Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V13_6/V13_625.ZIP/V13_625

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Subject: SPACE Digest V13 #625

SPACE Digest                                     Volume 13 : Issue 625

Today's Topics:
            What comes after Fred's death?
          Re: SPACE STATION FREEDOM WOUNDED
              Re: Privatization
             Re: Gravity vs. Mass
               Laser numbers sent to me
              Re: SPACE Digest V13 #541
              Re: Privatization
Re: Stepping back, asking why? (was Re: Rational next station design...)
              Re: Infrastructure
                Re: lifeboats
     usf (was Re: An International Civil Space Agency 93)

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Date: 20 May 91 17:48:37 GMT
From: snorkelwacker.mit.edu!hsdndev!cfa203![e-mail]  (Steve Willner)
Subject: What comes after Fred's death?


 [e-mail] (Allen W. Sherzer) writes:
> will likely involve two stations: one human tended for microgravity and
> another for life sciences which may be permanently crewed or tended.

Hasn't it occurred to anyone that life sciences research (keeping a
couple of astronauts in orbit for a year or so) can be done without a
space station?  All that should be needed are another couple of
shuttle orbiters, extended duration modifications (up to 30 days is
already planned), and rendezvous capability.

[Thanks, Allen, for keeping us up to date.]
--
-------------------------------------------------------------------------
Steve Willner            Phone [phone]         Bitnet:   willner@cfa
60 Garden St.            FTS:      830-7123           UUCP:   willner@cfa
Cambridge, MA 02138 USA                 Internet: [e-mail]

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

Date: 19 May 91 15:57:59 GMT
From: swrinde!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!wa4mei!ke4zv![e-mail]  (Gary Coffman)
Subject: Re: SPACE STATION FREEDOM WOUNDED

In article <[e-mail]> [e-mail] writes:
>In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>
>>The House HUD/VA/IA Appropriations Subcommittee marked up the NASA
>>appropriation this morning. They zeroed out ALL station funding.
>
>>Unless the Senate restores the money and it survives conference,
>>the space station will be cancled.
>
>Good news!   GOOD NEWS  !!!!!!
>
>Congress is listening to the explorers !!  Hope for space exploration,
>space development, and _real_ space settlement lives on !!!!!!
>
>If this holds up, it will be time for DANCING IN THE STREETS !!!!!
>
>I haven't felt this good since the Pegasus launch.... whew....

Meanwhile, Congress takes the $3 billion they just saved and pour
it into HUD grants to perk up their S&L buddies. Their re-election
campaign chests benefit so much that they decide to go back and
chop out even more of the unpopular NASA budget, cancelling CRAF,
zeroing the Hubble repair budget, and since it isn't needed anymore,
mothballing the shuttle fleet. "Why waste money on science missions?"
they ask, "Since we still have moonrocks left over from 1970 that
nobody has looked at. After all, if all they want is pretty pictures,
we've spent enough on supercomputers that they can draw their own. Just
look what Lucasfilm can do with one old Cray."

ESA and NASDA sign long term agreements with a reliable partner, the
Soviet Union, and proceed to develop space, garnering all the benefits
while the US continues to slide into third world status.

Gary

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

Date: 21 May 91 11:53:03 GMT
From: eru!hagbard!sunic!fuug!funic!nntp.hut.fi!cs.hut.fi![e-mail]  (Harri Pasanen)
Subject: Re: Privatization

I'm kind of generally suspicious about privatization when long term research
is in question.  Private profit driven companies seldom make plans for
more than 5-10 years into the future.  Let's take large particle colliders
as an example.  I doubt there would be any private organization that would
foot the bill for CERN for instance.  Same logic can be applied to large
space projects.

Correct me if I'm wrong.


Harri Pasanen

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

Date: 21 May 91 15:23:15 GMT
From: olivea!samsung!uakari.primate.wisc.edu!sdd.hp.com!elroy.jpl.nasa.gov!euclid.jpl.nasa.gov![e-mail]  (Peter Scott)
Subject: Re: Gravity vs. Mass

In article <[e-mail]>, [e-mail] (Isildur) writes:
> I was having a debate with one of my friends over this one... You somehow
> dug a hole clean through the earth in a diameter through the core and it was
> completely insulated from the heat changes running through the planet.  When
> you climbed into the tunnel (fall into the the tunnel...) and reach the
> center of the planet, would your weight be incredibly multiplied because of
> your new relative location to the center of the earth (using the
> mass/gravitational constant formula) or would you have zero-weight because
> you were surrounded by virtually identical mass (and also assuming that the
> tunnel closes up outside your immediate location)?

