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Subject: SPACE Digest V10 #206

SPACE Digest                                     Volume 10 : Issue 206

Today's Topics:
              Re: Fragile Space Shuttle
             Design for Luna City
            Re: Moon Colonies / Ant Tanks?
            Re: Moon Colonies / Ant Tanks?
            Re: Moon Colonies / Ant Tanks?
            Re: Moon Colonies / Ant Tanks?
            Re: Moon Colonies / Ant Tanks?
         Re: Voyager/Galileo Camera function
               Re: Design for Luna City
----------------------------------------------------------------------

Date: 4 Nov 89 14:53:55 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Fragile Space Shuttle

(my thesis: it will never be practicable to design and build spacecraft
that don't require checking with a fine toothed comb after every flight
as the Shuttle does)

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>First, will NASA ever find it practicable to do so?  I think we both
>agree that the answer is no, although perhaps for different reasons. :-)

Or even for the same reasons.  Personally I think if NASA found such a
design they would have the designer assassinated -- it runs counter to
everything NASA exists for.

>Second, will *anybody* ever find it practicable to do so?  ...
[Max Hunter, who designed the Thor missile, says yes] ...

[Max points out that the Shuttle uses a zillion times more people/launch
than the kludgey, quirky, high tech SR-71]

 * The Thor is not a spacecraft in the sense of the current discussion.
It was a wonderful vehicle and a masterpiece (I am sure) of design, but
it was a nonreusable ballistic missile.  Care and maintenance BETWEEN
LAUNCHES was not a factor in design!  I would be more overwhelmed to
read the comments of someone who worked on X-15 or the shuttle.  To
paraphrase Hunter, going into space AND RETURNING and going again is
not for the faint of heart!

 * Anyway his point seems to be that the Blackbird gets it done with
fewer people, NOT that the checking doesn't have to be done.  I have no
problem with the assertion that we can recycle spacecraft a lot more
efficiently (although there is a limit to what can be done with the
current bird).  Getting the man-hour numbers down is not the same as
"landing, gassing up and taking off" though.  Every subsystem *must* be
checked.  We just have to learn to do it at the flick of some switches
rather than via ruinously expensive hand labor.

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

Date: 5 Nov 89 03:28:58 GMT
From: amdahl!drivax![e-mail]  (MacLeod)
Subject: Design for Luna City

[e-mail] (Tom Neff) says:

:Oh by the way, if you have to burrow underground to survive in a
:Moon colony, why bother to go?  Why not just build underground
:colonies here?  Sure is easier to ship stuff here.  If you have
:to spend your whole life in the basement, how much does it matter
:which basement?

There are basements and basements.  The first lunar cubics will be Spartan,
but later developments - I'll bet - will take your breath away.

I have been fooling around with designs for Luna City lately, based on
long-held conceptions of what it would (should) look like.  Unfortunately,
I have very little visual imagination, so my vision is kind of a
utilitarian right-angular conception.

I won't try to draw it in ASCII graphics, but my design has a  cubical
center area a kilometer high surrounded by four cubic extensions a
kilometer on a side.  The center cube is filled, or unfilled, with a
rhombic space (like a cube set on a vertex).  Lunar gravity and modern
materials should make it possible to build in the upper sides of the
rhomboid without undue trouble, save for earthworms' queasyness.

The open area inside would be available for human-powered flight, assuming
that it's possible, and to give inhabitants a feeling of space.  It also
serves as an O2 and thermal reservoir. I have no idea how to light it.

At the (whatever the opposite of apex is) of the rhomboid, at bottom level,
is Heinlein Square, which is, or course, triangular. Each vertex has a bust
- Heinlein, Wells, and Verne.

The cubic spaces extending from the center area are a more mundane
row-column-level scheme.  Minor ways run 100 meters apart; major ways every
500 meters.  There are 2 levels, plus utilities access passages, per 10
meters of hight, or 200 levels per kilometer.  If you look down from above
onn the city, you can see four lobes, which we can lable north, south,
east, and west for convenience.  Addresses would use Heinlein Square as a
0,0 coordinate, like Salt Lake City's use of Temple Square. In this scheme,
your address would be something like 147,S6.77,E2.  You live on level 147
about 677 meters south of the Square along the second way east of the square.

Not a bad neighborhood; it's actually largely commercial, since it's so close
to the Dome.

Obviously elevator technology will be important...I envisioned half a dozen
kinds of lifts, local, express, grab-strap-as-it-goes-slowly-by,
commercial, industrial, and so on.  Some private lifts might be located
together in the core of a rectangular group of cubics to limit access to
owners, and commercial lifts would likewise be located in the "rear" of
shops.

