Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_3/V15NO391.TXT

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Date: Sat,  7 Nov 92 05:05:58
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #391
To: Space Digest Readers
Precedence: bulk


Space Digest                Sat,  7 Nov 92       Volume 15 : Issue 391

Today's Topics:
                   AUSROC II Launch Campaign Review
            Automated space station construction (2 msgs)
                      Comet deflection & mining
          How "clean" can Orion-style nuclear propulsion be?
                           Hubble's mirror
                        NASA Coverup (4 msgs)
                      pocket satellite receivers
                      Russian Engines for DC-Y?
                   Scenario of comet hitting Earth
              Viking Photos Shows Evidence of Marsquakes

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

Date: 2 Nov 92 14:33:37 +1030
From: [e-mail]
Subject: AUSROC II Launch Campaign Review
Newsgroups: sci.space,rec.models.rockets

26th October 1992

AUSROC II LAUNCH CAMPAIGN REVIEW

        On Friday 16th October the AUSROC II rocket system and
launch crew left Adelaide for the Woomera Rocket Range. The
AUSROC launch crew consisted of the following personnel:

                Mark Blair                      Tzu-pei Chen
                Andrew Cheers                   John Colemen
                Norbert Leidinger               Robert Graham
                Warren Williams                 Richard Bromfield
                Ian Bryce                       Grant Waldram
                Peter Grounds                   David Emery
                Denis Robb                      Colin Biggs
                Brendan Coleman                 John Balatsas
                Peter Kantzos

        After arrival at the Rangehead, the rocket hardware and
support equipment was unloaded in Test Shop 1. For the duration
of the campaign the launch crew resided at the Travellers Village in
the Woomera Township.

        On Saturday the injector, engine and fin unit were attached
along with the pneumatic and electrical umbilical lines in Test Shop
1. At this stage the 3 ball valves on-board the rocket were tested
and found to be operating successfully. The ground cabling and
wiring loom layout was commenced to connect the launcher with
the launch sequencer in Equipment Centre 2 where the firing was to
be initiated from. The on-board electronics was in its final stages of
preparation but the flight software still required some further work
and was being worked on intensively for the majority of the
campaign period.

        The system pressure tests, with nitrogen gas, were
undertaken on the Sunday and about 4 leaks were discovered.
Three of these leaks were associated with connectors, which may
have been loosened during transit, and were re-sealed quite easily.
A small leak between the sections of the kerosene ball valve proved
to be more resistant to our attempts to seal it. Eventually, with
much effort, the leak was reduced to an apparently negligible rate .

        The telemetry antennas were installed onto the rocket on the
Monday and tested. These tests revealed that the antennas were
operating extremely well with quite a high level of efficiency. The
parachute recovery system was prepared for installation and the
launcher services were installed. These services included the
nitrogen purge system, the nitrogen actuation supply lines, the
electrical umbilicals and the fuelling equipment and scaffold. Since

the software still required more time, a 1 day hold was enforced to
allow further time for correction. Thus the nominal launch time
was delayed until 10.00 am Thursday morning.

        The rocket was rolled out of Test Shop 1 on the Tuesday
morning and installed horizontally on the 10m launcher rail. The
electrical and pneumatic circuits were attached and 3 dummy firing
sequences were performed to validate the ignition and valve
operations. These trials were also successful. A pre-flight brief was
held in the Instrumentation Building conference room for visitors,
sponsors and media in mid afternoon and this covered details of the
Ausroc program to date as well as future plans.

        Throughout Wednesday, further testing was performed on
the ground based telemetry receiving and recording equipment as
well as the flight electronics and software. Several changes were
made to the flight electronics and software and the package was
finally loaded into the rocket on the launcher around mid
afternoon. Several telemetry checks revealed that the video signal
was being transmitted well but the telemetry channel data would
require post flight processing to be useable. With the electronics
secured, the recovery system, complete with deployment
pyrotechnics, was installed.

        The launch day commenced with arrival at the range at
5.00am. Two more dummy launch sequence checks were performed
without fault. The helium pressure tank was loaded to 20 MPa and
checked for leaks. No leaks were detected so the upper valve fairing
hatch was replaced and the launcher was elevated to its nominal 70
degree launch angle. A series of telemetry checks were then
performed to check the transmitter and ground based receiving
equipment.

