HDTenEightyP/NetNews huggingface dataset:
From: wreck@fmsrl7.srl.ford.com (R. Cage)
Subject: Re: Electric Tethers
Summary: They push mostly east-west.
Organization: Ford Motor Company Scientific Research Labs, Dearborn, MI
Date: Wed, 19 Aug 1992 15:13:00 GMT

In article <Bt7H6x.13z.1@cs.cmu.edu> evert@CPSnet2.cps.edu (Mike Evert) writes:
>I have a question about the possibilites of an electric tether system
>like that the recent shuttle flight attempted to test.
>
>As I understand it, if a current is put into the tether, then that
>would cause the tether and spacecraft to gain kenetic energy and rise
>to a higher orbit.  The opposite will happen if current is drawn from
>the tether.  Would the acceleration always be in one direction and its
>reverse only?  I don't know if this would be in the direction of orbit
>or perpindicular to magnetic field.  Is it possible to use the tether
>for lateral motion?

Not really.  The limitation is due to simple physics:

1.)	The force is due to the I x B interaction between the
	current in the conductor and the magnetic field.  The
	vector cross-product means that the force must be
	perpendicular to the magnetic field, which goes mostly
	north-south, so you can only push in the 
	east-west-up-down (roughly) plane.

2.)	Gravity-gradient stabilization of the tether requires it
	to be vertical.  Since you can only push at right angles
	to the conductor, your only force is horizontal.  This
	limits you to east-west forces.

You could use a tether for lateral motion (plane changing) if you
were in a polar orbit, but then you wouldn't be able to use it
to raise or lower your orbit since the force would be at right
angles to your motion and the work done would be near zero.

>It seems possible to put a payload into a high orbit at a cheaper cost
>by launching the payload into low orbit.  If that payload carried a
>solar powered tether system (or if it could rendevous with one already
>in orbit), then the tether can be used to boost the payload the rest
>of the way for nearly free.

This only works so long as the ionospheric plasma is sufficiently
dense to carry the return current from the tether ends.  This stops
being the case above a fairly low altitude (memory does not serve
me right now, but it is below geosync).

>Mike
-- 
Russ Cage                  wreck@fmsrl7.srl.ford.com (until 8/28/92)
            russ%rsi.uucp@destroyer.rs.itd.umich.edu (until whenever)
  *  When Ford pays me for my opinions, THEN they can call them theirs. *
                           _Bad_ cop.  No donut.
From: bungee@Apple.COM (Chris Petersen)
Newsgroups: sci.space
Subject: REQUEST:  Mars face gif
Summary: mars face gif
Keywords: mars, face, gif
Date: 18 Aug 92 02:11:43 GMT
Organization: Apple Computer Inc, Cupertino, CA

I actually have a need for the GIF of the "face" on the surface of Mars.  I
grabbed it when it appeared in sci.space before...but I seemed to have
misplaced it.

Could someone please post it, or email it, or simply give me an address where
I can find it.

Thanks,

-chris
 bungee@apple.com
Newsgroups: sci.space
From: train@wixer.cactus.org (archangel)
Subject: Re: Parsecs?
Organization: Real/Time Communications
Date: Wed, 12 Aug 92 19:26:59 GMT

1992Aug11.211445.6928@csi.on.ca>
Sender:
Followup-To:
Distribution:
Organization: Real/Time Communications
Keywords:

In article <1992Aug11.211445.6928@csi.on.ca> richard@csi.on.ca (Richard Martin)

 writes:
>Please forgive my ignorance, but what the heck is a parsec?
>Richard.


The definition of a parsec is the distance at which the PARallax of an object
(star, galaxy, what have you) is one SECond.  This distance is about 3.21
light years if I remember correctly (Don't have any books near me to check
this).  Hope this is helpful.

