Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v16_0/v16no021.txt

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Date: Fri,  8 Jan 93 05:27:02
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #021
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri,  8 Jan 93       Volume 16 : Issue 021

Today's Topics:
                  *** BUSSARD RAMSCOOP *** (3 msgs)
        Antimatter reality (was Re: *** BUSSARD RAMSCOOP ***)
                            averting doom
                DC-1 and the $23M NASA Toilet (2 msgs)
        HST Discovers Double Nucleus in Core of Active Galaxy
         Justification for the Space Program <long> (2 msgs)
New Cosmic Background Explorer photos released [NTE 93-1] (Forwarded)
                      Perseid storms 1993/1862?
                         Question about SETI
                      RTG's on the Lunar Module
                         russian solar sail?+
      Shuttle a research tool (was: Re: Let's be more specific)
Universities fly ozone research balloon from Texas to Florida [Release 93-8] (Forwarded).
        was: question about SETI, now: planets around pulsars?

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

Date: Fri, 8 Jan 1993 00:24:58 GMT
From: Dave Michelson <[e-mail]>
Subject: *** BUSSARD RAMSCOOP ***
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>
>Reality check right back at you:  plot human antimatter production capacity
>versus time.  Interesting graph, no?  Sure, it's limited right now... but
>it's growing fast.

This was talked about in a recent issue of Scientific American.  Really
neat stuff.

>
>If we mounted a major effort, we could probably be test-firing antimatter
>rocket engines within ten years.  There are *NO* fundamental barriers that
>anyone has been able to find.  It's purely a matter of scaling up and
>optimizing the hardware -- the existing accelerators are optimized for
>production of Nobel prizes, not bulk antimatter -- and solving assorted
>straightforward engineering problems of handling and storage.  The idea
>has been investigated in depth; no show-stoppers have appeared.
>
>A production setup the size of the Hanford works could make enough
>antimatter to open up the solar system.  Interstellar propulsion is
>harder.  Kilogram quantities are probably going to have to be made in
>space, not so much for handling reasons (although those aren't trivial)
>as because of the sheer amounts of *energy* needed.  It would be a huge
>project, but there's no fundamental problem; we could start designing
>hardware tomorrow if it were urgent enough.

Sounds good to me!

--
Dave Michelson
[e-mail]

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

Date: 8 Jan 1993 01:47:27 GMT
From: "Kevin W. Plaxco" <[e-mail]>
Subject: *** BUSSARD RAMSCOOP ***
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>If we mounted a major effort, we could probably be test-firing antimatter
>rocket engines within ten years.  There are *NO* fundamental barriers that
>anyone has been able to find.

Electron-positron annilation generates a couple of gamma ray photons.
As gama ray photons don't couple well with matter, it would be very
difficult to use this energy source to heat reaction mass.

Does proton-antiproton anniliation differ?

-Kevin

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

Date: 8 Jan 93 03:28:19 GMT
From: "Gregory N. Bond" <[e-mail]>
Subject: *** BUSSARD RAMSCOOP ***
Newsgroups: sci.space

>>>>> On Thursday, 7 Jan 1993 12:03:40 PST, Jon J Thaler <[e-mail]> said:
Jon> This is about 13 orders of magnitude larger than the total number of
Jon> antiprotons ever created and stored (about 10**14)

Well, nobody said it would be easy!

Current antiproton production is geared towards physics, not
rocketry.  It is probably possible to create antimatter more
efficiently if that is the primary goal. However the energy cost is
huge because conservation tells you that you only create antimatter
with at least E=mc^2 input energy.  Think of the antiprotons as very
high energy density batteries!

So, even assuming 100% conversion efficiency, 1kg of antimatter =
10^19 Joules, or about 300 years output from a 1GW coal or nuclear
power station, to produce. It will release twice this amount when
mixed with ordinary matter.

Now if we could generate antiprotons with better than 50% efficiency,
we have an inexhaustible energy supply......

Anyone have estimates on the realistic estimates on achievable
conversion efficiency?  10^4?

