Conference 7.286::space

    	Not to burst your balloon, but the idea has been thought of
    sionce at least the 1950s, though it is a very good idea.
    
    	Larry
    

    I think the main proble with it would be the difficulty in getting
    the asteroid to suddenly be orbiting the earth.  Building an
    infrastructure in LEO and then on the moon might be the slow way,
    but it's going to produce other results along the way and can be
    done fairly slowly, where a mission to the asteroids to find one
    that's all ice and somehow get it back here is a one-shot deal that
    would be far far far too expensive to undertake from the surface
    of the planet.
    
    Willie
    

  I'd be willing to bet that it wouldn't be that bad, expense-wise.  I'm
sure the following idea was subconciously taken from somewhere else, but;

  We don't need any really sophisticated technology to do the job.  I saw
tests of a 10g mass driver (about a 5 foot section) in a science short a
couple years ago, so the beasts can be made.  It required superconducting
magnets, but that shouldn't be too big a deal if the mass driver could be
kept shaded in space.

  Place a *very* high powered mass driver (100g?) on a selected asteroid.  No
mean task, to be sure.  Run it with solar power.  Charge the sucker up and start
firing fused lumps of metal taken from the asteroid opposite to the required
thrust direction and you've got yourself a low-thrust engine.  The fusing of
lumps would come from a solar furnace.  I presume a fairly large solar collector
could be made without much regard to structure, even considering the thrust
induced by the mass driver, which would be minimal.  The solar collector
could be used to enhance the output of the solar cells used to produce the
power for the driver.

  Probably the toughest part of this would be to dynamically handle the 'mining'
of the surface so as to create the, say, 5-pound lumps.

  I back this up with absolutely no math or even the vaguest notion of how
many such lumps would have to be launched to move an X-ton asteroid from
its orbit.  The one nice thing in your favor is that all you've got to do
is compute the energy required to brake the asteroid into a path which will
leave it orbiting the Earth in Y years.

  Personally, I'd suggest going for something a bit more rocky and dumping
it at a LaGrange point.  Start drilling and you have a space station and
plenty of raw materials.

  Fun to think about, at any rate.

John

Well I am sorry several somebodies elses have already thought of it. I wanted
to be the first. ;-) No I knew such idea has been proposed before, but never
as a NOW project. Always as something we should do far into the future.

I say we should start NOW not after the space station, but in paralllel with it.

And I never said this should replace the Moon effort or anything else. This
mission would be one way to make easier the first stages of serious space 
efforts. Such as estabilishing ourselves on the Moon, Mars, and maned visits
to Jupiter, Saturn, etc. Thats why I called it a bootstrap idea.

Besides, estabilishing ourselves on the Moon shouldn't be our only long range
goal. We should extend ourselves in other directions at the same time. Or the
same thing that happened with the shuttle will happen with the Moon, once we
are done. There we will be, all ready, with no where to go.

Seriously, I have heard that the Air Force has re-opened research on nuclear
propultion engines. And an asteroid grab mission would be a perfect target
for such technology. Before it is transfered to maned spacecraft, let them
work the last bugs out of it on an unmaned craft.

It seems to me, an asteroid grab mission, not only would help us bootstrap
ourselves into space. It would also would be a great push, for nuclear engine
propultion. Something we need for (long time/long distance) maned missions to
the inner and outer solar system. <Nuclear propultion being better/faster
then other alternatives for an asteroid grab and long maned missions>

As for expenses, actually petty cheap I think one maybe two shuttle lunches
at the most. Plus all the hardware, control people time, etc. Not to say, that
you would get all your money back and them some, from the use of the asteroid.
If I had the money, I would do it myself. Great way to multiply your money.

    I don't see that it would be 'pretty cheap'.  If you figure out
    how long it's going to take, multiply by the number of people on
    the mission, and just figure consumables you are talking about more
    than a couple of shuttle launches.  Those asteroids are very very
    very very far away, and this sounds a lot like the Apollo project,
    way overstepping our capabilities to accomplish a single task.
    
    Not that it's not a good idea, but it would be a lot more useful
    to deliver an asteroid to near-earth space if there was already
    someone there to use it, and a near-earth infrastructure would make
    the project orders of magnitude easier to launch.
    
