Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v10_4/v10_401.txt

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Date: Tue,  9 Jan 90 15:58:50 -0500 (EST)
Subject: SPACE Digest V10 #401

SPACE Digest                                     Volume 10 : Issue 401

Today's Topics:
               Re: Simpler space suits?
            Re: Nuclear Reactors in Space
               Re: Simpler space suits?
            Re: Nuclear Reactors in Space
            Re: Nuclear Reactors in Space
            Re: Nuclear Reactors in Space
            Re: Nuclear Reactors in Space
            Re: Nuclear Reactors in Space
            Re: Nuclear Reactors in Space
               Re: Simpler space suits?
            Re: Nuclear Reactors in Space
----------------------------------------------------------------------

Date: 8 Jan 90 05:38:38 GMT
From: mnetor!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Simpler space suits?

In article <[e-mail]> [e-mail] (Tom Neff) writes:
>What about the other extreme -- capacious balloon or rigid suits
>within which the astronaut can move freely.  (To scratch, adjust
>controls, go #1m or #1f or #2 etc.) ...

The real problem is arms and legs, and they are just too useful to
replace with something mechanical.
--
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry [e-mail]

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

Date: 8 Jan 90 15:50:31 GMT
From: crdgw1!crdos1![e-mail]  (Wm E Davidsen Jr)
Subject: Re: Nuclear Reactors in Space


  An interesting question: where other than earth would we find
radioactives to manufacture RTGs in space (or at least off planet)?
Anyone have a good reason to point out some locations as (a) probable to
useful isotopes, and (b) of the set of places which are likely to have
anything useful how many are accessable using near term (0-20 years)
technology?
--
bill davidsen    ([e-mail] -or- uunet!crdgw1!crdos1!davidsen)
"The world is filled with fools. They blindly follow their so-called
'reason' in the face of the church and common sense. Any fool can see
that the world is flat!" - anon

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

Date: 8 Jan 90 15:42:47 GMT
From: crdgw1!crdos1![e-mail]  (Wm E Davidsen Jr)
Subject: Re: Simpler space suits?

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

| The current designs provide considerable protection, with a substantial
| outer suit that is basically thermal insulation plus armor.  My guess,
| made without checking the numbers, is that natural debris is not much
| of a concern, but in low orbit the man-made junk is a real issue.

  I would like more information on this... why is the man made stuff
such a problem? Things in the same orbit have the same velocity, or they
wouldn't be in the same orbit. Now some stuff may be in an eliptical
orbit, and cross the path of the EVA, but is likely to have a fairly
small closing speed, since highly eliptical orbits which cross LEO tend
to cross the atmosphere, too.

  Looking at what has been launched in terms of number of items, and the
volume of LEO, the term "empty space" still doesn't seem too far wrong.

  Could someone come up with some explanation of why the man-made junk
is an issue (or even confirm my gut feeling that it's not all that bad)?
--
bill davidsen    ([e-mail] -or- uunet!crdgw1!crdos1!davidsen)
"The world is filled with fools. They blindly follow their so-called
'reason' in the face of the church and common sense. Any fool can see
that the world is flat!" - anon

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

Date: 8 Jan 90 12:08:20 GMT
From: rochester![e-mail]  (Paul Dietz)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Tim Maroney) writes:

>I don't agree.  The energy requirements were not so much more exacting
>than those of Galileo.  If we had sunk one-tenth the money into
>light-weight electrical batteries that we have sunk into fission and
>fusion research, space vehicles would be able to generate all the power
>they would need for outer-solar-system missions while still in the
>inner system and store it.  But propagandizing for "our friend the
>atom" has always been a far higher government priority than research
>for actual social benefit.

Your ignorance is showing again, Tim.  The energy demands of a Galileo
far exceed what could be stored chemically in a battery of
acceptable mass, even in theory.  But then what do the hard facts
matter when we're cooking up conspiracy theories?

    Paul F. Dietz
    [e-mail]

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

Date: 8 Jan 90 15:43:06 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Terry Conklin) writes:
>There's _no_ way solar cells could generate that kind of power. In the
>same vein, nuclear power will remain strong and reliable regardless of
>distance from the sun.

Well, reactors don't care how far from the sun they are per se (as long
as you don't get too close!), but they do need fuel, and when that runs
out you have a lot of complicated hardware doing nothing.  Solar arrays
diminish in effectiveness as distance from the sun increases, but while
they are effective at all they are just about *permanently* effective.
And simple, where reactors are complex.  Radioisotope thermal generators
(RTGs) have the virtue of simplicity but they DO run down -- they are
in effect a kind of nuclear 'battery' discharging over the decades.
Full blown reactors present many more points of failure -- public
safety aside.
--
"NASA Awards Acronym Generation       :(%( :  Tom Neff
System (AGS) Contract For Space       : )%):  [e-mail]
Station Freedom" - release 1989-9891  :(%( :  ...!uunet!bfmny0!tneff

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

Date: 8 Jan 90 05:57:18 GMT
From: mnetor!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Tim Maroney) writes:
>>It sounds like "The Nation" has made a mistake common among the ignorant
>>and prejudiced:  confusing RTGs and reactors.  They are completely different.
>
>No, they consistently use the phrase "generators".  If there is an
>error, it's mine.  And yours; there are obvious similarities between
>conventional reactors and RTGs.  "Completely different"?  Sure, sure.

