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Subject: SPACE Digest V8 #280

SPACE Digest                                      Volume 8 : Issue 280

Today's Topics:
            The  ASTRA Connection
               Re: spacecraft computers
   Postcard from Lewis: Having a wonderful time, wish you were here
          Re: Long Term Effects of Weightlessness...
 Re: Postcard from Lewis: Having a wonderful time, wish you were here
            Space cities--replies
----------------------------------------------------------------------

Date: 26 Jun 88 04:45:30 GMT
From: agate![e-mail]  (William Baxter)
Subject: The  ASTRA Connection

Is anybody who reads this group connected with ASTRA?  Or is there
someone from Glasgow who wouldn't mind passing the occasional message?
Thanks.

William Baxter

ARPA: web@{garnet,brahms,math}.Berkeley.EDU
UUCP: {sun,dual,decwrl,decvax,hplabs,...}!ucbvax!{garnet,brahms,math}!web

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

Date: 26 Jun 88 05:19:34 GMT
From: [e-mail]  (Joe Beckenbach)
Subject: Re: spacecraft computers


    Onboard computer systems have to be small; the more room they take,
the less room for the instruments. Aside: the information I am presenting
is approxiamate, since I remember images and orders of magnitude much better
than the numbers.

    The Mars Observer Camera (MOC) is very data-intensive and therefore is
"computer-heavy". George Pauls, our mechanics and electrical engineer, is
doing his damnest to fit everything onto both sides of two flat circular
electronics boards about the area of a car window. He's probably just barely
going to be able to shoe-horn it all in, God willing, without trying to sneak
in another board. I'm guessing really off-the-cuff that about half of it deals
directly with keeping the camera aimed and synchronized with the surface it's
imaging, and the other half is analyzing and compressing the data for storage
and/or return.

    Now friends, no NASA instrument has yet tried flying parts that we
need. I raised an eyebrow when I was told that no-one has tried flying a gate
array before, and was annoyed to hear that the highest size memory chip flown
before was 16K bytes. Of course, now that I think about it, I'm not too surprised:
MOC is doing some pretty intense data-grabbing. Still, the only way to get the
memory needed is to go to megabit RAMs, which means radiation-testing &etc.

    Oh, here's a neat image: stick your arms straight out in front of you.
Imagine you're holding one end of a short barrel to your chest. The barrel is
about as long as your arms, and about as wide as your torso. Slap a pair of
binoculars as long as the barrel on top of that. The barrel is the narrow-angle
camera [the telescope]; the left binocular lens is the red-sensitive wide-angle
fisheye (140 degree) camera, and the right binocular lens is the blue-sensitive
wide-angle fish-eye camera. The electronics board is pressed against your chest,
exactly where the camera will have the rest of the orbiter. Now look through the
binoculars at Mars.
    Well, at least that image keeps -me- excited.

--
Joe Beckenbach    [e-mail]    Caltech 1-58, Pasadena CA 91125
Mars Observer Camera Project            Caltech Planetary Sciences Division
Ground Support Engineering, programmer        "This is space? Neat."

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

Date:         Sun, 26 Jun 88 16:50:55 EDT
From: [e-mail]
Subject:      Postcard from Lewis: Having a wonderful time, wish you were here

FROM: GEOFFREY A. LANDIS,
        FORMERLY: BROWN UNIVERSITY
        CURRENTLY: NASA LEWIS RESEARCH CENTER, 302-1
                   CLEVELAND, OH 44135

Hi, everybody--
    Just back at Brown temporarily and using a friend's computer account
to catch up on things, so DON'T reply to me at this account--I won't be
here and I'm not hooked up to the net at work (which saves me a few
hours everyday--it's hard to believe what a time waste computers are.)
It's interesting to view NASA from the inside--or, at least as close to
inside as a two-year postdoc gets--
     There seems to be intermittant episodes of NASA bashing that occur
on the net.  You have to keep in mind that most of NASA consists of
dedicated people who working hard.  Decisions on what direction to go
are made by a very few top management--i.e., politicians.
    An encouraging thing that I've found is that people here really are
interested in the good stuff.  There's a lot of interest in establishing a
lunar base, manufacturing oxygen, etc; and comparitively little interest in
going to Mars--although Phobos seems interesting.
     There's also an interesting proposal to use a tether concept to deorbit
the space shuttle from the space-station, simultaneously reboosting the station
everytime you drop a shuttle off.  This seems like a great idea, and I hope
it gets implemented, although the space station looks like it's going to be
another bare-bones minimum budget thing with all the emphasis on keeping the
up-front cost low, regardless of operational cost.  Sigh.
     But that's the province of the politicians and beaurocrats.
    It's also hard to believe just how conservative the actual spacecraft
manufacturers are.  Nobody wants to fly anything that hasn't already been
demonstrated in space already.  This is very frustrating to those people who
want to advance the technology--but nobody wants to risk a few million dollars
on something new that might work a tiny bit better if there's any chance at
all that something unforseen might go wrong.
     I've been having a good time.  Basically the people at Lewis are very
nice and easy to work with.  I've been working on my main project, which is
investigating higher-efficiency solar cells, but also looking at other things,
ranging from investigating the effect of array orientation on the space-station
orbit, to a study of the feasability of making solar cells on the moon, and
even looking into space suit design.
     I've also been getting involved with a new informal group called
"VISION-21" which is looking into the possibilities of new ideas.  They
may have a conference sometime next year.
   Speaking of which, I assume that everybody has now had a chance to see
Brian O'Leary's new book, advocating a joint US-Soviet trip to Phobos, with
a short (few hour) sortie to the Martian surface, in 1999. It's an interesting
plan, including propellant processing from materials mined from the Martian
moons to establish an infrastructure that uses extraterrestrial materials--
although I could very easily see the Phobos propellant processing part of the
mission somehow getting pushed off into the (nebulous) future in the shadow
of a perceived goal of "landing a man on Mars before the end of the Millenium."