Greg.
--
Gregory Bond <[e-mail]> Burdett Buckeridge & Young Ltd Melbourne Australia
            Dizzy Gillespie: RIP.

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

Date: 8 Jan 93 00:40:16 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: Antimatter reality (was Re: *** BUSSARD RAMSCOOP ***)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
> In article <[e-mail]> Jon J Thaler <[e-mail]> writes:
>>> Kilogram quantities of antimatter are quite adequate for early interstellar
>>> probes, given modest vehicles... it looks plausible.
>>
>>A reality check:
>>This is about 13 orders of magnitude larger than the total number of
>>antiprotons ever created and stored (about 10**14)

A quick call to the Main Control Room disclosed that the largest
"p-bar stack" ever stored at Fermilab was 121 milliamps in the
Accumulator (1.21E12 antiprotons) on 7 January 1991.  I don't know if
CERN in Geneva has exceeded this, but if they have, it's not by much.
(The largest stack ever dumped by accident, in a power glitch, was 81
mA, by the way.)

As for Henry, most of what he says is true but you gotta take it with
a big grain of salt:

> Reality check right back at you:  plot human antimatter production capacity
> versus time.  Interesting graph, no?  Sure, it's limited right now... but
> it's growing fast.

I would have to look at antiproton production projections for the new
120-GeV Main Injector which we are planning to build.  But I wouldn't
say it's growing all that fast, especially since *nobody* is planning
to build any new antimatter sources outside Fermilab and CERN, any
time in the next decade or more.  These two labs will continue to
tinker with modest improvements in the existing sources.

The big demand for antiprotons-- to come up with fat negative
particles you can run backwards through the Tevatron and SPS
synchrotrons, and collide with protons-- has gone away.  Future
machines, such as the Superconducting Supercollider (how I hate that
name), the Large Hadron Collider, and the UNK lab, will have dual
rings circulating protons.  P-bars have proved to be just too much
hassle.  And outside of high-energy physics experiments, nobody can
afford them.

> If we mounted a major effort, we could probably be test-firing antimatter
> rocket engines within ten years.  There are *NO* fundamental barriers that
> anyone has been able to find.  It's purely a matter of scaling up and
> optimizing the hardware -- the existing accelerators are optimized for
> production of Nobel prizes, not bulk antimatter -- and solving assorted
> straightforward engineering problems of handling and storage.  The idea
> has been investigated in depth; no show-stoppers have appeared.

I don't appreciate the gratuitous sneer at the people who sweated to
get the production rates *this* high.  They solved difficult
engineering problems and had to make use of technology available at
HEP labs rather than some blue-sky paper scheme.  And, yes, Simon van
der Meer did win a Nobel prize for stochastic cooling, an essential
process in the storage of antiprotons.  So what?

Stack rate this afternoon is 2.35E10 p-bars per hour; Fermilab's
record is near 4E10, about 111 million per second or 3.3E15 per year.
We can get you a milligram in 200,000 years if you bring your own
bag-- our storage system won't preserve antiprotons that long.

> A production setup the size of the Hanford works could make enough
> antimatter to open up the solar system.  Interstellar propulsion is
> harder.

Interstellar propulsion is very hard using any technique.  I concede
that making and storing kilograms of antimatter is pretty easy
compared to making a workable ramscoop, or (the original subject of
discussion) causing p-p fusion in a stream of hydrogen flowing through
your reactor at relativistic speeds.

> Kilogram quantities are probably going to have to be made in
> space, not so much for handling reasons (although those aren't trivial)
> as because of the sheer amounts of *energy* needed.

At the moment, to make one antiproton, we buy from Commonwealth Edison
as much electrical energy as you'd get from annihilating a billion
antiprotons.  It's a lousy way to store energy.

> It would be a huge
> project, but there's no fundamental problem; we could start designing
> hardware tomorrow if it were urgent enough.

I've got stuff to do tomorrow.  How about Saturday?

[I guess I should add that opinions expressed are not those of
Fermilab, Universities Research Association, or the Department of
Energy.]