    Willie

    	The Soviets have plans within the next twenty years to send
    probes to certain planetoids to test them for scientific and mineral
    resource purposes.
    
    	Larry
    

>    I don't see that it would be 'pretty cheap'.  If you figure out
>    how long it's going to take, multiply by the number of people on
>    the mission, and just figure consumables you are talking about more
>    than a couple of shuttle launches.  Those asteroids are very very
>    very very far away, and this sounds a lot like the Apollo project,
>    way overstepping our capabilities to accomplish a single task.

  I believe that the assumption is that this would be an unmanned mission.

John

>      I believe that the assumption is that this would be an unmanned mission.
 
    Then it's even worse!  You not only have to have everything quadruply
    redundant because there's no-one there to repair it (can you say
    expensive?), but the vehicle has to have a fair amount of that
    non-existant stuff called AI so it can 'find' a 'good' asteroid
    and bring it back.  Without people on board, the mission becomes
    incredibly complicated and very very hardware intensive.
    
    Willie

    I'm sure machines cannot do it now, but what a national objective
    to catalyze the development of AI.  In all seriousness, if we could
    develop the AI technology to perofrm the task of managing such a
    mission, the benefits from the development oof such an AI capability
    ALONE might pay for the mission.  
    
    Isn't a major goal of NASA to develop and transfer new technology
    to the private sector.
    
    Tony

    There may already be matter trapped in the lagrange points around
    the moon.  The question is, how big are the largest pieces?  It
    seems that I've read about the possability that there is already
    matter there, eccept we can't see it with our earth based telescopes.
    If we sent a small radar probe there, we may be pleasantly supprised.
    
    Ron

    	I would say it is definetely worth investigating, but if the
    debris is too small (and possibly too few) to be seen so relatively
    close to Earth (240,000 miles - the average distance between Earth
    and Luna), then there may not be enough useful material at the Legrange
    Points.
    
    	Larry
    

  There's no need to make the beast autonomous.  With a delay of several
light-minutes it should be possible to reprogram manipulators built into
the system which could fix a variety of failures.  Since robots today aren't
very good at doing things, the design of the machine (in my case, a mass
driver) would be such that robots *would* be able to access failure points.
They call it "design for maintenance".  It's an extremely foreign concept
to many industrial manufacturers.

  Also, the delay of a couple minutes would not make interactive waldo-like
repairs impossible when robots couldn't do the job.  In all of this, I'm
assuming only slightly more advanced robots than we have in industry today.
Because of the delay, selection of an asteroid would not have to be done
autonomously.  Pictures and, perhaps, sample analysis could be transmitted
back to Earth for decision making.  Or a series of probes could go to 4 or
5 likely candidates to decide before sending up the big one.

  Finally, even if a crew were sent along to fix things, spares would have
to be taken along anyway, so I don't see a big deal about making stuff backed
up by redundant systems...

  With a little ingenuity it could be done.  Getting two men on the Moon
with 1960's technology is fairly incredible.  It's pretty reasonably to thing
that we could remotely bring back an asteroid.

John

    can't it be as simple as this!?
    we send a series of nuclear devices to a predetermined astroid,
    where we simulated the orbital mechanic to death, on where it is
    and how many explosions will slow down the rock bringing it in
    on a sharp eliptical trajectory where we could have one of the inner
    planets gravity brake it into the earth's L5. good old newtonian
    planetary billards! ( ah but pollyanna what happens when you "scratch
    the billard ball into the atlantic?)
    pete

    A couple of minutes teleop delay?  Seems to me that Mars was 20(?)
    minutes each way, and a 40 minute feedback delay would make waldo-style
    repairs somewhat (umm) tedious.
    
    There aint no such thing as AI (all media and marketing hype to
    the contrary), and I contend that there is no reason to expect the
    breakthroughs that would allow it.  But I guess that's the attitude
    you might expect to someone who listens to the likes of Marvin
    Minsky....  :+}
    
    Willie

    I had something in mind, like re.12 mentions.  All decisions not
    time critical (i.e. that can wait comm delay) would be done on earth.
    After all, not that many things would need be done in that much
    of a hurry.
    
