Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_2/V11_256.TXT

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Subject: SPACE Digest V11 #256

SPACE Digest                                     Volume 11 : Issue 256

Today's Topics:
          Re: Pegasus launch from Valkyrie  (or ...
               Re: Interstellar travel
      Satellites close-up ? (was Re: Observations of STS 36...)
            Re: HST Images (long)
                Re: sci.astro
          Re: Pegasus launch from Valkyrie  (or ...
              New Launch Date For STS-31
----------------------------------------------------------------------

Date: 12 Apr 90 20:04:12 GMT
From: skipper![e-mail]  (Al Bowers)
Subject: Re: Pegasus launch from Valkyrie  (or ...

In article <[e-mail]> [e-mail] (Henry Spencer) writes:

>>What can the B-1 and B-2 do?

>The B-1A was supersonic, but not greatly so; I think the B-1B abandoned
>supersonic capability when its engine inlets were redesigned to reduce
>radar signature.  The B-2 is subsonic.

B-1A was capable of Mach 2.2 at altitude.  It had all sorts of ramps
and hydraulics in the inlets (not very stealthy) to do it though.  The
B-1B is a Mach 1.2 bird at about 40,000 feet.  The variable geometry
inlets were deleted to save cost (and improve stealth).  There was
also a proposal to delete the wing sweep feature, but that was shot
down as it would have cost even more for the redesign to do so (?!?).
So we are left with a low altitude penetrator strategic bomber that
has a high altitude (marginally) supersonic capability that is not a
part of the specification.  BTW, the F/A-18 has fixed inlets too and
has a reasonable supersonic capability (1.8) as does the F-16 (2.2).

--
Albion H. Bowers  [e-mail] ames!elxsi.dfrf.nasa.gov!bowers

`In the changing of the times, they were like autumn lightning, a
thing out of season, an empty promise of rain that would fall unheeded
on fields already bare.'
                              attributed to Abe Shosaburo by Dave Lowery

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

Date: 12 Apr 90 17:01:51 GMT
From: zaphod.mps.ohio-state.edu!samsung!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Interstellar travel

In article <[e-mail]> [e-mail] (Jeffrey Kirk Bennett) writes:
>1. The goal is to find intelligent life and/or a habitable planet. It
>seems to me that both are extremely
>    rare events...

This is unproven, and there is reason for doubt.  It looks as if planets
are normal around small stars like the Sun, and there is a reasonable
chance of them being habitable.  (The evidence for the first part is
fairly strong, the second part is the current best guess.)  The chances
for intelligent life are highly controversial:  theoretical arguments
suggest that it should be common, but the Fermi Paradox observes that
we should have had visitors by now in that case.  That's an unsolved
puzzle at present.

>    ...Though I've no doubt that there is life somewhere else
>in the universe, I'm sure it is
>    an exceedingly rare event...

Can you elaborate on the reasoning that leads you to this conclusion?

>2. I don't see mankind inventing practical anti-matter propulsion or
>whatever the current idea is in the next century or two.

If one believes Robert Forward, antimatter propulsion in particular could
be practical within decades if a concerted effort were made.  A number of
starship-propulsion schemes have been proposed, and several of them are
not too far beyond our current abilities.  Barring disaster, the odds
are good that at least one will be practical within a hundred years.
Interstellar travel is expensive, but it's not all that difficult.

>related question is- are there
>    thermodynamic efficiency considerations which limit the maximum
>possible speed?...

No.  For example, if you assume very large quantities of antimatter and
solutions to some related problems, fairly close approaches to the speed
of light are possible.  Similarly, a well-designed Bussard ramjet could
approach the speed of light very closely.  (Periodically someone discovers
the "ramjet speed limit" and trumpets interstellar ramjets as an obvious
fallacy.  Then he reads the ramjet literature and, if he's honest, makes a
public apology for his blunder.)  The energy requirements are formidable
but there are no truly fundamental barriers.

>    The point is, due to relativistic mechanics, wouldn't it be a 1-way
>trip? If you travelled to a
>     star 5 light-years away at .9c, wouldn't a few centuries or
>millenium pass on Earth?...

No.  Travelling five light-years at roughly the speed of light takes roughly
five years, Earth time.  Rather less aboard ship, due to time dilation.

>What happens to time during
>     the acceleration and deceleration...

More complicated versions of the same thing.

>3. Assuming all the fuel is burned during the acceleration and
>deceleration phases, how would
>    the craft return?

Refuelling in the target system is the easiest way, assuming it's possible
with the propulsion system used.  Ambitious antimatter-based systems might
be able to just take along the fuel for the return trip.  Or you can simply
accept that it's a one-way trip, either for colonization or as a scientific
expedition.  (There is no shortage of people who would be willing to spend
the rest of their lives exploring a new solar system.)

