Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_0/V10_022.TXT

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Subject: SPACE Digest V10 #22

SPACE Digest                                      Volume 10 : Issue 22

Today's Topics:
         Re: Eugene Cernan talks for dollars
        Re: Voyager Pictures moved to another machine
      Re: Where the hell are electric-ion thrusters????
               Galileo Mission
            Re: Selling moon rocks
             Re: PHONE TREE ALERT
             Re: How is Voyager powered?
----------------------------------------------------------------------

Date: 29 Aug 89 17:23:13 GMT
From: cs.dal.ca!dal1![e-mail]
Subject: Re: Eugene Cernan talks for dollars

In article <[e-mail]>, [e-mail] (Steve Stein) writes:
> Astronaut Captain Eugene Cernan, the last man to walk on the moon,
> will be speaking at Acton-Boxboro (MA) Regional High School on
> Thursday, October 12 from 6:30-8:00 PM.  Tickets are $12 for an
> adult, $10 for children.  Proceeds will benefit the Acton
> Discovery Museums.
>
> There will be a reception following the talk at the Acton
> Science Discovery Museum.  A limited number of tickets are
> available for the reception at $35 apiece.

Whew, steep prices! I am not surprised to see these costs when
I realize it is for a "good cause".  However, Gene came and
spoke to my High School Graduation Class in rural Calgary back in 1980.
There was no charge.  As I recall, the main point he had
to say was that when one saw the earth as a globe in space (if you recall,
Apollo 17's return trajectory brought it between the earth and the sun giving
us the "whole earth" photo) one good not deny the possibility of God.
Thankfully, he didn't dwell on this too long and we saw some great slides of
the mission and had Gene's running commentary to boot.  All for free.

I wonder if I would have paid to go to my grad?

Peter J. Russell
Bitnet: [e-mail]    or   [e-mail]
"Just as Hank Williams is to Neil Armstrong, baby you were meant for me"
    -I forgot who wrote this lyric, so sue me!

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

Date: 29 Aug 89 15:58:30 GMT
From: jarvis.csri.toronto.edu!utgpu!attcan!ncrcan![e-mail]  (Tim Nelson)
Subject: Re: Voyager Pictures moved to another machine

In article <[e-mail]> [e-mail] (Joe Dellinger) writes:
>
>    But all is not lost! The Voyager pictures which were formerly
>available on hanauma.stanford.edu are now available on
>
>mazama.stanford.edu (IP address 36.51.0.8)
>^^^^^^                                  ^

O.K. it is nice that you are moving the pictures, but are they available
anywhere to those of us who do not have access to FTP?
(perhaps anonymous uucp?)

==========
tim (nelson)         | uucp        ...!uunet!attcan!ncrcan!tim
ncr canada           | internet     [e-mail]
[phone] x442  | 6865 Century Ave, Mississauga, Ontario
==========
* Have a good day, and a great forever.

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

Date: 29 Aug 89 09:50:41 GMT
From: [e-mail]  (Terry Hancock)
Subject: Re: Where the hell are electric-ion thrusters????

In article <[e-mail]> [e-mail] (Neal Woodall) writes:
>In article <[e-mail]> [e-mail] (Terry Hancock) writes:
>
>>1> Depends on what you mean by "current technology" -- Ion
>>drives capable of doing this (with the appropriate power source),

>Now here is a subject that I have been meaning to bring up lately:
>ion thrusters. Where the hell are they? I understand that the US has
>had one tested and ready to go for over seven years now. I uses
>(mercury, cesium....I cannot remember which) as the reaction mass, and
>uses very high voltages to shoot the charged particles out at HIGH
>velocities....not much thrust, but an exceedingly high specific
>impulse (although I have read that some tested designs will produce
>about 50 lbs of thrust!).
>
    The most powerful Ion drive designed and built (to my
knowledge) is the 30-centimeter-diameter thruster developed at
NASA Lewis Research Center:

        NASA Lewis Research Center
        Cleveland, Ohio 44135

    It uses electrostatically accelerated mercury (cesium would
by bad news, by the way, it's both very reactive, and radioactive),
mercury will just give you heavy metal poisoning if you ingest it.

    50 lbs thrust is TOTAL B.S.  for an (electrostatic) ion drive,
certainly any one tested.  The specifications for the 30-cm are:

    Power Required:        2.75 kW
    Thrust:            0.135 N     (0.03 lb)
    Specific Impulse:    3000 lbf-s/lbm *
    Thruster Efficiency:    0.71
    Design Lifetime:    15,000 hours  (at full thrust)

    All specifications above are for full thrust.  The engine is
designed to be throttleable over a 4:1 range.  Multiple restarts are
no problem.  This design thruster has never been flown, although it
has undergone over 25,000 hours of vacuum chamber testing, with the
longest individual test lasting 4000 hours.  The data was current
in *1977*!  (i.e. this is NOT new technology).

    Oh, by the way, the J-2 engines used on the Saturn V second
and third stage had a specific impulse of 421 lbf-s/lbm, the F-1
a specific impulse of 263 lbf-s/lbm.  The ion drive is therefore
nearly an order of magnitude improvement.