    Well, good to type at you all again for a while.  Gotta sign off now--
                           --Geoff

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

Date: 24 Jun 88 18:29:57 GMT
From: trwrb!aero!venera.isi.edu![e-mail]  (Rodney Doyle Van Meter III)
Subject: Re: Long Term Effects of Weightlessness...


Re: long-term 0G effects.

I know exercise is considered a must for keeping the muscle tone from
deteriorating too much. I believe there's some evidence that calcium
loss from bones stops after a certain point, which is encouraging when
considering long-term missions.

    --Rod

P.S. Ask the Soviets.

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

Date: 27 Jun 88 00:23:50 GMT
From: b.gp.cs.cmu.edu![e-mail]  (Ralf Brown)
Subject: Re: Postcard from Lewis: Having a wonderful time, wish you were here

In article <[e-mail]> [e-mail] writes:
}     There's also an interesting proposal to use a tether concept to deorbit
}the space shuttle from the space-station, simultaneously reboosting the station
}everytime you drop a shuttle off.

This isn't all that new an idea.  See the SF novel "Descent of A????" (it's
been at least five years since I read it), which gives a nice account of
using just this concept to deorbit a shuttle (though the other end was its
payload, rather than the space station).  Written ca. 1980.
--
{harvard,uunet,ucbvax}!b.gp.cs.cmu.edu!ralf -=-=- AT&T: [phone] (school)
ARPA: [e-mail] |"Tolerance means excusing the mistakes others make.
FIDO: Ralf Brown at 129/31 | Tact means not noticing them." --Arthur Schnitzler
BITnet: RALF%B.GP.CS.CMU.EDU@CMUCCVMA -=-=- DISCLAIMER? I claimed something?

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

Date: 27 Jun 88 01:24:01 GMT
From: uflorida!novavax![e-mail]  (Thomas Maddox)
Subject: Space cities--replies



     A short while ago, I posted a list of queries about the
design and functioning of space cities.  As I explained in that
posting, I am currently working on a novel in which a
space city figures prominently.

     So, as promised, here are excerpts from the replies I got.

J. Storrs Hall ("JoSH," moderator of the sci.nanotech newsgroup)
says, with regard to the overall design:

     I would expect as much variation in space cities as ground
     cities--lots of room for style, random variation,
     "historical reasons", etc.  Not to mention differences in
     overall functionality.

Concerning the ecology of the city:

     Genetic engineering will almost certainly be able to create
     systems of artificial life that are specifically designed to
     be the "opposite half" of a human-bearing ecology.

     [A]ll the plants are designed for the job.  I would expect
     the plants to be the bio-engineered terminal nodes of the
     climate control system.  All wired into the "nerve net" of
     the city.  They act as sensors and controllers for humidity
     and gas content of the air.  They, and the lights and the
     doors and a zillion other things are the "fingers" of an
     intelligent environment.  I suspect the intelligent
     environment is not only a fancy extra, but will be
     considered a necessity for safety reasons.

And the economic infrastructure:

     An early occupation of the space city will probably be the
     manufacture of antimatter, and genetic engineering, and
     other pursuits that involve tiny, dangerous things,
     presumably carried out in nearby, detached, facilities.

And the politics:

     Take a population of smart, intellectually aggressive people
     in close (confined) social contact, all dependent on the
     same integrated system for their lives, and you have a sure
     recipe for the hairiest, fieriest, politics in human
     history.