        The kerosene was then loaded and it was observed that there
were no leaks present from the kerosene ball valve while the tank
was at ambient filling pressure. The lower valve fairing hatch was
then replaced in preparation for the lox fuelling. A spray pack of
freon was used to remove any kerosene spillage around and within
the intertank fairing. A dry nitrogen gas purge operation was
conducted to ensure that no water vapour was present in the lox
system that could cause freezing problems. The lox fill line was
attached to the rocket from the cryogenic storage canister located
on the back of a transport truck. The lox fuelling went much
smoother than we had anticipated and the uninsulated external
walls of the tank only had a light frost buildup when the tank was
full. The lox tank bleed plug was replaced, the scaffold was
removed and the ignition flare leads were connected.

        With the lox tank bleed plug replaced, the lox tank pressure
increased under its own boil-off vapour pressure to the nominal
tank vent pressure of 4.5 MPa. It was discovered that with the
helium valve closed, there was some back-flow of oxygen vapour
through the lox tank regulator and down into the kerosene tank,
thus increasing the kerosene tank pressure. The early increase in
kerosene tank pressure brought about a slow leak of kerosene
which probably found its way onto the pneumatic supply line. This
was the same leak that had been detected during the pressurisation
tests in Test Shop 1. Further checks should have been made in Test
Shop 1 to ensure that the leak was completely sealed.

        The ignition flare was fired, by the sequencer, at T-5sec. The
flare may have then ignited the leaked kerosene causing a fire
around the pneumatic supply lines. The Helium valve opened
successfully at T-3sec. as did the kerosene valve at T-0.25sec. The
lox valve was to have fully opened at T-0sec. The lox ball valve
opened approximately 10 degrees before it lost its actuation
pressure. This implies that the pneumatic supply lines must have
been severed some instant immediately after the lox valve solenoid
had opened. In this regard the system was about 200 milliseconds
short of successful operation.

        With the lox valve only partially open, the kerosene continued
to rush out and was ignited by the flare producing a very fuel rich
black billowing cloud and no useful thrust. The recovery system was
set to deploy on a timer and since the electrical umbilicals and
remaining pneumatic hose were also severed by the kerosene
flame, it was impossible to abort the sequence. As a result of this,
the nose deployment sequence was initiated very successfully at its
correct time in the launch sequence.

        With the helium and kerosene tanks essentially empty, the
back flow of oxygen through the lox tank regulator continued to
bleed oxygen vapour into the kerosene tank and out through the
kerosene passages to the motor. At around T+4mins, the remaining
small kero flame in the motor initiated the oxygen/kerosene vapour
mixture in the kerosene tank causing it to detonate and rupture at
the intertank end of the lox conduit passage. This event broke the
vehicle in half at the intertank fairing and severed the lox hose. The
resulting expansion of the lox from the base of the lox tank pushed
the forward section of the rocket off the rail and sent it sliding
along the ground where it eventually came to rest next to the 2
ground power supplies.

        The violent nature of the kerosene tank rupture sent a black
kerosene soot through every cavity and conduit in the rocket
making the post-mortem all the more difficult. At this stage it
appears as though the motor, injector and recovery system could be
reused but new tanks and structure will be required.

        Much has been learned from this experience and the majority
of the AUSROC Program objectives have still been achieved. We
are presently reviewing the AUSROC II systems and anticipate
some changes to the vehicle design and launch operations. We have
listed some of these here for your information:

        1. Installation of check valves in both propellant systems.

        2. Re-routing and/or flameproofing pneumatic and electrical
                umbilical lines.

        3. Replacement of all internal plastic pneumatic lines with
                flameproof lines

        4. Review of quality control procedures and standards

        5. Review of launch operations including Abort/Hold criteria,
                program management and media liaison

        6. Review of lox and kero ball valve and actuator operation
                including the effects of ice buildup

        7. Review of vehicle manufacturing techniques to enable a
                more simplified construction of a second vehicle.

        8. Modification and simplification of flight electronics and
                software and simulation of possible flight regimes.

        The launch crew is now more determined than ever to solve
these initial problems and construct a second AUSROC II
derivative for a possible second launch campaign in 1993. For as
little as $30-40,000 a revised and improved system can be
constructed. Design review teams are already being formed and
construction could begin as early as January '93. The media and
sponsor response to the program has been exceptionally positive
and we look forward to working with them again in the future.

