Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V08/V8_337.TXT

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Date: Thu, 25 Aug 88 01:05:23 PDT
From: Ted Anderson <[e-mail]>
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Subject: SPACE Digest V8 #337

SPACE Digest                                      Volume 8 : Issue 337

Today's Topics:
               Re: SETI (& STI)
               Re: Ozone layers
             Re: HOTOL funding cancelled
                Re: Aerospike
             'prestigious' space programs
                   Feedback
                Space Bloopers
         Re: SDI, Asats, and access to orbit
               Not in the line of duty
        Re: SETI: Why don't we hear anything?
          Re: space news from Juen 27 AW&ST
----------------------------------------------------------------------

Date: 15 Aug 88 17:44:20 GMT
From: spacely![e-mail]  (Edward Olsen)
Subject: Re: SETI (& STI)

The NASA SETI program will only be a SEARCH.  It will be listen only.  No
Transmissions are not part of the program.  The search space presently
envisioned is (1) High Sensitivity Target Search of the nearly 800 solar
type stars within 25 pc and (2) Low Sensitivity, Broad Band All Sky Survey.
The Target Search will be carried out with a frequency resolution of about 1 Hz
between 1 GHz and 3 GHz.  Integration times will be 100 -> 1000 seconds using
Arecibo and other large antennae (i.e. 70m DSN net, OSU, etc).  Instantaneous
bandpass will be 10 MHz to 40 MHz and polarization dual circular.  Sensitivity
achieved will be approximately 10**-26 watts/m**2.
The Sky Survey will be carried out with a frequency resolution of 10 Hz to
30 Hz between 1 GHz and 10 GHz (and higher frequency spot bands).  Integration
times will be 1/3 -> 3 seconds using the DSN 34m net and possibly the NRAO
300 ft.  Instantaneous bandpass will be 300 MHz and polarization dual circular.
Sensitivity achieved will be approximately 10**-23 watts/m**2.
The big problem is radio frequency interference --- keeping our signal detectorsfrom saturating with reports of all the local intelligent signals.

                  Edward Olsen



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

Date: Mon, 15 Aug 88 18:50:57 PDT
From: Eugene Miya <[e-mail]>
Subject: Re: Ozone layers

18:45 PDT start out bound.
Peter Scott asks about Ozone, unfortunately, Bob Watson, one of the best
men to ask this question isn't at JPL anymore, but there's lots of
other people you can ask.

Basically, inversion layers don't completely have much to do with it.
1st: we don't really understand the production (your word was regeneration)
mechanism.  Anything anyone tells you is a theory. 2nd: we don't
completely understand the transport mechanism.  It was only recently
discovered that CFCs could convect so quickly, because the O3 doesn't
(don't forget it's heavy).  So generation is largely "in place."
The "in place mechanisms are largely molecular and atomic oxygen up high
combining.  Some argued lightning was a production mechanism,
largely too low in altitude, largely discounted.  One person asked
about working on scrubbers for CFCs up high, the problem here is the sheer
size of the upper atmosphere.  Prevention is a better treatment, but
who knows, we may have passed points of no-return, maybe not.

--eugene
18:54 PDT

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

Date: 15 Aug 88 19:58:41 GMT
From: concertina![e-mail]  (Steve Hix)
Subject: Re: HOTOL funding cancelled

In article <[e-mail]>, [e-mail] (Knudsen) writes:
>
> If I remember right, we were very interested a few years ago in
> the British HOTOL (Reagan's "space plane", not heard of lately)

Two different aircraft (air?).  Similar missions, though.

> and approached the British Govt about sharing the development.
> We were rebuffed, the Brits saying tht the technology was too
> advanced to share with anyone (secret, proprietary, ya know).

Apparently Rolls Royce had solved some problems bugging US
engine designers up to that point.  Maybe it'll get out now.

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

Date: 15 Aug 88 14:14:49 GMT
From: att!whuts![e-mail]  (WARMINK)
Subject: Re: Aerospike

In article <[e-mail]>, [e-mail] (J Storrs Hall) writes:

> What is an aerospike?  What is meant by its being (or not being)
> "plugged"?
An aerospike is a sharp extension of a (usually) blunt nose cone. The idea is that by
starting the shockwave ahead of the main nose cone, as far as the airflow is concerned,
the nose cone has the same shape as the shockwave rather than its real, blunt, shape.
This will reduce the supersonic drag quite considerably. I believe this is used on
some of the submarine lauched ICBMs, like Trident, which are rather blunt-nosed so
as to pack as much volume as possible into the limited space available.

I'm not sure what 'plugged' refers to, I would hazard a guess at 'stored (i.e.
retracted) position' or maybe it is a reference to the small cone at the end of the
spike (the angle at the vertex (?) of the cone is the same as the angle of the
shockwave at the velocity for which the spike is optimized).

>
> What is the specific impulse of hydrazine?
Already been answered by another mailing.

