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Date: Mon,  6 May 91 02:03:47 -0400 (EDT)
Subject: SPACE Digest V13 #491

SPACE Digest                                     Volume 13 : Issue 491

Today's Topics:
			Re: Terraforming Venus
			SPACE Digest V13 #476
	     Re: Launch Advisory for 04/22/91 (Forwarded)
	       Re: Transportation Tethers (Beanstalks)
  Astronaut Mary Cleave joins NASA environmental project (Forwarded)
			 Re: Laser launchers

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

Date: 2 May 91 00:35:55 GMT
From: wuarchive!rex!rouge!dlbres10@decwrl.dec.com  (Fraering Philip)
Subject: Re: Terraforming Venus

In article <1991May1.173813.17587@en.ecn.purdue.edu>
irvine@en.ecn.purdue.edu (/dev/null) writes: 

>I think Venus might be a bit easier to Terraform than Mars.  With
>Mars, you have to find a way to add air pressure, with Venus, you have
>to find a way to decrease it (never minding the fact that both are
>poisonous right now ... :) )

>This could be an opportunity to try out bio-technology.  Send a group of
>microbes that "eat" sulphur in sulphuric acid, cleaning the air.

>I know that there are lots of toxins other than H2SO4, but similar approaches
>could be used.

>Mars may be much more tough than Venus.

[Note: I did not change the content of the above, but I used the 
re-fill command of emacs to put linefeeds in the right places]

Anyway, from a physics point of view, terraforming Venus is much less
trivial than terraforming Mars. Even the early probes to Mars showed
that in the past there was an earthlike enviornment, with could
possibly be duplicated today. However, "reducing the atmospheric
pressure" of Venus involves reducing the atmosphere, which is a
non-trivial task. So might giving the planet a day-night cycle; and
the solution better be different than spinning it up. The energy
required for that would also be sufficient to send a _lot_ of people
on long interstellar trips on some very large ships.  Anyway, this is
all from a physics point of view, and therefore probably not important
compared to all the experts in nanotechnology and direct mass/energy
conversion (I think there's a department in all of this stuff over at
Miskatonic U.)

>+-----------------------------------------------------------------------+
>| Society of Philosophers, Luminaries,          | Brent L. Irvine       | 
>| and Other Professional Thinking People.....   | Only my own ramblings |
>+-----------------------------------------------------------------------+

Were physics courses required in order to join this group?

--
Phil Fraering
dlbres10@pc.usl.edu
Joke going around: "How many country music singers does it take to
change a light bulb? Four. One to change the bulb, and three to sing
about the old one."

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

Date: Thu, 2 May 91 13:15:56 EDT
From: johns@calvin.ee.cornell.edu (John Sahr)
Subject: SPACE Digest V13 #476


Tommy Mac wrote:
   Subject: Laser Launchers (summary).

   Dave wrote:
[somebody else wrote:]
   >> Get an ice cube (well, a big ice cube).  Hit it on one end with a
   >> laser.  The top millimeter or so undergoes a process sometimes
   >> called Laser Induced Detonation.  It more or less explodes ... []

   So in other words - We'd have a steam-powered rocket!

   So much for blasting the Satrun V for being 'old' technology  ;-}

Actually a steam-powered rocket engine is newer technology than the
Saturn.  Harken back, if you will, to the mid 1970's, when Evel
Knievel attempted to jump the Snake River Canyon with a steam-powered
"motorcycle."  The rocket worked just fine; unfortunately the
parachute deployed at launch, slowing the works up a bit.

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

Date: 25 Apr 91 04:49:04 GMT
From: unisoft!fai!sequent!crg5!szabo@ucbvax.Berkeley.EDU  (Nick Szabo)
Subject: Re: Launch Advisory for 04/22/91 (Forwarded)

>      The launch of Joust 1, a commercial suborbital rocket 
>carrying 10 materials and biotechnology experiments....

I would like to point this out and congratulate NASA and OSC for
an example of good, efficient, and effective microgravity studies.   
Similar studies are being done in Japan and Europe; there is intense 
competition to gain the high ground in the potentially lucrative fields 
of microgravity and vacuum manufacturing.  I urge NASA to continue and 
grow this kind of support for microgravity science and materials 
processing efforts.