     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
 /       \                          (_) (_)                    / | \
 |       |     Bill Higgins   Fermi National Accelerator Laboratory
 \       /     Bitnet:     [e-mail]
   -   -       Internet:  [e-mail]
     ~         SPAN/Hepnet:      43011::HIGGINS

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

Date: 7 Jan 1993 23:13:00 GMT
From: "Blair P. Houghton" <[e-mail]>
Subject: averting doom
Newsgroups: sci.astro,sci.space,sci.physics,sci.environment,talk.bizarre

In article <[e-mail]> [e-mail] (Craig "Powderkeg" DeForest) writes:
>In article <bar> [e-mail] writes:
>>         WASHINGTON (UPI) -- Life on Earth as we know it will
>>     come to an end in 1,500 million years and the planet will
>>     look more like its dusty, volcanic sister Venus in 2,500
>>     million years, scientists said Wednesday.
>
>Not too likely, on a planet with over five billion potential planetary civil
>engineers and over 10^9 years to think of a solution!

Do you seriously believe that a species capable of creating
and enjoying The Love Boat is capable also of learning
galactic engineering?

                --Blair
                  "I got dibs on the thinking-cap
                   and daiquiri concessions!"

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

Date: Fri, 8 Jan 1993 00:20:29 GMT
From: Dave Michelson <[e-mail]>
Subject: DC-1 and the $23M NASA Toilet
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Michael F. Santangelo) writes:
>
>But, let me ask (since I don't know the specifics): how well did the
>Skylab toilet work and what does the new $23M Shuttle toilet do that
>the Skylab didn't do?
>
>There is also a reference to the Gemini program in this thread, what did
>they do?
>

Gemini (and Apollo) used a suction hose to collect urine (which was then
dumped overboard) and fecal collection bags for "solid matter".  Fecal
collection bags are hard to use in free-fall so they came with a plastic
glove called the "shit mitt" to help... well, you get the idea.  When
all was said and done, a tablet of bactericide was inserted into the
bag which was then closed.  The astronaut was then required to knead the
bag to evenly distribute the bactericide amongst the solid matter.


The astronauts like dumping the urine overboard (it froze into tiny
ice crytals which Schirra dubbed the constellation Urinus) but *hated*
the fecal collection bags for obvious reasons.



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

Date: 7 Jan 93 20:29:34 GMT
From: Curtis Roelle <roelle@uars_mag.jhuapl.edu>
Subject: DC-1 and the $23M NASA Toilet
Newsgroups: sci.space

[e-mail] (Richard A. Schumacher) writes:


>>Unnecessarily, if so, since the solutions developed for Skylab actually
>>worked pretty well.  (Notably, the Skylab toilet worked.)  For rather
>>longer than a week, too.

>Uhhh... why didn't NASA just reuse the Skylab toilet on Shuttle?

Perhaps because not much was left of it after reentry over Australia? <:-)

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

Date: 8 Jan 93 06:29:56 GMT
From: Jerry Bowman <[e-mail]>
Subject: HST Discovers Double Nucleus in Core of Active Galaxy
Newsgroups: sci.space

[e-mail] (Ron Baalke) writes:
:
: HUBBLE  DISCOVERS A DOUBLE NUCLEUS IN CORE OF ACTIVE GALAXY
:
:      Astronomers, using the Hubble Space Telescope, now
: believe that a galaxy they have observed for a decade
: actually is composed of two merged galaxies and that the
: collision has provided new fuel for a massive black hole
: which is spewing out a jet of gas and other matter 240,000
: light-years long.
:
: [text deleted]
:
: NOTE TO EDITORS:  A photograph to illustrate this story is
: available by calling NASA's Broadcast and Imaging Branch on
: 202/358-1900.
:
:              Color:   92-HC-733              B&W:   92-H-794

Is this photograph going to be available somewhere for FTP access?