Completely different is what I said and what I meant.  I'd be interested
to hear your explanations of those obvious similarities.  I'd also be
interested to hear either your explanation or "The Nation"'s of how
RTGs -- good for hundreds of watts, kilowatts if pushed -- are of vital
importance to SDI, which really wants megawatts.  Oh, there are incidental
support functions that could benefit from them, but again, radical new
designs are not needed.  Anyone claiming that NASA is finding "excuses"
for launching hardware for SDI should first explain why decade-old RTG
designs, good for a few hundred watts, considered sufficiently low-risk
to be used on a high-profile no-backup planetary mission, somehow are
advanced technology that has to be tested in space with elaborate
subterfuges.  It makes absolutely no sense to me.  I would really like
to see an *explanation* of this.

>>Incidentally, most current work on concentrator-equipped solar arrays is
>>being done by the military.
>
>Ever hear the phrase "co-opt", Spencer?  Of course they'd grab control
>of the project if they want to suppress it...

Tim, Tim, Tim.  The big reason they're working on concentrator arrays is
simply that they're afraid they won't be allowed to launch nuclear power
systems.  There is no need to invoke sinister ulterior motives.  They
didn't "grab control" of the "project"; there was no project until they
started several.

>The fact is, by NASA's own
>studies, we'd have the technology now if it had been funded...

There are many useful technologies that we would probably have if they
had been funded.  There has been a serious dearth of civilian technology
funding.

>But
>somehow, with the military in charge of the research, nothing seems to
>be getting done.

I see things being done, actually, albeit slowly.  One reason why things
are a bit slow is that the military has a bunch of extra objectives for
the systems, like anti-laser hardening.  They also aren't even slightly
interested in low-light-level systems for planetary missions, which is
why you don't see NASA eagerly adopting their systems for future missions.
Even within the mission types they are interested in, they're not exactly
funding things abundantly -- concentrator solar systems are a possible
long-term enhancement for next-generation routine military programs, plus
a low-priority backup for SDI's nuclear sources (which are not getting
exactly tremendous funding themselves).  There are perfectly mundane
reasons why simply isn't much money or priority going into them.
--
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry [e-mail]

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

Date: 8 Jan 90 07:24:56 GMT
From: ucsdhub!celit![e-mail]  (Dave Smith)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Tim Maroney) writes:
>In article <[e-mail]> [e-mail] (Tim Maroney) writes:
>>>... But then the military wouldn't have any excuse to go testing
>>>RTG's in space, and this vital component of SDI technology would
>>>languish.
>
>In article <[e-mail]> [e-mail] (Henry Spencer)
>writes:
>>It sounds like "The Nation" has made a mistake common among the ignorant
>>and prejudiced:  confusing RTGs and reactors.  They are completely different.
>
>No, they consistently use the phrase "generators".  If there is an
>error, it's mine.  And yours; there are obvious similarities between
>conventional reactors and RTGs.  "Completely different"?  Sure, sure.
>
>As for your personal attacks, a hearty fuck you in return.
>

Tim, please go back to sf-lovers where you are at least expected, if not
well loved.  (This is a personal attack.  I didn't see any of these in Henry's
posting).

Henry made the good point that SDI requires power outputs far in excess of
that supplied by RTG's, ergo SDI isn't driving RTG development.  Yes, there
are obvious similarities between RTG's and reactors.  They both send people
running in circles screaming "Nuclear! Nuclear!".  They're also both chock-full
of nasty radioactive thingies, but other than that, not a whole lot of
similarities.
--
David L. Smith
FPS Computing, San Diego
ucsd!celerity!dave or [e-mail]
"I'm trying to think, but nothing happens!" - Curly Howard

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

Date: 8 Jan 90 20:22:23 GMT
From: vsi1!v7fs1![e-mail]  (Mike Van Pelt)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Kieran A. Carroll) writes:
>A question: if it turns out to be impossible to produce batteries
>significantly better than those currently available, would
>[Tim Maroney] still object to the use of RTGs on spacecraft?

Ha!  You've gotta be kidding.  RTG's are NOOOKLIER,
made of ATOMS just like ATOMIC BOMBS.

It's an unfortunate fact of life that there are a number of people out
there who react to any mention of the "N-word" with mindless,
unreasoning, superstitious dread, and no arguments, no matter how well
reasoned and firmly based in fact, will sway them in the slightest.

(I have heard some reasoned, though, in my opinion, quite mistaken
arguments against nuclear power.  Tim's wild-eyed paraoid rantings
against anything containing the "N-word" are not among them.)
--
Mike Van Pelt          | What happens if a big asteroid hits Earth?
Headland Technology    | Judging from realistic simulations involving a
(was: Video Seven)     | sledge hammer and a common laboratory frog, we
...ames!vsi1!v7fs1!mvp | can assume it will be pretty bad. -- Dave Barry

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

Date: 9 Jan 90 01:36:36 GMT
From: rochester![e-mail]  (Paul Dietz)
Subject: Re: Nuclear Reactors in Space

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

>Incidentally, most current work on concentrator-equipped solar arrays is
>being done by the military.