You'd be in freefall the whole time.  This is, BTW, a very cheap way
of getting to China, not counting capital investment :-)

Question: assume the ends of the hole are open to the atmosphere.
What's the pressure function of the air in the hole?

--
This is news.  This is your       |    Peter Scott, NASA/JPL/Caltech
brain on news.  Any questions?    |    ([e-mail])

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

Date: 21 May 91 17:51:48 GMT
From: agate!spool.mu.edu!samsung!caen!ox.com!fmsrl7![e-mail]  (Ron Carter)
Subject: Laser numbers sent to me

I'm sure Doug wouldn't mind me posting this information rather
than having to sum it up in my own words.
=====================================================================
Date: Tue, 21 May 91 11:45:46 -0500
Message-Id: <[e-mail]>
From: sharkey!citi!gatech!aries.scs.uiuc.edu!mcdonald (Doug McDonald)
To: fmsrl7!wreck (Ron Carter)
Subject: Re: Laser launchers

In article <[e-mail]> [e-mail] (Ron Carter) writes:
>Incidentally, the characteristic impedance of free space is about
>377 ohms per square, if memory serves.  1 KW/cm^2 implies an RMS
>electric field strength of 614 volts/cm, which is nowhere near
>the dielectric breakdown point of air.  100 GW/m^2 is 10 MW/cm^2,
>implying an RMS FS of about 61 KV/cm.   That's where I'd start
>to worry about things turning to plasma.

Examples: a 10 joule 1 microsecond CO2 laser produces 10 megawatts. This
produces breakdown in air at a cross section of roughly 1 square millimeter,
or 1 gigawatt per square centimeter, 10^15 watts per square meter.

At 20 gigawatts per square centimeterat 1.06 microns I have not observed
breakdown, for 10^-10 second pulses.

HOWEVER, this is really an unimportant point for laser launchers. Those
figures are  for air at ONE ATMOSPHERE. At lower pressures the powers get less -
much less indeed. I have no hard numbers, though. You probably
could count on not having breakdown problems up to maybe 5 or 10 miles.
Then, of course, at say 50 or 100 miles up again lasers will for sure
propagate nicely.

Doug McDonald
=====================================================================

[Ron again.]  Doug appears to have confused his numbers for the CO2
laser; that power density is 10 GW/cm^2, not 1 GW/cm^2.

It appears that a system running a peak power of 1 GW/m^2 would have
a rather large safety factor before breakdown of air becomes a problem.
If necessary, it could run higher power levels early and late, and
coast through troublesomely conductive parts of the atmosphere.

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

Date: 21 May 91 05:10:54 GMT
From: rex!samsung!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!news-server.csri.toronto.edu!torsqnt!hybrid!torag!w-dnes![e-mail]  (Walter Dnes )
Subject: Re: SPACE Digest V13 #541


Tommy Mac <18084TM@MSU> at [e-mail] writes:

> Re: Shuttle on tether
>
> >to the higher orbit in the first place !!! Reeling in the shuttle to
> >raise its orbit is no different than firing the shuttle's engines
>                     ^^^^^^^^^^^^
> >to raise its orbit. In both cases you're looking at raising an object
> >against gravity. The net work is the same...
>
> Isnt the advantage that tethers don't require reaction mass?  And that
> is also a cascading advantage 'cuz you don't need to carry it around
> until you use it?              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ^^^^^^^^^^^^^^^^

     So we no longer burn a hydrogen-oxygen mixture in the shuttle's
rockets... instead we react hydrogen & oxygen in a fuel cell to
generate electricity to power the motor that reels/unreels the
tether. I still fail to see the difference. Now, how do you get the
hydrogen/oxygen up to the station ?

> >shuttle will tend to remain in the same orbit as the station, *UNLESS
> >IT FIRES ITS ROCKET ENGINES TO DE-ORBIT*. That's what the shuttle has
> >to do right now.
>
> It doesn't have to fire it's engines.  It has to expel enough mass at
> high enough speed to match the momentum change it wants.  Rockets are
> traditional, but in this case, you could use the station itself as
> 'reaction mass'.

     Assuming that the station can maintain its structural
integrity through several years of heavy-duty jolting to kick
the shuttles out, *WHERE DOES THE ENERGY FOR THE "KICK" COME
FROM* ? A magnetic-repulsion launcher would require electricity,
which would take us back to fuel cells.

     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
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 ?!?!?!

