Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_4/V15NO447.TXT

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Date: Sun, 22 Nov 92 05:02:03
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #447
To: Space Digest Readers
Precedence: bulk


Space Digest                Sun, 22 Nov 92       Volume 15 : Issue 447

Today's Topics:
      Aerobraking [was Re: Magellan Update - 11/20/92] (2 msgs)
       Clinton's address (was Re: Feynmann's legacy)  (2 msgs)
                           Hubble's mirror
                      Laser Divergence (4 msgs)
                      Magellan Update - 11/20/92
                          Scientific method
                      shuttle computers (3 msgs)
                     Shuttle replacement (3 msgs)
                        Solar Sailing (2 msgs)
              SSTO Viability (was: Shuttle replacement)

    Welcome to the Space Digest!!  Please send your messages to
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----------------------------------------------------------------------

Date: 21 Nov 92 17:14:10 EST
From: Chris Jones <[e-mail]>
Subject: Aerobraking [was Re: Magellan Update - 11/20/92]
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]>, henry@zoo (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Claudio Egalon) writes:
>>BTW, I think Magellan will become the first spacecraft to conduct an
>>aerobraking maneuver to change its orbit, right???
>
>Wrong.  Hiten -- the Japanese engineering-test mission that's been batting
>around the Earth-Moon system for a couple of years -- 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.  The descent module entered the
atmosphere at an angle low enough to "skip" off back into space, having shed
enough velociy so the second reentry would have been more comfortable for the
human occupant(s) on the presumed followon flight (never flown since Apollo 8
got there firstest with the mostest).  I recall that the Zond flights which
reentered directly underwent over 15 Gs, while the "skip return" trajectory
subjected the craft to around 5 Gs.
--
Chris Jones    [e-mail]

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

Date: Sat, 21 Nov 1992 23:00:05 GMT
From: Henry Spencer <[e-mail]>
Subject: Aerobraking [was Re: Magellan Update - 11/20/92]
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (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)|  [e-mail]  utzoo!henry

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

Date: Sat, 21 Nov 1992 18:35:16 GMT
From: [e-mail]
Subject: Clinton's address (was Re: Feynmann's legacy)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Edmund Hack) writes:
> In article <[e-mail]> [e-mail] writes:
>>For such a together dude, why doesn't Clinton (and Gore) have an e-mail
>>address and access to the NET???  They'll Never know what's going on
>>unless they be on-line.  They should at least be FAQed in.
>>
> Until recently, there was a set of email bridges between all 4 of the
> major campaigns and a set of alt.politics.canditate groups.  The Clinton
> group is in transition :-) to a more permanent setup.  It is my
> understanding that the Clinton an Bush campaigns answered 1500+
> questions each.  In addition, all 3 of biggest candidates had some kind
> of presence on Prodigy, with 250k+ messages generated.
>
> Maybe someday there will be an [e-mail]
> mail address.......
>
> --
> Edmund Hack - Lockheed Engineering & Sciences Co. - Houston, TX
> [e-mail] - I speak only for myself, unless blah, blah..


Thank you - we don't get much in the way of alt. groups here - nor Prodigy.
BTW, what was the 4th 'major campaign'?   I heard of a bunch of others that
b&m'ed that they weren't being taking seriously, but I didn't take
them seriously... <-).

WHH

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

Date: 21 Nov 1992 22:43:14 GMT
From: Jeffrey Alan Foust <[e-mail]>
Subject: Clinton's address (was Re: Feynmann's legacy)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>
>Thank you - we don't get much in the way of alt. groups here - nor Prodigy.
>BTW, what was the 4th 'major campaign'?   I heard of a bunch of others that
>b&m'ed that they weren't being taking seriously, but I didn't take
>them seriously... <-).

The Libtertarian candidate, Andre Marrou.  Marrou/Lord, along with
Clinton/Gore, Bush/Quayle, and Perot/Stockdale, were considered to be "major"
because their names were on the ballot in all fifty states.
--
Jeff Foust                        Senior, Geophysics/Planetary Science, Caltech
[e-mail]                       [e-mail]
        Tom Seaver: "Hey, Yogi, what time is it?"
        Yogi Berra: "You mean now?"

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

Date: 20 Nov 92 22:39:24 GMT
From: Mario Wolczko <[e-mail]>
Subject: Hubble's mirror
Newsgroups: sci.astro,sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
> I would guess that the null-corrector tests were done with the mirror
> flat on its back; it would seem the obvious approach.  The problem with
> gravitational distortion -- I would think -- is simply that it requires
> doing the test in a vertical orientation, which considerably complicates
> the test facility (if for no other reason, because you need a vertical
> shaft of considerable height to mount everything in).

