HDTenEightyP/NetNews huggingface dataset:
From: claudio@nmsb.larc.nasa.gov (Claudio Egalon)
Newsgroups: sci.space,sci.astro,alt.sci.planetary
Subject: Re: Magellan Update - 11/20/92
Date: 21 Nov 1992 15:50:17 GMT
Organization: NASA Langley Research Center, Hampton, VA  USA
Distribution: world
Reply-To: claudio@nmsb.larc.nasa.gov (Claudio Egalon)
NNTP-Posting-Host: b1230bmac9.larc.nasa.gov

*3.   Tuesday, November 17, the project conducted a design
*    review of an aerobraking experiment to be conducted at
*    the end of Cycle 4.  Preliminary modeling of dynamic
*   pressures, temperatures and attitude control indicate
*     that circularizing the orbit on an aerobraking plan which
*     proceeds aggressively for the first several weeks, and
*     backs off in the later stages, appears to be very
*     feasible.


I have a question about the aerobraking maneuver that the Magellan 
will perform; Is there any possibility that any of the components of 
the Magellan be damaged during this maneuver??? Since the 
spacecraft is going to suffer some friction with the Venusian 
atmosphere I would expect some kind of risk involved. Is it a concern 
for people at the JPL???

BTW, I think Magellan will become the first spacecraft to conduct an 
aerobraking maneuver to change its orbit, right??? Unless AAFE 
(Aeroassist Flight Experiment) catches up, of course...

Claudio Egalon

claudio@nmsb.larc.nasa.gov
From: perrine@nic.cerf.net (Tom Perrine)
Newsgroups: sci.space
Subject: man-rated centrifuge in So. California??
Date: 20 Nov 92 18:22:11 GMT
Organization: CERFnet

I'm posting this query for a friend with no net access, so please respond
via e-mail to tep@logicon.COM.

Are there any man-rated centrifuges in Southern California?  My friend is
specifically interested in any near San Diego, although anywhere in the state
would be of interest.

Thanks,
Tom Perrine	tep@logicon.com
Newsgroups: sci.space
From: aws@iti.org (Allen W. Sherzer)
Subject: Re: Shuttle replacement
Organization: Evil Geniuses for a Better Tomorrow
Date: Fri, 20 Nov 1992 14:24:45 GMT

In article <q!z1l0f@rpi.edu> kentm@aix.rpi.edu (Michael V. Kent) writes:

>The Shuttle does many many things that nothing else in the fleet will do.  The
>most obvious is serve as a manned spacecraft.  

Nonsense. In a pinch we can stick a Soyuz on an Atlas or Titan.

>The original article in this thread listed many more.

All of which have existing or near term alternatives. 

>>Titan IV can lift any existing or planned payload Shuttle can lift.

>The Shuttle has twice the payload capacity of the Titan IV.  

Nonsense. 

>It can also
>launch cargoes the Titan IV can't touch.  Would _you_ volunteer to fly a
>Spacelab mission in a Titan IV payload fairing?

What I would do is to use the Titan to launch it, dock with any of the
simple, easially built space station ideas exising today and operate it
year round. That way we can use Spacelab 365 days a year instead of
a week or so every two years.

Let's not forget that one capability of the Shuttle is the ability to
insure that key experiments are only done once every few years or so.
It is only one of the many ways that the space shuttle is hampering
routine cheap access to space.

  Allen
-- 
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  aws@iti.org     |  nothing undone"                                       |
+----------------------155 DAYS TO FIRST FLIGHT OF DCX----------------------+
From: neufeld@helios.physics.utoronto.ca (Christopher Neufeld)
Subject: Re: Solar sailing
Organization: University of Toronto Physics/Astronomy/CITA
Distribution: sci
Date: Mon, 23 Nov 1992 16:48:24 GMT

