Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_0/V13_015.TXT

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Subject: SPACE Digest V13 #015

SPACE Digest                                      Volume 13 : Issue 15

Today's Topics:
             Re: Interstellar Light Sails
            Mir Lottery questions
      Re: orbiting Earth in the stratosphere by balloon.
           Re: space news from Nov 5 AW&ST
      Re: You can help clear cloud over MIR SWEERSTAKES.
               Re: Interstellar travel
               Re: Interstellar travel
               Re: Interstellar travel

Administrivia:

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Date: 30 Dec 90 22:32:13 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Organization: U of Toronto Zoology
Subject: Re: Interstellar Light Sails
References: <[e-mail]>, <[e-mail]>, <[e-mail]>
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In article <[e-mail]> [e-mail] (Paul M. Koloc) writes:
>>                          .. .      If you can build the laser system
>>on the necessary colossal scale, laser sails are workable.
>
>Let's look into the future hazards of this approach:
>
>A fleet of Sophians  were vaporized when they cut through the beam
>(during a heated debate).

Depends on the power density of the beam.  Something a few times the
density of sunlight is still very useful for propulsion -- because it
is available to much greater distances -- without being terribly
dangerous (although you probably wouldn't want to look into it).

>After a few decades of flawless performance, the mirror was sabotaged
>by the Helicons (a tribe of radical solar orbital environmentalists).

Any scheme using "ground"-based power to run spaceships is vulnerable
to disruptions at the power station.
--
"The average pointer, statistically,    |Henry Spencer at U of Toronto Zoology
points somewhere in X." -Hugh Redelmeier| [e-mail]   utzoo!henry

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Date: 30 Dec 90 06:36:01 GMT
From: cs.utexas.edu!asuvax!mcdphx!xroads![e-mail]  (Jerry Rightnour)
Organization: Crossroads, Phoenix, AZ 85046
Subject: Mir Lottery questions
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It would be a lot easier to believe in the Mir Lottery if someone
would answer many of the unanswered questions surrounding it.

How is it being financed?  Apparently the revenue from phone
calls can only be expected to pay a small portion of the
expenses.  Who is putting up the rest?  Is this envisioned as an
investment that will pay back a return in time, or just a
philanthropic giveaway, possibly to stir up American interest in
space travel or to embarrass NASA?

What is Space Travel Services Corp?  Is it intended to be an
ongoing business?  What do they expect to market?  Additional Mir
trips?  This is an extremely expensive way to introduce a
business with such a limited market.

Why are the principals allowing these questions to go unanswered?
If it is for real, I would think they would be anxious to dispel
any questions concerning the legitimacy of the enterprise.

Personal endorsements from netters who know the principals are
reassuring, but they don't dispel skepticism when the overall
proposal just don't make sense.  If I am missing information I
need to understand this, I would be most happy to be informed.  I
would like to believe in this, and will certainly enter if shown
that it is for real, but for now I remain a skeptic.

Jerry Rightnour   [e-mail]
                  [e-mail]
--
\  /  C r o s s r o a d s  C o m m u n i c a t i o n s
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Date: 30 Dec 90 23:29:35 GMT
From: uvaarpa!murdoch!faraday.clas.Virginia.EDU![e-mail]  (Laura Hayes Burchard)
Organization: University of Virginia
Subject: Re: orbiting Earth in the stratosphere by balloon.
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In article <[e-mail]> [e-mail] writes:
>There was an item in an aerospace magazine last October about a planned nonstop
>flight around the world in a high altitude balloon.  The international crew in
>the pressurized gondola was to have included a Soviet cosmonaut.  Cruising
>altitude was to be at 35,000 ft, or higher in the jet stream.  The trip was
>supposed to begin and end in Akron, Ohio.  It was to have embarked some time in
>November with a duration of perhaps 21 days expected.  I have seen nothing
>further on this and do not know whether they ever left Akron.  Does anyone know
>the latest status of this interesting project?


I saw a documentary on this on ESPN a couple of days ago.  Apparently they
are behind schedule but on course for a flight in the new year.  The most
vital element - a test flight of their revolutionary and totally untried
double balloon system - went off perfectly.

This is one bizarre looking balloon, though.

Laura Burchard


--
Laura Burchard    [e-mail]    [e-mail]
October 3:  After 45 bitter years of separation, East and West Germany
unite to form a single nation, chastened by the past, hopeful for the future.
October 4:  Germany invades Poland.      --Dave Barry's Year in Review 1990

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Date: 31 Dec 90 02:26:33 GMT
From: att!pacbell.com!mips!spool2.mu.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!news.funet.fi!tukki.jyu.fi!jyu.fi![e-mail]  (Otto J. Makela)
Organization: Turing Police, Criminal AI section
Subject: Re: space news from Nov 5 AW&ST
References: <[e-mail]>, <[e-mail]>
Sender: [e-mail]
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In article <[e-mail]> [e-mail] (Tim McDaniel) writes:
   In article <[e-mail]> [e-mail] (Nick Szabo) writes:
      >Pegasus development costs (to first launch): $50 million
      >Shuttle development costs (to first launch): $25 billion

   In article <[e-mail]> [e-mail] (Gary Coffman) writes:
      So your original article was wrong. Instead of 2% the development cost
      of the shuttle it's 0.02% the cost of the shuttle. Now that's a better
      deal.

