Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_5/V13_506.TXT

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Subject: SPACE Digest V13 #506

SPACE Digest                                     Volume 13 : Issue 506

Today's Topics:
     Re: Holding Down an Atmosphere (was Re: Teraforming Venus?)
         .Gifs Of Planets in Our Solar System
             Wanted: Info on Biosphere II
               Re: Gas Guns and Tethers
        Re: Terraforming Mars?  Why not Venus?
          Re: Teflon (Was  Space technology)
       Re: Japanese satellite destroyed on NASA rocket.
              Re: Why the space station?
               Re: Saturn V and the ALS
          Re: why _I_ think we need a space station
               Re: Saturn V and the ALS

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]

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Date: 4 May 91 08:03:35 GMT
From: agate!lightning.Berkeley.EDU![e-mail]  (Frank Crary)
Subject: Re: Holding Down an Atmosphere (was Re: Teraforming Venus?)

In article <[e-mail]> [e-mail] (Jonathan Monsarrat) writes:
>does anyone know how long it would take for the atmosphere to bleed off?
>How much gravity does a body need to have an atmosphere anyway?
>
Very crudely, a planet can keep a gas if its surface escape velocity,
Sqrt( 2*G*M/R ), is greater than the mean thermal velocity of the gas,
Sqrt( 3*k*T/m ). Putting the two togather,

A gas is retained in the atmosphere if T/m < 3GM/2kR.
G = gravitational constant = 6.67EE-11 (kms metric)
M = planet (or moon)'s mass in kg
R = planet's radius
k = boltzmann's constant = 1.38EE-23
T = Temperature in kelvin
m = molecular mass of gas (in kg)

>And if it were a satellite (Ganymede), would its focus (Jupiter) steal
>the atmosphere away anyway?

No, these effects are important only (to a first order) near the Roche
limit. None of the major moons in the solar system are near this limit.

                         Frank Crary
                         UC Berkeley

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Date: 4 May 91 21:03:27 GMT
From: mips!zaphod.mps.ohio-state.edu!casbah.acns.nwu.edu![e-mail]  (Jerry Campbell)
Subject: .Gifs Of Planets in Our Solar System

I am looking for any .Gif files that NASA may have put out. I am looking
for pictures of Saturn and of the Earth or anything else that they might
have put out. I just recieved a .Gif viewer, from a friend the other day. I
would like to use it to study our solar system. If there are any Gifs out
there of anything that you feel that might interest me send them to me or
a list of Ftp sights that have them.



Send E-mail to [e-mail]

Jerry

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

Date: 5 May 91 20:45:28 GMT
From: mips!zaphod.mps.ohio-state.edu!menudo.uh.edu!jetson.uh.edu![e-mail]
Subject: Wanted: Info on Biosphere II

Howdy.  I don't know if this is the right place for this but I figure
it's somewhat related.  Could someone give me any information on
Biosphere II?  Stuff like whether they have a newsletter, where I can
write for more info, etc.  Please send your replies direct.  Thanks
in advance.
R. Arora ([e-mail])
--
-------------------------------------------------------------------------------
                .............                    |       Rikhit Arora
 And, while with silent, lifting mind I've trod  |    [e-mail]
    The high untrespassed sanctity of space,     |       [e-mail]
  Put out my hand, and touched the face of God.  |    ~~~~~~~~~~~~~~~~~~
-------------------------------------------------------------------------------

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

Date: 1 May 91 14:55:18 GMT
From: agate!bionet!uwm.edu!cs.utexas.edu!news-server.csri.toronto.edu!helios.physics.utoronto.ca!aurora.physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Gas Guns and Tethers