--

Alton Pouncey                              train@wixer.cactus.org
From: Frederick.A.Ringwald@dartmouth.edu (Frederick A. Ringwald)
Newsgroups: sci.space
Subject: Re: Cosmic strings & supralight
Date: 21 Aug 92 01:06:46 GMT
 <5729@transfer.stratus.com>
Organization: Dartmouth College, Hanover, NH

In article <5729@transfer.stratus.com>
btarbox@sw.stratus.com (Brian Tarbox) writes:

> Can someone explain (simply, please), what superstrings are?

OK, but I meant to say COSMIC STRINGS, not superstrings - my mistake.
(Superstrings are microscopic, and very popular these days for unifying
the forces of nature; the theory is still being thrashed out, though,
so they may or may not exist.)

Cosmic strings are defects in the structure of space and time
("spacetime," for short), left over from the origin of the Universe,
when the whole Universe was hot and cooling rapidly. They resemble
one-dimensional black holes, can be very massive, and are STILL
HYPOTHETICAL: no one has yet detected one definitively. 

When something undergoes a phase transition, such as water turning 
into ice, small fluctuations can get amplified. In ice, you can see
this as the little lines in an ice cube, formed by trapped air 
bubbles. Crystals do this, too. Cosmic strings are roughly 
analogous to this, being defects in spacetime. 

The jist of general relativity is that matter gives shape to space and
time. So, two moving, parallel massive cosmic strings might bend
spacetime so much, it might curve back on itself, giving you a closed
timelike curve (CTC) and faster-than-light travel...MAYBE...maybe!

(And to think grownups spend all day on such stuff! (And it should be
in sci.physics anyway.) I should be getting back to something more
practical, such as an eruption around a neutron star...)

Fred
From: brettvs@hardy.u.washington.edu (Brett Vansteenwyk)
Newsgroups: sci.space
Subject: RE:  Saturn Class Dreams (was RE:  ... and other space development)
Date: 16 Aug 92 05:35:32 GMT
Article-I.D.: u.1992Aug16.053532.19731
Reply-To: brettvs@u.washington.edu
Distribution: na
Organization: University of Washington, Seattle

>>5.  Using an F-1 will imply a design philosophy that is variant with what has
>>prevailed in recent years.  It would seem that the vehicle has a whole booster
>>stage, and does not really depend on strap-ons.  Or---could you develop a
>>strap on booster with an F-1?
>
>This design philosphy comes from trying to get as much as possible out of 
>the infrastucture of basically small payload vehicles.  The cost for 
>manufacturing tooling for longer tanks with strap ons is small. Building new
>jigs for larger diameter tanks is hellishly expensive.  That is the primary
>reason for using the solid strap ons in recent years.  Usually the cheapest
>part of the existing launchers upgrade in capability is from the strap ons.
>With the big bird and little bird Saturn you build two jigs and stretch the
>tanks to fit the desired payload class.

Okay, the only question I have here is whether or not these engines are part
of a stage that will eventually drop off so that a LH2/LOX burning stage can
take over.  From my understanding, a kerosine burner does a great job for
vehicles getting off the pad and accelerating through most of the atmosphere
(its a dirty job but somebody's got to do it), but when you need more
efficiency higher up, you can't beat LH2/LOX.  Is there a big penalty in
keeping an RP1-burner going up to orbit, or is this tradeoff overshadowed
by other factors?

By strap-on, do you mean strap-on booster (self-contained), or do you mean
strap-on engine (a la Atlas)?

I would love to see a picture of an F1 firing again, especially since I seem
to be out of earshot :-).

		--Brett Van Steenwyk
From: sysmgr@king.eng.umd.edu (Doug Mohney)
Newsgroups: sci.space
Subject: Re: ACRV/Soyuz P # of Passengers
Date: 18 Aug 92 18:02:56 GMT
Reply-To: sysmgr@king.eng.umd.edu
Organization: Computer Aided Design Lab, U. of Maryland College Park

In article <1992Aug18.125111.15553@iti.org>, aws@iti.org (Allen W. Sherzer) writes:
>In article <1992Aug17.150641.23766@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes:
>
>>The problem with this scenario is *the service isn't provided*. That
>>can't be tolerated when there are crews up there. So the government
>>*will* pay, and the contractor knows it.
>
>Does the word 'comeptition' ring a bell? If GD says "Ah Uncle Sam, we
>got you by the balls now!" then Uncle Sam replies: "Screw you, I'm taking
>my buisness to Martin Marrietta".

