Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_6/V13_630.TXT

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Subject: SPACE Digest V13 #630

SPACE Digest                                     Volume 13 : Issue 630

Today's Topics:
      Re: Fred vs. Exploration: head-to-head competition
                Re: lifeboats
              Re: Privatization
       Re: Request For Discussion: sci.space.moderated
       More on tethers (was Re: SPACE Digest V13 #541)
                Re: lifeboats
            Re: lifeboats....ACRV
             Re: Gravity vs. Mass
         Kelly Act (was: Re: Building Infrastructure)
           Re: Rational next station design process
           Re: Rational next station design process
           Re: Rational next station design process
           Re: Rational next station design process

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: 21 May 91 13:41:12 GMT
From: swrinde!cs.utexas.edu!sun-barr!ccut!wnoc-tyo-news!astemgw!kuis!rins![e-mail]  (will)
Subject: Re: Fred vs. Exploration: head-to-head competition


    Actually it seems to me that congress is really just doing their what
    they were hired to do, that is play the game (the game of Politics,
    I mean).  So, some congressman have to get elected and if the station
    will get in the way, they are going to veto it.  It may just be that
    NASA management has wasted so much money or even miss-apropritated
    some money and congress wants to get thier attention.  Clean up your
    act NASA or else.  In any case it is just a game, and the ones who
    play it well will win, the others will lose or have some damage done.

    What I would like to see become of all this is that NASA does clean
    up its management system.  NASA wastes large volumes of money, (but
    I am sure not half as much as HUD).  HUD should have been taken out
    a long time ago, it has no usefull purpose anymore( in my opinion).
    Likewise perhaps the welfare system should also be cancelled.  Then
    maybe lazy Americans will finally get a job.  It would also save
    Billions for America.


                        Will.....

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

Date: 21 May 91 22:25:32 GMT
From: agate!headcrash.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Re: lifeboats

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>
>Nope, not correct.  The CM had its own RCS for reentry.  If you want to do
>orbital maneuvering -- it's not clear why -- then yes, you'd have to add
>something for that.  Take the RCS thruster "quads" from the SM, which were
>self-contained (each quad had its own little tank set just underneath it)
>and put them on whatever adapter you're using to hold the solid retros.

Why?  The Soviets use over 100 m/s to dock with Mir.  If we're using a capsule
for any rendezvous mission, which is what we're talking about, you need
the maneuver capability...

-george william herbert
[e-mail]

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

Date: 22 May 91 03:56:25 GMT
From: agate!lightning.Berkeley.EDU![e-mail]  (Frank Crary)
Subject: Re: Privatization

In article <[e-mail]> [e-mail] (Harri Pasanen) writes:
> Private profit driven companies seldom make plans for
>more than 5-10 years into the future.

It really depends on the company. Japanese consortiums of private companies
have been very active in space infrastructure. These efforts began in about
1975 and have yet to show a profit. They will begin to make money (but not
yet cover the initial investment.) in about 1995 if everything goes well.
This is an over 20-year investment. Also, here in the US, there are also
companies willing to invest in research and technology. 3M, for example,
makes most of its money from products that did not even exist ten years
ago.

                        Frank Crary
                        UC Berkeley

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

Date: 22 May 91 08:07:33 GMT
From: spool.mu.edu!agate!lightning.Berkeley.EDU![e-mail]  (Frank Crary)
Subject: Re: Request For Discussion: sci.space.moderated

In article <[e-mail]> [e-mail] (Phil Ngai) writes:
>But it didn't change the fact that you didn't/don't have a clue as to
>what was going on.
1: For the record: I began to read sci.military about one week before the
change in moderators. I did not have a chance to become familiar with the
old (and, I stand corrected, regular) moderator. I was, however, seriously
thinking of dropping it, untill [CDR], the present, temporary, moderator
reduced the excess postings somewhat.

2: Other than lowering your blood pressure, did your post, which consisted
only of a personal attack, have any purpose at all?