Now, I realize that Bechtel is not ready to run out and build this city, but
you have to admit that it has room.  For example, if we alot a 100 by 100
meter square - considerable space - to a family of four, that gives us
space (in the lobes alone) for 1600 people per level, and we have 200 levels.
With a comfortable allowance for industrial, commercial, and farm space,
we should be able to maintain a quarter million in relatively spacious
surroundings.  This is a far cry from a basement.

Oh, you want to go there >now<?  Sorry, friends, too few Americans agree
with you.  Our retreat from the sciences is unprecedented and
heartbreaking.  Last I heard, State "educators" were advising high-school
students to keep journals to document their "feelings" about mathematics.

Michael Sloan MacLeod  (amdahl!drivax!macleod)

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

Date: 4 Nov 89 16:38:22 GMT
From: att!cbnewsh![e-mail]  (ihor.j.kinal)
Subject: Re: Moon Colonies / Ant Tanks?

>
> >How deep would you have to dig to get 1/6th earth gravity?  :-)
>
> From what I learnt from school, I recall that the gravitational force
> is inversely proportional to the distance between the center of masses. Hence
> the gravitational force will increase as you go towards the center of the earth.

WRONG!  Or at least misleading.

This probably belongs in the PHYSICS group, but since it was started
here, I feel we need to CLEAR this up.

If the EARTH were a uniform density object, the force of gravity
would go DOWN as you dig into the earth.  The reason is, that given
the inverse square law, INSIDE a hollow sphere, there is no influence
from that sphere. [See your typical college physics text for an
explanation]. So all the dirt in the shells above you no longer pulls,

Note, that for the earth, since the density in the center is higher, that
as you dig a tunnel, gravity does indeed go up, since you are getting
closer to a denser effective mass.

Ihor Kinal
STANDARD DISCLAIMER + I'm currently a software person - I haven't played
at being a physicist for almost 20 years now.

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

Date: 4 Nov 89 16:38:35 GMT
From: mailrus!jarvis.csri.toronto.edu!db.toronto.edu![e-mail]  (John Hogg)
Subject: Re: Moon Colonies / Ant Tanks?

In article <[e-mail]> [e-mail] writes:
>>How deep would you have to dig to get 1/6th earth gravity?  :-)
>
>From what I learnt from school, I recall that the gravitational force is
>inversely proportional to the distance between the center of masses. Hence the
>gravitational force will increase as you go towards the center of the earth.

Good point.  At least we have a very convenient singularity at the
Earth's centre for the next time we want one, but we'll have to find
another solution.  But don't worry, I already have it.  Since we have
~1G at the earth's surface, and ~0G in LEO, all we have to do is go
*five sixths* of the way to orbit to get a nice 1/6th G to play around in.

(Don't I have something better to do than waste bandwidth?)

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

Date: 4 Nov 89 20:02:43 GMT
From: uceng![e-mail]  (daniel mocsny)
Subject: Re: Moon Colonies / Ant Tanks?

In article <[e-mail]>, [e-mail] (George William Herbert) writes:
> In article <[e-mail]> [e-mail] writes:
> >I recall that the gravitational force is inversely proportional to the
> > distance between the center of masses. Hence the gravitational force
> > will increase as you go towards the center of the earth.
>
> Nope.  The force is inversely porportional to the distances and directly
> porportional to the enclosed mass... anything beyond the distance
> of the smaller object has no effect.  You decrease off towards zero-g
> within an object, with max. at the surface.

Every atom of the earth exerts a gravitational attraction on every
atom of a body at the earth's surface. The resultant of all the
gravitational force vectors is a vector lying on the line through the
center of masses of the two bodies. If the body is at or above the
earth's surface, the resultant vector has the same magnitude as would
result if the earth were really a point mass located where the center
of the earth is now.

If you dig down into the earth, part of the earth's mass is now above
your head, gravitationally attracting you back upstairs. (Something
similar happens if you are standing in a valley next to a large
mountain...this throws off your surveyor's level, complicating
the job of triangulating to obtain the mountain's height.) I believe
that you can show with some calculus that the net gravitational
force you feel a distance X away from the earth's center, with X<r,
where r=1 earth radius, is the same gravitational force you would
feel if you were standing on the surface of planet of radius X.
I.e., gravitationally speaking, the resultant force from all the
earth atoms at a depth X or less is zero.

If I haven't botched my handwaving, one result of this is that if the
earth had a centered spherical void inside it, you would be weightless
everywhere in that void. Is this correct? The hollow planet would
still want to cave in, though, because objects at the surface would
still have weight. However, the thinner you made the hollow planet's
shell, the less weight the shell would have. If the shell were
infinitely thin, could it have infinite mass without tending to
collapse?  That can't be right. What am I doing wrong here?