Some interesting work on an exciting new kind of concentrator cell by
Boeing is described in IEEE AES Magazine, Nov. 1989, pages 3-9.  As
far as I can tell, it's internally funded, although Entech (who
provided the prismatic covers) receives NASA and SDIO funding.
These are those 31% (AM0) / 37% (AM1.5) GaAs/GaSb stack cells that
promise to shrink the size of space solar arrays by 50%.


In all this talk of nuclear vs. solar arrays for outer planetary
missions, another possibility hasn't been mentioned.  A spacecraft in
orbit around Jupiter is moving rapidly through a strong magnetic
field.  It should be possible to generate power with an electrodynamic
tether, especially when very near the planet.  Now, this will slow the
spacecraft, but the available kinetic energy is very large (Jupiter
has a very deep gravity well), and the orbit could be pumped up again
by slingshoting off Jupiter's moons.

I doubt this would have been feasible for Galileo, but it is an
interesting possibility for future Jupiter probes.  It would let
you, for example, place a spacecraft into low circular orbit
(not possible with ordinary chemical rockets without aerobraking),
and would give that LJO spacecraft a lot of power to play with
(maybe for radar observations of Jupiter's atmosphere?).

    Paul F. Dietz
    [e-mail]

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

Date: 9 Jan 90 00:56:42 GMT
From: calvin.spp.cornell.edu![e-mail]  (John Sahr)
Subject: Re: Simpler space suits?

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Tom Neff) writes:
>>What about the other extreme -- capacious balloon or rigid suits
>>within which the astronaut can move freely.  (To scratch, adjust
>>controls, go #1m or #1f or #2 etc.) ...
>
>The real problem is arms and legs, and they are just too useful to
>replace with something mechanical.

One does not obviously preclude the other.  It is not clear to me why
a suit must be strictly anthropomorphic.  Why not have a suit which is
more like a walking glovebox rather than a walking glove?  In other
words, allow considerable internal room, enough so that the human
could completely retract his or her arms, allowing among other things
internal comfort, eating, scratching, as well as more than two arms
(special purpose arms, for example).  This would be unwieldy on
planets with gravity approaching Earth's, of course.  But how about
the moon?  And how about free fall?


--
John Sahr,                   | Electrical Engineering - Space Plasma Physics
[e-mail] | Cornell University,         Ithaca, NY  14853

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

Date: 9 Jan 90 02:37:22 GMT
From: moonzappa![e-mail]  (Loren Petrich)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail] (Tim Maroney) writes:
>Those interested in the subject should be sure to read the November 20
>editorial in "The Nation" documenting the fact that NASA's own studies
>have shown that concentrated solar array technology would have worked
>as well as nuclear reactor technology, as well as the followup in the
>letters column in the current (January 8/15) issue.
>
    It really must be said that some space missions would be
difficult or impossible without nuclear power. Consider those infamous
RTG's. Without them, no missions to the outer solar system would have
been possible. Sunlight just gets TOO diluted out there. Currently,
the Pioneer and Voyager craft are being tracked for as long as one can
get a signal from them, which will be (if all goes well) at least the
next couple of decades. These craft send direct information of the
solar wind (from where they are at), and if we are lucky, they may
cross the "heliopause" (where the solar wind stops) and provide our
first direct probe of the interstellar medium. These craft are also
affected by the gravity of solar-system objects, and they will
certainly be affected by any solar-system mass outside of Neptune's
orbit, such as the Oort cloud of comets. So one should not complain
too loudly about RTG's and the like.

    There are some other nice features about RTG's. They have no
moving parts, they are always "on", and they are invulnerable to
radiation damage.  The same cannot be said about solar panels, which
are degraded by strong radiation, and which must always be pointed
towards the Sun. Though nuclear reactors may have some mechanical
reliability problems, connected with moving control rods and pumping
coolant, they share with RTG's of not needing to be pointed at the
Sun.

    I wonder if anyone has evaluated any solar power source that
is radiation-proof, such as some thermal cycle? How much progress has
been made in attempting to make photovoltaic cells resistant to
radiation degradation?

    I have a feeling that the likes of the Christic Institute
enjoy tying up big organizations like NASA with lawsuits, and that's
why they do stuff like that.

                                ^
Loren Petrich, the Master Blaster             \  ^  /
    [e-mail]              \ ^ /
One may need to route through any of:               \^/
    sunlight.llnl.gov            <<<<<<<<+>>>>>>>>
    lll-lcc.llnl.gov                   /v\
    lll-crg.llnl.gov                  / v \
    star.stanford.edu                 /  v  \
                                v
"What do you MEAN it's not in the computer?!?" -- Madonna

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

End of SPACE Digest V10 #401
*******************