                        Regards,
                                                        Mark Blair
                                        AUSROC Program Coordinator


Previous AUSROC updates can be obtained by anonymous ftp to
audrey.levels.unisa.edu.au in directory space/AUSROC

--
Steven S. Pietrobon,  Australian Space Centre for Signal Processing
Signal Processing Research Institute, University of South Australia
The Levels, SA 5095, Australia.      [e-mail]

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

Date: 7 Nov 92 04:59:22 GMT
From: Henry Spencer <[e-mail]>
Subject: Automated space station construction
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Carl Hage) writes:
>: >Can robots be launched to build the space station?
>:
>: Robotics technology is nowhere near building robots capable of such things.
>
>Is this partly due to a focus on manned space missions? How much research
>is done on developing space based robotic/remote-operated technology and
>designing space hardware suited for robotics vs research on manned space
>technology? Could this be somewhat of a self fulfilling prophesy...

In one sense, I'd agree, because teleoperation research hasn't exactly been
vigorous and ambitious.  On the other hand... just how much *research* do
you think is being done on "manned space technology"?  Damn near zero.
Everything's being done with Apollo-vintage technology.  That's part of
the problem.

>What's the point of automating assembly of a manned space station? Wouldn't
>that be an unfair labor practice? A good part of the mission is to develop
>manned space technology, e.g. assembly.

One of the reasons why Fred is so expensive is that it is developing
technology in lots of areas where it's not at all necessary.  Look, guys,
we *know* how to do in-space assembly, as witness a wide variety of things
including the Intelsat salvage mission.  The only thing that's getting
"developed" is a lot of contractors' financial statements.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 7 Nov 92 05:02:18 GMT
From: Henry Spencer <[e-mail]>
Subject: Automated space station construction
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (I am a terminator.) writes:
>Gimme a few hours worth of money (n x 55000) and some rockets and I bet
>I can whip up robots that'll put together a space station...

Same way you can "whip up" hardware to grapple with an Intelsat?  That one
didn't work, remember?  The test of your hardware is not whether it can do
what you expect, but whether it can cope with the unexpected... which *will*
happen.

>... I can cut costs by
>not worrying about paperwork and all that. I can follow standard procedure
>to avoid colliding with satellites and such stuff. Don't those people at NASA
>have skunkworks?

Nope.  Congress won't allow it.  Doesn't cost enough.
--
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, 7 Nov 1992 07:06:11 GMT
From: Josh 'K' Hopkins <[e-mail]>
Subject: Comet deflection & mining
Newsgroups: sci.space,alt.sci.planetary

[e-mail] (Nick Szabo) writes:

>Deflecting anything but the strongest nickle-iron asteroid
>with a nuclear explosive is silly.  Many asteroids are probably
>rubble piles, not single big rocks, and comets are so fragile we've
>seen some calve off big chunks and obliterate themselves just from
>internal gas pressure.  For a comet, farting can be suicide!

I don't see why this is a probelm.  If the comet shatters, there's a good
chance that most of the material will have enough transverse velocity to spread
out, thus limiting the amount that would hit the Earth.  Increasing the number
of bits would also increase the loss from solar heating and spread the chunks
out further due to natural rocket forces.  As long as you intercept the
comet far enough out, I fail to understand why it's a problem.

>Back to the P/Swift-Tuttle deflection problem.

>If upper-stage technology advances sufficiently over the next 30-40
>years, eg magsails powered by the solar wind + a very advanced nuclear
>electric second stage, we might be able to catch up with P/Swift-Tuttle
>at perihelion in 2057 to track it.  Alternately, we might develop very
>good telescopes capable of tracking it that far out, eg huge microgravity-
>based reflectors combined with optical interferometry.

I always cringe when I hear about optical interferometers in microgravity. They
remind me of screen doors on submarines.  A _far_ better solution is to build
them on the Moon, allowing much higher resolution among other things.

Who knows what
>technology we will have after 2100, but one possibility is to focus
>sunlight with a large parabolic mirror over the period of several
>months to change the time P/Swift-Tuttle crosses earth orbit by one day.
>Anyone want to tackle the math on how large a mirror would be needed?

My that would be big!

>Even with this gentle method, we need to gaurd against the possibility
>of disrupting the comet rather than deflecting it.  Rendesvous with 50 km/s
>incoming will also be a challenge, perhaps several years with a tacking
>magsail.

There's a big difference between rendezvous and intercept.  A sidewinder missile
does not match speed with its target.  Not that an intercept would be all that
easy, but it's not impossible.
--
Josh Hopkins                                          [e-mail]

"We can lick gravity, but the paperwork's a bit tougher."  Wernher von Braun

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

Date: 6 Nov 92 16:43:23 GMT
From: "John M. Owen" <[e-mail]>
Subject: How "clean" can Orion-style nuclear propulsion be?
Newsgroups: sci.space

How "clean" can a nuclear explosion be? I remember reading in sci-am
some years back that different effects could be optimised at the
expense of others. Recent postings suggested blast might be optimised
over radiation.

