Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_3/V11_341.TXT

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Subject: SPACE Digest V11 #341

SPACE Digest                                     Volume 11 : Issue 341

Today's Topics:
      Re: >>... Hermes will be mostly aluminum, for example, not
            Re: Re: Dyson spheres?
     Niven's inertialess drive (was Re: Dyson spheres, heat flow)
Re: Giant crawler transporter to pass 1000 miles on STS-35 rollout (Forwarded)
   European Unsubscribed user would like contacts and some help!!!
     Re: PegBlimp (was Re: Pegasus launch from Valkyrie (or ...)
Re: Giant crawler transporter to pass 1000 miles on STS-35 rollout (Forwarded)
                  Re: [help]
            Re: Re: Dyson spheres?
         NASA Headline News for 05/01/90 (Forwarded)
----------------------------------------------------------------------

Date: 30 Apr 90 19:37:35 GMT
From: usc!elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!ofa123![e-mail]  (Mark Perew)
Subject: Re: >>... Hermes will be mostly aluminum, for example, not

I heard somewhere that Dyna-soar would have been made out of
titanium.  According to that source a titanium vehicle would not
need the tiles used by the shuttle.  The reason the shuttle uses
tiles is that titanium is so blasted hard to work with that it
was "expected" to be cheaper to  develop the tile technology than
to use known processes using titanium.

Can someone shed some light on the veracity of these comments?


--- Opus-CBCS 1.12
 * Origin: Universal Electronics, Inc. (1:103/302.0)
--
Mark Perew
...!{dhw68k,zardoz,lawnet,conexch}!ofa123!Mark.Perew                             [e-mail]
714 544-0934 2400/1200/300

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

Date: Tue, 1 May 90 18:50:09 EDT
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Re: Re: Dyson spheres?


>From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!helios.physics.utoronto.ca!physics.utoronto.ca![e-mail]  (Christopher Neufeld)
>Subject: Re: Dyson spheres?

>In article <[e-mail]> [e-mail] (John Roberts) writes:
>
>>With nonreflecting sails, you *have* to allow radiation in both directions, or
>>else the photon pressure of the radiation (dependent only on energy, not
>>wavelength) will offset the photon pressure of the incident light, and there
>>will be no net force.
>
>   No. The reasoning is almost right, but you have to consider geometric
>effects. The light radiated as heat from your habitat doesn't go only
>parallel to the light incident on it from the Sun. Consider the
>following case: I have a spherical habitat near the Sun. The temperature
>of the surface is regulated by circulating a coolant fluid or something,
>and the temperature is essentially constant over the front and back
>surfaces. Now, there is obviously no net force on the sphere due to its
>own radiation, since that is spherically symmetric. Add in the effect of
>the Sun, which puts an unbalanced force on the sphere, and the sphere
>must experience a net force.
>   Essentially, you argued that the waste heat would radiate ONLY to the
>outside, and then only straight away from the Sun. In fact, the inside
>would also radiate heat.

You misunderstood what I said. The original topic of discussion was a large
hollow sphere, *enclosing* the sun, and using the photon pressure of the light
from the sun to keep it from collapsing due to gravitational effects. Henry
suggested that it might be designed (active pumping of heat, etc.) so that it
would radiate only to the outside. I pointed out that if this were done, the
radiation pressure of the waste heat would work against the intended action
of the sail, and that one could avoid this problem only by allowing the heat
to radiate from both the inner and outer surfaces of the sphere.

I did not imply that this principle applies in the same way to all geometric
configurations. I do, however, think it would be relevant in this case.

>   By the way, even if we ignored the effect of radiation back toward
>the Sun, the non-parallel nature of the heat radiation on the far side
>of the habitat would result in a lower net force than the force incident
>from the Sun's side.