Company #2 could not afford to develop the vehicle further. Go look at ATF. One
winner, one fighter. One winner, one launch system. 


                 Support U.N. military force against Serbia

  -- >                  SYSMGR@CADLAB.ENG.UMD.EDU                        < --
Newsgroups: sci.space
From: aws@iti.org (Allen W. Sherzer)
Subject: Re: What is DCX
Organization: Evil Geniuses for a Better Tomorrow
Distribution: sci
Date: Mon, 17 Aug 1992 13:33:22 GMT

In article <Bt3ovy.L12.1@cs.cmu.edu> evert@CPSnet2.cps.edu (Mike Evert) writes:

>What is DCX?  A previous acronyms posting tells me that is the Delta Clipper.
>What is it designed to do and how far along is it to being operational?

DCX is a vehicle being developed by McDonnell Douglas under the SDIO
Single Stage Rocket Technology (SSRT) program. The goal is to build
a Single Stage to Orbit (SSTO) spacecraft which is fully reusable and
will reduce the cost of access to LEO by one to two orders of
magnitude.

DCX is a 1/3 scale prototype designed to prove some of the concepts and
was to be follwoed by the DCY which was a full scale orbital prototype.

Alas, SDIO is not going to fund DCY and we are working to find a new
home (perhaps in the Air Force) to continue development.

   Allen

-- 
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "If they can put a man on the Moon, why can't they     |
|  aws@iti.org     |  put a man on the Moon?"                               |
+----------------------249 DAYS TO FIRST FLIGHT OF DCX----------------------+
Newsgroups: sci.space
From: privette@frodo.colorado.edu (Jeff Privette)
Subject: Re: GOP space platform text
Organization: Colorado Center for Astrodynamics Research
Distribution: usa
Date: Sun, 23 Aug 1992 00:41:57 GMT

|> As received by FAX from Houston:
|> 
|> GOP Platform on Space

As Charlie Brown's schoolteacher said, "Blah bla bla blah blah blah."
Xref: sparky sci.space:11748 sci.physics:12780
Newsgroups: sci.space,sci.physics
Subject: Re: Parsecs?
From: mcirvin@husc8.harvard.edu (Mcirvin)
Date: 13 Aug 92 12:24:48 EDT
Organization: Harvard University Science Center
Summary: No, it's NOT a coincidence

In article <1992Aug13.144737.1884@trentu.ca> pyacm@trentu.ca (A Colin Morton) writes:
>As other posts have stated, one parsec is equal to ~3.2616 light years.
>As we, on Earth, are only ~8 light minutes from the Sun, I don't think
>the Earth-Sun distance defines a parsec.
>
It's not the Earth-Sun distance, it's the distance from which the
Earth-Sun distance subtends an angle of one second of arc.  That's
*not* a coincidence; it follows from the definition.

The definition comes from the use of parallax to measure the distances
of nearby stars.  You can observe parallax easily by holding your
thumb in front of your face and looking at it with one eye: if you
look at it with your left eye, then your right, the thumb appears
to be in different places with respect to more distant objects.  The
effect is larger if the thumb is closer, and smaller if it is
further away.

In much the same way, nearby stars appear to move very slightly with
respect to more distant ones as the Earth moves.  The Earth moves
in several ways, but a component that can be isolated easily is
its motion around the Sun.  This causes the images of nearby stars
to describe small yearly ellipses in the sky.  The semimajor axis of the
ellipse, measured in seconds of arc (one second of arc is 1/3600 of
a degree), is the parallax of the star.