    The technology to find, choose, and rendevous with an asteroid isn't
    that dificult.  We have already done things like that, the Viking
    landing on Mars, commets rendevous, etc.  This would merelly take
    a little longer and require a bit more fuel.
    
    The hard part as I see it, but still one we can solve right now,
    and without such things as "true AI" etc, would be securing and
    feeding the nuclear propultion engine on the asteroid.
    
    Securing the Engine, could be done by simply screwing 2 or 3 legs
    deeply into the asteroid.
    
    Feeding the engine, taking into accound that this would be a watery
    asteroid (i.e. volatile). Could be done by digging pieces of the
    asteroid, putting them into a chamber, then heating them up to some
    point above the melting point of water, then feeding the water to
    the Nuclear Propultion Engine and throwing away the rocks. It will
    not be as efficient as a single element engine, but it would do
    the job. After all the would be plenty of propelant mass.

    As for failures, sure you would have to make it as redundant as 
    possible, etc. but that can also be done so that it will work for
    the amount of time it would be needed. Just look at the Voyager.
    And remenber it wouldn't need to be that big.
    
    I see this asteroid barge, as a craft 30-40 feet long, 10-15 feet
    wide (i.e. 

  Okayokay.  Scrap the waldos.  Bad idea.  Except for the very patient...

  Just for the sake of argument, why are we going after a 'watery' asteroid
(assuming such a thing exists)?  I'd rather have raw mass up there in orbit
from which a space station can be made.  Go after a metallic asteroid.  *Then*
go and get a watery asteroid. If they exist.  Personally, I can't see such a
thing.

  As for nuclear detonations to move the asteroid, I have my doubts that
many people would want nuclear devices moved into space.  It would tend to
make a few people nervous.  And no doubt it would require a bunch of them.

John

    Yeah, polluting space with really big fusion reactors and inadequate
    containers is a really bad idea. All kinds of radiation could leak out
    in all directions. Who thought of that idea first? 

>   Yeah, polluting space with really big fusion reactors and inadequate
>   containers is a really bad idea. All kinds of radiation could leak out
>   in all directions. Who thought of that idea first?

Sure are right! Look at that big one up in the sky every day and all
those other we can see at night....;-}

	-SES

    It is a fact that the radiation that could "leak out" from several
    multi-megaton bombs is absolutely inconsequential when compared
    to the hard radiation environment of space (yes we will need mucho
    shielding for any permanant habitat outside the earth's magnetic
    protection, the radiation emitted by a small solar flare is awesome.
    I believe that there was some concern that if a solar flare erupted
    while the Apollo capsules were outside the protection of the earth's
    magnetic field, the astronauts would have died).  
    
    However the concern expressed about fusion bombs in space could
    be related to the process of getting the bomb off the earth.  What
    is the risk of either a bomb exploding or or nuclear material
    contaminating the earth in a Challenger-type accident?  This is
    my principle concern.
    
    Tony

    Re .19
    
    First, a nuclear propultion engine is not a nuclear bomb, what would 
    be the use of pulverizing the asteroid you want to use. And if anything
    was left over, it would be radioactive, etc.
    
    Second, there is NO danger of nuclear materials exploding on the way
    up. They are NOT bombs in themselves. Even if somebody did send a
    bomb, they would send it in separate parts, disarmed, etc. Unless
    its in a missile.

    Third, if proper precautions are taken, sending up radioactive
    materials in explosion/abrasive/radiation rsistent containers, etc.
    The danger of harmfull contamination is about the same as you or
    the average person getting hit by lightning.

    Some nuclear propulsion concepts are not for bombs.  The most 
    prominent nuclear propulsion concept, Orion is a bomb concept.
    
    Also, there has been discussion of developing clean (perhaps neutron?)
    shaped nuclear charges for asteroid propulsion (and other SDI uses).  
    
    A nuclear engine would have to use some of the mass of the asteroid 
    as propellant as, if I am not mistaken the concept invloves using
    nuclear heat to expand gas.  It would be impractical to take enough
    gas to the asteroid to make a recovery worthwhile.  Also, it would
    rule out metallic asteroids as they have few volitiles.  
    