Thanks,
Jerry Bowman
Internet: [e-mail]
--
---------------------------------------------------------------------------
Jerry Bowman
Internet: [e-mail]
Compuserve: 71174,1201

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

Date: 8 Jan 93 02:04:05 GMT
From: Jeff Greason ~ <[e-mail]>
Subject: Justification for the Space Program <long>
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> [e-mail] (James L. Felder) writes:
>
>Premise 1.  We live on a finite planet with finite resources.
>
>Premise 2.  Our technological society is highly dependent on resources that
>are being used up faster than they can be replaced.
>
>Premise 3.  Economists seem to insist that we must continue to grow to
>increase our standard of living, and the public and politicians seemed to
>have bought into this premise.  For proof one only has to look at the last
>election to see cries that we are "loosing the American Dream" because we
>are not better off than our parents held up as worthy compaign issues.  The
>strong implication is that an ever increasing, I would hazard
>materialistic, standard of living is something we must all strive for.
>
>Premise 4.  We will not stumble across some unlimited sources of energy
>(fusion) or materials (say a way to mine the earths core) here on earth.
>
>Conclusions.  Energy and materials will become increasingly hard to obtain,
>and that eventually the net energy and material production will decline
>below what is required to maintain some existing standard of living.Unless
>we find a way to circumvent the limited resources of our planet, we as a
>technologically advanced society will cease to exist.  People will continue
>to exist, but society will not be as we know it.  I do not know the time
>frame, nor care to hazard a guess, but the end seems to me to be
>unavoidable.
>
I find this a very concise summary of the "limits to growth" argument.
I am also a strong believer in the need to expand to space -- but I find
this argument very unconvincing in this (the usual) form.

To rebut:

I will grant Premises 1, and 3.

Premise 2 I *almost* agree with -- but there is a slippery loophole which
I believe invalidates it.  "rate" and "resource" are very slippery words.
Your "rate" of using resources can be diminshed by improving technology.
What defines a "resource" is also changed by improving technology.  100
years ago, coal and iron were critical strategic resources, while petroleum
was of marginal value, and aluminum and uranium ores were essentially
valueless.  Needless to say, the situation has changed radically.
Postulating a (hypothetical) super increase in aluminum extraction
techniques, common clay (for aluminum) can become a valuable resource.

Given this, what of Premise 4?

We may not stumble across "unlimited" sources of materials, but, in the
discussion above, I show why this is not necessary.  Assuming (a key
assumption) that technology continues to advance at the unbelievable rate
of the last 200 years, you can start thinking about basing an economy
on recycled trash and dirt! 1/2 :-)

The energy argument is the most persuasive.  It seems that using less
"simple" materials takes more energy.  This requires an advancing EARTHBOUND
civilzation to increase the technology for energy production from EARTHBOUND
resources FASTER than a SPACEFARING civilization would have to.  A
spacefaring civilization can choose to use "simpler" materials on other
planets to do those manufacturing operations which require acess to those
materials.  If we use this argument, we need to argue that it is "cheaper"
IN ENERGY TERMS to do this than to do it on Earth.

For example: we want to mine asteroids for cheap iron.  So, we fly out and
do it.  This burns rocket fuel (or uranium for fission rockets or deuterium
for fusion rockets, etc.) which came from Earth.  This has energy content.
We could have used that energy to extract iron from less efficient ores or
to replace them with aluminum...etc.  So, while it is POSSIBLE that the
spacefaring civilization can survive with a slower rate of technological
advance, it is not OBVIOUS.  In either case, the rate of energy technology
must continuously improve.

Now we come to the critical point in Premise 4, which I would state as "the
rate of technological growth cannot be adequate unless we go to space".  For
that, I see no evidence.  Focused R&D efforts do produce spinoffs, and these
do accelerate technology if they "push the envelope" -- I believe.  However,
it seems clear that the technological advances of, say, the Manhattan
project were probably at least as great, if not greater than, the Apollow
program.  Just as a case in point, IC's, which are often credited to the
space program, depend heavily on ion implantation, which is a clear spinoff
of the Oak Ridge facility in the Manhattan project.  Etc, Etc.

So, I just don't see it.  "Limits to growth" in the material sense is not
a convincing argument for the space program.  PSYCHOLOGICAL "limits to
growth" may be much more convincing.