The word "parsec" stands for "parallax of one second."  A star one
parsec away would have a parallax of one second of arc.  Real stars
are all further away, so they have smaller parallaxes.  Since
with angles this small, sin theta = tan theta = theta (radians) to very
high precision, we can say that the distance in parsecs is the
reciprocal of the parallax in seconds of arc. 

The apparent elliptical motion of a star against a very distant
background, as seen from the orbiting Earth, is identical in 
apparent angular size on the sky to the motion of the Earth
around the Sun as seen from the star.  Therefore it is no coincidence
that the distance from the Earth to the Sun subtends an angle of
one second of arc when seen from a distance of one parsec.  It is
an immediate consequence of the definition of a parsec.

If I've gotten anything wrong, please correct me...

-- 
Matt McIrvin, professional gradgrind, amateur Usenet drifter
From: Wales.Larrison@ofa123.fidonet.org
Newsgroups: sci.space
Subject: GPS Info ...
Date: 19 Aug 92 02:27:38 GMT
X-Sender: newtout 0.01 Jul 13 1992

Jeff Bytof states:
  
>I have just read the famous 76-page brochure on GPS put out by
>Trimble Navigation.  It hardly qualifies as a manual or technical
>documentation. When I call Trimble Navigation for information, they
>give me the phone number of a guy that won't be back for two weeks.
>According to the brochure, US taxpayers are "investing over $12
>billion" on the system. I would think there would be at least an
>address I could write to for a good bibliography on the system
>without having to go through some company that makes it money
>keeping public information away from the public.
  
     Rather than asking someone else do your research for you, why
don't you try a good local library.  Since Trimble is only in the
business of providing receivers and user-specific applications
hardware and software, I don't think they need to provide random
callers with technical specs on GPS.  From your net address
(rabjab@golem.ucsd.edu), I am assuming you are near UCSD, which has
an excellent technical library.  I'll bet you money you could find
50 or more references in 15 minutes by looking in any of the
following ...
   - IAF abstracts
   - STAR (scientific and technical abstracts report)
   - AIAA abstracts
   - NTIS data base (National Technical Information System)
   - Aerospace data base.
   All of the above are available in hard copy (except for the last)
at just about any significant technical library.  All are available
on CD-ROM, or on-line. And they'll give you just about anything you
want to know from spacecraft constellation specifics and design, to
full technical specifications for any part of the system.
  
   And if you still don't want to do any of the (minimal) legwork,
ask the reference librarian at the library what would be the easiest
way...  She/he is paid to help answer questions like this -- but
she/he doesn't know exactly what questions you want answered.
  
  Sorry Jeff, but I'm in a rotten mood tonight.  I've just read
through about 50 K of useless drivel, posturing, and meaningless
speculation.  Your question can be answered simply, and I'm
surprized no one else has recommended you just look up the data in
any of the standard data bases.   If you really want to go the
horse's mouth, call the GPS Joint Program Office (GPS JPO) at Air
Force Space and Missiles Command in El Segundo, California.  But all
they'll do is reference to some of the reports and papers you'll
find in the above data bases.
 --------------------------------------------------------------
 Wales Larrison                         Space Technology Investor
  
  

--- Maximus 2.00
Newsgroups: sci.space
From: wdb3926@summa.tamu.edu (BRUTON, WILLIAM DANIEL)
Subject: Re: Hubble visible in evening sky
Followup-To: sci.space
News-Software: VAX/VMS VNEWS 1.41    
Organization: Texas A&M University, Academic Computing Services
Date: Fri, 21 Aug 1992 04:37:00 GMT

In article <26074@scicom.AlphaCDC.COM>, wats@scicom.AlphaCDC.COM (Bruce Watson) writes...
> 
>Just a reminder that the Hubble Space Telecope is appearing in the evening
>twilight for the next few weeks for northern hemisphere observers. For
>those of us much further north thatn approx. 35 degrees, it will
>be low on the horizon towards the south.
> 
>-- 
>Bruce Watson (wats@scicom)  Tumbra, Zorkovick; Sparkula zoom krackadomando.  