It seems to me the possible uses of an Orion-style propulsion scheme
depend greatly on how "clean" the devices are. A device which
produced little fall-out (which I gather is as much related to detonation
altitude as composition) might be suitable for launching. Earth-orbit
detonations might have unwanted effects w/r/t electromagnetic pulse or
the radiation of the Van Allen belts. Are there unwanted environmental
side-effects with interplanetary Orion propulsion?

I guess I'm wondering if Orion is still a viable propulsion scheme. Are
there any other effects of the explosion besides the blast that might
be exploited for propulsion?

-- [e-mail] (John M. Owen)
-- My .sig is bigger than yours - but I keep it offline.

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

Date: 7 Nov 92 07:18:37 GMT
From: Henry Spencer <[e-mail]>
Subject: Hubble's mirror
Newsgroups: sci.astro,sci.space

In article <[e-mail]> [e-mail] (Stick,CommoSigop) writes:
>>... put briefly, they
>>fouled up the test, performing it incorrectly, and never
>>checked by any independent method.
>
>   According to Dr. Steve Maran, who works on the HST project at the
>Goddard Flight Center, and who was recently a guest lecturer at my college,
>none of the above is true.  The company that ground the mirror did it
>exactly to the specs they were given.

You're sure that's what he said?  It's *not* what Lew Allen's review board
found (and documented in detail).  The grinding people at Perkin-Elmer did
indeed produce an essentially perfect mirror to the wrong spec.  But it was
Perkin-Elmer that botched the spec, by mis-building the reflective null
corrector that was used to measure the mirror shape, and Perkin-Elmer that
ignored three successive hints that something was wrong with the RNC.
(First, the error made it impossible to build the RNC without a slight
design change; the change was made without anyone asking why it was
necessary.  Second and third, results from two other measurements were
disregarded because the RNC was thought to be superior.)
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 7 Nov 92 05:23:48 GMT
From: Henry Spencer <[e-mail]>
Subject: NASA Coverup
Newsgroups: sci.space,alt.conspiracy

In article <[e-mail]> [e-mail] writes:
>A very easy way to blow this one up is to look at the weight of the Apollo
>LM and the thrust of the engine. The rocket equation says that there must be
>at least a 1.141 thrust to weight ratio. Remember the LM only had one
>Ascent stage. Henry can probably provide the numbers...

Ascent-stage liftoff weight was about 10000lbs on a 3500lb-thrust engine.

Of course, he'll just claim that the references are lying about these.
Really serious conspiracy theorists are religious fanatics, not rational
debaters; there is not much point in arguing with them, because any source
which disagrees with them is ipso facto lying.

>Astronauts suits and baggage were set up for 1/6 g and not .6 gee. If any of
>you out there know Buzz Aldrin, there is no way he would keep something like
>this covered up.

This is just a specific illustration of a point I should probably have made
at greater length:  there is just *no way* to keep something like that quiet
with so many people involved.  There's always somebody who's honest enough
or greedy enough or ethical enough or annoyed enough with the management
to spill the beans to the press... especially when it's big enough
and important enough to get his name into the history books and make him
a bundle of money.  Classifying something "secret" won't stop someone who
really thinks the public deserves to know, as witness the guy who went to
jail for leaking a spysat photo of a Soviet aircraft carrier being built.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 7 Nov 92 05:57:06 GMT
From: Henry Spencer <[e-mail]>
Subject: NASA Coverup
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>...things that weren't publicized. The trip back to Earth inside of Apollo 13
>was pure hell for one...

Actually, some of the recent books on Apollo give a reasonably good picture
of just how close to the edge that crew came...  It definitely didn't get
a lot of play at the time, though.
--
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, 7 Nov 1992 06:15:19 GMT
From: Henry Spencer <[e-mail]>
Subject: NASA COVERUP
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Elling Olsen) writes:
>HS> This is laughable.
>
>Why don't you do some work and disprove the claim that the
>earth/moon neutral point have changed from 20,000-25,000 miles
>to 43,495 miles from the center of the moon?

I have too much real, worthwhile work to do already.

>Or is it more
>confortable to sit in your couch judging and laughing?