     One of my central questions concerned an asteroid that my
city dwellers would discover, snag, and transport to the space
city.  JoSH says,

     To my surprise, when I worked out the math, this will
     actually work.  Solar orbital velocities in this area are
     about 30 km/sec, and for a 100-meter asteroid massing 1e11
     kg, that represents 3e14 watts of kinetic energy. Assume we
     can build a 10 gigawatt fusion plant (modern fission plants
     are 1 gigawatt) it can supply that amount of energy in a
     year.  Build more plants (or assume more powerful ones) and
     time shrinks.  You still need transit time after the thrust,
     of course.
     The thing could be up to a mile (multiply above numbers by
     200).  They could find it anywhere inside Jupiter's orbit,
     depending on the time constraints of the plot.  There are
     occasional asteroids that cross Earth's orbit, though most
     are found between Mars and Jupiter.  You would not be too
     far off base to assume the composition was any fairly small
     distortion of earth's.  Silicates, boron, nickel, iron.
     Spice it with rare earths to fit the plot.

Marc Ringuette says,

     The spokes are very useful things - probably exercise gyms
     and recreational facilities at anywhere from null to full
     gravity, as well as science research, hospital recovery
     facilities . . .

     I presume there'd be a fair bunch of non-rotating zero-g
     docking, communications, maintenance, and research modules.

     So what are some idea-generating features of the
     environment?
      - variable gravity available
      - vacuum available
      - linear organization of the city (a skinny loop)
      - closed society.  towns of 10,000 barely have a swimming
        pool!
      - high tech population - jobs are space, mining, science,
        astronomy

John Turner, from L5 Computing, Edmonds, Washington, writes:

     1) Be sure to portray the window shielding right.  I don't
     remember whether Heppenheimer's book mentioned the chevron
     shields.  They are cribs of some dense material faced with
     mirrors, supported on metal legs above the torus windows.
     Sunlight follows a crooked path through the mirror maze this
     creates, with the hard radiation absorbing harmlessly into
     the rock, metal, etc. that fills the cribs.  Try to find a
     diagram if you don't have one already; without the chevron
     shields a Stanford torus is a joke.

     2) Don't make your metal asteroid much larger than five
     hundred meters across, about one-half billion tonnes mass.
     The motors for moving such a beast would rate around 100,000
     tonnes thrust for a fairly speedy trip, less if a few
     microgravities is all you'll need.  Many plans for mining
     such small objects include a sort of bag surrounding the
     body, to catch flying shards during blasting or excavation.

     [. . .]

     5)  Spin gravity isn't the same as the real thing.  The
     coriolis effect in even a large structure like a Stanford
     torus could be *felt* as a weak vertigo if you rocked your
     head, twisted it side to side.  Gossip has it that you could
     find the spinward direction from anywhere in a Stanford
     torus by nodding your head a few times.

     6)  Space eats your brains out.  Even inside the stationary
     "bicycle tire" shield and window shielding of a Stanford
     torus, enough radiation gets through to make personal
     dosimeters a good idea.  Traveling through the unshielded
     spokes would cause blue splotches to dance before your eyes;
     they are called phosgenes and are a visible (to you)
     manifestation of dying brain cells.  Too many dead brain
     cells and you'll be a vegetable, fed blue liquid down a
     tube.
     Space settlers would be almost obsessive about tracking
     their radiation histories, and would forbid their children
     access to poorly shielded areas.

Douglas F. DeJulio, from Carnegie-Mellon, suggests,

     How 'bout several concentric toruses (torusi?) of different
     sizes, with different rotational speeds?  The closer to the
     center, the faster the spin.
     That way it covers more area (because you have people live
     at more than one radius) and you have similar gravity in
     each ring.  Travel from ring to ring would be interesting.
     Travel *within* a ring could be done by hopping to another
     ring, waiting, and hopping back in a new place.

And Jack Campin, from Glasgow University, asks:

     OK, what about radiation shielding? I don't recall any of
     the advocates of space colonies having an answer to the
     infrequent (every few decades) but REALLY lethal blasts of
     solar wind that are detectable in the tree-ring record by
     the C14 they generate (see last week's New Scientist). You
     could maybe have enough lead boxes for the humans, but for
     the whole ecosystem?

(The answer I have:  the rotating ring of the torus [and the
central hub] would be protected by a shield of crushed lunar
rock; light would be reflected into the ring through a system of
mirrors and shields, the chevron shields alluded to by John Turner
above.  Travel through the spokes would simply be prohibited
during radiation storms.  Anyone got a comment or refutation on
this topic?  It's obviously of overwhelming practical
importance.)

Dani Eder, who works for Boeing on the Space Station program,
writes:

     You are trying to retrieve a stony-iron type [of asteroid]
     (because of the variety of materials found within).  You
     start with a solar concentrator and heat up some metal found
     in the asteroid then roll it out in thin sheets.  Us this as a
     bigger solar concentrator to melt more metal, etc. bootstrapping.
     The sheets are attached to 'masts' made of extruded bar
     stock of the same metal.  Use refractory oxides from the
     'stony' part to make the dies through which the bars are
     extruded.
     This assemblage becomes a solar sail , so that the asteroid
     sails ITSELF to earth orbit.