If you are right about this part, and if I got my spherical-coordinate
integration correct (no guarantee of that :-), then a surface which radiates
in all directions (over half of a sphere) will experience an unbalanced force
with a value half of what it would experience if all the radiation were in
the same direction. Is this valid? Would it apply to the surface of a very
large flat plate?
                  John Roberts
                  [e-mail]

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

Date: 1 May 90 06:08:31 GMT
From: mcsun!ukc!acorn!ixi![e-mail]  (Clive Feather)
Subject: Niven's inertialess drive (was Re: Dyson spheres, heat flow)

[I've added rec.arts.sf-lovers to the newsgroups]

In article <[e-mail]> [e-mail] (Steven P Coltrin) writes:
>A pet idea I've had bouncing around awhile is that the 'reactionless drives'
>are actually neutrino drives analogous to the photon drives humans used before
>buying the hyperdrive shunt from the Outsiders.  Therefore they wouldn't
>violate any strange laws like Newton's, but would be essentially reactionless
>because the exhaust is thrown where it cannot be seen.  (Though in _The
>Ringworld Engineers_ it is revealed that ships using thrusters can be tracked
>by their neutrino exhaust.)

But in "Flatlander" an Outsider ship accelerates Beowulf and Elephant to 0.9c
in a matter of minutes. This can't be a simple reaction drive; it has to act
on the occupants as well as the ship, or they'd be squashed.

I always assumed that man had reinvented the drive. Beowulf seemed to think
that the price was too high, and anyway, knowing it can be done is 90% of the
battle.
--
Clive D.W. Feather  | IXI Limited           | [phone] (v)
[e-mail]     | 62-74 Burleigh Street | [phone] (fax)
...!uunet!ixi!clive | Cambridge  U.K.       |-----------------------------
                    | CB1  1OJ              | Silly quote being thought up

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

Date: 1 May 90 07:10:38 GMT
From: zaphod.mps.ohio-state.edu!rpi![e-mail]  (Jim Kasprzak)
Subject: Re: Giant crawler transporter to pass 1000 miles on STS-35 rollout (Forwarded)

In article <[e-mail]> [e-mail] (John Woods) writes:
>In article <[e-mail]>, [e-mail] (Peter E. Yee) writes:
>>   GIANT CRAWLER TRANSPORTER TO PASS 1000 MILES ON STS-35 ROLLOUT
>
>Another 2000 miles and it'll be time to change the oil.    ;-)

 This may sound like a totally silly trivia question, but I can't get it out
of my head and somebody here must know the answer. What sort of engine(s) does
that crawler thing have, and what kind of fuel do they run on?


--
 Jim Kasprzak          [e-mail] (internet)
 RPI, Troy, NY         [e-mail]
 "A spirit with a vision is a dream with a mission."  -Rush

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

Date: 1 May 90 16:56:24 GMT
From: nisca.ircc.ohio-state.edu!hpuxa.ircc.ohio-state.edu![e-mail]  (Alex Cruz)
Subject: European Unsubscribed user would like contacts and some help!!!





    I am posting the following request for a friend in Spain that does
    not have access to USENET.  He has a graduate degree in Physics and
    currently he is working on his Ph.D. dissertation, titled:
    "Primary Inhomogenuities of the Universe"

    He will appreciate it very much if anyone interested in the subject
    or simply willing to help him, would contact him to the following
    address:

             [e-mail]

    or simply

             [e-mail]

    Another issue:

    Is there anyone out there that could provide with some
    anonymous FTP sites where we could get archives, documents or
    programs related to astronomy?  We have access to FTP via
    Princeton and are very interested on finding out.

    If there is interest, I will post a summary.

    To those of you that respond, thanks in advance.

    Alex Cruz


**************************************************************************
**           Center for Advanced Study in Telecommunications            **
**************************************************************************
**       Alex Cruz                            1971 Neil Avenue          **
**  Graduate Associate                        210 Baker Systems         **
**                                            Columbus, OH 43210-1271   **
** INTERNET:   [e-mail]        Phone:  [phone]  **
**             [e-mail]   Fax:    [phone]  **
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**************************************************************************

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

Date: 1 May 90 15:33:59 GMT
From: eplrx7![e-mail]  (Walt Leipold)
Subject: Re: PegBlimp (was Re: Pegasus launch from Valkyrie (or ...)