>4. Even if it had the fuel to return, how would it find the Earth again,
>since it is not exactly
>    standing still, and may have moved unpredictably due to passing
>stars, black holes, etc...

This becomes a problem only when voyages of many thousands of years are
being considered.  That's not very likely to happen.  Interstellar flight
at sub-light speeds is much more likely to proceed by short hops between
nearby stars than by enormous leaps out into the farther reaches.

>... So who would fund this research, when the astronauts
>would be returning
>(if they ever returned) 20,000 years into the future...

Under our current setup, nobody is likely to fund it; it's hard enough
getting funding for projects that last longer than one US presidential
term.  In general, it will be difficult to rouse much enthusiasm for
starflight until it can get results within a human lifetime.  That was
one of the constraints of the old Daedalus study:  flight time (of an
unmanned Voyager-style probe) to Barnard's Star to be no longer than
40-50 years, so the younger participants would be alive when results
came back.  That study concluded that the technology to do it, while
not here yet, was not that far off.

>4. Wouldn't something decelerating from near light-speed in our solar
>system have to shed all
>     its relativistic mass as energy? In that case, it would probably be
>     [detectable]. Since we haven't seen this, doesn't
>that alone prove that there     are no UFO's?

UFOs unquestionably exist; remember that those initials stand for Unidentified
Flying Object, note the "U" part in particular.  It seems very unlikely that
they are extraterrestrial spaceships, for a number of reasons.  The above
argument actually isn't a very good one, because all it says is that the
little green men have to know more about physics than we do, which would
seem quite plausible.  (Actually, even we know of theoretical ways to go
places by means other than raw velocity -- e.g., general-relativistic
space warps -- even though right now we have no idea how such a thing
could be made practical.)

>... I can't imagine him
>    just buzzing some farmer in Arkansas and heading off into the sunset.

This, now, is one of the stronger arguments against the little-green-men
theory of UFOs:  their behavior fits atmospheric and optical phenomena --
plus the occasional fake -- much better than it fits spaceships.

>would say the other 1%
>    (from reliable sources, Air Force pilots, etc.) are military craft
>or experimental weapons, etc.
>    that don't officially exist...

Actually, the other 1% are almost certainly explainable in mundane ways
just like the first 99%, after discounting observer error, out-and-out
hoaxes, etc.  There is a prevailing myth that folks like professional
pilots are expert observers, which they are not:  they are trained to
try to figure out what's going on, so they can react accordingly, not to
simply observe as accurately as possible without introducing errors by
trying to interpret what they see.  There are documented cases of pilots
reporting UFOs pacing the plane, etc., when it is about as certain as
it can possibly be that what they were really seeing was a meteorite a
hundred miles away.
--
With features like this,      |     Henry Spencer at U of Toronto Zoology
who needs bugs?               | uunet!attcan!utzoo!henry [e-mail]

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

Date: Thu, 12 Apr 90 14:12:35 +0200
From: [e-mail] (Daniel Fischer)
Subject: Satellites close-up ? (was Re: Observations of STS 36...)
Cc: [e-mail]

 In <6 Apr 90 13:19 GMT> swrinde!zaphod... <real name unreconstructible> writes:
> ... you're figuring 1.5 deg/sec based on swinging an arc around your
> vantage point... As the shuttle "comes up" from the horizon it will be
> farther than 300 km from the observer and appear to move more slowly...
Right, but it also appears to shrink: if the shuttle's long axis is parallel
to the flight direction, the ratio of apparent speed and apparent size is
constant. If it flies with the long axis pointed towards earth, the situation
is slightly better, but you always have a trade-off between size and speed.
                In  <5 Apr 90 14:28 GMT> Dan Briggs writes:
> Remember the problem with the shuttle tiles coming off... the telescope
> responsible for many of those images ... at White Sands ... is a very dedi=
> cated instrument for imaging satellites, and it does indeed have a very
> specialized mount for the high tracking rates required.
Have any of these images been published? Who's running this instrument? Are
technical details available (in published literature) ?
                          Dan also had wondered:
> I don't know if he was talking about professional or amateur observers.
He (i.e. Roy Smith) talked about amateurs, but what I have in mind is something
inbetween: a network of satellite tracking telescopes run by/for a media
organization. How many newspaper columns have been filled during all those
secret STS and other missions, speculating about the payloads, but not even
knowing their actual dimensions. Every time something mysterious happens in
Libya etc., SPOT satellite images are being bought by the press (well, having
them and understanding them isn't the same...) - why not doing it the other way
around and pointing one of these MediaScopes at the satellite in question?!