In article <[e-mail]> [e-mail] writes:
>
>[e-mail] (Dani Eder) writes:
>
>>
>> This ignores the fact that you do not have to have a tether all
>> the way from orbit to the ground.  A shorter tether hanging vertically
>> in orbit will have it's lower end moving sub-orbitally.  A launch
>> system then only has to reach the bottom of the tether, rather than
>> orbit.  Anything that makes a launch vehicles' job easier is
>> beneficial.  The reminder of the ride to orbit (which is at the
>> center of mass of the tether) can be via elevator.
>> ___
> |___| Space            I think that you've fallen into the old
>   |   station   "pull-yourself-up-by-your-bootstraps" fallacy. Here's a
>   |             simplified diagram of the situation, just before the
>   |             launch vehicle grabs the bottom of the tether. Assuming
>   |          that the mass of the tether is small relative to the main
>   |          station, the centre of mass of station+tether will be near
>   |          the space station itself. When the shuttle grabs the
>   | |===|    tether, we have a new body, i.e. station+tether+shuttle.
>    shuttle   You have three problems to deal with...
>
>   [.....]
>     The theoretical problems are where many "perpetual-motion machines"
>trip over reality. It takes X joules of work to lift a specific payload
>to a specific orbit. TANSTAAFL... There Ain't No Such Thing As A Free
>Lunch.
>
   Sometimes there is, if you're patient. You've got an interesting
space station there, it seems to grow without limit, since all the mass
which goes up, you assume (from your objections) never comes down again.
Some astronauts are likely to get a craving even for a Big Mac(tm) after
twenty or thirty years of this exile you're imposing on them. The
angular momentum objection is not an issue. How many schemes for docking
the shuttle to the current space station design have you seen which
require no reaction mass for fine tuning on the approach to the station?
One simply fires a jet or two to cancel residual motion before climbing
the tether.
   Further, even if the mass doesn't ever go back down to the Earth, you
can still boost the orbit of the space station without expending
reaction mass. Put up a solar sail (if you're a few thousand kilometres
up or higher), or boost the orbit by running a current loop through your
tether and pushing against the Earth's magnetic field, powering the
whole assembly with solar cells. These two systems take time to achieve
significant delta-v, so you couldn't send up mass at an arbitrarily high
rate, but that doesn't seem to be a big problem with the current
launchers.
   The cost of spaceflight is not the cost of the joules of energy
required to get to orbit. That's a couple of dollars a kilogram. Delta-v
is cheap in orbit if you use the right schemes, but expensive in a
launcher. Ion engines, solar sails, or magnetic thrust approaches won't
be used to launch from the surface of the Earth, but are much cheaper to
run per m/s delta-v, if you've got the time to wait.

>Rather than a tether, how about a "Tower of Babel", reaching up
>to GEO ? Technologically impossible, but good for a sci-fi story or two.
>At least in the stories, you could take an elevator to the top.
>
   You should say, technologically infeasible for the Earth at the
moment. You could build a very nice tether in the centre of the lunar
face out of nylon which would let you carry significant payloads to L1.
Similarly, current technology could make a useful tether on Mars, though
you might have to deorbit the moons first (which can also be done with
tethers given some time).

>[e-mail]    <--- Use this address until I


--
 Christopher Neufeld....Just a graduate student  | Flash: morning star seen
 [e-mail]    Ad astra! | in evening! Baffled
 cneufeld@{pnet91,pro-cco}.cts.com               | astronomers: "could mean
 "Don't edit reality for the sake of simplicity" | second coming of Elvis!"

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

Date: 1 May 91 16:19:00 GMT
From: agate!bionet!uwm.edu!cs.utexas.edu!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Terraforming Mars?  Why not Venus?

In article <[e-mail]> [e-mail] writes:
>    Does it really matter if the skeletal system becomes week
>if you continue to live on mars for the duration of your life?

Good question.  We don't know.  It might be a bit embarrassing to break a
bone while trying to get a sticking garage door open.  This wouldn't be
an issue if your muscles weakened correspondingly... but that would be
a liability in many situations, e.g. opening sticking garage doors.

>    Does anyone know of any other biological problems that would be
>significant to an astronaut that decided to live in space and not return to
>Earth?

