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Subject: SPACE Digest V11 #518

SPACE Digest                                     Volume 11 : Issue 518

Today's Topics:
               Re: Missing mass
             Re: Lichens on Mars?
             10 psi overpressure
       Incoming asteroids, how to move them with nukes.
         Re: T.A.F.  --  Tough Apollo Trivia
             Re: Lichens on Mars?
              Nimbus-7 Update - 06/11/90
Re: Public Perception Of Space (was Re: US/Soviet Planetary Activity)

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription notices,
  should be sent to [e-mail], or, if urgent, to
             [e-mail]

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

Date: 11 Jun 90 16:27:00 GMT
From: sdd.hp.com!apollo![e-mail]  (Steve Rehrauer)
Subject: Re: Missing mass

In article <Added.QaPwDS_00Ui34=[e-mail]> [e-mail] ("Nick A. van Goor") writes:
>Here's the solution to the problem of the (until now)
>missing matter in the universe. At long last, a logic,
>yet subtle theory has emerged.....
>
>The mising matter all exists of disappeared socks.....

Along those lines, I once read a rather amusing SF short story,
in which a man tried to convince the world that we were being
invaded by aliens which could perfectly mimic mundane items
like paperclips, rubberbands, socks, etc.  "Think of it," he
would say, "No one pays heed to how many paperclips they have,
nor raises an eyebrow when they turn up in odd places."  In the
end, he was discovered dead, with a coat-hanger wrapped tightly
around his throat...

You have been warned...

:-)
--
   >>"Aaiiyeeee!  Death from above!"<<     | (Steve) [e-mail]
"Spontaneous human combustion - what luck!"| Apollo Computer (Hewlett-Packard)

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

Date: 11 Jun 90 16:55:49 GMT
From: mcgill-vision!quiche!calvin![e-mail]  (Mark SOKOLOWSKI)
Subject: Re: Lichens on Mars?

In article <[e-mail]> [e-mail] (Steve Rehrauer) writes:
>
>Ah, no.  Lichens would not grow under the conditions that various space
>probes have shown us to (actually) exist on Mars, but that was back before
>Dan Quayle revealed how habitable the planet wishfully is.
>
In fact, some alguaes and some worms can very well live on VEEEENNNUUUSSSS!!!
Venus is certainly not the hostile hell our current mediatic propaganda
and the mars/moon missions lobbyists are portraying!

Mark S.
-------

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

Date: 11 Jun 90 14:47:18 GMT
From: usc!elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!ofa123![e-mail]  (David Anderman)
Subject: 10 psi overpressure

I seem to recall that the Challenger was destroyed by air pressure,
rather than an explosion of the external tank. Wouldn't that indicate
the overpressure in the payload bay was somewhat higher than  10psi?


--- Opus-CBCS 1.12
 * Origin: Universal Electronics, Inc. (1:103/302.0)
--
uucp:     David Anderman
Internet: [e-mail]
BBS:      714 544-0934   2400/1200/300

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

Date: 11 Jun 90 22:06:13 GMT
From: ox.com!kitenet![e-mail]  (Russ Cage)
Subject: Incoming asteroids, how to move them with nukes.

[This thread comes from sci.astro, follow-ups are directed back there.]

This is inspired by John Smith, [e-mail].

[Speaking of whom, the less said the better, except that I
 have received mail from his site admin which indicates
 that we are not likely to be hearing too much from him
 in the future.  I hope he takes a physics class.]

    Novice's Guide To Moving Your Asteroid
          (or, Nuke It Till It Goes).

This is a treatment of the diversion of asteroids or other
objects using nuclear explosives.  It assumes knowledge of
basic physics, such as conservation of energy and momentum.
There is some guesswork involved here, since I do not have
figures on everything; this guesswork is marked with "###".
Perhaps some of the readers can fill in the holes with
numbers.  Footnotes are marked with numbers in parens,
and follow the body of the text.


             BASIC METHOD

The velocity of a small asteroid in space can be changed
using nuclear explosives.  Detonating a bomb nearby will
cause the part of the asteroid exposed to the blast to
be heated violently, vaporized, and ejected into space at
high speed.  The asteroid is pushed away from the bomb
by the reaction.  The push from any one bomb is small,
but many can be used to effect significant changes in
velocity.  This can be used to, for example, change the
orbit so that it misses, rather than strikes, the Earth.


          PART 1:  THE BOMB

Fission bombs release energy in many forms.  CRC publishes
these numbers for energy release from fission:

    Kinetic energy of fission fragments    82.5% < Blast
    Instantaneous gamma rays         3.5% < Blast
    Kinetic energy from fission neutrons     2.5% < Lost
    Gamma-rays from fission products     3.0% < Delayed
    Beta particles from fission products     3.5% < Delayed
    Neutrinos                 5.0% < Lost

In a bomb, only the blast energy is useful.  Energy from
neutrons, neutrinos and fission-product decay do not
contribute to blast effects.  This portion totals 14%.
86% of the total fission energy is available to drive
blast effects.  Of this portion, 96% is in the form of
kinetic energy of the plasma and 4% is gamma rays.

