Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_4/V13_493.TXT

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Subject: SPACE Digest V13 #493

SPACE Digest                                     Volume 13 : Issue 493

Today's Topics:
              Re: Galileo works?
    Re: "more appropriate questions" (was: Why the space station?)
                 Solar Power
              Re: Why the space station?
           What about ozone as an oxidant?
              Re: Galileo works?
  Re: Saturn V and Design Reuse: Saturn VI? (RBB: Real Big Booster)
            SPACE Digest V13 #474
             Re: Another Galileo Sulution

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

Date: 2 May 91 23:34:39 GMT
From: dog.ee.lbl.gov!hellgate.utah.edu!caen!uakari.primate.wisc.edu!samsung!rex!rouge![e-mail]  (Fraering Philip)
Subject: Re: Galileo works?

In article <[e-mail]> [e-mail] (Jose Pina Coelho) writes:

[I wrote:]
pg> I don't know, but maybe because the radio waves could become focused in
pg> such a way as to interfere with the spacecraft electronics. I don't know
pg> how much radio-frequency interference the circuits can take.

and Jose Pina Coelho wrote:

>They better be able to take a lot of it or they won't survive
>Jupiter's radiation belts (I mean, they are *strong* radiation
>fields, World War III would be peanuts arround Jupiter).

I think you're confusing different sorts and frequencies of
e-m radiation. And things work differntly at different frequencies.

--
Phil Fraering
[e-mail]
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: 2 May 91 19:30:07 GMT
From: newton.cs.jhu.edu![e-mail]  (Paul Callahan)
Subject: Re: "more appropriate questions" (was: Why the space station?)

In article <[e-mail]> [e-mail] (Nick Szabo) writes:
>>2. Why Space Station Freedom?
>
>If it isn't useful, and isn't really that entertaining (despite the
>astronauts), it has to have some very good PR.  Snappy names are key.
>Even most of the engineers on the project realize the ridiculous
>irrelevence between the name to the project, and have taken to calling
>it "Fred".

I always assumed the name was chosen to add a charming Orwellian touch to
the whole enterprise.  After all, the main result of such an undertaking will
probably be to limit the "freedom" of those who want to do serious space
exploration.

From a more optimistic perspective, I believe that a lot of research fundamental
to future space travel can be done without leaving this planet and without
dealing with NASA at all.  Automation is still getting better and better,
primarily because it has uses other than space travel.  Maybe by the time the
world wakes up and decides it's time to seriously look into, say, mining the
asteroid belt, we will have enough automated machinery for the job that the
notion of setting up a human colony will seem dangerous and ridiculous.

I have nothing against humans in space, but I think that a huge industrial
infrastructure in the near solar system will be necessary to make
regular space-travel feasible (as distinguished from dare-devil stunts like
the Apollo program).  There is no reason to believe that space industry,
including such things as mines and factories, will need any humans on the
spot at all, assuming sufficiently sophisticated computers controlling
it all.

The goal of a fully autonomous factory (complete with the ability to
fix errors that were not explicitly predicted) is a good deal less
ambitious than a lot of AI goals.  There are people interested in these
kinds of problems, they are not all being funded by the government, and
they can work without the cost of expensive boosters or the risk of
having their equipment blow up.  It is clear from the problems that occur,
for instance, with antenna deployment on satellites that we have not reached
a very high level of system reliability, but this is far from a proof that it is
impossible.

In my opinion, if the human race ever does become a space-faring civilization,
the late 20th century will not be seen as a long dry-spell, but rather as
a period when some of the most essential background research was being
performed (on Earth!).  This is not a substitute for a sensible space program,
of course, but it's at least a cheerful note to add to this otherwise
depressing issue.

--
Paul Callahan
[e-mail]

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

Date: 3 May 91 01:29:01 GMT
From: mcsun!ukc!slxsys!ibmpcug!demon![e-mail]  (Ian Stirling)
Subject: Solar Power

All of the thermal solar power schemes I have seen use moving
mirrors,moving mirrors are expensive,Why not use stationary mirrors?
This idea would work best in high or low latitudes.


###\/<mirrors,focused on one point.
####\/------------------------ O<-sun
#####\/\___       ^rays from /
######\/   \___       sun> /
#######\|      \___      /
########\|         \___/
#########\|          / \___
####HILL##\|        /    ^ \___
###########\\     /  reflected \___
############\\  /           rays>  \___
#############\\------------------------\-O <focus
##############\\
###############\\

I think that looks ok,but it's the best I can do with ASCII.
The mirrors aranged with various slopes on the hillside bring the sun
to focus on a point,this point moves as the sun moves,meaning a
moving energy converter is needed,perhaps this could be a rail guided
vehichle on a close-by hill?This probably would only provide power
simply for 6Hrs a day.Maybe this could be altered to work nearer the
equator.
Anyone see any problems with this?(I have no done any calculation to
see anything wrong).
Mail to either                            |PLEASE do not send large
[e-mail]|(>20K)mail messages as
[e-mail]                   |I get charged for them.
[e-mail]                           |
one of these may work                     |

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

Date: 5 May 91 19:25:24 GMT
From: agate!headcrash.Berkeley.EDU![e-mail]  (Frank Crary)
Subject: Re: Why the space station?