Now, IF we decide (for other reasons) to BUILD a spacefaring civilization,
then it will (in retrospect) appear to have been a great idea!  Because,
just like the Manhattan project and the Apollo program, the technology would
spin off, and it would look great, in hindsight.  However, if we decided to
spend what it takes to BUILD a self-directed AI, or BUILD a genetically
engineered mammal, etc., it would probably ALSO look great, in hindsight.

Disclaimer:  All opinions expressed are my own, and do not reflect the
     position of Intel, Portland State University, or Zippy the Pinhead.
============================================================================
Jeff Greason                  "You lock the door ... And throw away the key.
  <[e-mail]>   There's someone in my head, but it's not me."
  <[e-mail]>                -- Pink Floyd

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

Date: 8 Jan 93 03:59:25 GMT
From: Paul Dietz <[e-mail]>
Subject: Justification for the Space Program <long>
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> [e-mail] (Jeff Greason ~) writes:

> Postulating a (hypothetical) super increase in aluminum extraction
> techniques, common clay (for aluminum) can become a valuable resource.

Hardly "super".  Extraction of alumina from kaolinite is a
demonstrated technology.  It's just not competitive now when bauxites
with > 50% alumina are plentiful.  High grade bauxite reserves should
last ~ 300 years at current consumption rates; somewhat lower grade
bauxite for 1000 years.  Only then would we go after clays or
feldspars.

Note also that the cost of producing alumina is a rather small part of
the cost (both dollar and energy) of producing aluminum.

    Paul F. Dietz
    [e-mail]

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

Date: Fri, 8 Jan 1993 06:22:25 GMT
From: Jerry Bowman <[e-mail]>
Subject: New Cosmic Background Explorer photos released [NTE 93-1] (Forwarded)
Newsgroups: sci.space

[e-mail] (Peter Yee) writes:
:
: EDITORS NOTE:  93-1
:
: NEW COSMIC BACKGROUND EXPLORER PHOTOS RELEASED
:
:
:      Four new images from NASA's Cosmic Background Explorer are
: available to media representatives through the Broadcast and
: Imaging Branch, 202/358-1741.  Today, these images are being
: presented at the 181st Meeting of the American Astronomical
: Society in Phoenix, Ariz.
:

Are these going to be available somewhere on Internet for FTP?

Thanks,
Jerry Bowman
Internet: [e-mail]
--
---------------------------------------------------------------------------
Jerry Bowman
Internet: [e-mail]
Compuserve: 71174,1201

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

Date: 8 Jan 93 02:47:53 GMT
From: [e-mail]
Subject: Perseid storms 1993/1862?
Newsgroups: sci.astro,sci.space

We are looking for information to help get some idea of what to expect with
regard to the Perseid meteor storm predicted for August 1993. We presume that
the comet's return to perihelion in 1862 (what date was perihelion?) should
have caused storm levels also, particularly given its close approach of 32
million miles, but no one seems to have seen anything. In his 1988 book "Meteor
Showers", Gary Kronk, only refers to good rates (up to 215/hour, not really
storm rates) in 1861 and 1863 (no rates are given for 1862).

Was there a Full Moon on Aug. 9 1862 i.e. was moonlight the problem?

Did the comet and Earth's orbits not cross as closely as they do now?

Could it be that as the storm only lasts about 1 hour, an unpopulated part of
the dark side of the Earth was facing into the radiant (or poor weather)?

Does anyone have the precise times of maxima and Full Moons from 1860 to 1864?
It would then be interesting to see where in the world was favoured for seeing
the very best activity and if those places recorded anything unusual or not.

T.Ryan and D.Moore, Astronomy Ireland, P.O.Box 2888, Dublin 1, Ireland.

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

Date: 8 Jan 93 04:10:48 GMT
From: Francois Yergeau <[e-mail]>
Subject: Question about SETI
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>From "New Scientist", 12 December 1992:
>
>WHEN WILL EARTHLINGS SEE THE LIGHT?
>
>Nigel Henbest believes that NASA's search for ET is on the wrong wavelength

[ long discussion of SETI at radio frequencies deleted ]

>  And if you want to send an interstellar message, radio, as a medium,
>has one overriding drawback. Its frequencies are so low that you can
>transmit information only at quite a slow rate.