If a balloon/blimp/dirigible can indeed go higher than the B-52/Pegasus
combination, why not use your LTA capability to get Pegasus up to about
80,000' and drop the silly thing?  By the time it gets down to the
altitude that the B-52 launches it from (50k feet?), it should be going
at least Mach 0.7 or so, and you can fly the original flight profile
from there.  If LTA is really a cheaper way to get payloads to high
altitudes, then you can get identical performance at a lower cost.

--
"As long as you've lit one candle,                         Walt Leipold
you're allowed to curse the darkness."       ([e-mail])
--
--
The UUCP Mailer

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

Date: 1 May 90 15:41:45 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Giant crawler transporter to pass 1000 miles on STS-35 rollout (Forwarded)

In article <?H3#T#[e-mail]> [e-mail] (Jim Kasprzak) writes:
>... What sort of engine(s) does
>that crawler thing have, and what kind of fuel do they run on?

Like most really heavy machinery, the crawlers are Diesel-electric, with
big Diesels running generators and electric motors actually driving the
wheels or treads.  (Diesel locomotives are really Diesel-electric too.)
If I recall correctly, main power for the crawler is four Diesels at a
few thousand horsepower apiece, plus a couple of smaller ones for auxiliary
power.  They burn Diesel oil; mileage is something like 30 ft per gallon.
--
If OSI is the answer, what is |     Henry Spencer at U of Toronto Zoology
the question?? -Rolf Nordhagen| uunet!attcan!utzoo!henry [e-mail]

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

Date: Tue, 1 May 90 10:47:00 PDT
From: [e-mail]
X-Vmsmail-To: UTADNX::UTSPAN::AMES::"[e-mail]"
Subject: Re: [help]


In SPACE Digest V11 #340, a person with an incredibly long address, i.e.,
zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!ux1.cso.uiuc.edu!ux1.cso.uiuc.edu!m.cs.uiuc.edu!bucc2![e-mail] writes:

>    I had been taught that (and read this in Patrick Moore's THE
>    AMATEUR ASTRONOMER) any planet inside the Earth's orbit, and
>    including the Earth, was an inner planet. Asimov's various
>    scientific writings back me up here too.
>
>Craig\The Moonman\Levin
>Bitnet {?}: [e-mail]      |  uiucdcs\
>Internet: [e-mail] |      noao>bradley!bucc2!moonman

    This is wrong.  The inner planets are Mercury, Venus, Earth and Mars,
confirmed by several sources in our library here at UTD.  If you've ever seen a
diagram of the planets, you might have noticed that the four innermost ones are
clustered very closely to the Sun, and that there is a relatively large gap
from Mars to Jupiter.
    In fact, the four inner planets' orbits are all within .5 AU of their
nearest neighbors', with Mars being 1.5 AU from the Sun, while Jupiter is 5.2
AU out, so that its orbit is seven times as far from Mars' orbit as Mars' orbit
is from the Earth's.  So it's this order of magnitude difference in
interplanetary distances that discriminates the inner from the outer planets.
    Also, the inner planets sometimes share the descriptor "terrestrial",
by which is meant rocky rather than gaseous like the outer planets (except
Pluto/Charon).  This is because most of the gases of the inner planets were
blown away when the Sun reached critical denisity and "flamed-on". (According
to some theories.  My references were somewhat vague on this.)
    I guess if the Sun had been bigger, the outer planets might be rocky
too, but then it would have to have been so much bigger that the entire
character of the Solar System would be different.  Earth would certainly be
uninhabitable if the Sun were big enough to blow the gas off Jupiter.  Maybe
Mercury would have fallen into the Sun due to drag decay of its orbit.
Hmmm...the Sun must have a rocky core, I wonder how it affects solar dynamics?
    Finally, perhaps the source of error here is that Mercury and Venus are
called the inferior planets, being as they are "below" the Earth, while those
from Mars on out, being "above" the Earth, are called the superior planets.