Walter Dnes
--------------------------------------------------------------------------
[e-mail]             [e-mail]
...hybrid!torag!w-dnes!waltdnes  [e-mail]

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

Date: 21 May 91 21:36:13 GMT
From: [e-mail]  (Jonathan Leech)
Subject: Re: Privatization

In article <[e-mail]> [e-mail] (Fraering Philip) writes:
>The Keck Telescope, which a short while ago passed the 200-inch
>Hale Telescope in observing area, is mainly privately funded by the
>W.M. Keck Foundation. For a while it will be the world's largest
>telescope. A second Keck scope is to be built, next to the first,
>for interferometry use.

    Showing the potential for private funding of projects in the $160
million range (roughly the cost of the two scopes, I believe), but not
the 10x greater cost for a major planetary mission.  Even funding
SSI's relatively cheap Lunar Polar Probe from private sources is a
pain.  Further, no planetary mission will return as much science in
its brief lifetime as the Keck will over decades, and the risk factor
is very high.

    The space science folks have the unfortunate problem that the
majority of their costs have nothing to do with science per se.  If
the cost of launching and space-qualifying hardware comes within a
sane distance of terrestrial analogs, I imagine there will be private
funding available. Hopefully that won't be too many decades from now.

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

Date: 22 May 91 08:00:29 GMT
From: spool.mu.edu!agate!lightning.Berkeley.EDU![e-mail]  (Frank Crary)
Subject: Re: Stepping back, asking why? (was Re: Rational next station design...)

In article <[e-mail]> [e-mail] (Brian Yamauchi) writes:
>1) Why do we (space enthusiasts) want to explore space?

Manifest Destiny

                       Frank Crary
                       UC Berkeley

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

Date: 22 May 91 14:15:21 GMT
From: agate!spool.mu.edu!rex!rouge![e-mail]  (Fraering Philip)
Subject: Re: Infrastructure

In the interests of brevity (and that I don't want to spend the time
to unindent with spaces and reindent with slashes his whole article)
I would simply like to point out to Nick that having a government
intervention that produces the same thing as the free market (but
faster) may not be entirely possible.

Deceiding which is better I think I will now leave to the flamewar
(what? me have opinions? )

--
Phil Fraering || Usenet (?):[e-mail] || YellNet: 318/365-5418
''It hardly mattered now; it was, in fact, a fine and enviable
madness, this delusion that all questions have answers, and nothing is
beyond the reach of a strong left arm.`` - Larry Niven and Jerry
Pournelle, _The Mote in God's Eye_

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

Date: 22 May 91 16:40:23 GMT
From: usc!zaphod.mps.ohio-state.edu!rpi!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: lifeboats

In article <[e-mail]> [e-mail] (George William Herbert) 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...
>
>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...

I thought we were talking about lifeboats, which can get by with a spring
for separation from the station.  (Actually, you can get by with just
leaving the docking tunnel pressurized when you release the latches, as
flight-proven on Apollo 13.)

The more you try to turn the lifeboat into a jack-of-all-trades manned
capsule, the more complex it will get.  In particular, if you want it to
be able to fly substantial semi-independent missions, then you *do* need
something like the Apollo SM and that is *not* wasted mass any more.

If all you want is a bit of maneuverability for rendezvous, given an
accurate launch I think you can get by with my suggestion -- mount the
SM thruster quads on whatever adapter you're using to hold retros.
--
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  [e-mail]  utzoo!henry

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

Date: 24 May 91 04:24:40 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!samsung!transfer!lectroid!sw.stratus.com![e-mail]  (Tarl Neustaedter)
Subject: usf (was Re: An International Civil Space Agency 93)

I sent an email enquiry to the following effect a while ago, and got no
answer (the USF is probably too busy to answer). Could someone tell me:

In article <[e-mail]>, [e-mail] writes:
>....
> 2)  To create the Space Planning Commission (SPC) and the Space Regulation
> Commission (SRC).  These two commissions will propose, debate, and plan
> international space projects and draft and enforce international space law
> documents.  The SPC and SRC will mandate all USF operations.

Where does the USF obtain the authority to
     "draft and enforce international space law?"

> 4)  To achieve direct communications with the United Nations and, therefore,
> the international community, in order to gain critical insight into world
> events that may affect USF operations or agreements, and to allow non-member
> nations an alternate, neutral forum in which to communicate with the USF.

Does a list of member nations exist?
What requirements did these nations fulfill to achieve membership?

> 4)  To create a network of orbital refueling, staging and supply facilities to
> support USF operations and to provide emergency and rescue capabilities in
> support of manned space missions and facilities, not only for the USF, but also
> for other space agencies around the globe.

What kind of funding does the USF have? From whom?

A last question: Why are these manifestoes being posted here?
--
         Tarl Neustaedter    [e-mail]
         Marlboro, Mass.    Stratus Computer
Disclaimer: My employer is not responsible for my opinions.

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

End of SPACE Digest V13 #625
*******************