Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_7/V13_739.TXT

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Subject: SPACE Digest V13 #739

SPACE Digest                                     Volume 13 : Issue 739

Today's Topics:
         Regular postings of Sky + Telescope
              Re: SPACE Digest V13 #617
            Re: Fred Vote Thursday
                 Solar Flares
               Re: NASA Budget
       Re: Earth Gravity Assist and Aerobraking Safety
            SPACE Digest V13 #623
            Re: Fred Vote Thursday
               Re: Risks of technology
             Re: Lost satellites
              Re: Microgravity?

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription requests,
  should be sent to [e-mail], or, if urgent, to
             [e-mail]

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

Date:         Wed, 12 Jun 91 18:41:47 EDT
From: Tom McWilliams <[e-mail]>
Subject:      Regular postings of Sky + Telescope

Re: Sky and telescope postings

This thought just occured to me.

Would anybody be interested in regular factoids from Sky + Telescope
magazine, similar to what Henry does with AW&ST?

BTW, does any one know the legal situation of such an idea?  (assuming
anyone's interested, of course).

Tom
Acknowledge-To: <18084TM@MSU>

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

Date: 13 Jun 91 02:20:35 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!ub!galileo.cc.rochester.edu!rochester![e-mail]  (Paul Dietz)
Subject: Re: SPACE Digest V13 #617

In article <[e-mail]> [e-mail] writes:
>Re : Future of energy and materials (was asteroid mining)

>>There are multiple possibilities in the wings for new energy sources
>>when the oil runs out (various forms of nuclear and solar power
>>have nearly unlimited potential; obstacles of cost can be
>>confidently predicted to be overcome if a strong incentive is there).

>Quite idyllic, if untrue.

  Bullshit, as I will argue...

>SOLAR ENERGY, besides being inefficient (on Earth, but then, who's going
>to build solar-energy collectors in space witout asteroids?) are dependent
>on clouds, lack of space, and night.  Very good for passive use, but then,
>solar will never power cars, trucks, planes, heat (and cool) large builidngs,
>toast bread, run refridgerators, refine metal, etc, on Earth.

Nonsense.  Drop the cost of PV cells by a factor of ten -- and no law
of physics prevents us from doing this -- and PV electricity becomes
competitive with just about all existing sources, (except in Rochester
:-)).  Now, yes, the storage problem does have to be overcome, but
there are ways to do this at lesser or greater cost.  Note that PV
cells have dropped in cost by much more than a factor of ten since
their invention.

>NUCLEAR (fission) depends on Uranium, which, like oil, will become more and
>more difficult to find and refine.  (reserves are about equal to oil right now

Wrong.  Reserves of uranium are fairly small IF WE DON'T BREED.

If we do breed, either in fast breeders, in thermal breeders using the
thorium-U233 cycle, or in other schemes (electronuclear, fusion
hybrid, etc.) the available fuel becomes enormously larger, because
(1) the energy produced from a given quantity of uranium ore that are
used increases by a factor of 60 or so, (2) it becomes economical
to mine much leaner ores, which contain, in aggregate, far more
uranium, and (3) thorium can be used.  Thorium breeding is possible in
some of today's reactors (CANDUs and HTGRs).  Thorium is about 4 times
as abundant in the earth's crust as uranium.

>FUSION is still a pipe-dream.  Since your post was presenting evidence that
>supported the pipe-dream-ness of Asteroid mining, I will assume that Being A
>Pipe Dream is sufficient to exlude an energy option.

Wait -- I wasn't saying that asteroid mining is a pipe dream.  I was
arguing that it wasn't *necessary*.  Plenty of unnecessary things are
feasible and profitable.

Also, your point is technically false.  Mankind has been constructing
devices which achieve thermonuclear ignition since the 1950's.  It is
feasible to explode H-bombs in steam-filled underground cavities for
the purpose of power generation or breeding.  This isn't done now for
obvious political reasons, but it could be done if necessary without
great technical advances.

    Paul F. Dietz
    [e-mail]

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

Date: 13 Jun 91 05:04:49 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!ptimtc!nntp-server.caltech.edu![e-mail]  (Steinn Sigurdsson)
Subject: Re: Fred Vote Thursday

In article <[e-mail]>, 3001crad@ucsbuxa (Charles Frank Radley) writes:
>
>
>Design by successive approximation is attractive to reduce
>risk, but it is VERY expensive.

The cost so far is not in the "expensive" category?

>    These days as systems get more complex there is greater
>reliance on communal computer databases, everybody inputs their
>status and the other player view it to see what is going on.
>   And simulations, cheaper than flight testing.