                      Frank Crary
                      UC Berkeley

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

Date: 22 May 91 02:37:43 GMT
From: usc!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!news-server.csri.toronto.edu!helios.physics.utoronto.ca!aurora.physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: More on tethers (was Re: SPACE Digest V13 #541)

In article <[e-mail]> [e-mail] (Walter Dnes    ) writes:
>     The tether may or may not work once it's set up, but it begs
>a question that I haven't seen addressed before... *HOW DO YOU
>GET ALL THAT MATERIAL UP THERE IN THE FIRST PLACE* ??? Let's
>assume that the first tether is a 1-meter-thick cable 500km long.
>Cross section = pi * r^2 = 3.14 m^2. Since 500km = 500000m, the
                             ^ This means r=1m, so d=2m
>solid volume of the tether cable is 3.14 m * 500000 m^2 =
>1.57 * 10^6 m^3 = 1.57 * 10^9 litres. One litre of water has a
>mass of one kilogram. Since we're presumably talking some heavy-
>duty material, let's assume specific gravity = 3.2. The tether
>would have a mass of 5 * 10^9 kg = 5 MILLION METRIC TONNES !
>Let's get serious folks. How many shuttle flights is it going to
>take to get it all up ?!?!?!
>
   Wow!!!! A two metre thick cable! Well, no wonder you can't get it to
work. Consider that two metre thick of drawn steel will break only after
exerting a force in excess of 5.16e10 Newtons. This would hold a mass of
about 4e+10 kg or 40 million metric tons in an orbit 500 km further away
from the Earth (ie in the situation of maximum tidal stress and ignoring
the mass of the tether itself). So, ask rather how many shuttle flights
it will take to get that much cargo into space to make such a tether
useful. Now, take a strong polymer instead of steel wire, and see what
happens. You're more likely to need a tether about a half centimetre in
diameter of Kevlar or Nylon, which would weigh about 25 tons for 500 km
length (and shuttles don't go that high). That's one shuttle cargo size.

>Walter Dnes
>[e-mail]             [e-mail]


--
 Christopher Neufeld....Just a graduate student  | There no place like $FC58
 [e-mail]    Ad astra! | They're $FF69-ing my
 cneufeld@{pnet91,pro-cco}.cts.com               | every word! Send for a
 "Don't edit reality for the sake of simplicity" | free $A56E.

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

Date: 22 May 91 04:23:18 GMT
From: agate!lightning.Berkeley.EDU![e-mail]  (Frank Crary)
Subject: Re: lifeboats

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>Nope, not correct.  The CM had its own RCS for reentry.  If you want to do
>orbital maneuvering -- it's not clear why -- then yes, you'd have to add
>something for that.

You would definitly need an orbital manuvering system for a crew transport.
Approching and docking to a space station takes some doing. The soviets'
standard two-day approch and docking manuvers require a 50 - 75 m/s delta-
v. A quicker approch would (and did untill the sovs changed their standards)
require more fuel. An American launch vehicle could put a crew transport into a
closer orbit to the station, which might cut down to trip time or fuel needed,
but I doubt any launch vehicle could eliminate the need to manuver.

                   Frank Crary
                   UC Berkeley

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

Date: 23 May 91 17:53:00 GMT
From: csus.edu!wuarchive!zaphod.mps.ohio-state.edu!rpi!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: lifeboats....ACRV

In article <[e-mail]> [e-mail] writes:
>...partialy correct.  A spring would work in translating away from the Space
>Station.  However, even more clever is just releasing the docking lock/latches
>and letting the release of the 14.7 PSI atmosphere push the vehicle away.  This
>works really great if the station is not out of control and you don't have to
>worry about station restrike.

The other side of this, of course, is that either one is more reliable after
storage for years in orbit than a set of maneuvering engines.  If David
can postulate a violently-out-of-control station, I can postulate undetected
equipment failure in the lifeboat. :-)  You can always find situations where
adding system X would turn failure into success, but equally you can find
situations where system X turns success into failure.  My point is that a
maneuvering system is not *essential* for most lifeboat situations, and
it is not ridiculous to consider a lifeboat without one.
--
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  [e-mail]  utzoo!henry

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

Date: 22 May 91 07:52:19 GMT
From: eru!hagbard!sunic!lth.se![e-mail]  (Magnus Olsson)
Subject: Re: Gravity vs. Mass

In article <[e-mail]> I write:
>You'd be weightless. It's relatively easy to show that if you're inside a
>spherically symmetric body, at a distance R from its centre, the gravitational
>forces from the parts of the body at distances greater than R from the centre
>will all cancel.
(...)
>The proof is done using Gauss' theorem; see any textbook on vector caclulus.