I don't know what the spacing between primary and corrector(s) was,
but I would be surprised if it was substantially less than the
primary-secondary spacing.  So maybe there was a setup in use for the
corrector tests that didn't need a huge amount of change for a
primary-secondary test.  Of course, this is all easy to say in
hindsight.   The real problem is that the existing tests should have
caused alarm bells to ring, but the bells were ignored.
As they say, you can make something foolproof, but not bloody
foolproof..

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

Date: Sat, 21 Nov 92 17:34:48 EST
From: Paul Klinkman <[e-mail]>
Subject: Laser Divergence

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.

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

Date: Sat, 21 Nov 1992 23:48:25 GMT
From: Henry Spencer <[e-mail]>
Subject: Laser Divergence
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Paul Klinkman) writes:
>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?

Nothing.  It does diverge.  But with good optics on the sending end, it's
relatively slow divergence.

>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.

Run it through the right optics -- basically, a telescope -- and divergence
will be much slower.  You can't get rid of all of it, because of diffraction,
but your laser's unassisted output is definitely not "diffraction-limited"
quality.  A modest astronomical telescope can hold a visible laser down to
a 1-2km spot size on the Moon.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 21 Nov 1992 19:44 CST
From: [e-mail]
Subject: Laser Divergence
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes...
>In article <[e-mail]> [e-mail] (Paul Klinkman) writes:
>>I'm looking for information about interstellar lasers.

>Run it through the right optics -- basically, a telescope -- and divergence
>will be much slower.  You can't get rid of all of it, because of diffraction,
>but your laser's unassisted output is definitely not "diffraction-limited"
>quality.  A modest astronomical telescope can hold a visible laser down to
>a 1-2km spot size on the Moon.
>--

The articles that I have been reading about Lunar power beaming state that the
divergence of a laser beam, with a modest mirror system (I forgot how big)
would keep the divergece from the Moon down to 38 meters.

Also, in Conversations with folks at JPL in 1989, I found out that the
divergence from Saturn with a 800 mw Solid state laser would be 14,000 miles.
This assumed relatively poor (read light weight) optics on the transmitter.
This laser was proposed for Cassini in the early days.

Just some random information that I have.

Dennis, University of Alabama in Huntsville

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

Date: Sun, 22 Nov 1992 01:56:21 GMT
From: Henry Spencer <[e-mail]>
Subject: Laser Divergence
Newsgroups: sci.space

I wrote
>>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.
>
>Run it through the right optics -- basically, a telescope -- and divergence
>will be much slower.  You can't get rid of all of it, because of diffraction,
>but your laser's unassisted output is definitely not "diffraction-limited"
>quality...

Doug McDonald pointed out (in mail) that I'm being sloppy about terminology
here.  More precisely, "your laser's unassisted output isn't a properly-
focussed diffraction-limited beam".  It may just need focussing, whence the
suggestion of adding optics.

He also pointed out something I missed:  if this is a 10.6um laser, then
depending on how long your lab is and what "one inch or two inch" means
exactly, it might be close to focussed diffraction-limited performance
after all.  10.6um is a rather long wavelength, and diffraction gets worse
as wavelength grows.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 21 Nov 92 20:39:32 GMT
From: Henry Spencer <[e-mail]>
Subject: Magellan Update - 11/20/92
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]> [e-mail] (Claudio Egalon) writes:
>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??? ...

It's a concern.  This is why Magellan aerobraking would be done gradually
over many orbits, rather than in one blazing high-drag pass.  Magellan isn't
really designed for it.

>BTW, I think Magellan will become the first spacecraft to conduct an
>aerobraking maneuver to change its orbit, right???

Wrong.  Hiten -- the Japanese engineering-test mission that's been batting
around the Earth-Moon system for a couple of years -- did a small Earth
aerobraking maneuver in spring 1991.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: Sat, 21 Nov 92 13:43:24 EST
From: John Roberts <[e-mail]>
Subject: Scientific method

-From: [e-mail] (Henry Spencer)
-Subject: Re: Scientific method
-Date: 20 Nov 92 18:38:27 GMT

-In article <[e-mail]> [e-mail] (John Roberts) writes:
->... for instance, for instance, the Earth-impact model of the formation
->of the moon has risen from obscurity to the "most favored model", with
->(as far as I know) little or no new input of information - it's based on
->mathematical models and old Apollo and Voyager data...