--
------------------------------------------------------------------------------
If all the statisticians were laid end to    |  Stuart Warmink, APT UK Ltd.
end across the Atlantic, 99% would drown :-) |  <att>!whuts!sw Whippany NJ USA
-----------> My opinions are not necessarily those of APT UK Ltd. <-----------

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

Date: 16 Aug 88 01:04:03 GMT
From: spdcc![e-mail]  (Steve Elias)
Subject: 'prestigious' space programs

In article <[e-mail]> [e-mail] (Macros) writes:
>In another article, ?? writes:

>>program, the ESA's space program, Japan, China, India, Brazil, and

>Controlling these countries might not even be too bad an idea. They should do
>more in fighting poverty, starvation and their population
>explosion, than diving into some prstigious space programs.

    why does this argument apply to other countries
    if it does not apply to the US & Soviets ?

(leaving followups here, for lack of a better 'space' for them).

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

Date: 15 Aug 88 12:48:11 GMT
From: nyser!cmx![e-mail]  (Rangachari Anand)
Subject: Feedback


  Did anyone on the net catch an interesting call-in talk show on Public
  radio called "Feedback" last night? Last night's program was devoted
  entirely to space. There were several people on hand from NASA and
  from the Commerce department to answer questions about the US space
  program.

  Many of the callers appeared to be quite enthusiastic about the space
  program in general but more than one caller seemed to be very worried
  about the increasing role of the military in the space program. In
  response to this, the person from NASA said that the space station was
  to be devoted entirely to civilian activities.[This seemed to contradict
  reports published in Aviation week]. The other popular question was on
  whether the spinoffs from the space program justified the investment.
  NASA has apparently calculated that $8 is returned for every $ spent.

  I myself was able to get in a question on the topic of expendable
  launch vehicles. I tried to point out the virtues of a simple and
  cheap launcher. As an example, I mentioned that the reliable Proton rocket
  was essentialy unchanged from the 1960's. I also mentioned the Pegasus
  rocket being developed by Hercules/OSC in this regard.

  The person from NASA replied that the Russians were in the process of
  building a space shuttle and in his words "... were desperately trying
  catch up with us" !. His view was that the shuttle is all that is needed
  for now.

  In marked contrast, the person from the Commerce department was in
  complete agreement with me. He was very enthusiastic about the
  Pegasus project and said that they were trying to give all the
  encouragement they could. He went so far as to say that had the
  Saturn Vs not been scrapped, they would have probably been cheaper
  than the shuttle.

  I can tell you that I was more reassured by the Commerce department than
  NASA !

                                                         R. Anand

  Internet: [e-mail]
  Bitnet: ranand@sunrise

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

Date: 16 Aug 88 01:24:19 GMT
From: [e-mail]  (Mark William Hopkins)
Subject: Space Bloopers

In article <[e-mail]> [e-mail] (Jonathan McDowell) writes:
>From article <[e-mail]>, by [e-mail] (Steve Hix):
...
When space travel DOES become common, we're going to have to keep on a constant
lookout for the remains of all the "missed shots"; because in space, what goes
around, comes around ...
...
>
>AMS "Luna"      Solar orbit, missed moon, called Luna-1 now.
>Ranger 3    missed moon...

What did they call IT after it missed the moon?

>Ranger 5    missed moon...
>Mariner 2      flew past Venus
>Luna-4         missed moon, perturbed into solar orbit
>Zond-1         failed Venus probe
>Mariner 3    Mars flyby failed
>Luna 6     Lunar soft lander missed moon
>Venera 2    passed Venus, no data
>Venera-3      HIT Venus, no data

BULLSEYE!

(20 years is enough time to look back and laugh.)

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

Date: 15 Aug 88 19:57:18 GMT
From: tektronix!tekcae!vice![e-mail]  (Keith Lofstrom)
Subject: Re: SDI, Asats, and access to orbit

bobmon@iuvax writes:
> Years ago, somebody British proposed (in Punch?  New Scientist?
> Lancet?) a nice, cheap anti-ICBM solution to be used preemptively in
> times of tension:  Just throw a few tons of gravel into LEO.

This sort of thing comes up about once a year.  Time for some math, kiddies:

Assume, by some miracle, we are able to orbit all these tons of gravel in
a thin shell at 120 Km altitude (Radius = 6.5e6 meters).  Assume a third stage
moving at 4000 meters per second and still boosting, 5 meters long and 2
meters in diameter.  Assume a 10 gram pellet moving at orbital velocity
(8000 m/s) will destroy it and its warheads.

The booster will spend (5 m)/(4000 m/s) or 1.25 msec traversing the shell.
It will collide with any pellets in a patch  2 meters x 1.25 msec x 8000 m/s
in area, or 20 square meters (crude description; see a good book on statistical
mechanics for a better description yielding the same result).

If N pellets are randomly distributed, they will have a density of N/(4*pi*R^2)
per square meter, and the probability of finding one or more pellets in a given
area is   Probability =  1 - exp( - Area * density )  [see the book again].