Rick Crownover, from Duke University, promises more and writes
concerning the city's orbit:

     A quick note on the design: oblate and prolate ellipses are
     ok also, and if you look in the letters section of IASFM's
     June issue, there is discussion of a counterbalanced
     "pendulum" which might suit your needs quite well -- even
     has a useful place to park the asteroid.

J. Eric Thompson writes from "Flatline" (I'll tell Gibson about
it, if J. Eric will tell me what it is) in Houston, concerning the
city's biological functioning:

     Soybeans.  Lots and lots of soybeans.  You can make lots of
     stuff from soybeans.  :-).  Seriously, though, everything
     from food to clothes, and that's just from non-genetically
     engineered plants.  No telling what you could do with a
     mutant strain or three...

And concerning social life:

     A closed environment of 10,000 people can be really nasty.
     (Says he who lived in a small town of 10,000 people for a
     few years).
     Without a changing population (immigrants and uh . . .
     outer-grants?) stable family lines may develop. Also, the
     "everybody knows everybody else" starts to develop.
     Minorities.  Especially blacks, hispanics and homosexuals.
     They seem to get left out of most future-novels . . .
     Especially blacks and homosexuals.  There're a thousand
     orientals it seems, and a hispanic every now and then, but
     they're mostly minor characters.  There seem to be no blacks
     in science fiction.  Well, in Gor... :-)
     I take that back.  My SO just read a book where the central
     character was a black female.  I can't remember the author's
     name, though . . .

(Wouldn't be Octavia Butler, would it?)

     Homosexuals.  Mistreated more than females....  Oh well.
     It'd be nice to see a future community where a wide spread
     of people are represented. . . .

Beverly Erlebacher writes from Toronto:

     the most land-efficient agriculture is found in southern
     china and other parts of southeast asia. under very good
     climatic conditions and meticulous hand cultivation, an acre
     can support about 5 people with enough calories for
     reasonable health. . . . a closed ecology with cheap power
     and labour might optimise for maximal nutritional value
     produced per square or cubic footage per unit time.

     under such a system, green vegetables would be cheap and
     plentiful, most carbohydrates would come from root crops
     like potatoes and tropical yams rather than from grains, and
     tree fruits would be incredible luxuries.  small amounts of
     meat, eggs and milk could be produced by rabbits, chickens
     and goats or cattle consuming garbage and agriculture waste.

     on the other hand, fish would be much more available. as
     part of the water recycling system, there are large tanks of
     algae cultures feeding fish such as tilapia and possibly
     some invertebrates.  nutrients for the hydroponics come from
     the same system.

     in your book, you might consider some of the lush tropical
     vegetation being food plants like fruit trees and squash,
     bean, melon and grape vines.

     on another topic, that of air, you might want to read the
     may issue of scientific american which had an article on
     indoor air pollution.  up here in the north, in order to
     save heat, new buildings are often tightly sealed and air is
     recirculated.  these buildings are really awful to live and
     work in.  the air has a bad character to it, and people
     often get headaches or a sort of general dopey feeling after
     a few hours. colds are much more common. unions have been
     trying to get things changed for their workers on these
     issues.

     i could do some hand waving about 'wild' animals and birds
     in your space city, but for now, i think i would just
     recommend you avoid importing rats, mice, pigeons, sparrows,
     starlings, rabbits and red deer. on the other hand, these
     critters are pretty well guaranteed to succeed. :-)

Finally, Graeme Williams writes from somewhere I won't mention:

     I have one observation on what sort of society might develop
     in a space city, assuming that it is driven by technology
     and doesn't end up re-creating small-town Kansas.

     Fashion is possible (only?) when trivial changes in form are
     possible with negligible changes in function.  Observing my
     colleagues . . . we have that in spades.

     This sort of change interacts with our organizational
     culture, which seems basically tribal.  We are of course
     organized in a hierarchy, but as you might expect this has
     the most impact at the level of sections (up to about 10
     people) and departments (up to about 50, although above
     about 35 it doesn't really seem stable).

     This posting having grown quite large, I'll abandon it
(though I may return to the topic later with comments and further
queries) by saying thank you to all who took the considerable
trouble of thinking about and replying to my questions.  All the
replies were intelligent and well-informed, many gave gratifying
detail.  I have benefitted enormously from reading them, and you
may consider me in your debt.
     If I have slighted anyone, or improperly identified anyone
or his or her affiliation, my apologies:  I simply wanted to give
proper credit.
     By the way, I'm still happy to receive responses.

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

End of SPACE Digest V8 #280
*******************