Dan (what? Do the math?) Mocsny
[e-mail]

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

Date: 4 Nov 89 05:09:23 GMT
From: att!occrsh!uokmax![e-mail]  (Thomas Lynn Egelston Ii)
Subject: Re: Moon Colonies / Ant Tanks?

In article <[e-mail]> [e-mail] writes:
>In article <[e-mail]>, [e-mail] questions
>>How deep would you have to dig to get 1/6th earth gravity?  :-)
>
>From what I learnt from school, I recall that the gravitational force
>is inversely proportional to the distance between the center of masses. Hence
>the gravitational force will increase as you go towards the center of the earth.

    That assumes we have two point masses.  Once you dig underground,
there is some mass of the earth pulling upward on you, and some still pulling
downward, resulting in a smaller net force.

--
          Tom Egelston      Internet: [e-mail]
All opinions expressed are mine. Universities aren't allowed to have opinions.
"I'm out of it for a little while and everyone gets delusions of grandeur!"
                                         -Captain Han Solo

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

Date: 4 Nov 89 23:41:15 GMT
From: thorin!alanine![e-mail]  (Jonathan Leech)
Subject: Re: Moon Colonies / Ant Tanks?

In article <[e-mail]> [e-mail] (John McKernan) writes:
>In a larger sense man's mass migration into space is exactly like his
>migration to other parts of the Earth. Whenever it was possible to move to
>an area with new resources to exploit, we have moved there and exploited
>those resources. Once it is possible for mankind to move in large numbers
>into space, all of man's history shows that it is inevitable that man
>will do so.

    I suspect you've been reading too much Pournelle and Stine.
People could move in large numbers to Antarctica or the ocean floor,
but aren't doing so.  The millenia+ delay between the enabling
technology for crossing the Atlantic and large scale immigration to
the New World provides no encouragement.
--
    Jon Leech ([e-mail])    __@/
    ``God is more interested in your future and your relationships
      than you are.'' - Billy Graham

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

Date: 4 Nov 89 11:35:40 GMT
From: nuchat![e-mail]  (Steve Nuchia)
Subject: Re: Voyager/Galileo Camera function

In article <[e-mail]> [e-mail] (Stuart Warmink) writes:
>(Fred Kokaska) writes:
>> Can the cameras on the Voyager and Galileo spacecrafts be aimed back at

>Even if the cameras could be pointed in such a fashion, the picture would be
>hopelessly out of focus...the depth of field of telelens cameras, especially

What is "hopeless" with modern image processing?  We have excelent
knowledge of the optics, the imaging geometry, and the object being
imaged.  From what little I know about image processing I think that
makes for a doable deal.
--
Steve Nuchia          South Coast Computing Services
uunet!nuchat!steve    POB 270249  Houston, Texas  77277
[phone]          Consultation & Systems, Support for PD Software.

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

Date: 5 Nov 89 05:16:31 GMT
From: voder!dtg.nsc.com![e-mail]  (Lord Snooty @ The Giant Poisoned Electric Head )
Subject: Re: Design for Luna City

In article <[e-mail]>, [e-mail] (MacLeod) writes:
> [e-mail] (Tom Neff) says:
> :Oh by the way, if you have to burrow underground to survive in a
> :Moon colony, why bother to go?  Why not just build underground
> :colonies here?  Sure is easier to ship stuff here.  If you have
> :to spend your whole life in the basement, how much does it matter
> :which basement?
>
> There are basements and basements.  The first lunar cubics will be Spartan,
> but later developments - I'll bet - will take your breath away.

The one overriding factor which attracts me, for one, is that LOW GRAVITY
ENVIRONMENT. This is not only enjoyable inside - simply getting around
would be so ...unique, deserving of creative approaches, etc.... but,
with the development of more flexible and less cumbersome vacuum-suits,
R&R outside would truly be something to look forward to.

Even scientists need a break from research, and what a place that would
be to discover and participate in new kinds of sport and friendly
competition. I truly don't think boredom is a problem; especially since,
in the next decade, high-bandwidth telecomms will be prevalent, so
Earthly diversions can be experienced and participated in, albeit vicariously.

What a great place that would be to grow up.
Just a few problems left like money, motivation and the supporting
infrastructure...
--
...........................................................................
Andrew Palfreyman    a wet bird never flies at night        time sucks
[e-mail]    there are always two sides to a broken window

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

End of SPACE Digest V10 #206
*******************