Of course, if you're in the exact centre of the earth, you don't need any
calculus to see that you're weightless: since you have equal  amounts of mass
in all directions, gravity pulls equally hard in all directions, and the
forces neutralize each other.

And, as someone pointed out, if you jumped down the hole, you'd be in free fall
all the time, so you wouldn't feel any gravity as long as you were falling.

Magnus Olsson                   | \e+      /_
Dept. of Theoretical Physics    |  \  Z   / q
University of Lund, Sweden      |   >----<
Internet: [e-mail]     |  /      \===== g
Bitnet: THEPMO@SELDC52          | /e-      \q

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

Date: 22 May 91 12:58:56 GMT
From: agate!spool.mu.edu!sdd.hp.com!usc!hela![e-mail]  (Allen W. Sherzer)
Subject: Kelly Act (was: Re: Building Infrastructure)

In article <[e-mail]> [e-mail] writes:

>>My understanding has always been that there was
>>no particular market for *air* mail before the Kelly Act.  Customers just
>>didn't think the faster delivery was worth anything to them.

>This is a nit.  Mail was a very large current market, and it was well
>known and much desired that mail be delivered as quickly as possible.

You miss the point Nick. The Kelly Act (actually acts since it was amended
so often) existed to CREATE a market for large scale passenger traffic. The
government moved mail because it was there. The backers of the bill would
have been just as happy if they where hauling sand or even nothing.

There where lots of reasons WHY this was done ranging from a desire to
create infrastructure to helping defense. Moving mail was NOT a reason
for the bill.

>Airplanes were proven as mail carriers before the Act.

Actually, in the early days they where very poor carriers. They
crashed often (most of the original pilots died in the first ten
years on the job). Sending mail via airplane turned out to cost
far more than the existing mechanism. This was not seen as a problem
since moving mail had nothing to do with the intent of the act.

>"bean counters" -- people who actually do the arithmetic instead
>of daydreaming -- did market surveys and worked out the dollar figures.

Not in the sense I think you mean (since they lost mooney and intended
to lose money). What they did do was to provide a market for air transport
and with incentives move that market toward widespread passenger travel.
For example, you where paid more if your aircraft had multiple engines
or advanced navigation equipment (even if they whern't needed). To make
airframes bigger (to support passengers) the govenrment even paid for
carriers to have empty space on their aircraft (which could then be
sold to passengers).

   Allen
--
+---------------------------------------------------------------------------+
|Allen W. Sherzer |        Allen's tactics are too tricky to deal with      |
|   [e-mail]   |             -- Harel Barzilai                           |
+---------------------------------------------------------------------------+

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

Date: 22 May 91 18:42:48 GMT
From: van-bc!rsoft!mindlink![e-mail]  (Nick Janow)
Subject: Re: Rational next station design process

[e-mail] (Frank Crary) writes:

> To satisfy Nick Szabo and others, who think that a station would be a
> unproductive waste, let me suggest a step 2.

I'm a different Nick, but I think the statement applies to me too, so I'll
respond.

I think that the present space station project would be a waste.  However, I'm
not objecting to a space station built to serve a properly-defined goal, with
proper economic study and proper planning.  Your "Step 2" seems to satisfy
those criteria.

I somewhat doubt that Space Station Freedom would have passed your "step 2".  I
also doubt that the space shuttle would have passed.

[e-mail]

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

Date: 23 May 91 22:56:16 GMT
From: sequent!muncher.sequent.com![e-mail]
Subject: Re: Rational next station design process

In article <[e-mail]> [e-mail] (Frank Crary) writes:

>Then calculate the value of these missions.

Now _there's_ a good idea.

Note that value is relative.  To calculate the value of the missions,
we need to compare the value to _alternate_ designs and the importance
of _other_ needs.  In other words, the opportunity costs.

This requires looking at alternate needs and designs, rather than
remaining glued on the narrow concept of a "space station" and the
narrow set of needs it might meet.