>These things don't give very high accelerations, but they can run
>continuously for *months*.....thrust all the way! Accelerate for half the
>
    Quite correct.   The 30-cm drive was intended for use as
a primary propulsion system for interplanetary missions, particularly
in the inner solar system (where power can be supplied by solar
panels).  A nuclear-powered system for outer solar system applications
was suggested later.  I have already pointed out that appropriately
designed missions could use an inner solar system boost phase (using
solar panel power) to reach outer solar system targets.

>Didn't the US conduct a test called SERT a few years ago? (SERT = Space
>Electric Rocket Test) What was the outcome of the test??
>

    There were at least two vehicles: SERT I and SERT II.   Each was
used to test smaller, auxillary thrust systems (for attitude control
and stationkeeping of geosynchronous satellites).  This class of
thrusters, I have heard is in service on some European satellites.
SERT I and II were both quite successful, as is implied by the current
use of the systems they tested.

>Also, it seems that an electric-ion thruster is perfect for earth orbit
>transfer vehicles....you could move large masses with them, it would just
>take awhile.
>
    A very good idea, suggested in several space-colonization plans
that I have seen.  This is particularly useful for transferring bulk
cargo and non-perishables.  An "Ion Barge" like this would take two or
three months, travelling in a spiral orbit out to the moon, and a similar
time back.  With a fleet of such barges, a continual supply line could
be maintained with relatively little fuel use.
    The cost effectiveness of this depends also on the expense of
mercury (anyone know what Hg costs?), which ought to be fairly rare,
given its atomic weight (>Fe).  Probably cheaper to use kilos of Hg
than kilotonnes of hydrogen, though.


-------------------------------------------------------------------
* I would like to take this opportunity to rag on the engineer who
decided to cancel 1 lbf with 1 lbm and thereby arrive at seconds as
the unit of Specific Impulse.  I would also like to state, for those
who may have been confused by this @#&^$(!! that:

SPECIFIC IMPULSE IS *NOT* MEASURED IN UNITS OF *TIME* !!!!!!!

IT IS MEASURED IN *UNIT IMPULSE PER UNIT MASS*

OR EVEN *UNIT FORCE PER UNIT MASS-RATE-OF-FLOW*

OR EVEN *UNIT VELOCITY*    (All of these are equivalent).

    This causes problems particularly in converting to metric:

    1 second = 1 second  (same in both systems)
    1 lbf    = 4.46 N
    1 lbm    = 0.454 kg
    therefore:

    1 lbf-s/lbm = (4.46 N)(1 sec)/(0.454 kg) =  9.8 N-s/kg

    (actually the factor is exactly 1 gee in m/s^2 =~ 9.81)

    This made it extremely hard for me to understand rocket
propulsion, and I hope posting it will save someone else that
trouble.
-------------------------------------------------------------------




**************************
Terry Hancock
[e-mail]
**************************
**************************

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

Date: 29 Aug 89 15:00:34 GMT
From: cdp![e-mail]
Subject: Galileo Mission


The following is from the Christic Institute in Washington, D.C.

In October the next NASA shuttle will launch the Galileo mission
to Jupiter. Galileo will be powered by 50 pounds of plutonium.
Florida citizens already have protested that the mission's
radioactive power supply, if dispersed in an accident over the
skies of their state, could represent a serious threat to human
life and health. A new development, however, indicates that
Galileo could also carry the threat of biological contamination
of Jupiter.

Despite the severe conditions that exist on Jupiter, Planetary
Society President Carl Sagan and other space scientists have
speculated that life could exist on the giant planet. A paper
published in 1982 by Sagan with a group of other scientists
argued that future exploration may find ecological niches in the
Jovian atmosphere in which life could have evolved. Sagan's
paper concluded that "it seems judicious not to exclude
prematurely the possibility of biological contamination of
Jupiter by terrestrial microorganisms."

The United States and the Soviet Union are parties to a 1967
treaty requiring appropriate measures to prevent the harmful
contamination of outer space. In the past, NASA used high
temperatures to sterilize spacecraft, but has discontinued this
practice. A number of experts believe that despite the harsh
environment of outer space, a large colony of earth
microorganisms will survive the journey to Jupiter in the
interior of the spacecraft.

When Galileo reaches Jupiter, the spacecraft will launch a
smaller probe into the Jovian atmosphere. The probe's
unsterilized parachute will probably carry billions of live
microbes. Although conditions on Jupiter are very different from
earth, the planet's atmosphere includes clouds of liquid water at
temperatures at which earth microbes could survive and grow.
Even if the microbes could not survive on their own, the Sagan
paper suggests they could find a supportive environment inside
native organisms on the planet.

The probe will also carry small heating units powered by
plutonium. The radioactive material will be released when the
probe is crushed by the intense pressures of the Jovian
atmosphere.

Our first direct contact with Jupiter therefore will pollute the
planet with toxic plutonium and probably with alien biological
life.

The effects of this biological contamination are, of course,
impossible to predict. If life already exists on Jupiter, it
could be wiped out by the new microorganisms. On the other hand,
its evolutionary path might be permanently altered by the
introduction of alien life.