In article <By32vF.GD6.1@cs.cmu.edu> roberts@cmr.ncsl.nist.gov (John Roberts) writes:
>
>Most proposed solar sails are reflective, not black. That's because the
>principles of conservation of momentum show that reflecting the beam of
>light can greatly increase the thrust of the sail. The best results
>are with a 100% reflective sail perpendicular to the beam of light (theta = 0);
>that doubles the thrust.
>
   Well, yes, for certain definitions of 'best results'. Unless your
sail+payload has a very low mean mass per unit area, though, the net
force on the sail is still going to be sunward. Since the solar pressure
falls off as the square of distance just the way gravity does, the effect
of setting the sail at normal incidence to the sun is the same (from a
mathematical point of view) as instantaneously reducing the mass of the
sun while maintaining the position and velocity of the spacecraft fixed
over that instant. The result is a new orbit which circumscribes the old
one and is tangent to it at the point where the sail was unfurled. This
new orbit, of course, is closed, like any bounded orbit in an inverse
square field.  Now, for some trajectories this is desirable, but for most
it probably will not do.
   The usual trick is to set the sail at an angle to the spacecraft-sun
line. Since the radial component of the thrust does no net work over one
complete orbit (to first order, it helps a bit to second order if the
sail is not at normal incidence), the sail should be set at an angle to
maximize the tangential thrust. This angle is about 35 degrees for a
perfectly reflecting, planar sail. The sail can be angled to thrust along
the velocity vector or against it, and the orbital energy of the sail can
be raised or lowered this way, allowing the sail to move sunward just as
easily as it moves outward.
   A higher generation sail might be designed with a collector area at
normal incidence to the sun but which focusses the light onto a small
secondary reflector which can be steered rapidly to new directions. The
sail can be smaller for a given thrust. There will be some weight and
design penalties on making the reflector (which has to handle a very high
power flux) and making a sail which can focus accurately onto the second
reflector.

>John Roberts
>roberts@cmr.ncsl.nist.gov


-- 
 Christopher Neufeld....Just a graduate student  | Don't let your mind
 neufeld@helios.physics.utoronto.ca    Ad astra  | wander -- it's too little
 utzoo.utoronto.ca!generic!cneufeld              | to be let out alone.
 "Don't edit reality for the sake of simplicity" |
From: jfw@ksr.com (John F. Woods)
Newsgroups: sci.space
Subject: Re: Shuttle replacement
Date: 23 Nov 92 10:09:00 EST

aws@iti.org (Allen W. Sherzer) writes:
>In article <69996@cup.portal.com> BrianT@cup.portal.com (Brian Stuart Thorn) writes:
>>Whether or not it is efficient to do so is another question. I posted
>>another question about why Hubble Space Telescope is not brought back
>>home for repairs. There are many reasons in this case, mostly concerning
>>cost and loss of productivity (however limited it would be).
>Brinning Hubble back and flying it again would cost well over a billion
>$$. For less, we could build a new one and launch on a Titan.

And, of course, since Hubble wasn't designed to withstand the rigors of
being brought back (though that was the original intention), doing so could
result in *needing* to build a new one -- after having spent a billion dollars
:-).  [The ride down is not all that smooth, and Hubble is a big, delicate
piece of optics.]

Newsgroups: sci.space,alt.sci.planetary
From: sysmgr@king.eng.umd.edu (Doug Mohney)
Subject: Re: Lunar "colony" reality check
Date: Tue, 17 Nov 92 16:48:14 GMT
Organization: Computer Aided Design Lab, U. of Maryland College Park
Reply-To: sysmgr@king.eng.umd.edu

In article <1992Nov13.183354.11877@ke4zv.uucp>, gary@ke4zv.uucp (Gary Coffman) writes:

>But first you have to mine them, build the processing plants, build the
>machine shops, do site preparation, and actually install the equipment.
>A Lunar base is unlikely to have more than a dozen workers at first, and
>they will have other tasks, like staying alive, that will consume much
>of their time. The infrastructure needed to do large scale mining, refining,
>fabrication, and civil engineering needed to build a power system from 
>scratch is rather staggering. Let me drop you and a dozen of your friends
>in the vastly more friendly environment of the Sahara desert and see how
>long it takes you to build a multi-gigawatt power array and then transport
>yourselves to the Gobi desert and build another and interconnect them.
>I don't think Bechtel, with all their resources, could do it here in
>less than decades.

Of course they couldn't. You'd get chewed out for ruining the pristine
environment of the desert. :)

And the native materials of the Sahara aren't available to make solar cells,
for one thing...

Staying alive is mickey mouse in the scheme of things. We know how to do it, and
we have good ideas on how to make it comfortable for long-term stays. 

Figuring out the total number of packages needed to provide a "reproducing 
and prospering" infrastructure which can produce O2, metals, and silicon or 
GaAs for solar cells hasn't been done. I don't think anyone has done
handwaving on it, other than in some general outlines.

I'd say 8-10 years from the initial package set down to at least one and
possibly two sun farms to beam back significant (i.e.: to make a buck) amounts
of power, assuming a serious effort. 