 Any idea how many degrees above the horizon for latitude of 35 degrees
for some day this week?  Or where to find info on Hubble's coordinates?
Thanks,
Dan
From: mwallis@clubzen.fidonet.org (Michael Wallis)
Newsgroups: sci.space
Subject: Re: space industry
Date: Sat, 22 Aug 92 14:04:10 PST
Organization: Club Zen BBS - Fidonet/Internet - +1 408 734 2289

aws@iti.org (Allen W. Sherzer) writes:

> In article <1469100011@igc.apc.org> Mark Goodman <mwgoodman@igc.apc.org> writ
> 
> >There are really no private space launch providers
> >outside the United States -- Arianespace is the closest thing.
> 
> So what are Atlas, Delta, and Titan, chopped liver?

No, they're INSIDE the United States.

------------------------------------------------------------------------------
mwallis@clubzen.fidonet.org - Michael Wallis
Xref: sparky sci.space:11780 sci.physics:12825
From: mcirvin@husc8.harvard.edu (Mcirvin)
Newsgroups: sci.space,sci.physics
Subject: Re: Parsecs?
Date: 14 Aug 92 01:26:18 GMT
 <1992Aug13.144737.1884@trentu.ca> <1992Aug13.122450.14694@husc3.harvard.edu> <13AUG199218134665@zeus.tamu.edu>

dwr2560@zeus.tamu.edu (RING, DAVID WAYNE) writes:

>mcirvin@husc8.harvard.edu (Mcirvin) writes...
>>If I've gotten anything wrong, please correct me...

>Forgive me if I'm being stupid, but isn't everybody ignoring a factor of 2 
>somewhere?

Good question, but the answer is no.  Everyone so far who's given
even remotely the right definition has gotten the factor of 2 right.
The parallax of a star is the semimajor axis of the ellipse its
image performs in the sky, and correspondingly it's the AU, not the
width of the Earth's orbit, that subtends a second of arc.
*That* I do remember.  Think of the parallax as the amplitude of
a yearly apparent oscillation. 

Let's check the calculation, in fact.  There are 1.296E6 arc-seconds
in a circle, or about 2.06E5 in a radian.  So 2.06E5 times the AU
(1.5E11 m) should be the parsec.  That comes to 3.1E16 m, which is
about right, since the light-year is about 1E16m.  So we definitely
have the right factor of 2 here, at least.  Rounding and probably
arithmetic errors are undoubtedly rampant in the above, since I did
it by hand.

-- 
Matt McIrvin, professional gradgrind, amateur Usenet drifter
From: szabo@techbook.com (Nick Szabo)
Newsgroups: sci.space
Subject: Re: With telepresence, who needs people in Earth orbit?
Date: 21 Aug 92 09:18:31 GMT
Article-I.D.: techbook.1992Aug21.091831.4590
Organization: TECHbooks --- Public Access UNIX --- (503) 644-8135

Those in search of government pork.  They consider astronauts a good
money-raising technique, much like Greenpeace & their whales.

(But at least donations to Greenpeace are voluntary). 

Save the astronauts!  Write your Congressman & join NSS now!  :-)


-- 
szabo@techbook.COM  Public Access User --- Not affiliated with TECHbooks
Public Access UNIX and Internet at (503) 644-8135 (1200/2400, N81)
From: dj@ssd.kodak.com (Dave Jones)
Newsgroups: sci.space
Subject: Re: superstrings & supralight (was SPS feasibility and other space development)
Date: 20 Aug 92 17:36:14 GMT
Article-I.D.: pixel.1992Aug20.173614.12418
Distribution: sci
Organization: :noitazinagrO

In article <5729@transfer.stratus.com> btarbox@sw.stratus.com (Brian Tarbox) writes:
>Can someone explain (simply, please), what superstrings are?

I think the terms are misused in this context.  Superstrings per se are
theoretical entities in the realm of particle physics which are used as
models for fundamental particles, such as quarks, in order to represent
them as "extended objects" rather than dimensionless points, in an
attempt to resolve problems with infinite quantities arising from the
calculations.