-- 
Nick Szabo				szabo@sequent.com
"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 05:43:07 GMT
From: unisoft!fai!sequent!crg5!szabo@ucbvax.Berkeley.EDU  (Nick Szabo)
Subject: Re: Transportation Tethers (Beanstalks)

In article <1022@igor.Rational.COM> wab@rutabaga.Rational.COM (Bill Baker) writes:
>...you seem to be saying that Kevlar has the requisite tensile
>strength.  

Correct.  Put enough of it in parallel, put a big enough asteroid
on the other side to balance the mass, and we have it.  Of course,
the economics and technology of manufacturing such large quantities
of this material from asteroids or comets are not even close to being 
in place.  Thus, progress in space manufacturing, asteroid/comet astronomy, 
and/or tensile strength/mass ratios is needed to bring us to a point where 
beanstalks are affordable.  At that point GEO tethers offer, by far and 
away, the cheapest way for people to leave earth's gravity well -- the 
potential for true migration.  

None of this research is "fundamental".  The progress could come 
from all three, two, or just one of these directions and be 
sufficient.  The progress in each field relies heavily on government 
financial support and academic attention being payed to these fields, 
instead of fields like chem rockets that government-sponsored
programs have researched to death, and where research is inefficiently 
and unfairly competing with private R&D.  Tethers are an example of 
the long-term type of research that truly is the responsibility of 
government labs, since the potential advance is very large (over four 
orders of magnitude) but too long-term to be contemplated by private 
industry at this time.


>I would think that you could "bootstrap" a
>space-based energy system once you had the beanstalk established.

Indeed.  Not only this, but the theoretical energy requirement is
zero, as long as we are moving as much mass down as we are up -- either
with dummy mass or by exporting space manufactured products to earth.  
Consider the typical office building elevator.  As long as people are 
going up and down at the same time, it takes very little energy to run 
the elevator.  

With some fancy orbital mechanics and scheduling, this principle can 
also be applied to mass-anchored rotating tethers throughout the solar 
system.


-- 
Nick Szabo				szabo@sequent.com
"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 19:22:22 GMT
From: usenet@ames.arc.nasa.gov  (Peter E. Yee)
Subject: Astronaut Mary Cleave joins NASA environmental project (Forwarded)

Ed Campion
Headquarters, Washington, D.C.                             May 2, 1991
(Phone:  202/453-1134)

Barbara Schwartz 
Johnson Space Center, Houston
(Phone:  713/483-5111)


RELEASE:  91-68

ASTRONAUT MARY CLEAVE JOINS NASA ENVIRONMENTAL PROJECT

	Astronaut Mary L. Cleave, Ph.D., P.E., will become Deputy 
Project Manager for SeaWiFS, Sea Viewing Wide Field Sensors, at 
the NASA Goddard Spaceflight Center, Greenbelt, Md., beginning May 
19, 1991.

	SeaWiFS is a joint NASA and commercial project to learn about 
the biological mass in the ocean by studying the chlorophyll 
content to determine how much plankton is produced.  Information 
on whether plants in the ocean can absorb enough carbon dioxide 
and produce necessary oxygen to prevent global warming will be one 
focal point for this research.  An eight-channel data collection 
camera will be launched using a Pegasus booster.

	"Earth observations experience I gained as an astronaut will 
be beneficial to me in this new capacity.  I'm eager to have this 
opportunity to make a contribution to environmental research," 
Cleave said.

	"We are sorry to see Mary leave JSC (Johnson Space Center) but 
are happy that she will stay in the NASA family.  We wish her success 
in her new job," Director of Flight Crew Operations Donald R. Puddy 
said.

	Cleave has flown on two Space Shuttle missions.  During STS-
61B, three telecommunication satellites were deployed and two 6-
hour "spacewalks" were conducted to demonstrate Space Station 
Freedom construction techniques.  Cleave controlled the Shuttle's 
robot arm to assist in these activities.  On STS-30, crew members 
successfully deployed the Magellan Venus-exploration spacecraft 
and performed numerous middeck experiments.

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

Date: 25 Apr 91 01:05:59 GMT
From: unisoft!fai!sequent!crg5!szabo@ucbvax.Berkeley.EDU  (Nick Szabo)
Subject: Re: Laser launchers

In article <2753@ke4zv.UUCP> gary@ke4zv.UUCP (Gary Coffman) writes:

>Well consider that for an electrically powered laser, conversion of
>primary fuel to electricity is, at best, 40% efficient.