Most of the energy transferred to the asteroid (96%)
will be as an extremely hot plasma, the vapor of the
bomb itself.  4% of the energy will arrive as high-
energy gamma rays(2), immediately before the plasma wave.

A 100 kiloton explosion releases approximately 4.2e14
joules of energy.  About 4.0e14 joules is plasma energy,
and 1.7e13 joules is gamma-ray energy.


        PART 2:  THE ASTEROID

The asteroid is likely to be made of stone; stony
asteroids comprise the majority of the ones known.  This
treatment will assume a density of 3.5 g/cc.  Numbers
for gamma-absorption will be assumed to be the same
as for concrete(3) ###.  Nickel-iron asteroids will be
denser, carbonaceous chondrites and comets less dense.


    PART 3:  THE EXPLOSION REACHES THE ASTEROID

We will assume that the bomb explodes 100 m from the asteroid.
(This may not be the optimal distance; it is used for the sake
of argument.)  To simplify the calculations, it will be assumed
that a disc 100 m in radius on the asteroid is affected (where
the bomb is up to 45 degrees from the zenith).  3/16 of the
explosion energy strikes this disc.

The gamma rays, moving at the speed of light, arrive first.
They are absorbed very near the surface, 90% in the first 25
cm.  At 100 m, the surfaces nearest the explosion will receive
1.4e8 J/m^2 of gamma energy.  The top 25 cm absorb 5.4e2 J/cc
of energy, or 1.6e2 J/gm.  3/16 of the total gamma energy hits
the asteroid, or 3.2e12 joules.

If the specific heat of the stone is the same as silicon
dioxide (.3 cal/gm.deg C or less), this amount of energy will
heat the stone by 500 degrees C or more.  Silicon dioxide
melts at ~1700 C.  Therefore, the gamma rays from a single
bomb will heat the top 25 cm of the asteroid's surface to
glowing red heat.  The gammas from further bombs will melt
and then vaporize this hot material.

On the heels of the gamma rays comes the plasma wave.  The
plasma deposits 3.3e9 J/m^2 of energy on the heated or
molten stone.  Plasma is absorbed in a very thin layer;
ions do not penetrate deeply.  Assuming that a layer 2 cm
thick is heated uniformly ###, the surface rock (which will
be molten, after the first few bombs) will absorb this
energy, approximately 4.8e4 J/gm.  This it is 30 times
the energy required to melt the rock; the vapor expands
into space.  If the expansion is 50% efficient in con-
verting heat to velocity ###, the "exhaust velocity" will
be 6900 m/sec.  The total energy is 7.5e13 Joules, and
the mass of the vaporized rock is 1.6e9 gm (1600 tons).
These quantities are all per bomb.

By the time the 2 cm thick layer of rock plasma has become
2 meters thick, it has expanded by a factor of 100 and
dropped in pressure by a similar amount.  Since it loses
almost all its starting pressure before becoming anywhere
near as thick as its 100 meter radius, it can be assumed
to expand as a plane wave rather than isotropically.  This
increases its propulsive efficiency.


        PART 4:  THE EFFECTS

The total impulse delivered to the asteroid per bomb is
1.6e6 kg * 6.9e3 m/sec = 1.1e10 kg-m/sec.  A billion-ton
asteroid will change its velocity by 1.1 cm/sec in response
to this impulse.  To change its velocity by 10 m/sec
requires about 900 bombs of 100 kilotons yield each.


        PART 5:  FEASIBILITY

We have this many bombs.  We have several times this
many bombs.  Delivering them is much more of a problem
than availability.  For instance, modern fusion bombs
weigh about a ton per megaton of yield.  This gives a
total mass of about 90 tons for the 900 bombs.  Add
in booster rockets, radar and radio gear, and shields,
and we are talking several hundred tons which must be
launched from the ground into low-earth orbit.  It's
a big job, but not impossible.  Call it a couple tens
of Titan 4 launches, or a Saturn V or two.

In other words, given the necessity and time to plan,
we can do it.
---
Footnotes:

(1)  CRC Handbook of Tables for Applied Engineering Science,
    2nd ed. p. 433

(2)    In the real world, some of the energy will be radiated
    as X-rays.  These are absorbed in a thin layer at the
    surface, however, so it seems reasonable to count this
    X-ray enery with the plasma energy.  The inaccuracy
    introduced will not be large enough to seriously
    affect the results of these calculations.