The danger of contamination raises profound moral and ethical
questions for our space program. The Galileo probe could have the
same effect on Jovian life as the European settlers who wiped out
entire native American communities with the smallpox virus.

The Christic Institute supports the exploration of the outer
planets, but urges NASA to postpone the Galileo mission until the
spacecraft is sterilized and its plutonium generators are
replaced by a safer alternative energy source. To learn more
about how you can help postpone the Galileo launch, please call
or write: The Christic Institute, Public Education Department,
1324 North Capitol Street, N.W., Washington, D.C. 20002. Our phone
number is [phone].

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

Date: Tue, 29 Aug 89 09:32:39 PDT
From: [e-mail]
X-Vmsmail-To: SPAN::AMES::"[e-mail]"
Subject: Re: Selling moon rocks


>From: eplrx7![e-mail]  (leipold)

>$1.  (As a matter of fact, I think allowing people to vote with their
>taxes would be a good idea.  Let Congress and the IRS make up forms so
>you can figure how much you owe, but then _you_ decide what percentage
>of what you owe goes to what part of government.  But I digress from
>sci.space...)

    Say, I had that idea too.  I've included it on my list of
justifications for Space Exploration.  About a hundred million income
tax returns are filed each year in this country, and it would only take
four million taxpayers paying an average of $3500 a year to fund space
exploration at its current level.  It's helpful to imagine that it's
already happening that way, so if someone gripes about having to pay
for Voyager, say, just tell them you paid for it and they can pay for
whatever they want.
    Another good statistic is that Americans spent $17G on entertainment
last year!  People who say space program money would be better spent on
<insert worthy cause here> should be asked to forgo movies, TV, music,
all forms of entertainment.  Nor, for that matter, should they be allowed
information or activity of any kind which is not conducive to the
furtherance of <insert worthy cause here>.
    One more thing is that most people overestimate the amount of
money spent on space exploration by 10 to 30 times!  A friend of mine
who teaches a beginner's astronomy class tells me that none of his students
has ever guessed as low as NASA's actual budget, which amounts to about
1% of the total.  Most students guess in the 10% to 30% range.  In a
similar vein, some people respond well to a "rearrangement of priorities"
argument, for example, the fact that about 30 Voyager missions could be done
for the price of the one B2 bomber developed so far is a real eye opener.
    Of course, there are always those incorrigibles who say that all
tax monies are taken by force and that we shouldn't even be arguing about
how to spend them but should just stop taxing.

----
"Drive Friendly or Die"            |         Dale M. Greer
  Proposed Texas License Plate Motto    |   Center for Space Sciences
              -- Anonymous    | University of Texas at Dallas
                    | UTSPAN::UTADNX::UTDSSA::GREER
The opinions are my own, and may or may not reflect those of my employer.

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

Date: 30 Aug 89 00:43:35 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: PHONE TREE ALERT

Baxter does not identify himself as representing the NSS in any way.
Are "innocent new NSS members" (nice ring to that) taught that any
advocacy announcement should be presumed of NSS origin unless a specific
disclaimer appears?  If so, why is it Baxter's responsibility to
disabuse them of the notion?  Finally, if Baxter urges phone support for
a bill the NSS likes, why pick that moment to post a "dissociation"
article, if not for the pursuit of petty politics?

I'm soiling my keyboard composing this.  Enough!  Down with stupid
political squabbling and up with space.
--
"We walked on the moon --    ((    Tom Neff
    you be polite"         ))     [e-mail]

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

Date: 30 Aug 89 02:11:58 GMT
From: calvin![e-mail]  (John Sahr)
Subject: Re: How is Voyager powered?

In article <[e-mail]> [e-mail] (Neal Woodall) writes:
>
>I read recently (in the Wall Street Journal maybe) about a company that
>wants to market a commercial RTG in the US! The design was their own, was
>based on decay of strontium 90, ...
[]
>[..]envision a larger version that will be about the size of a 5 gallon water
>container (like is used on a water cooler) and will produce about 300
>watts! Now we are talking about some useful power!
[]
>"Who would buy them", you ask? Well, how about survivalists, or people who
>live in very remote areas, or even people who are pissed off at the electric
>utilities (assuming the cost is not prohibitively high). I would buy one of
>the large ones if it were less than 2500 $ or so.....it would be a great way
>to power a VERY remote mountain retreat.

Why screw around with strontium?  If you are willing to pay $2500 for
300 watts, solar cells can do that right now, including the batteries
to get you through the night.  Several outfits will sell you kits
to do precisely this.

"P"TG's are in use in the Cascade Mountains*, to power remote weather data
gathering stations (rain, snow depth).  They have some solar cell power as
well, but people know what they are, and steal the panels.  Not too many
people know a "P"TG when they see it.  "P" is for propane, by the way.

*and probably elsewhere...

-john
--
John Sahr,     Dept. of Electrical Eng., Cornell University, Ithaca, NY 14853
johns@{alfven,calvin}.ee.cornell.edu,  {rochester,cmcl2}!cornell!calvin!johns
--When the dust settles, each B2 bomber will fund NSF for more than a year--

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

End of SPACE Digest V10 #22
*******************