--
Nick Szabo                [e-mail]
"If you understand something the first time you see it, you probably
knew it already.  The more bewildered you are, the more successful
the mission was." -- Ed Stone, Voyager space explorer

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

Date: 24 May 91 00:28:37 GMT
From: sequent!muncher.sequent.com![e-mail]
Subject: Re: Rational next station design process

In article <[e-mail]> [e-mail] (Nick Janow) writes:

>There is likely still quite a bit of preparatory research that can be done with
>test animals in zero-g, biochemical reactions in zero-g, short-term human
>experiments (monitoring shuttle crew, etc) and computer simulations based on
>all those results.

As well as (spin-induced) lunar, Martian, and Earth gravities.
Also, the radiation levels at LEO are quite unlike those in and beyond
the Van Allen belts. Studying the effects of solar protons, cosmic rays,
etc. is also quite important to the design of space habitats for humans
and other organisms.  In addition, the effects of various kinds of
shielding in the various radiation environments need to be studied.


--
Nick Szabo                [e-mail]
"If you understand something the first time you see it, you probably
knew it already.  The more bewildered you are, the more successful
the mission was." -- Ed Stone, Voyager space explorer

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

Date: 24 May 91 05:29:40 GMT
From: agate!headcrash.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Re: Rational next station design process

In article <[e-mail]> [e-mail] writes:
>In article <[e-mail]> [e-mail] (Nick Janow) writes:
>>There is likely still quite a bit of preparatory research that can be done with
>>test animals in zero-g, biochemical reactions in zero-g, short-term human
>>experiments (monitoring shuttle crew, etc) and computer simulations based on
>>all those results.
>As well as (spin-induced) lunar, Martian, and Earth gravities.
>Also, the radiation levels at LEO are quite unlike those in and beyond
>the Van Allen belts. Studying the effects of solar protons, cosmic rays,
>etc. is also quite important to the design of space habitats for humans
>and other organisms.  In addition, the effects of various kinds of
>shielding in the various radiation environments need to be studied.

    There are two problems with non-station based zero-G biological
research: number one is that it's almost always conducted over a short
length of time, and number two, it's not easy to get detailed information
on the subjects.
    The US has #2 beat pretty well in the bio research we've been doing
from the Shuttle.  We've got non-intrusive data from just about all the
astronauts, and intrusive from a number of lab animals (though not enough).
    The Russians have #1 beat, but they're still not very good at getting
good depth of data out of their subjects.
    You could do a cheap compromise and fly an unmanned "LabRatSat" for
a year or two, but I don't know if it's feasable to handle lab animals for
that long purely by machinery.  Reinserting IV test lines etc. by teleoperation
is an (as far as I know) untested idea... I'd count this as of questionable
practicality.
    We could do a second compromise and fly US biological science on Mir.
I don't want to count on political or Soviet stability. ( IMHO )

    Flying short term projects simply won't cut it if we're looking at
long term effects.  The Russian long-term data indicates that there are
significant changes in the nature of long-term biological response to zero-G
that remain for the most part uncharacterized.  We just don't have enough
data points (US are only to 10 days, Russian are too sketchy) to model what's
happening, and computer and biochemical models aren't useful if the data
that they're based on is so sketchy.

    Nick has good points about the effects of spin (variable, zero to
partial (earth, Mars (1/3), and Lunar (1/6) ) gravity and radiation.  We
don't know _anything_ about spin gravity (though nobody has any reason to
suspect that it will have effects beyond disorientation, so far).  We also
only have sketchy guesses of what radiation will do to the body, and what the
radiation levels will be (especially during Flares).  Given that there is
a relatively low-radiation environment in LEO, it might be best to do two
steps to this; a LEO station to determine effects of it's environment, then
a HEO/GEO/Further? test lab to see what happens further out.  Admittedly,
there's been a lot of modeling done on the subject, but it would be nice
to see some hard data 8-) [besides the lunar astronauts blue flashes]

    Again, looking at the needs of long-term human bio research,
I can't see any solution other than doing research on a manned station.
I'm open to having my mind changed, but all the research into bioscience
needs that I've done says 'Station!' all over it 8-)

-george william herbert
[e-mail]

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

End of SPACE Digest V13 #630
*******************