_____________
Dale M. "Is it just me, or what?!" Greer,
whose opinions are not to be confused with those of the
Center for Space Sciences, U.T. at Dallas, UTSPAN::UTADNX::UTDSSA::GREER

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

Date: 1 May 90 14:02:43 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!watserv1!maytag!watdragon!watyew![e-mail]  (Brian or James)
Subject: Re: Re: Dyson spheres?


 A orbit with an aphelion of 1 AU and a perhelion of 0 AU should
have a period of 130 days, if I haven't screwed up the math. That'd
put you at the core in half that time, if you were a bucketful of
very cold neutrinos [if they have rest mass]. Normal folks would
experience some degree of difficulty due to the precense of a star
between them and 0 AU. I don't know at what distance the heat
would evaporate you, but I'd lay odds against pulling this orbit
for more than one half orbit :).
 I'd like to point out that my 'second rate' Dyson sphere at least
requires no superstrong materials or phenominal orbit coordination
to build and maintain. The heat problem is a pain, but I suspect it
can be dealt with, with perhaps a minor cost in the Sun's life
expectancy :).
                            JDN

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

Date: 1 May 90 18:16:15 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: NASA Headline News for 05/01/90 (Forwarded)

-----------------------------------------------------------------
Tuesday, May 1, 1990                  Audio Service: 202/755-1788
-----------------------------------------------------------------
This is NASA Headline News for Tuesday, May 1...


The Dryden Flight Research Facility reports ground crews at
Edwards Air Force Base in California give the orbiter Discovery a
clean bill of health.  Approximately 33 tiles were slightly
damaged and only 5 appear to need replacement.  The one-day ferry
flight return to Kennedy Space Center is scheduled for Saturday,
May 5 with a stop over to refuel at Kelly Air Force Base in San
Antonio, Texas.


An OMS/RCS maneuvering thruster has been sent to the malfunction
laboratory at Kennedy Space Center for analysis.  The orbiter has
been towed to the Mate/Demate Device and connected to the sling
that will be used to lift the vehicle onto the 747 Shuttle
Carrier Aircraft.  Later today, workers will continue post-flight
inspections of the thermal protection system.

                            ********

The Galileo spacecraft has now logged over 340 million miles.  It
takes 16 1/2 minutes for a radio signal to reach the spacecraft
and return while travelling over 71,000 miles per hour in orbit
around the Sun.  Normal cruise activities this week included Sun-
pointing turns, propulsion system maintenance and science
observations by the magnetometer all governed by the new
operating sequence covering the period from April 23 through June
10.
                            ********

Meanwhile, the Magellan spacecraft is over 103 million miles from
Earth and nearly 21 million miles from Venus.  Travelling at
66,824 miles per hour relative to the sun, the spacecraft last
week successfully completed memory readouts of all command data
system.

                            ********

Astronomer Carl Sagan told USA Today he and Soviet space
scientist Roald Sagdeev plan to send a message to the superpowers
during the talks scheduled in Washington through June 3.  The two
scientists will urge President Bush and Mikhail Gorbachev to take
an early step toward the grand exploratory endeavor of sending
missions to the Moon and Mars. The National Research Council has
recommended the U.S. and Soviet Union conduct coordinated but
independent missions.
                            ********








----------------------------------------------------------------
Here's the broadcast schedule for Public Affairs events on NASA
Select TV.  The following times listed are Eastern.


Wednesday, May 2.....


                    10:00 A.M.       STS-35 Astro-1 mission and
                                     science briefing at Kennedy
                                     Space Center.



----------------------------------------------------------------
All events and times are subject to change without notice.
These reports are filed daily, Monday through Friday, at 12:00
Noon, EDT.  This is a service of the Internal Communications
Branch, NASA Headquarters.

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

End of SPACE Digest V11 #341
*******************