Simulations are cheaper then testing, but testing tells you if
it will work! The best way of learning is by doing.
- even if it means making mistakes along the way (maybe that should
read _especially_ if...)

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

Date: 13 Jun 91 17:59:37 GMT
From: mcsun!ukc!edcastle!hwcs![e-mail]  (Stewart Fleming)
Subject: Solar Flares

A front page article in the British "Independent" newspaper today warns of the
dangers of severe magnetic storms (as pointed out by the regular solar flare
postings on this newsgroup).

The British Geological Survey in Edinburgh reported the detection of the shock
wave produced by an extra large solar flare.

Any reports of actual disturbance from anywhere else on the ground ?
[We have one (possibly true) story of a Computer Scientist being transformed
into a Psychologist due to a bit flipping in an admin computer.]

The article also mentions that international computer networks could be
affected since they rely on satellites to route me%^#.)*{|{@

STF
--
[e-mail]                        ...ukc!cs.hw.ac.uk!sfleming
[phone] x553
"I saw Sean Connery eating mushroom soup and watching the Repulican march."

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

Date: 11 Jun 91 16:56:20 GMT
From: snorkelwacker.mit.edu!usc!wuarchive!emory!wa4mei!ke4zv![e-mail]  (Gary Coffman)
Subject: Re: NASA Budget

In article <[e-mail]> [e-mail] writes:
>In article <[e-mail]> [e-mail] (Craig E. Ward) writes:
>
>>>The American Geophysical Union recognizes that passage of this
>>>amendment would do serious damage to future space science programs
>>
>>With all due respect, the AGU is wrong and is playing the role of a patsy for
>>non-space special interests.
>
>With all due respect, you don't know what the hell you are talking
>about.  The AGU was one of the main forces behind the 1957 IGY, which
>led to Sputnik and Explorer and started the whole civilian space
>program off in the first place.  Much of the subject matter and
>experimentation in the field of geophysics takes place in space.
>Calling the AGU "non-space" is like calling Boeing "non-airplane"
>or Toyota "non-automobile".  Pretty silly.

With all due respect, Sputnik and Explorer were spawned by Cold War
ballistic missile posturing. That a few instruments managed to hitch
a ride is peripheral. Nor did Craig say the AGU was "non-space". He
said they were, perhaps unwittingly, playing into the hands of non-space
interests like HUD.

Gary

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

Date: 12 Jun 91 21:30:44 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!caen!ox.com!fmsrl7![e-mail]  (Ron Carter)
Subject: Re: Earth Gravity Assist and Aerobraking Safety

In article <[e-mail]> [e-mail] (Jonathan Burns) writes:
>Is there any percentage in magnetic braking, in which a conducting
>body passes transverse to the geomagnetic field, and experiences
>drag as the field does work generating eddy currents?

Not as you lay it out; the magnetic field varies only slowly
over space and time as seen by a passing asteroid, so the
possible coupling (and energy dissipation) is very small.
It is necessary to couple to the ambient plasma medium to
achieve much braking.

>A possibly useful complication would appear if the body could be strung
>out along a cable like beads, and connected by conducting wire, so as
>to intercept more flux.

You would need to either put substantial masses at either end of
a conductor to hold it taut, or spin the conductor ditto.  A long
conductor is required to get more voltage induced; power dissipated
is equal to I*E, and E = integral((B x V).dl).  Current will be
limited by the plasma density.

The idea of a pinwheel conductor, with the downward-pointing
half conducting current and the upward-pointing half not carrying
current, is possibly useful.  It would tend to spin itself up,
rolling like a wheel.  To keep it from overspeeding, chunks of
the asteroid carrying the pinwheel tether could be released
from the ends.  If the asteroid was in a very eccentric orbit,
the releases could put the chunks into near-circular orbits;
a high circle at the top, and a low one at the bottom.  In this
way, the entire asteroid could be returned to LEO in small,
innocuous pieces, with the main body held high enough that it
presents no danger of inadvertent re-entry.

Excellent idea, Jon!  It has many possibilities to build on.

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

ReSent-Message-ID: <[e-mail]>
Resent-Date:  Wed, 12 Jun 91 18:13:31 EDT
Resent-From: Tom McWilliams <[e-mail]>
Resent-To: [e-mail]
Date:         Sat, 8 Jun 91 05:00:10 EDT
Reply-To: [e-mail]
From: [e-mail]
Subject:      SPACE Digest V13 #623
Comments: To: [e-mail]
To: david polito <[e-mail]>, Tom McWilliams <[e-mail]>

Subject: Re: Asteroid mining

>If I were
>company, I would not invest in asteroid mining unless I had good reason to
>believe I could meet current market prices with my products and current
>technology does not seem to be able to do this wrt nickel production in
>space.