"Cosmic" strings are also theoretical (so far) and represent leftovers
from the Big Bang, or rather the hypothetical "inflation" that preceded
it.  The Universe supposedly underwent a "phase transition" in which
the energy level of space itself changed.  As in a liquid freezing, this
didn't happen at the same rate everywhere, but tended to be uniform
across small regions.  The boundaries between regions, like the
boundaries within the crystalline structure of a solid, have different
energy levels than the rest of the Universe.

I forget the details, but Cosmic String manifests this in a form which
is small in cross-section (many times smaller than a nucleus) and very
long (some strings may span the Universe).  The concentration of energy
is manifested in a large mass (millions of tons per inch?).


-- 
||)) Dump the Whatizit!  Ren and Stimpy for Olympic mascots in '96 ! )))))))|
||)) "What is it, man?!?" ))))))))))))))))))))))))))))))))))))))))))))))))))|
||))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))|
||Dave Jones (dj@ekcolor.ssd.kodak.com) | Eastman Kodak Co. Rochester, NY   |
From: jch+@cs.cmu.edu (Jonathan Hardwick)
Newsgroups: sci.space
Subject: Re: Soyuz as ACRV
Date: 19 Aug 92 16:34:11 GMT
Article-I.D.: cs.Bt8op4.8y3.1
Organization: School of Computer Science, Carnegie Mellon

gary@ke4zv.UUCP (Gary Coffman) writes
> aws@iti.org (Allen W. Sherzer) writes:
> >Besides, in an earlier post you stated that ALL shuttle cargo's had to be
> >certified to 10 G in the direction of motion and 6 or so transverse. Any
> >capsule can do that easy.
> 
> Those are engineering *safety* margins. Operating at the outside edge
> of the engineering envelope is never good engineering practice. One
> wind gust against your parachute, and you've exceeded engineering limits.
> Not acceptable.

How closely do SMEs approach the outside edge of the engineering
envelope?  Is this good engineering practice?

> I think that if SSTO doesn't pan out, and there's a good chance
> it won't, then we should be considering Shuttle II, a low maintenance,
> low turnaround follow on vehicle to a proven system. 

Here I was thinking that Shuttle I was supposed to be the
low-maintenance low-turnaround vehicle.  The space truck, right?  Any
bets that Shuttle II turns into another expensive boondoggle?

> Taking lessons
> learned, and advances in aerospace technology over the 20 years since
> Shuttle was designed, we should be able to make as large an incremental
> improvement as the step from the 707 to the 767 in the Shuttle. This
> would take advantage of existing, and *paid for*, facilities at the
> Cape and at Rockwell while cutting ground servicing personel costs
> sharply. That's what really drives Shuttle launch costs.

Uh-huh.  Wings are great for getting back down cheaply.  Wings suck
for getting up there in the first place.  Spam-in-a-can is going to be
economically justified for a long time to come, and if the US space
program sticks exclusively with winged vehicles, it's going to be
throwing money away that could be used for something else.

Jonathan H.
Newsgroups: sci.space
From: richard@csi.on.ca (Richard Martin)
Subject: Re: GEO coverage, aurorae (was Re: SPS fouling astronomy)
Organization: Carp Systems International, Kanata, ON
Date: Tue, 18 Aug 1992 13:58:13 GMT

In article <1992Aug17.052502.1@fnalf.fnal.gov> higgins@fnalf.fnal.gov (Bill Higgins-- Beam Jockey) writes:
>This is the reason the youthful Arthur C. Clarke recommended three
>geosynchronous comsats.  Two don't *quite* cover the world.
This topic was covered in the Mathematical Games column of
Scientific American recently--the satellite coverage problem
turned out to have many interesting spin-offs.
Richard. 8
	 ^
        / \
       #   #
      --- ---
-- 
Richard Martin               	richard@csi.on.ca
Sorry, no NeXTmail. <sniff> :(
"Don't Panic Yet!  Things are about to get much worse!"