Using the 21 cm line of hydrogen, you can transmit about 100 Mbits/s.
Not bad.  Other factors are going to limit you to much, much lower
speed, especially over interstellar distances.

>So let me rewrite the
>history books a bit. Suppose the idea of SETI had come along a decade
>later than it did. The leading edge of technology is now the laser.
>Scientists regard the laser as the ideal mean of communication.

In a fiber, it's pretty good.  But it doesn't go through clouds.

>  But surely a laser's light would be overwhelmed by the brilliance of
>starlight - especially by the light from the sun of the civilisation
>sending the message? In fact, that is not a problem either. A laser
>crams all its energy into just one specific wavelength. If you are
>receiving the signal, you split the light into a spectrum. Now stretch
>out the spectrum. The whitish light from the star is diluted more and
>more as it is stretched, while the single narrow spectral line from the
>laser keeps its intensity. With enough stretching of the spectrum, the
>laser will eventually stand out clearly.

Wrong.  No laser has an infinitely narrow linewidth.  Even if you could
build one, you would induce a finite linewidth by modulating it to
carry your message.  Thus spectral dispersion stops being beneficial at
some point, and if you haven't recovered your signal by then, you're
dead.

>  Laser communication has two great advantages. Due to its high
>frequency, you can send a lot of information very quickly.

Only if you have enough power available.  To transmit a bit of
information, you need _at least_ a few photons to overcome the shot
noise.  But photons in the near IR have about 100,000 more energy than
photons at 21 cm, so much more power needs to reach the receiver for
_the same_ bit rate.

> Laser beams
>are also narrow: whereas a radio signal spreads out as it travels
>through space, diluting its power all the way, you can use comparatively
>little power with a laser because it does not spread out.

Completely bogus.  All electromagnetic beams diffract.  In fact, you
can make a radio beam just as well collimated as a given laser beam;
you just need a much larger antenna.

>  For these reasons, NASA spacecraft engineers are planning to use
>lasers to communicate on its future missions to the outer parts of the
>Solar System. Lasers are small, too, so spacecraft will not need large
>radio antennas to communicate with Earth.

It will need a sizeable, delicate and precisely figured focusing mirror
instead.  And downlinks will be cut off when it's cloudy.  But lasers
have advantages for satellite-to-satellite communications.

>This will avoid some
>embarrassing debacles: the Galileo spacecraft, for example, on its way
>to Jupiter, is gagged because its umbrella-like antenna has not

--
Francois Yergeau ([e-mail]) |  De gustibus et coloribus
Centre d'Optique, Photonique et Laser    |  non disputandum
Departement de Physique                  |          -proverbe scolastique
Universite Laval, Ste-Foy, QC, Canada    |

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

Date: 7 Jan 93 20:36:22 GMT
From: Curtis Roelle <roelle@uars_mag.jhuapl.edu>
Subject: RTG's on the Lunar Module
Newsgroups: sci.space

[e-mail] (Dave Garnett) writes:

>Peering at a cut-away drawing of the Lunar Module the other day
>I noticed what appears to be a Radioisotope Thermal Generator
>mounted on the outside low down.

>Was this intended to power some experiment - I don't think
>that they generate very much power (order 80 watts ?)

>What are the radiation hazards (to the crew) associated
>with such a thing, as I understand that they comprise an
>unshielded lump of plutonium ?

>Dave

I recall watching a live moonwalk on T.V. (before reruns of I LOVE LUCY
took precedence over live lunar feeds) during one of the later Apollos
(color lunar camera) while the astronauts prepared one of the lunar
surface experiment packages.  A pole several feet long was used to
lift the RTG and place it into the power generator, before carrying
the generator to the deployment site.

While the astronaut was carrying the RTG-on-a-stick, he commented that
he could feel the heat right through the suit.  Was he joking?  I didn't
think so.  There is a vague recollection of an expert network sidekick
talking about how hot it was to Mr. Conkrite.  The temperature that comes
to mind was 1500 F.  Any comments?  Is this value real or just faulty
recollection?