There are a long list of changes that occur in the body in free fall.  How
many of them also occur in low gravity is unknown.  How low is low is unknown.
Whether any of them have serious long-term consequences is unknown.
--
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  [e-mail]  utzoo!henry

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

Date: 24 Apr 91 16:25:29 GMT
From: mips!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!pitt!nss![e-mail]  (Paul Blase)
Subject: Re: Teflon (Was  Space technology)

To: [e-mail] (Daniel Briggs)

 [...[story of discovery of Teflon]]
 DB> Now this maybe should go in sci.physics.folklore, since I could
 DB> well have hashed most of the details, but I think the fact is
 DB> that the discovery of teflon was largely an accident by some
 DB> chemist types who kept their eyes open.  Even if the lab turns
 DB> out to have been a NASA one, it probably wasn't a substance
 DB> produced on demand according to NASA specs.  Even though
 DB> non-stick frying pans are often used as an example of spin-off
 DB> technology, maybe teflon itself isn't such a good example.
 DB> Anyone with more details care to correct me or give the full
 DB> poop on the story?

The point is not where it was developed, but who paid for the development
to figure out how to do something useful with it.

--- via Silver Xpress V2.26 [NR]
--
Paul Blase - via FidoNet node 1:129/104
UUCP: ...!pitt!nss!Paul.Blase
INTERNET: [e-mail]

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

Date: 25 Apr 91 06:18:21 GMT
From: unisoft!fai!sequent!crg5![e-mail]  (Nick Szabo)
Subject: Re: Japanese satellite destroyed on NASA rocket.

This was not a NASA rocket, but a General Dynamics commercial rocket.
NASA, contrary to popular opinion, is not even close to being "the
space program" in the United States.  Most U.S. rockets are launched by
somebody other than NASA.

Atlas has a rather unreliable history and I would guess General Dynamics
is going to withdraw from the business, as the market is about to
shrink and they are losing money.  Europe's Ariane is an equally unreliable
rocket, in which the Japanese have also had the misfortune of their
satellites being blown to bits.  I expect Ariane will be heavily subsidized
in face of competition from the commercial Delta and Titan launchers,
which are the most reliable rockets in the market.  OSC's Pegasus has a
monopoly, for now, in the rapidly growing market market it has created
at the entry level.  Japan does not yet have a signficant commercial
space launch capability.



--
Nick Szabo                [e-mail]
"Living below your means allows you to live better than living above your
means." -- Dave Boyd    The above opinions are my own and not related to
those of any organization I may be affiliated with.

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

Date: 27 Apr 91 05:46:20 GMT
From: unisoft!fai!sequent!crg5![e-mail]  (Nick Szabo)
Subject: Re: Why the space station?

In article <[e-mail]> [e-mail] (Gaurang Hirpara) writes:
>
>I think the point is that a space station is the first step to returning
>to the moon to set up a more permanent base.

We can justify a horribly expensive project of little use with the
potential for an even more horribly expensive project of little use?
Good grief.


--
Nick Szabo                [e-mail]
"Living below your means allows you to live better than living above your
means." -- Dave Boyd    The above opinions are my own and not related to
those of any organization I may be affiliated with.

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

Date: 29 Apr 91 00:09:46 GMT
From: unisoft!fai!sequent!crg5![e-mail]  (Nick Szabo)
Subject: Re: Saturn V and the ALS

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:

>Saturn on the other hand cost about $17 billion to develop in 1986
>dollars (source: NASA testimony to the House Science Committee, March
>1991). The same testimony stated that a Saturn V costs about $590 million
>(average cost of the first lot of 50) in 1986 dollars. This gives us
>a cost of $2360/pound which is far less than Shuttle costs.

These estimates are from the same people that price STS launches
at $150e6/launch, given an actual cost of $950e6/launch.  Furthermore,
far less than 50 Saturn V's were built or launched.  Is there any
independent (non-NASA) estimate for Saturn V costs?  The Apollo
program as a whole was $121,000 million ($'90) not counting Skylab,
or $11,000 million per launch over 11 flights.  If 40% of that is
attributable to the launcher itself (aerospace rule of thumb),
that gives us $4,400 million per launch, divided by 280,000 max kg is
$16,000 per max kg, or $7,300/max lb., which is less than the Shuttle's
$18,000/max lb. but 2.4 times higher than Ariane's $3,000/max lb.