This can be boiled down to the following equation:

                     V missile   4 pi (Orbit Radius)^2
Number of pellets =  --------- * --------------------- * -ln( 1 - Probability )
                     V orbit         Area Missile

for a 25% intercept rate (typical SDI number) about 8e12 pellets will be
needed; about 80 million tons.  More than "a few tons".  For a 99.9%
intercept rate (as claimed by many Anti-SDI folk) about 2 billion tons
will be needed.

----
Smart interceptors (which can cover vastly more territory) are a whole
different kettle of fish.  If the booster has been visible for 60 seconds,
and the interceptor can change velocity by 2000 meters/second in that time,
it can intercept boosters over a "patch" of around 1e10 square meters.
A 25% intercept rate would require 15,000 interceptors.
----

Please don't construe this message as being pro-SDI.  Most bureaucrats and
their political allies live in cities.  The only way to eliminate this
infestation may be for them to fry each other, as they seem hell-bent to do.
If it wasn't for all the innocent people in cities it might even be a good
idea :-).  Hopefully, I just caused apoplexy for a few of the deserving :-).


I DO want to show that space is a BIG place;  the Earth is not too small,
either.  Village-scale thinking doesn't work any more.  You have to
do some math until the new scale of things gets imbedded in the culture;
"common sense" isn't calibrated in this regime.


--
Keith Lofstrom   ...!tektronix!vice!keithl   [e-mail]
MS 59-316, Tektronix, PO 500, Beaverton OR 97077  (503)-627-4052

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

Date: 16 Aug 88 01:46:13 GMT
From: stsci![e-mail]  (Mike Berman)
Subject: Not in the line of duty

Ten of our astronauts' deaths have been widely publicized - namely the
three aboard Apollo 1 and the seven aboard the Challenger. I'm curious
as to who is no longer with us as the result of a more "normal" demise?
Are all of the crews of the successful Mercury, Gemini, Apollo, and
shuttle missions still alive?
--
                      Space Telescope Science Institute, Baltimore, MD 21218
       Mike           ARPA:   [e-mail]      BITNET:   berman@stsci
      Berman          UUCP:   {arizona,decvax,hao}!noao!stsci!berman
                      SPAN:   {SCIVAX,KEPLER}::BERMAN

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

Date: 16 Aug 88 01:41:15 GMT
From: vsi1!unisv![e-mail]  (Mike Van Pelt)
Subject: Re: SETI: Why don't we hear anything?

In article <[e-mail]> [e-mail] (Peter Kinsella) writes:
>     Aren't we making a few rather large assumptions. If we assume that
>life exists elswhere in the universe.

>     1.  That the warring society can travel to conquer the broadcasting
>         world before that society developes sufficent technology to defend
>         itself.   (faster then the speed of light ?)
>     2.  That it can travel in such numbers as to conquer a whole planet.
>     3.  If it had the technology to transfer enough people to take over
>         the planet of a lesser thechnology what would it gain ?
>         (welfare recipients? )

Who knows?  Now, I don't really believe this, but suppose the
warlike society wasn't interested in conquest, just in extermination?
There's lots of talk about making self-replicating explorers to
go through all the galaxy collecting data and eventually returning it
to Earth -- Suppose a sufficiently xenophobic civilization decided
to use the technique for eliminated threats/rivals?  You can postulate
that they get along fine with each other, but are horrified at the
idea of "others", so the "destroy themselves before they advance that
far" argument wouldn't hold.  Presumably it wouldn't be all that
difficult for an advanced civilization to build probes that would be
more than a match for any civilization that had only a few years
before mastered the use of radio, on which the probes would home in.

I like to think of this as preposterously unlikely.  (After all,
we've been broadcasting like mad for decades, and haven't been
blasted yet.)  But then again, there's all those Biilyons and
Biilyons * of stars out there, for all those Biilyons and Biilyons *
of years ... and it only has to happen once for us all to be in
deep yoghurt.
--
* "Biilyons and Biilyons" is a trademark of Carl Sagan Enterprises, Inc.
--
Mike Van Pelt                       When the fog came in on little cat feet
Unisys, Silicon Valley              last night, it left these little muddy
[e-mail]                  paw prints on the hood of my car.

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

Date: 15 Aug 88 22:48:43 GMT
From: phri!dasys1![e-mail]  (Tom Betz)
Subject: Re: space news from Juen 27 AW&ST

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>  The Chinese have just signed their first firm commercial
>launch deal, to launch AsiaSat 1 (the former Westar 6, retrieved by the
>shuttle in 1985) as Asia's first regional comsat, with a Hong Kong /
>British consortium.)

I think the most significant bit of news this month is contained in the
sentence above...


China has the honor and privilege of launching the first remarketed used
communications satellite in the history of space technology!


Let us hope there will be many more such launches to follow.

--
  "Through practice, I have become one of the      |Tom Betz
      better liars in the English language.        |ZCNY, Yonkers, NY 10701-2509
I wouldn't say it if I didn't know it wasn't true" |UUCP: [e-mail] or
           - Emmanuel Transmission -               | ...!cmcl2!phri!dasys1!tbetz

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

End of SPACE Digest V8 #337
*******************