Of course, if you want to be petty about it, it will take a couple of decades
to power most of the earth :-)

 
                 Play in the intelluctual sandbox of Usenet 

  -- >                  SYSMGR@CADLAB.ENG.UMD.EDU                        < --
Newsgroups: sci.space
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Space suit research?
Date: Mon, 16 Nov 1992 00:53:16 GMT
Organization: U of Toronto Zoology

In article <BxqsoH.MBq@access.digex.com> prb@access.digex.com (Pat) writes:
>What's the big push for a earth normal type atmosphere?
>apollo, etc, ran fine on low pressure pure O2,  does better pressure 
>greatly improve cooling.  or are there long term bio effects????

The cooling issue is a serious one.  Apollo didn't have that concern --
since doing an EVA required depressurizing the entire cabin, air-cooled
equipment could not be used at all.  This was okay, more or less, for
Apollo, but simply isn't appropriate for a laboratory environment:
air cooling is by *far* the easiest way to cool electronics, and the
cost of the hardware goes way up without it.

And yes, there is some concern about possible long-term biological
effects, although there is little firm knowledge.
-- 
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  henry@zoo.toronto.edu  utzoo!henry
Newsgroups: sci.space
From: roberts@cmr.ncsl.nist.gov (John Roberts)
Subject: Upcoming HST lecture
X-Added: Forwarded by Space Digest
Organization: National Institute of Standards and Technology formerly National Bureau of Standards
Original-Sender: isu@VACATION.VENARI.CS.CMU.EDU
Distribution: sci
Date: Wed, 18 Nov 1992 03:14:55 GMT


[Sorry about the late post - I just found out about it. I'll try to attend
and take notes, but no promises. JWR]

IEEE Instrumentation and Measurement Society Chapter Meeting

"The Hubble Space Telescope: an Instrument that Takes Exceedingly Good
Care of Itself"

Thursday, November 19, 1992, 8:00 pm
Mr. Dana L. Mitchell - Lead Instrument Engineer at the Space Telescope
  Science Institute

>From the level of a single detector on up to the entire telescope as a 
system, the HST does an exceptional job of protecting itself. We will
hear a recent saga of problems both internal and external to the spacecraft,
and how the HST automatically rode through it all without a scratch.

Mr. Mitchell is Lead Instrument Engineer and Deputy Chief of the Engineering
Support Branch at the Space Telescope Science Institute, Baltimore MD. He
heads the group of engineers who monitor the performance of the Hubble
Space Telescope's instruments. Prior to this, he was the Technical Director
of the Steward Observatory at the University of Arizona. His initial
satellite instrumentation experience was gained as Chief Engineer of the
Columbia University Astrophysics Laboratory where he followed a number of
instruments from design through to in-orbit operation.

Hazelton's Restaurant, Gaithersburg Marriott, Gaithersburg MD.
Social 6:15 pm; Dinner 6:45 pm; Talk 8:00 pm. For dinner reservations,
contact Jerry Stenbakken before November 18, 1992 on 301-975-2440.

John Roberts
roberts@cmr.ncsl.nist.gov
From: "UTADNX::UTDSSA::GREER"@utspan.span.nasa.gov
Newsgroups: sci.space
Subject: All NASA Science In-House?
Date: 17 Nov 92 16:06:04 GMT
Article-I.D.: cs.BxvBn4.G1z.1
Distribution: sci
Organization: [via International Space University]
X-Added: Forwarded by Space Digest
Original-Sender: isu@VACATION.VENARI.CS.CMU.EDU


I skimmed over the news about NASA's reorganization, thinking it was mainly
some kind of bureaucratic busywork, but now I'm hearing that NASA plans to do
all science in-house.  If this is true, it would mean that space science
departments in universities would no longer get funding from NASA, and I guess
it would also mean that an organization like JPL would no longer receive such
funding either.

If this is true, and if the NSF also shirks its responsibility to fund basic
research [i.e., if Walter Massey has his way], then US space scientists of all
stripes will have to rely increasingly on US military funding [at least THEY
still understand the value of basic research] and certain other nations which
are amenable to international cooperation in this area. 

Does anyone out there still have a copy of the NASA reorganization story,
and/or could they tell me what they think this means to the space science
community? 