Curt [e-mail]

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

Date: 8 Jan 93 06:08:53 GMT
From: David Goldschmidt <ida@atomic>
Subject: russian solar sail?+
Newsgroups: sci.space

[e-mail] (Henry Spencer) writes:

>The stability produced by that spin is actively undesirable if you have
>a maneuverability requirement.  A sail designed to be deployed in Earth
>orbit, in particular, has to do 90-degree turns twice per orbit (to get
>full advantage of sunlight in the "downwind" half of the orbit and
>minimize losses during the "upwind" half).  JPL got away with it because
>their design was launched to escape by conventional propulsion.

Heliogyros would actually be quite good at this.  You wouldn't have to
turn the plane of rotation; you could just "feather" the blades
when moving towards the sun.

  Unfortunately for the heliogyro, this isn't the best way to escape.
Except when you are moving directly into the sun, the sail can always
be tilted to produce some positive change in energy.  (Sometimes it's tilted at
an extreme angle).  The sail angle changes continually, so as to always
maximize the component of thrust along the velocity vector, and thus maximize
the change in kinetic energy.  I have made some computer models of this, and
this does seem to be the best method.

  The heliogyro isn't so unmanueverable as to be impossible for planetary
orbits.  I figured the maximum rate of precession to be about 55 degrees/hour
This rules out very low orbits, but they were impossible anyway due to drag.

   Dave Patterson, Guest on this account



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

Date: Thu, 7 Jan 1993 23:17:47 GMT
From: Henry Spencer <[e-mail]>
Subject: Shuttle a research tool (was: Re: Let's be more specific)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Francois Yergeau) writes:
>>Actually, it is not at all uncommon for airlines to lease planes complete
>>with crews,
>
>NASA could consider leasing shuttle services if a provider were
>available;  but there's none, and with orbiters at $1.5 billion a pop,
>plus gigadollar infrastructure, none is likely to appear...

Several *have* appeared.  That much money is not all that hard to find;
Boeing spent more than that (its own money, not borrowed) on the 757/767
program, and it's small potatoes compared to the (private) investment
in big electric-power projects.  Privately-funded orbiters have been
proposed repeatedly.

So why hasn't it been done already?  Because NASA hates the idea and has
consistently done its best to obstruct, stall, and kill such proposals.
--
"God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
       -Gene Cernan, the Moon, Dec 1972 |  [e-mail]  utzoo!henry

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

Date: Fri, 8 Jan 1993 05:39:28 GMT
From: "Thomas E. Smith [LORAL]" <gothamcity!tes>
Subject: Universities fly ozone research balloon from Texas to Florida [Release 93-8] (Forwarded).
Newsgroups: sci.space

Going to launch a balloon in League City Texas? Ha! Don't you need clear calm
weather for that ;)


--
____________________________________________________________________________
| It's not my damn planet Monkey Boy!  | Tom E. Smith                      |
|                       Dr. Lizardo    | [e-mail]       |
----------------------------------------------------------------------------

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

Date: 8 Jan 93 02:05:59 GMT
From: "robert.f.casey" <[e-mail]>
Subject: was: question about SETI, now: planets around pulsars?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>Actually very little, as these things go.  The ongoing SETI efforts are
>quite small.
>Astronomers are very interested in the immediate vicinity of pulsars,
>because it's an excellent bet that you can find objects of great theoretical
>interest (accretion disks and such) there.  Peculiar and conspicuous objects
>thereabouts would not be missed.  And yes, astronomers take the possibility
>of finding an extraterrestrial beacon quite seriously -- the first pulsars
>caused a considerable stir until it was clear that they were just natural
>phenomena.

About a year or so ago, some astronomers thought that they might have
found planets orbiting a pulsar.  One suspect pulsar planetary system
turned out to be false (orbit of one "planet" was 1/2 the time of Earth's,
and thus suspect), but another looked good then.  Anyone know if this
other (at the time) good detection has held up?  Confirmed?

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End of Space Digest Volume 16 : Issue 021
------------------------------