    I must admit that the idea of space assembly of any bomb propulsion
    hadn't occurred to me, and with a space station to assemble such
    missions such a concept may be valid.  However, the base discussion
    is where to get the mass to build space structures.  The possibility
    of space assembly may be problematical.
    
    Also, the absolute assurance you have that any nuclear material
    would be shielded abalative, etc I find reminiscient of those who
    promised in the 60's that nuclear power would be too cheatp to meter.
    I am not a technophobe, however I shy away from those who make safety
    claims comparing the risks from a relatively known and easily
    quantifiable happening (getting struck by lightening) to a very
    much less well known and certainly much harder to quantify occurance
    (the chance of a launch with nuclear material onboard).  In fact
    one is totally at the whim of nature (weather, as modified by location,
    season, etc) while the other includes the whims of nature and the
    variance of human nature and performance.
    
    Tony

    In a recent issue of the Space Studies Institute is an article on
    Retrieval and mining asteroids.  They mention retrieval of an asteroid
    by attaching a mass driver and expelling chunks of matter as reaction
    mass to propel the useful portion to the vicinity of Earth.  They
    also mention the point that I brought up in a previous reply.
    
    Here is an excerpt from the article in a recent issue of SSI.
    
    EARTH-SUN TROJAN ASTEROIDS
    
      In the late 70's SSI Senior Advisor and Nobel Laureate in Physics,
    Dr. Hannes Alfven, suggested that objects might be trapped in the
    Lagrange points along the Earth's orbit.  Under support from the
    Institute, R. Scott Dunbar studied the possibility of material at
    these locations.
    
      However, the geometry of these locations complicates the search
    for objects at the Trojan points.  An Earth-based search for these
    objects requires looking in the direction of the Sun.  Because of
    these difficulties, to date only asteroids several tens of kilometers
    in size have been ruled out from portions of the Trojan regions.
    At present, the Institure is engaged in a study of an inexpensive
    probe to search for these and other easily-accessible asteroids
    from space.
    
    End of article.
    
    ASTEROID SCAN PROBE - Article from SSI Update.
    
      The Institute is presently investigating the requirements for
    a small, inexpensive probe to look for asteroids in the Earth-Sun
    Trojan locations.  In addition the study is examining the prospects
    for using unanalyzed IRAS data or Earth-orbiting wide-field telescopes
    for the search.  These techniques also lend themselves to the search
    for Near Earth Asteroids other than those which may exist at the
    Trojan points.
    
    End of article.
    
    SSI MEMBERSHIP INFORMATION - article from SSI Update.
    
    You can subscribe to SSI and recieve by-weekly newsleters.
    Send your name, address, and tax-deductible donation for $15.00
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    End of article.
    
    I recieved this SSI Update for free in an attempt to obtain my
    membership.  I was very impressed with the quality of the material
    covered.  I plan to send them my check right away.

Article: 77212
From: [email protected] (Tim McDaniel)
Newsgroups: sci.space
Subject: Returning asteroids
Date: 8 Nov 1993 07:46:24 GMT
Organization: Engineering, CONVEX Computer Corp, Richardson, TX USA
 
In article <[email protected]>,
George William Herbert <[email protected]> wrote:

>...or Nick Sazbo's recent work (published only here online to my
>knowledge) of assessing the risks of various braking options for
>returning asteroids of various sizes to LEO or Earth's surface for use.
 
Hmmm ... I must have missed that.
 
There was a story in _Analog_ recently about a company that lands
asteroid metal on Earth.  ["To Bring _Down_ the Steel", _Analog
Science Fiction and Fact_, vol. CXIII No. 12, Oct. 1993, pp. 74-89. 
Stupid and tendentious story, but an interesting idea.]  The stated
idea was to take a two kilometer diameter sphere of rock, cut it in
half, hollow it to 15 cm thick walls, weld the halves together, add
ablative coatings and steering jets and all, and skip it into the
atmosphere to aerobrake. He said it would be hover as a balloon for
several days -- a balloon weighing on the order of a megaton. 
 
Has anyone considered this before?  Any opinions on whether it would
be likely to work? 
 
-- 
Tim McDaniel, Convex Computer Corporation, Richardson, TX (near Dallas)
If [email protected] fails, try [email protected] or
   [email protected]