>        Decrease transport and production costs in space, and maybe ths will
>change. What reason wqould a mining company to have to expect this in the
>short run?

My question has been: "What reason would a company have to get into the
space transportation business, thus increasing efficiency and decreasing
costs, as NASA seems to find impossible?"

How about a big, salable asteroid?

Tom
Acknowledge-To: <18084TM@MSU>

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

Date: 12 Jun 91 21:01:53 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!ptimtc!nntp-server.caltech.edu![e-mail]  (Steinn Sigurdsson)
Subject: Re: Fred Vote Thursday

In article <[e-mail]>, carl@juliet (Lydick, Carl) writes:
>In article <[e-mail]>, [e-mail] (Charles Frank Radley) writes...
>>>>Maybe this near-death will scare the Freedom people into getting some
>>>>hardware built...
>
>OK, I'm about to play devil's advocate here (I'd personally like to see a space
>station built and manned in the near future).

ditto

>
>>The schedules we have been working to do not require delivery of
>>hardware until 1993.
>>   We have been on schedule all along.     Why do people
>>keep complaining the hardware has not been built, we have to design
>>it first.....and we have not even had a PDR yet.
>
>There are lots of ways to design and build just about anything.  Some
>techniques tend to work better than others.  The technique that I've found
>works best over a wide area of technology is what I like to call "design by
>successive approximations".


    I think Carl has hit the essence of the problem here, it
sounds as if NASA has produced $5G of CAD drawings in the last 8
years, when one would think that building test assemblies and flying
small pieces of the station should be taking a large fraction of the
budget. My current impression is that the money spent so far has only
produced blueprints, and no pieces of hardware to see how they fit
together, or operate in orbit - I would love it if someone would prove
me wrong on this and tell us of $2G worth of components has been built and
tested?

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

Date: 13 Jun 91 02:58:31 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!wuarchive!rex!rouge![e-mail]  (Fraering Philip)
Subject: Re: Risks of technology

I think there is a risks group possibly as appropriate to discuss
this stuff. Maybe people posting on that subject should crosspost.

And my 2 cents: Well, the material will probably be broken up and shipped
in small 10 ton pieces anyway...

And there seems to be the possibility of Tungusta style events in the
future. If someone is worried about risks, now is the time to develop
the technology to move the stuff...

Phil F.
[e-mail]

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

Date: 13 Jun 91 12:33:17 GMT
From: agate!spool.mu.edu!sdd.hp.com!think.com!rpi!news-server.csri.toronto.edu!utgpu!cunews!semifs3!testeng1![e-mail]  (Chris Stanfield)
Subject: Re: Lost satellites

In article <[e-mail]> [e-mail] writes:
>In article <[e-mail]> [e-mail] (Wolfgang Lieff) writes:

Deleted discussion about broken GEO satellites

>>- If this sum is a considerable amount, what would be a competitive
>>  price the Soviets could charge for stationing a technician and a
>>  Soyuz modified as an 'Inter-orbit-toolshed' (maybe without re-entry
>>  capabilities) onboard their space station ?
>
>Olympus, like most satcoms, is in GEO.   Mir is limited to an
>inclined low earth orbit, far away from GEO.
>
Still a little quick to flame aren't we Nick? I think the original
poster was suggesting using a modified Soyuz as a "space tug" for
either going to the satellite and repairing it, or bringing the
satellite down to an orbit where it could be recovered for return to
earth. Like the original poster, I don't know if that is possible -
that is why the question was asked - but I think we are both aware of
the relative orbits of MIR and GEO satellites.


Chris Stanfield, Mitel Corporation: E-mail to:- uunet!mitel!testeng1!stanfiel
[phone] Ext.4960
We do not inherit the world from our parents - we borrow it from our children.

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

Date: 10 Jun 91 18:17:00 GMT
From: cix.compulink.co.uk![e-mail]  (Codesmiths)
Subject: Re: Microgravity?

In-Reply-To:  [e-mail] (joefish)

Good grief ! Real facts !
As you've seen this thing, could you answer a couple of points:

   What diameter is the shaft ?

   What sort of experiment mass can this thing handle ?

The catapult trick is neat, that simply hadn't occurred to me
|-(  <-- stupid smiley
   _
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End of SPACE Digest V13 #739
*******************