-There is no problem testing a new theory quite rigorously using old data,
-if you do it carefully.  The trick is simply to get some testable predictions
-out of the theory before you look (closely) at the data, and then see if it
-checks.  This does get more difficult if the new theory has to be calibrated
-using the same data, but sometimes it can still be done.  It is more
-satisfying to have prediction precede experiment, because that *guarantees*
-that the theory was not custom-cooked to match the results,

I agree it can be done, but there are some potential difficulties that
investigators have to watch out for. Most obvious is "cheating" - theorists
making use of information that they pretend not to have when constructing
their models. To prevent that, somebody might get the idea of keeping
significant portions of the observational data "secret" - to be released
only after theories have been formulated. This of course would inhibit
the distribution of information (slowing the development of better theories),
and bring about the risk of "insider trading" of information ("so *that's*
why Fred Smith keeps coming up with the best theories"). I'm also not sure
how modifications of theories should be regarded in this context - if you
come up with a theory based on partial information, and analysis of more of
the data shows that some aspect of the theory needs to be modified, does
that mean that the theory is now considered questionable until it can be
checked against still more data? If so, there has to be some established
mechanism of releasing the data in small portions, so that a theory can be
taken through several iterations of evolution. But how can we be sure that
the decision on what data to release each time doesn't introduce biases into
the direction of development of the theory?

-but having a
-theory derived from general principles precisely explain measured phenomena
-in detail is a valid test, and often a fairly good one.

That seems to be the most straightforward approach in this context. I would
guess that in *most* cases, doing it this way rather than trying to force
in into the traditional mold would give the best results. (Spinoffs from
other research may provide additional confirmation anyway.) Of course, as you
say, the reason for the traditional method is to guard against researchers
inadvertently convincing themselves that events *had* to take place a certain
way because that's what was observed.

John Roberts
[e-mail]

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

Date: Sat, 21 Nov 92 13:13:42 EST
From: John Roberts <[e-mail]>
Subject: Shuttle computers

-From: [e-mail]
-Subject: Re: Shuttle computers
-Date: 20 Nov 92 14:31:48 GMT

-John:

-TO my knowledge they only load the machines from tape on board. They
-do have the ability to override and to take out machines manually via
-a set of buttons at the front of the shuttle. I think they are in the
-center position, reachable from either left or right hand seat.

-I'd have to pull out my copy of the control panel documentation (the
-REAL thing :-) to be sure.

I wonder if they've ever considered a system by which a spare tape can be
written by instructions from the ground, for checking and subsequent loading
into the GPCs. That could be useful if (for instance) one of the flight
control surfaces is damaged in an unanticipated way, and the basic flight
protocol has to be modified. Writing to a tape would overcome some of the
objections to direct loading of programs from the ground.

John Roberts
[e-mail]

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

Date: Sat, 21 Nov 92 19:29:02 GMT
From: Ross Borden <[e-mail]>
Subject: shuttle computers
Newsgroups: sci.space

>-Do the GPC's have hard drives?

>I'm virtually certain they don't. Hard disks *are* used in personal
>computers on the Shuttle (after all, they're mighty convenient),
>but they don't have anywhere near 5000 hours MTBF under the conditions
>in the Shuttle. (As I said before, one hard drive on a personal computer
>seized up on the last flight.)

>-If so, how do they guard against
>-shock, vibration, etc?

>-|                           [e-mail]                                |

>I would guess that they're powered down during launch and landing. (There
>could well be military disk drives that would have a better chance to work
>under those conditions, but even those would be likely to reduce the
>reliability of the GPCs if used in them.)

>John Roberts
>[e-mail]

    Do you have any references on the shuttle computers?  I'd be
interested to find out what kind of fault tolerance they have.

-------------------------------------------------------------------------------
      "I'd rather have an apendectomy with a burning spatula."
                [e-mail]
-------------------------------------------------------------------------------

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

Date: Sat, 21 Nov 1992 20:36:47 GMT
From: Henry Spencer <[e-mail]>
Subject: shuttle computers
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Ross Borden) writes:
>>They are routinely reloaded with different software from onboard storage
>>(tape, I think)...
>
>    Do the GPC's have hard drives?  If so, how do they guard against
>shock, vibration, etc?