In article <[e-mail]> [e-mail] (John A. Weeks III) writes:
>I really do not understand this argument.  How can Fred help us get to
>the moon?  The only help that I think Fred might be is as a rest stop
>on the way.  You are not going to be building moon ships in orbit (Fred
>is not going to be an assembly hanger), and I doubt that you are going to
>see Fred used as a gas station.  As far as testing the crew modules, you

NASA thinks about things in an unusual way... In the late 1960's and
early 1970's they thought: "We want a lunar base, and manned Mars missions.
What can we do to make this cheap and reasonable?" The answer they came
to was that a space station, supporting in-orbit tugs/shuttles (e.g.
specialized zero-g transports) would drastically lower the cost of a lunar
base. They also decided that a lunar base could return Lunar oxygen to
the orbital station (a debatable point). This oxygen could go to supporting
a Mars mission. Finally they concluded that an orbital station would need
a re-usable ground-to-orbit craft to build/support the station.

From these conclusions, NASA went to Congress and President Nixon. Neither
wanted to pay for the whole package... So NASA thought "Well, the first
thing we will need is the reusable Earth-to-orbit transport. Lets get
that done first." So NASA focused on the Space Shuttle (without really
remembering why they needed it). They got Congress to pay for it,
but the final product is not well suited for its origional purpose:
building and supporting a space station.

Now, having the shuttle, NASA wants to proceed with their origional plan:
The "Next Logical Step" is a space station. So NASA, again forgeting WHY
it wants the station, is cutting whatever deals with Congress and/or
the station users that are required to get the station. This results
in a design that does not fit into the "grand plan" any better that
the shuttle does.

                   Frank Crary
                   UC Berkeley

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

Date:         Fri, 03 May 91 21:41:23 EDT
From: Richard Ristow <[e-mail]>
Subject:      What about ozone as an oxidant?

There's been some discussion about alternative propellant chemistry.  Does
anybody know the current thinking on using ozone as the oxidant?  I haven't
kept current (!), but back in 1957 Willy Ley wrote,

   ... a tank that holds 6 pounds of liquid oxygen holds almost 10 pounds
   of liquid ozone  ... [and] calculation shows that a fuel burned with
   ozone would produce an exhaust velocity some 10 percent higher than
   ... the same fuel burned with oxygen.  [Ozone is dangerously unstable,
   but there may be a way to counteract this;]  all one can say at the
   moment is that the other characteristics of liquid ozone are worth
   some effort. (1)

Now, some comments.  First, the '10% increase in exhaust velocity' has to be
an average;  ozone will contribute a fixed amount of energy per weight of
oxygen consumed.  It will contribute a smaller increment in a higher-energy
propellant combination (the extra energy adds a fixed amount to the SQUARE
of the exhaust velocity, and is a smaller absolute, not just relative,
addition to a larger exhaust velocity), but a larger amount when the
greater proportion of the propellant weight is oxygen.  (Actually, since
the two changes are in opposite directions as one moves from hydrcarbons
to hydrogen as fuel, they may roughly cancel.)

Higher density -- smaller tanks -- is always valuable, but of relatively
low importance with hydrogen as fuel, as the tankage is so dominated by
the hydrogen already.  On the other hand, while reducing the size of first-
stage tanks (and so dry weight) is always useful, it's precisely in the first
stage that accepting some extra weight to avoid exotic techniques pays best.

There ought to be a place for ozone, however, where performance is crucial.
Obvious cases are upper stages, where ozone ought to increase payload or
performance of a given booster significantly;  and SSTO, hydrogen-fueled
or dual-stage, which are at the edge of the performance envelope at best
With a large launch market to amortize the cost of making them work,
hydrocarbon-ozone (perhaps propane-ozone) first stages should be significantly
smaller, and so cheaper, than equivalent oxygen-hydrocarbon stages.

All high-energy oxidants (including LOx) are hard to manage, and ozone
would be no exception.  Spontaneous decomposition, especially rapid, is
a hazard most others do not present.  In other respects ozone should be
more benign than, say, flourine-containing oxidants.  It is toxic, but
the toxicity can be ended by reconverting it to oxygen.  The exhaust from
an ozone rocket should be similar to that from a rocket burning the same
fuel with oxygen.  Most launch accidents end in fires that consume the
large bulk of the propellants.  Routine boil-off could probably be handled
by catalytic converters.  Large-scale spills during transport and storage
would seem the worst hazard.