_____________
Dale M. Greer, whose opinions are not to be confused with those of the
Center for Space Sciences, U.T. at Dallas, UTSPAN::UTADNX::UTDSSA::GREER
"Pave Paradise, put up a parking lot." -- Joni Mitchell
Newsgroups: sci.space
From: abond@rvgs.vak12ed.edu (Andrew H. Bond)
Subject: Re: Laser Divergence
Organization: Virginia's Public Education Network (Roanoke)
Distribution: sci
Date: Sun, 22 Nov 92 08:49:32 GMT

GFH101@URIACC.URI.EDU  writes:
> 
> Hi.  I look in from time to time.
> 
> I'm looking for information about interstellar lasers.  They sound like a
> great idea.  My question is: what keeps the laser beam from diverging
> over long distances?
> 
> A carbon dioxide laser in a physics lab has a 1/4 inch beam when it leaves
> the laser and a one inch or two inch spotlight on the far wall.
> 
> Can I make the following assumptions?:
> 
> 1.  The divergence of the beam is inversely related to the square of
> the beam width, at any certain distance.
> 
> 2.  The divergence of the beam is somehow related to the wavelength.
> ------------------------------------------------------------------------
> Thanks,
> Paul Klinkman
> Scavenger of arcania.

A laser beam diverges as a gaussian beam. i.e. the cross
section has a gaussian distribution as it propogates through
space. Over a very long distance, the spot size is asymptotic
to an angle.

The expansion angle of the beam is:

         Theta            2 * Lambda0
	--------    =    ---------------
	   2              pi * n * w0

where:

Theta   = expansion angle
Lambda0 = wavelength
w0      = radius of beam waist (waist = min. spot size)
n       = index of refraction of medium 

To make a long story short interstellar lasers will diverge no
matter what! All we can hope to do is make this divergence very
small. We can do this by

1. using a very short wavelength 
2. having a very large beam waist 

note: for most lasers the beam waist is in the middle of the
lasing cavity: diam of beam at aperture is a good approx.

Hope this helps. --AHB
-- 
Andrew H. Bond, Roanoke Valley Graduate Center
Newsgroups: sci.space
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Aerobraking [was Re: Magellan Update - 11/20/92]
Date: Sat, 21 Nov 1992 23:00:05 GMT
Organization: U of Toronto Zoology

In article <19117@ksr.com> clj@ksr.com (Chris Jones) writes:
>>>BTW, I think Magellan will become the first spacecraft to conduct an 
>>>aerobraking maneuver to change its orbit, right???
>>Wrong.  Hiten ... did a small Earth aerobraking maneuver in spring 1991.
>
>At least two of the Soviet circumlunar Zond flights used an aerobraking
>maneuver to minimize the G forces on reentry...

All the Apollo lunar missions, and various other spacecraft, likewise did
two-phase reentries.  But maneuvering during reentry is not normally referred
to as aerobraking, and such reentries are *not* composed of two separate
encounters with the atmosphere; they're one encounter following a complex
down-up-down trajectory.

The question was about *changing orbits* with aerobraking.
-- 
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  henry@zoo.toronto.edu  utzoo!henry
Newsgroups: sci.space
From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: Galileo HGA: Hypothesis
Organization: Simon Fraser University
Date: Fri, 20 Nov 1992 00:09:16 GMT

In article <246900037@peg.pegasus.oz.au> wlmss@peg.pegasus.oz.au writes:
>
> 
> 
>        Another naive query about Galileo's HGA problem.
> 
>        Can it send data at a high rate but with little power?
> 
>        If so, what if a relay craft were sent after it to gather and
>        send information back at the intended rate?
> 
>        Would this work?
> 
> 
>      o < < < < < < < < < < < <  )-x  . . . . )-G
> 
>      earth                     relay       Galileo
> 

Sure, but how are you going to *keep* the relay at that point between Earth and
Galileo? You'd pretty much have to put it in orbit around Jupiter or place it
in the inner Lagrangian point. In any smaller orbit it'd orbit faster than
Jupiter, and thus spend most of its time at least as far from Galileo as Earth
is now.

Another idea: Put a really large radiotelescope in Earth orbit and hook it to
the Deep Space Network. I saw a marvelous scheme for doing this once in a story
about nitinol, the memory alloy. One makes a flimsy lacework paraboloidal
antenna which has a conductive path arranged such that applied current flows
through all the nitinol wires in the structure. It is fabricated at high
temperature and then cooled off, wadded into a much smaller package, and
shipped to orbit. Once there a large current throgh the wires restores the
paraboloid to its original shape!