Of course, the 40% rule is a crude method of estimate, but with government
programs, which do not have to follow standard accounting methods, it is
perhaps as good as we can do.

Apollo cost and Saturn V LEO launch max mass from _Space Mission Analysis
and Design_, Wertz & Larson eds. Kluwer Academic Publishers 1991.  Number of
flights from _World Almanac_ 1990.


--
Nick Szabo                [e-mail]
"Living below your means allows you to live better than living above your
means." -- Dave Boyd    The above opinions are my own and not related to
those of any organization I may be affiliated with.

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

Date: 25 Apr 91 01:46:18 GMT
From: unisoft!fai!sequent!crg5![e-mail]  (Nick Szabo)
Subject: Re: why _I_ think we need a space station

In article <[e-mail]> [e-mail] (Bill Seward) writes:

>We need a space station as a first step to getting a group (preferably a
>rather large group) off this planet permanently.

Bad news, if you hadn't heard -- but four astronauts is not a very large
group of people.  A Winnebago-sized habitat costing 1,000,000 times the
amount of that funky portable home we know and love, in no way resembles
or contributes to the technology we need for space colonization.

[asteroid threat]

On that subject, here is a step that _would_ contribute significantly
to space colonization -- the development of extraterrestrial resources
and industries.  With our recent hard-won gains in orbital mechanics,
gravity assist, and aerobraking, there are potentially hundreds of
thousands of small asteroids and comets a surprisingly small amount of
delta-v away from sitting in Earth orbit -- a much more diverse, much
more complete, and much easier to obtain and process, set of materials
than those found on the lunar surface.

Here is a field that is vastly underfunded relative to astronaut program.
We have discovered less than 1/10 of 1% of the asteroids and comets that
are known, from crater frequency studies, to exist.  We have thousands of
asteroid samples already sitting here on Earth -- very easy to obtain by
looking at areas where the ice has concentrated them in Antartica -- but
the funding for these manned missions and the study of these samples is
10,000 times lower than what we spent to return a few samples from the Moon.
The telescopic search to discover and track comets and asteroids --
important both for space colonization and preventing the asteroid threat
you raised -- is equally underfunded.

Space colonization _is_ important and as such it is very important
that we who favor space colonization think hard and clearly about it
rather than just assuming that our fondest dreams can come true with a
handful of people spending billions of our tax money.



--
Nick Szabo                [e-mail]
"Living below your means allows you to live better than living above your
means." -- Dave Boyd    The above opinions are my own and not related to
those of any organization I may be affiliated with.

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

Date: 2 May 91 18:37:04 GMT
From: snorkelwacker.mit.edu!usc!samsung!caen!ox.com!hela![e-mail]  (Allen W. Sherzer)
Subject: Re: Saturn V and the ALS

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

[Estimate at cost of rebuilding Saturn V deleted]

>These estimates are from the same people that price STS launches
>at $150e6/launch, given an actual cost of $950e6/launch.

I think these figures are if anything an overestimation. Consider:

1. The presenter was opposed to rebuilding Saturn V and wanted
   to convince the House to back ALS. The presenter thus had
   every incentive to inflate costs. There is also some proof
   that costs where in fact inflated: Rocketdyne offered to
   develop (under a fixed price contract) F-1 engines for a
   tenth the NASA estimate and for half the unit cost.

2. Procurement would be under the FAR's which would add greatly
   (perhaps double) costs. A commercial acquisition of Saturn Vs
   would cost less.

3. Schedules look pesamistic. For example, they allocate four years
   to delivery of first F-1; Rocketdyne says it can be done in two.

4. This includes cost of the S-IVB stage even though it wouldn't be used.


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

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End of SPACE Digest V13 #506
*******************