I don't believe there are any hard drives currently in existence that can
meet the reliability specs under those conditions.  The GPCs have none.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: Sat, 21 Nov 92 20:15:33 GMT
From: [e-mail]
Subject: Shuttle replacement

> That means all it needs for the second launch is to be re-fueled.
>


Well, I'll pick a rather important nit: No pilot in their right mind
gets behind the wheel/stick without doing a careful walkaround
pre-flight. I expect that an operational DC1 vehicle will put the
pilot back into the loop in a way they never were or could be on the
Shuttle. With aviation style operations and complexity comes aviation
style checklists and hands on pilot responsibility. And a hearty amen
to that, brother.

                a former almost-pilot
                priced out of the air
                by lawyers and bureaucrats,

                    Dale Amon

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

Date: 21 Nov 92 20:35:20 GMT
From: Henry Spencer <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space.shuttle,sci.space

In article <[e-mail]> [e-mail] (Steven Bellovin) writes:
>The question is whether or not there's enough profit to recoup that kind
>of up-front development.  In the space market, I sincerely doubt it,
>unless the launch rate goes *way* up (see below)...

Anybody considering sinking a bunch of cash into developing a much cheaper
launcher is automatically assuming new markets, not existing ones.  The
existing markets aren't badly hampered by existing launch prices -- they
shop for lowest price, sure, but they don't object to paying the going
rate if it buys them things they care about, like reliability -- and are
not going to respond to lower prices with great increases in volume.

This is one of the bigger obstacles to novel launcher development:  it's
not enough to build the launcher, you also need to have the resources to
hang in there while patiently nurturing a new market to use the new
capabilities.  If there was an assured market that you could point to,
commercial launcher development would be underway all over the place.
It's not an accident that the more farsighted schemes for encouraging
commercial launchers focus on guaranteeing a market, not on providing
direct support.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: Sat, 21 Nov 92 19:06:36 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

Allen...

There is still *one* thing that the Space Shuttle can do that no other
launch system is capable of... bringing things back from orbit.

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).

The Shuttle, as you continually point out, is enormously expensive to
operate and inefficient when it is operating. But I don't think putting
a Soyuz on an Atlas (which *doesn't* have the lift capacity, BTW) or a
Titan IV (which isn't much better than Shuttle) is a reasonable solution.

Shuttle certainly does not have 'twice the lift capacity' of Titan IV as
an earlier poster contended, but it does have about one-third more, I
believe. NASA just doesn't use that capability. Instead, NASA is flying
Shuttles with half-full payload bays (STS-52). Someday, we might actually
have a payload requiring all that lift, or return capacity, and as we did
after the demise of Saturn V, we'll be saying "why did we abandon it?"

Or maybe not.

On a related topic (your informative background on Delta Clipper) this
sounds like an excellent idea, but I'm nervous about it. Having grown up
in the Cape Canaveral area, and seen my share of boosters blow up or go
tumbling into the Atlantic, the idea of a powered descent and vertical
landing gives me the willies... I sure hope that thing has plenty of
redundancy... rocket engines have a way of conking out at innopportune
times.

-Brian

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

Date: Sat, 21 Nov 1992 19:14:20 GMT
From: Frank Crary <[e-mail]>
Subject: Solar Sailing
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (SCOTT I CHASE) writes:
>There is more to Solar sailing, however, than just the radiation pressure.
>The Solar wind contains massive particles which will also hit your
>sail.  I don't have data handy for what the flux is, but you would
>need to look it up and make some kind of correction for it.  It might
>even dominate!

Solar wind pressures are about three orders of magnitude less than
light pressures. For any conventional sail design, they can pretty
much be ignored.

                                                     Frank Crary
                                                     CU Boulder

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

Date: Sat, 21 Nov 92 15:41:39 EST
From: John Roberts <[e-mail]>
Subject: Solar sailing

-From: [e-mail] (Bob McGwier)
-Subject: Solar Sailing
-Date: 20 Nov 92 16:15:35 GMT
-Organization: IDA Center for Communications Research

-I have a local high school student asking me for information on Solar
-sailing.  I have programs that will allow him to manipulate the sail
-if I knew how to calculate `thrusts' etc. from the photon pressure.
-Any details you care to send, primarily references, that will allow me
-to help this very bright student, I would appreciate it.

Let P be the power per unit area of an incident beam of directed light
(in other words, all the photons are moving in the same direction - a
reasonable approximation for a solar sail at a considerable distance from
the sun).