Oh well, so much for the science fiction writing today. I'll go finish marking
exams.

Leigh

Leigh
Newsgroups: sci.space
From: pgf@srl06.cacs.usl.edu ("Phil G. Fraering")
Subject: Re: World in danger
X-Added: Forwarded by Space Digest
Organization: [via International Space University]
Original-Sender: isu@VACATION.VENARI.CS.CMU.EDU
Distribution: sci
Date: Fri, 20 Nov 1992 16:49:19 GMT



-From: rjp1@cbnewsc.cb.att.com (be here now)
-Subject: world in danger
-Date: 19 Nov 92 18:51:33 GMT

-Yesterday evening (11/17) on Headline News a short (~1 minute) news
-item was read about a group of scientists who had published a document
-warning us of the danger we're all in becuase of the rapid depletion
-of the ozone and the also rapid extinction of many species of animals.
-The news item was very brief and did not mention any names nor even
-the title of the paper that was published.

-It seems to me that if something as (seemingly) important as this
-ought to have had more attention paid to it than a one-minute news
-blurb without references.  

-Bob Pietkivitch     | "Moon, my long lost friend, is smiling from above."
-rjp1@ihspa.att.com  |  -- Genesis, Stagnation 1970

Possibly because if it's covered in more than a 30 second blurb they
might have to mention that many scientists _don't_ think the world
is ending.

And CNN isn't any better: they don't have enough time to cover science,
they're too busy covering stuff like the men's movement and how you
have to get in touch with your spear etc. (I'm serious! Who saw that
this morning?) although the political bias of the owner is going to
ensure that you won't hear about it when someone finds evidence that
the sky _isn't_ falling.


-- 
Phil Fraering
In the country of the blind....
60 minutes doesn't run stories about people trying to ban hearing
Newsgroups: sci.space,alt.sci.planetary
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Lunar "colony" reality check
Date: Thu, 19 Nov 1992 22:31:16 GMT
Organization: U of Toronto Zoology

In article <1992Nov19.020207.11499@gucis.cit.gu.edu.au> wharvey@gucis.cit.gu.edu.au (Wayne Harvey) writes:
>I seem to remember some theory a while back that the moon was actually 
>*captured* by Earth at some stage (I think it was about 800 million
>years ago)...

The three classical theories of lunar formation -- fission from Earth,
formation in orbit around Earth, and capture -- were all pretty much
destroyed by analysis of the Apollo samples.  Earth and Moon are too
similar to have formed far apart, and too different to have formed
together unless you add some extra factor to give them very different
histories.  The giant-impact theory fits the bill, and the facts.

>... when you assume that the only mineral explorations done on
>the lunar surface were conducted in the equivalent of the Sahara.

Not a very tenable assumption.  For one thing, those explorations got
samples from a much wider range of locations, courtesy of splashes
from meteorite impacts.  For another, even the "local" rocks differed
a great deal between sites.  (The lunar scientists were against landing
Apollo 12 at a site that looked so similar to the Apollo 11 site, but
they shut up when they saw the preliminary results from the Apollo 12
samples.)  There's no doubt that we've sampled only a little of the Moon's
geological diversity -- and useful ore bodies are often very localized
things, the results of extreme conditions -- but we do have enough data
to be fairly confident of the average composition.
-- 
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  henry@zoo.toronto.edu  utzoo!henry
Newsgroups: sci.space
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Galileo HGA: Hypothesis
Date: Thu, 19 Nov 1992 23:29:23 GMT
Organization: U of Toronto Zoology

In article <246900037@peg.pegasus.oz.au> wlmss@peg.pegasus.oz.au writes:
>        Another naive query about Galileo's HGA problem.
>        Can it send data at a high rate but with little power?

The HGA is useless in its current state.  The low-gain antennas can send
high-rate data, if a receiver is relatively close.

>        If so, what if a relay craft were sent after it to gather and
>        send information back at the intended rate?

This was the most technically-feasible way to salvage the complete mission.
Put the relay craft in high orbit around Jupiter, and the Galileo LGAs
can get the high data rate that far.  A light relay craft could be
launched on a more direct trajectory to reach Jupiter in time.  It hasn't
been done, basically because it required commitment to a modest but
substantial expenditure very quickly, and NASA can't *do* that nowadays.
-- 
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  henry@zoo.toronto.edu  utzoo!henry
Newsgroups: sci.space