   50e6/25e9 is 0.002, or 0.2%.  I can e-mail "ic", a good UNIX-based
   calculator, to anyone who wants it, like these two people.

And here I was thinking of billion = 1e12 (T), as it is in other languages
than english.  I really should try to remember that Anglosaxons can't count :-)
(1e9 (G) = "milliard" in most other languages)

Say, I could use that ic also...
--
   /* * * Otto J. Makela <[e-mail]> * * * * * * * * * * * * * * * * * * */
  /* Phone: [phone], BBS: [phone] (CCITT, Bell 24/12/300) */
 /* Mail: Kauppakatu 1 B 18, SF-40100 Jyvaskyla, Finland, EUROPE         */
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Date: 31 Dec 90 03:28:04 GMT
From: att!emory!ogicse![e-mail]  (M. Edward Borasky)
Organization: Oregon Graduate Institute (formerly OGC), Beaverton, OR
Subject: Re: You can help clear cloud over MIR SWEERSTAKES.
References: <[e-mail]>, <[e-mail]>, <[e-mail]>
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In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>
>Temper. Temper. If this lottery really results in an ordinary American
>civilian actually going to Mir, the attendant publicity could result
>in the biggest boost to the American space program since Sputnik.
Oh, the END justifies the MEANS, eh?

Look, I'm as big a believer in space exploration (I used to work at
Goddard) as anybody.  I'm just as sick at the budget cuts (that's why
I LEFT Goddard) as anybody.  But please don't justify a ripoff by say-
ing the publicity will be good for the space program.  Space exploration
will have to sell itself and its own benefits, just as anything else
has to, in this age of scarce resources.  I happen also to believe that
there should be a network of Cray-2-class and Intel Touchstone-class
supercomputers so that EVERY UNDERGRADUATE at every state university
in the USA can have access to a supercomputer, but if some jerk tells
me that I can buy a $10 ticket along with lots of other people and that
the winner can have 1000 hours of time on the machine and the other guys
can't, then I'm going to yell just as loud about it.  That's NOT the
way we do science here in the USA!
>Frankly I don't care if the organizers make a mint or lose their
>shirts. I don't care if a lot of people waste $3 calling the number.
Frankly, I DO care.  And my point is that I think OTHERS should care
as well.
>I do care that this may be the last chance in a long time to wake up
>the American public to the stretch out, phase out, give up, being planned
>for the US space program while the Soviet program plods ahead with a
>real permanent presence in space.
I don't think you have to worry about the American public knowing about
NASA's problems, either in budgets or in how they spend those budgets.
NASA's budgets and the American space program are beleaguered precisely
BECAUSE that is what the American public wants -- it's the message they
have sent AGAIN and AGAIN through their elected representatives.  We
the people have decided that affordable health care, the environment,
a STRONG MILITARY, etc., are more important to us than what is on the
surface of the moons of Neptune.  I don't like it, I don't agree with
it, but that's just the way it is.  I remember a time not too long ago
when NASA was telling us that the Shuttle would make it possible for
ordinary Americans -- poets, artists, even, presumably, bus drivers,
to go into space.  Well, there was Senator Jake Garn, who survived, and
Christa McAuliffe, who didn't, and now there is a Japanese journalist
on a Soviet spacecraft.  I don't particularly even want to go into
space myself any more; I did when I was 16, but I suppose everybody
does at that age.

So if YOU want to see NASA's budget increased, write to YOUR congress-
man and senators -- or Dan "no rocket scientist" Quayle.  And don't
support ripoffs -- in the long run they do only damage.

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Date: 30 Dec 90 10:07:36 GMT
From: prometheus![e-mail]  (Paul M. Koloc)
Organization: Prometheus II, Ltd.
Subject: Re: Interstellar travel
References: <[e-mail]>, <[e-mail]>, <[e-mail]>
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In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (John McCarthy) writes:
>>Here's a method of interstellar travel based entirely on present science
>>and technology...
>>The idea is to use an ordinary fission reactor to generate electricity,
>>and use the electricity to expel a working fluid at an appropriate
>>velocity...

>I'm not sure I would call this entirely based on current technology, since
>it puts very heavy demands on the reactor technology, given the weight
>constraints.  (Any electrical-propulsion system suffers badly on this,
>in fact, since electricity is a very cumbersome way of handling large
>amounts of power.  A chemical rocket engine the size of a large man has
>the same useful power output as the very biggest power plants.)