This is significantly higher than the efficiency of converting that
same primary fuel to rocket fuel -- which is around 5-15% for fuels
that are reasonably efficient as rocket propellant.  Many rocket
fuels themselves require significant input of electric power.  


>Transmission,
>control, and application of the electrical energy is, at best, 80%
>efficient. And laser conversion is, at best, 10% efficient. 

8% better than the extra fuel needed to lift tank and
fuel in rockets, due to the fuel being on board.


>That's
>an overall efficiency of 3.2% right there.

Which is better than chemical rockets (1-2% starting with a 
primary fuel like refined oil).  


>[more inefficiency from blooming]

Eliminating blooming is a major problem that needs to be worked on 
by R&D.  In one regime -- using lasers to power suborbital regime 
payloads into orbit -- blooming is not a problem at all.  A 
paradigm shift needs to occur here for those stuck in the chem 
rocket paradigm -- an upper stage, especially one operating in 
vacuum, does not need to resemble in any way the lower stage.  It
is quite possible, perhaps even probable, that we will have a suborbital
regime consisting of chem rocket, laser (if blooming is solved), EML, 
gas gun, or airplane-slung tether, and a vacuum orbital regime consisting 
of laser or tethers.  The technologies we are discussing can be an imortant 
piece in a hybrid system, it is not necessary and perhaps not even 
desirable that they perform the entire task on their own.

The desirability of eliminating blooming and increasing laser efficiency
is the big reason we are talking about government R&D funding here, 
not funding for an operational system which is the role of industry.


>>  ....this tank and controlling this
>>  tank through flight is a major part of chem rocket launch costs
>>  and reliability problems.
>
>This is *the* advantage of the laser scheme. 

It is all the advantage it needs.  Storing massive amounts of 
volatile gas with the payload has produced unreliable transportation, 
from dirgibles to rockets.  Laser launch gets us out of that mode.


>I wasn't arguing that R&D engineering problems need to be solved so
>much as I was arguing that fundamental physical laws prevent the system 
>from being a practical, efficient, alternative to rockets.

What "fundamental law" says that blooming can't be solved?
The solution may require adaptive optics on the launch site, to
be sure.  In the end, it _may_ prove intractable.  Or it may not.
The whole point of doing R&D is to find out for sure.  By just
throwing our hands up we could throw away the best opportunity.
We don't have too many good opportunities to throw away.


>Railgun, coilgun, gasgun, whatever, all are technically feasible for
>small payloads that don't mind thousands of Gs. 

With some extra civil engineering there could also be low-G versions, 
including suborbital versions linked with tethers or space-based 
lasers that avoid blooming by operating in vacuum.  The other
90% of the payloads we launch into space are fairly easy to harden 
from the G forces, the military does this all the time for smart 
munitions.


>Tethers need to exceed the theoretical strength of materials limits by
>orders of magnitude to work. 

Kevlar can work today for most of the scenarios envisioned.  
The major problem is launch cost of the mass.  This can be brought
way down by (a) manufacturing the tethers in space, (b) producing
better tensile materials -- a very important and woefully underfunded
field of R&D, (c) bootstrapping larger tethers into orbit with smaller
tethers, or (d) a combination of the above.


>Again, a fundamental scientific breakthrough,
>not engineering R&D, needs to occur before tethers can become reality, if
>ever.

Materials strength is applied, not fundamental science.
The other problems are engineering.  Your rhetoric is way out
of whack with reality here.


>Science fiction is all well and good,
>but the best way we know to go
>up through the atmosphere is with wings and air breathing engines.

So far, you haven't come out in favor of any kind of new ideas.
Keep the rocket engineers at work, keep launch costs high, don't
rock the rocket.  This sort of short-sightedness in the last thing
needed in government R&D work, which by its very rationale is supposed
to be working on promising but difficult problems that are too long
term for private R&D.  In the twenties you could have, and perhaps would 
have, used these very same arguments against chem rockets.   "Goddard needs 
to take a refresher on elementary physics.  Everybody knows rockets can't 
operate in a vacuum" (paraphrase of New York Times...).  


-- 
Nick Szabo				szabo@sequent.com
"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.

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

End of SPACE Digest V13 #491
*******************