Ley's statement that "the other properies of ozone could use some work"
seems to stand.  What thinking and work has been done since?

(1) Ley, Willy, *Rockets, Missiles and Space Travel:  Revised Edition*,
    The Viking Press, New York, 1957, pp. 307-308.

-------------------------------------------------------------------------
Richard Ristow       [e-mail]       (BROWNVM on BITNET)

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

Date: 3 May 91 17:02:40 GMT
From: dog.ee.lbl.gov!hellgate.utah.edu!caen!uakari.primate.wisc.edu!samsung!rex!rouge![e-mail]  (Fraering Philip)
Subject: Re: Galileo works?

In article <[e-mail]> [e-mail] (Magnus Olsson) writes:

>It's even worse: He's confusing radio waves with ionizing radiation. The
>radiation belts of Jupiter, like the earth's Van Allen belts, contain
>a lot of electrically charged particles - electrons, protons etc. Making
>a piece of harware resistant to ionizing radiation like this is a totally
>different thing from making it resistant to radio frequency interference.

 Yes, but I couldn't tell whether he was talking about _that_ or
the synchotron radiation caused by said particles.

More and more people are throwing around words like "electromagnetic
fields" or "electromagnetic radiation," as in the recent 60 minutes
spot on "stray voltage" (which they never explained in physical terms)
without realizing that the terms encompass everything from gamma rays and
x-rays through visible light (yes, you spend your whole day bathed in
e-m radiation!) to microwaves and radio waves.

--
Phil Fraering
[e-mail]
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: 4 May 91 02:39:35 GMT
From: news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Saturn V and Design Reuse: Saturn VI? (RBB: Real Big Booster)

In article <[e-mail]> [e-mail] (/dev/null) writes:
>No, life DOES NOT have a value that can be estimated.  The LEGAL
>COSTS of a trial does not equate to a human life.

Life may not have a value that can be estimated, in some theoretical sense,
but for practical planning one *must* assign it some specific value.  There
is *NO LIMIT* to how much you can spend making the hardware a little bit
safer.  If you want to get anything done, sooner or later you have to say
"enough".  Whether you like it or not, when you say that, you have set the
value you put on life.

"For perfect safety... sit on a fence and watch the birds." --Wilbur Wright

--
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  [e-mail]  utzoo!henry

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

ReSent-Message-ID: <[e-mail]>
Resent-Date:  Wed, 01 May 91 13:49:22 EDT
Resent-From: Tommy Mac <[e-mail]>
Resent-To: [e-mail]
Date:         Sun, 28 Apr 91 02:02:40 EDT
Reply-To: [e-mail]
From: [e-mail]
Subject:      SPACE Digest V13 #474
Comments: To: [e-mail]
To: david polito <[e-mail]>, Tom McWilliams <[e-mail]>

>Subject: Orbital Elements of Saturnian system

>Does anyone have a table of orbital elements for the moons of Saturn?

>I would love to have the elements for all 17, but I doubt they've been
>computed yet.

>I need: The longitude of the perigee, longitude of the ascending node, and the
>mass. (All geocentric)
            ^^^^^^^^^^
I think he meant "chronocentric"
Acknowledge-To: <18084TM@MSU>

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

Date: 1 May 91 17:24:53 GMT
From: mintaka!think.com!rpi!uupsi!pbs.org![e-mail]
Subject: Re: Another Galileo Sulution

In article <[e-mail]>, [e-mail] writes:
> Although putting a communications relay satellite in orbit around Jupiter
> is a good idea, one must remember that Jupiter's position changes during
> it's year, sometimes making it even further away from Galileo than Earth
> would be.
>
> Another possibility would be to launch a relay station into a trajectory
> aimed directly at Galileo, thus the relative position between it and
> Galileo remain unchanged. Relay-1 can then take on the task of tracking
> Earth. Later, as Relay-1 gets far enough away from Earth, Relay-2 can
> be launched to follow behind Relay-1 making it theoretically possible to
> follow Galileo as long as we keep launching relay probes.

While this might work, it is a more complicated and costly solution than
necessary.  I don't believe the concern is so much about loosing data while in
transit to Jupiter, but once Galileo arrives there and goes into orbit.  The
easiest way to solve this concern would be to have a relay comsat ready and
waiting in orbit there, as was already suggested.  I believe JPL may
even be prepared to give up some of the later transit data.  The main mission
is after all at Jupiter.  It is irrelevant how many times that planet may be
father away from Galileo than Galileo is from Earth during the transit stage,
since the planned for mission doesn't really start until Galileo is in orbit
around Jupiter.

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

End of SPACE Digest V13 #493
*******************