.
I'm sure that Saturn V builders (as opposed to designers) had a similar
laundry list.
                        dps

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

Date: 18 Nov 89 22:46:07 GMT
From: cs.utexas.edu!mailrus!jarvis.csri.toronto.edu!ists!yunexus!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Looking for US launcher family tree

In article <[e-mail]> [e-mail] (Nick Watkins) writes:
>>The Japanese H-1 is a Delta spinoff...
>I gather they have to buy Delta fuel (kerosene) from Japan also, as it
>is no longer made in the US.

Depends on the variant of the main engine.  The modern variants use
US-made fuel, but there are still one or two old engines that McD-D
wants to use up, and they've bought Japanese fuel for them.
--
A bit of tolerance is worth a  |     Henry Spencer at U of Toronto Zoology
megabyte of flaming.           | uunet!attcan!utzoo!henry [e-mail]

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

Date: 19 Nov 89 00:58:06 GMT
From: gem.mps.ohio-state.edu!uakari.primate.wisc.edu!uwm.edu!ux1.cso.uiuc.edu!pequod.cso.uiuc.edu![e-mail]  (Andrew Higgins)
Subject: Re: Air launches


From: [e-mail] (Patrick Foster)

>I seem to vaguely remember a passing reference to
>the Navy performing some experiments launching sounding rockets from
>one of their lighter-than-air vehicles (I cannot remember whether it
>was a blimp or a dirigible, or something else).  My questions are:
>
>Did these experiments actually take place?  If so, when, where, and
>to what effect?
>
>Is there any study being done on using some type of lighter than air
>vehicle for a launch platform at the present time?  Once again, when,
>where, with what results, and additionally, who?

This idea of a "rockoon" has been around for quite a while.  It was
pioneered by Dr. James Van Allen (forgive me, Henry) in 1952 for cosmic ray
research.

In 1957, the Air Force fired a series of balloon-suspended rockets into
space.  Known as Project Farside, the experiments were a pioneering
achievement and succeeded in setting an altitude record which remained
unbroken even after Sputnik I.

The Farside vehicle was lifted to an altitude of 100,000 ft by a large
helium-filled polyethylene balloon.  The rocket itself consisted of four
solid fueled stages (Thiokol Recruits and Arrow II's) with a small (4 X 6
inches) payload package.

The six Farside tests were conducted from the remote Eniwetok Atoll (yes,
the same as the first megaton H-bomb test) at the Marshall Islands in the
Fall of 1957.  The balloon-rocket assembly took two hours to rise to the
designated altitude.  The rockets were spectacularly launched *through* the
balloon (the Air Force captured some impressive ground based pictures).
Because the rocket was already above 90% of the Earth's atmosphere, the
vehicle was allowed to accelerated at a rate which would burn up a similar
ground launched vehicle.  The total duration of powered flight was around
30 seconds.

Unfortunately, the rocket traveled too fast for radar tracking, so altitude
was judged by crude optical and radio means.  The highest officially
recorded altitude was 3,100 miles, although the vehicle could have easily
reached 4,000 miles.

The payloads on the Farside rockets were alternated between magnetometers
and Geiger counters.  Had the most successful Farside launch carried a
Geiger counter rather than a magnetometer, it very likely would have
discovered the Van Allen radiation belts.

More elaborate plans were drawn up for Farside II, which would have been
able to deliver a payload to the Moon, thus living true to its name.
Farside II, however, was not able to compete with the Thor Able Moon
rocket, which was chosen for the job in January 1958.  Farside II never got
farther than the design stage.

After the IGY, larger rockets became more accessible, and the ideal of
balloon launched rockets slipped out of vogue, with the exception of a
single Japanese firing in 1961.  The Japanese continue to use balloons to
test launch scaled models of the H-II.

>This is a first posting for me, so please forgive any stylistic
>crudities.

Style?  On sci.space???
--
 Andrew J. Higgins              |     Illini Space Development Society
 [e-mail]     |     a chapter of the National Space Society
 phone: [phone]-0321   |     at the University of Illinois
          P.O. Box 2255 - Station A, Champaign, IL  61825
"Someone once defined a crank as an enthusiast without a sense of humor, and
 I have always believed that nothing is so important that you cannot make
 fun of it."                - Arthur C. Clarke

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

End of SPACE Digest V10 #262
*******************