This is true.  However, perhaps tomorrow's technology will include an
compact, extremely high efficiency inductive MHD generators.  To use this
technique the temperature of the energized plasma must GREATLY exceed
the operating temperature of any of today's thermoelectric convertors.
The power density of a PLASMAK(tm) aneutronic fusion burner will be able
to heat the liquid dense fluid blanket to extraordinary temperatures
(by today's standards).  The fusion heated blanket could be then
magnetically contained only long enough to do piping into the energy
convertor, through an inductive MHD  (IMHD) chamber.  Since such a system
will utilize initial blanket temperatures far in excess of today's
chemical propulsion systems, its conversion efficiency will greatly
exceed, and the overall conversion power density would about equal that
of the today's big chemical rocket motors.  The BIG saving is in weight
(mass), since the energy density of fusion FUEL is several million times
that of chemical systems.  That makes for a huge fuel inventory (mass)
difference.  Any second order differences in the mass trade off would
be overcome just getting the chemical engines to lift off thrust from
a cold start.  As pointed out above, fission systems (also worse: fusion
tokamaks) are not power/mass efficient.  Unfortunately, the more elegant
fusion approach may get you to the stars, but you will arrive there in a
frozen state.

                          I'm hungry
            Ah!  There is an old fusion burner ahead.
             Let's "Stop and Pop" a couple of Frozen ones
                       into the microwave
+---------------------------------------------------------+**********+
|                                                         +Commercial*
| Paul M. Koloc, President          [phone]        ***FUSION***
| Prometheus II, Ltd.; College Park, MD 20740-0222        ***in the***
| mimsy!prometheus!pmk; [e-mail]               **Nineties**
+---------------------------------------------------------************

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Date: 31 Dec 90 00:28:20 GMT
From: agate!shelby!neon!Neon![e-mail]  (John McCarthy)
Organization: /u/jmc/.organization
Subject: Re: Interstellar travel
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This is actually a reply to the following quotation from Henry Spencer,
which somewhow I missed.

   >In article <[e-mail]> [e-mail] (John McCarthy) writes:
   >>Here's a method of interstellar travel based entirely on present science
   >>and technology...
   >>The idea is to use an ordinary fission reactor to generate electricity,
   >>and use the electricity to expel a working fluid at an appropriate
   >>velocity...

   >I'm not sure I would call this entirely based on current technology, since
   >it puts very heavy demands on the reactor technology, given the weight
   >constraints.  (Any electrical-propulsion system suffers badly on this,
   >in fact, since electricity is a very cumbersome way of handling large
   >amounts of power.  A chemical rocket engine the size of a large man has
   >the same useful power output as the very biggest power plants.)

The formula for the time taken for a journey of distance  s  is

    t = 2.1 p^(- 1/3) s^(2/3).

Here  p  is the power handled per unit mass by the system, and it's
what Henry Spencer is grumbling about.  However, since it enters to
the - 1/3 power, if it's too low by a factor of 1000 compared to
a chemical rocket, this only means that the journey takes 10 times
as long.  Since the journeys are multi-generation anyway, the
qualitative conclusion that interstellar colonization is feasible
is still supported.

Naturally, it would be nice to have fission (or fusion) power plants
with the power density of chemical rockets.  By the way, the main
idea of the above proposal is to allow using a working fluid
distinct from the debris of the power generation.

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

Date: 29 Dec 90 20:12:19 GMT
From: [e-mail]  (Kevin William Ryan)
Subject: Re: Interstellar travel

From: [e-mail] (Paul Dietz)
>In article <[e-mail]>
[e-mail] (Henr
>y Spencer) writes:
>>
>>Antimatter is probably easier than fusion, unless some seriously oddball
>>approach to fusion gives us a practical way to use the high-order reactions
>>with minimum neutron emission, or we find some way to reflect fast neutrons
>>efficiently.  Even the D-He3 reaction produces enough neutrons to be
>>troublesome [...]
>
> [...]
>
>That aside, the very low efficiency of antimatter production (.1%,
>maybe, if we're real good) is a real constraint.  A low performance
>inertial fusion rocket might have a power output in the gigawatts.
>You'd need terawatts of input power (expensive power, in the form of
>electricity) to make enough antimatter to achieve the same performance
>for extended periods.  For really low performance, why not just
>use fission-thermal rockets?

    As I recall, reading Robert Forwards books, the extremely low
production efficiency seen so far is a result of the generation process
- where the antimatter is produced in research accelerators. There the
emphasis is on exact quantitation, and the machinery is far from
optimized for the generation process. Antimatter generators designed
specifically for the job should be much more efficient. I don't have
figures on hand, but I think that the compact energy available from
antimatter argues strongly in its favor.

                                                    kwr

Internet: [e-mail]

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End of SPACE Digest V13 #015
*******************