(3)  CRC Handbook of Tables for Applied Engineering Science,
    2nd ed. p. 439
--
  I am paid to write all of RSI's opinions.  Want me to write some for you?
[phone]        Forewarned is half an octopus.
Russ Cage, Robust Software Inc.            [e-mail]

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

Date: 11 Jun 90 13:15:50 GMT
From: mcsun!ukc!icdoc!syma![e-mail]  (Nick Watkins)
Subject: Re: T.A.F.  --  Tough Apollo Trivia

From article <[e-mail]>, by [e-mail] (Henry Spencer):
> "Trouble plagued"?  The F-1 development was, on the whole, fairly smooth,
> and apart from a bit of a problem with pogo oscillation -- not uncommon
> in new rockets -- it never gave the slightest trouble in flight.
"Apollo", by Murray & Cox, now out in paperback, begs to differ and
devotes a fair part of Chapter 10 to describing the efforts made at
Rocketdyne in dealing with combustion instabilities in the F-1. Excellent
book  btw, as has been said already in this group. No trouble in flight though,
as you say.
 Covers role of ex Avro Canadians (inc John Hodge ), among other many other
little known aspects of Mercury/Gemini/Apollo history ... :-)

Nick

P.S. Anybody know how long it takes to fix an RL10 ... ? (the CRRES
community waits with bated breath).
--
Dr. Nick Watkins, Space & Plasma Physics Group, School of Mathematical
& Physical Sciences, Univ. of Sussex, Brighton, E.Sussex, BN1 9QH, ENGLAND
JANET: [e-mail]   BITNET: [e-mail]

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

Date: 12 Jun 90 04:10:52 GMT
From: rochester![e-mail]  (Paul Dietz)
Subject: Re: Lichens on Mars?

In article <[e-mail]> [e-mail] (Christopher Neufeld) writes:
>>     Dream on!!  Name me one Earth-based life form that lives at temperatures
>>several hundred degrees above the boiling point of water.
>>
>   Let's see if I can beat Mark to the 'answer.' How about that
>ubiquitous example in the popular science press, the deep sea vent
>micro-ecosystem?

But the deep sea vent life *doesn't* live several hundred degrees
above the boiling point of water.  It exists in the surrounding,
somewhat cooler water.

There was a report some years back (in Nature) claiming that organisms
had been found that grew in the vents themselves, at very high
temperature.  This proved to be an artifact.  It is very unlikely that
terrestrial life could exist at that temperature.  Common biochemicals
like glycine are destroyed in minutes under the conditions that exist
in the vents.

The upper limit of known terrestrial life is a few degrees
above 100 C (certain archaebacteria that live in boiling pools).

    Paul F. Dietz
    [e-mail]

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

Date: 11 Jun 90 16:41:22 GMT
From: swrinde!cs.utexas.edu!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Nimbus-7 Update - 06/11/90


                         Nimbus-7 Update
                         June 11, 1990

     The Nimbus project declared a spacecraft emergency over the weekend
when the project was unable to command the spacecraft transponder off
due to antenna problems.  The 9 meter antenna at Wallops was stuck in the
Y-axis, and the 26 meter antenna (DSS16) in Goldstone, California, was then
used to fix the problem, at which time the spacecraft emergency was lifted.
The Hipparcos project was originally scheduled to use the 26 meter antenna,
but with the European Space Operation Agency's (ESOC) concurrence, the
antenna was freed up to support the Nimbus-7 emergency.
       _   _____    _
      | | |  __ \  | |       Ron Baalke           |  [e-mail]
      | | | |__) | | |       Jet Propulsion Lab   |  [e-mail]
   ___| | |  ___/  | |___    M/S 301-355          |
  |_____/ |_|      |_____|   Pasadena, CA 91109   |

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

Date: 11 Jun 90 18:34:33 GMT
From: att!cbnewsh![e-mail]  (lawrence.m.geary)
Subject: Re: Public Perception Of Space (was Re: US/Soviet Planetary Activity)

In article <[e-mail]> [e-mail] (John A. Weeks III) writes:
>
>The only hope NASA has to rescue it's new Moon program would be to
>send a mission to "the dark side" of the Moon.  Maybe they could con
>the public on this.  After all, the commies have never seen the dark
>side of the moon!  8-)

In fact, they photographed it before we did.

>Recently I was talking with a co-worker about the early history of the
>shuttle.  Another co-worker butted in and told me the "real" story
>as he remembered it.  NASA was dropping Shuttles off of a 747, but
>they kept crashing because they couldn't fly.  So they added rockets
>to it to make it work.  He knew this was true because he watched two
>of the early lanuch attempts on TV.  He obviously was confused with the
>Enterprise glide tests.  Oh well...

And there are people today convinced that space launches cause rain,
and that the Challenger was destroyed by God because they were searching
for heaven. Such is the level of education in this country.

>One thing that NASA could try is a TV show on network tv.  How about
>a 15 minute weekly or hour monthly show to give NASA news, mission updates,
>behind the scenes views, and review past missions.

NASA has their own cable channel. Who watches? You want a NETWORK show?
You'll have to make it compete with "America's Funniest Home Videos". It's
difficult to convey scientific subtleties when you have to degrade material
to retain the attention of ill educated lamebrains.

--

Larry Geary: [e-mail] | Dislexics of the world, untie!
         [e-mail]         |

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

End of SPACE Digest V11 #518
*******************