The pressure per unit area (call it p) of such a beam of light is P/c,
where c is the speed of light. If your solar sail is black and perpendicular
to the beam of light, then that's the outward force your sail will
experience. If your sail is black and is tilted at an angle of theta with
respect to the beam (where theta=0 means that the beam is perpendicular
to the surface), then you get an outward force of P/c * cos(theta), and a
"sideways" force of P/c * sin(theta) (valid for absolute value of theta
between 0 and 90 degrees). However, it should be noted that this formula is
valid only with respect to the power that is actually intercepted by the
sail - a tilted sail has less "effective" area, varying with cos(theta).
So the amount of thrust you'd actually get with your black sail (per unit
area of sail) is P/c * (cos(theta))^2 outward, and
P/c * cos(theta) * sin(theta) sideways.

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. If theta is nonzero, then the reflected beam will
have an angle of 2 * theta, so the formulas for a completely reflective
sail are modified to

p(outward)  = P/c * cos(theta) * (cos(theta) + cos(2 * theta))

p(sideways) = P/c * cos(theta) * (sin(theta) + sin(2 * theta))

(Note that if abs(theta) is between 45 and 90 degrees (pi/4 and pi/2 radians),
the reflection term actually decreases the outward thrust - under those
conditions, a black sail would actually provide more outward thrust than
a reflective sail. Also, if your sail is less than 100% reflective, then the
reflection term in the above equations is directly proportional to the
reflectivity.)

Now for something more difficult, and not directly relevant to traditional
solar sail designs: suppose the incoming beam is diffuse rather than
directed, and suppose the sail is a diffuse reflector rather than a
specular reflector? If the light is reaching the surface with equal
intensity from all directions, then a spherical integration shows that the
*net* effect is an outward thrust perpendicular to the surface, with an
intensity equal to *half* of what would be expected from a directed beam
of equal power. If the incoming light is a directed beam and the surface
of the sail is a diffuse reflector (in other words, if it reflects the light
equally in all directions), then the reflective component of the thrust
is again perpendicular to the surface, and equal to half of that of a
specular reflection.

If the incoming light is diffuse, and the solar sail is reflective, then
I *think* that the reflective component is the same whether the sail is a
specular or a diffuse reflector. I don't know of any easy way to work out
the math, but it seems to me that the reflected light would be equally
distributed in either case.

(Could somebody please verify that? I need it for my Dyson sphere
calculations.)

John Roberts
[e-mail]

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

Date: Sat, 21 Nov 92 19:07:09 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: SSTO Viability (was: Shuttle replacement)
Newsgroups: sci.space.shuttle,sci.space

>In <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>
>>Hmmm... this gives me an idea. Maybe the way to sell SSTO to Gore is
>>to emphasize the non-poluting fuel it uses. Deltas and Titans burn
>>nasty stuff which wold cause problems in large quantities.
>
>Actually, the biggest polluter is the Space Shuttle.  (Hydrochloric
>acid and other byproducts from those big SRBs.)
>

Yep, lots of nasty stuff in those SRBs. But I can say from observation
that the wildlife at Merritt Island National Wildlife Refuge, surrounding
Launch Complex 39, doesn't seem effected one bit. If pollution from the
SRBs were a serious threat, it should show up there first, right?
More Bald Eagles and alligators there than most places. Not to mention
all those fish, snakes, birds, and insects inhabiting the place.

I grew up around there too, and there's nothing wrong (hack hack) with
me (cough) either. ;-)

-Brian

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

Date: Sat, 21 Nov 92 13:02:08 EST
From: John Roberts <[e-mail]>

To: [e-mail]
Subject: Re: "Beyond 2000"


-From: [e-mail] (Hugh Emberson)
-Subject: Re: SSTO Viability (was: Shuttle replacement)
-Date: 21 Nov 92 04:40:26 GMT
-Organization: Computer Science Dept., University of Canterbury, New Zealand

-My mother tells me that a TV show we get here (NZ) called "Beyond
-2000" (its Austrailian, but I believe that lots of countries get it)
-had a segment on DC-{X,Y,1} a couple of weeks ago.  I missed it :-(.
-Anyway the segment was enough to get my mother excited enough to rave
-about it to me.  This leads me to believe that it could have quite an
-public appeal if it was sold to the public properly.

"Beyond 2000" is shown in the US on the Discovery Channel. It's an interesting
show, but I usually forget to watch it. :-)

John Roberts
[e-mail]

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

End of Space Digest Volume 15 : Issue 447
------------------------------