+- [e-mail] --- Daniel Fischer --- [e-mail] -+
| Max-Planck-Institut f. Radioastronomie, Auf dem Huegel 69, D-5300 Bonn 1,FRG |
+----- Enjoy the Universe - it's the only one you're likely to experience -----+

BTW: only a groundbased telescope will be able to photograph the - hopefully -
marvellous sight of DISCOVERY separating from the HST. Under average seeing
conditions both S/C should be resolvable. HST is predicted to be -3rd mag!

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

Date: 12 Apr 90 16:31:58 GMT
From: cs.utexas.edu!usc!elroy.jpl.nasa.gov!aristotle![e-mail]  (Peter Scott)
Subject: Re: HST Images (long)

In article <[e-mail]>, [e-mail] (Joseph M. Knapp) writes:

> Also, I would like to know if there is a good source for Voyager photographs.
> Magazine photos digitize on my scanner pretty well if they are 1/2 page
> or larger, but with smaller photos I start seeing evidence of the four-color
> printing process when the image is blown up. I'd love to get 8x11 or larger
> glossies.

Call or write the Public Information Office at your nearest NASA center and
they'll send you more 8x11 glossies than you know what to do with.  They're
very good at this.

BTW, I've noticed some common misconceptions among people about JPL which may
be out there in this newsgroup, this seems like a good time to overturn
a few...

MYTH #1: There are ~300 people working at JPL.  Actually it's about 9,000,
the majority being Caltech employees, the rest contractors.  There are even
rumored to be a handful of NASA employees lurking around :-)

MYTH #2: We all talk to each other and know each other.  See myth #1 for
infeasibility estimates.

MYTH #3: About half of those 300 work on processing deep space images, the
rest on building spacecraft.  In fact I'd guess that maybe 100 people tops
are directly involved with s/c images, including the opnav people who use
them to feedback to the trajectory folks.  No idea how many people work on
s/c manufacture.  There is a sizeable crowd involved with operations of
one kind of another (I'm in a group that develops software that figures out
when and where spacecraft should maneuver).  Then there are people involved
in stuff like robotics, medical imaging, earth sciences, you name it.

MYTH #4: We are all on the net.  Informal studies (:-) suggest that at least
half of the population here is barely aware that the net exists, and that it
is of no importance to their work anyway.  While this may come as a shock to
the folk that can't understand why they are unable to order pizza via netmail
:-) things seem to work pretty well anyway.  The population of Unix machines
and workstations has taken off here in the last year so this data may change
soon.

Anyway, take all this with a grain of salt; if I'm not supposed to speak
on behalf of JPL I may just be making it all up  ;-)


This is news.  This is your       |    Peter Scott, NASA/JPL/Caltech
brain on news.  Any questions?    |    ([e-mail])

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

Date:     Thu, 12 Apr 1990 16:08 EDT
From: DAVID SIMMONS <[e-mail]>
Subject:  Re: sci.astro
To: <[e-mail]>

 Dan Charrois writes:
>  I have heard much disscussion of a sci.astro list, and I am sure I would
>find it very interesting. So, I have a question on how I might subscribe
>to the list. I currently only have access to a Bitnet site ( all my mail
>to and from sci.space gets packaged up ona bitnet site and send through
>whatever network is the home for sci.space, as I understand it..)
>  Does a similar situation exist for sci.astro, and if not, is there any
>way I can subscribe to the distribution from Bitnet at all?

     I would also like to get on sci.astro, and am in the same situation
that Dan is in; only having access to a Bitnet site. I would greatly
appreciate any assistance.

     David Simmons
     04703@AECLCR

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

Date: 12 Apr 90 14:16:11 GMT
From: pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!samsung!umich!umeecs!itivax!vax3.iti.org![e-mail]  (Allen W. Sherzer)
Subject: Re: Pegasus launch from Valkyrie  (or ...

In article <[e-mail]> [e-mail] (David Smith) writes:
>>>I don't really know what current planes could carry 40,000 lbs at such speeds;

>>I was wondering if a FB-111 would do?

>It's not exactly in the same speed class as B-70 or FB-111,

Agreed. What I was thinking was that it might be a lot cheaper to buy and
operate a FB-111. I believe 747's cost ~$150 mil but a doubt a FB-111 costs
more that ~$70 mil. I don't know about operating costs however.

After I wrote the above another thought occured to me. Using a 747 or B-52
they could launch 2 or 3 at a time. Anybody know if there are any plans to
do that?

  Allen
-----------------------------------------------------------------------------
| Allen W. Sherzer         |         If guns are outlawed,                  |
|   [e-mail]            |         how will we shoot the liberals?        |
-----------------------------------------------------------------------------

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

Date: 12 Apr 90 18:56:46 GMT
From: cs.utexas.edu!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: New Launch Date For STS-31



Just heard that the new launch date for STS-31 is April 25.

 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

End of SPACE Digest V11 #256
*******************