"They laughed at Fulton."

"Yes, but they also laughed at Rube Goldberg."
--
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, 7 Nov 1992 06:11:27 GMT
From: Henry Spencer <[e-mail]>
Subject: NASA Coverup
Newsgroups: sci.space,alt.conspiracy

In article <[e-mail]> [e-mail] (Tom Nugent       ) writes:
>I thought that the reason Ranger 6 didn't send back pictures was because
>they forgot to take off the 'lens cap' before launch.  Seriously.  That's
>why they now have little red tags all over new probes etc. which say "Remove
>before launch."  At least that's the story I heard from a JPL engineer.

I'd say he was pulling your leg.  The electrical system on Ranger 6's
cameras was ruined during launch by a complicated accident.  It was a
design error, not a procedural mistake.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 7 Nov 92 05:54:39 GMT
From: Henry Spencer <[e-mail]>
Subject: pocket satellite receivers
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Carl Hage) writes:
>... Suppose we end up with a president who places
>a higher priority on commerce rather than restricting the military buildup
>of countries like Iraq, and accurate navigation information is declassified.
>
>  1. Can the "noise" be turned off, or do we need new satellites?

The noise is entirely controlled from the ground, and can be turned off.
It was turned off during the Gulf War because US military forces were making
extensive use of commercial GPS receivers.

Certain commercial users, like aviation, are never going to be comfortable
with a system that might get noisy again without warning (any time that DoD
convinces the president that there's an emergency).  They would really like
to see a navsat system that was not run by the military.

>  2. I thought selective availability mean't that noise was injected only
>     during a military operation, e.g. the Gulf War...

Nope.  DoD's position is that selective availability is *on* by default
and is turned off only for good reason, e.g. the Gulf War.

>     ...Why do I read that commercial units still don't
>     have the accuracy that military units have, i.e. how is full precision
>     information transmitted?

The military units also make use of a more sophisticated (and potentially
secret) high-precision timing code and multi-frequency operation.

>  3. Would special or extra hardware be required to receive full precision
>     information over existing receivers?

You can get the full benefit of the low-precision code with off-the-shelf
commercial receivers.  (Well, except that there are a lot of people looking
at clever ways to get better precision out of it, so this situation might
change.)  Fancier gear is needed for the high-precision code etc.

>  4. Is differential GPS used just to overcome the selective availability
>     noise, or are there other sources of error?

There are other sources, although the primary motive for differential GPS
certainly is selective availability.
--
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, 7 Nov 1992 06:47:12 GMT
From: Henry Spencer <[e-mail]>
Subject: Russian Engines for DC-Y?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Robert B. Whitehurst) writes:
>    The interesting thing about this article was that it said that
>the RD-701 used only two turbopumps, with the LOX and kerosene being
>pumped by one, and the LH2 by the other.  I read it quickly, so I
>might have this wrong, but that sounds rather intriguing.  Is
>fuel/oxidizer premixed in other engines? ...

I haven't seen the article yet... but almost certainly that means a
common turbine driving two separate pumps.  It's fairly normal to
use a separate pump turbine for hydrogen, because a hydrogen pump is
a very different animal due to hydrogen's very low density, but a
common turbine for more normal propellants is nothing unusual.  The
thought of trying to pump premixed propellants would make any sane
rocket engineer dive for cover, even disregarding the fact that you
*can't* premix LOX and kerosene due to temperature differences...
--
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, 7 Nov 1992 06:41:23 GMT
From: Henry Spencer <[e-mail]>
Subject: Scenario of comet hitting Earth
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>I get the feeling that there has been a serious over-estimate of the ability
>of a nuclear warhead to significantly change the delta-v of an asteroid.
>Project Icarus (from what I remember) suggested exploding a device at
>the aphelion point so as to move the asteroid away from the earths orbit.
>I can't recall anything about doing it "near" the earth...

You need to run some diagnostics on that memory. :-)  Project Icarus's
timescale permitted nothing of the kind.  "...to make the rendezvous at
Icarus's aphelion of November 1967, the space vehicle would have to have
been launched 8 months earlier, that is, within a few weeks after the
problem was posed.  Such a launch time was of course impossible...
Launch dates in 1968 were accepted as feasible only on the basis of
adaptation of existing hardware and by postulating top emergency priority
in all related technical and industrial efforts..."

The first Icarus interception was to be at 20 million miles, 13 days
before impact, this being about the farthest possible with the assumed
hardware.  Three more would take place over the next eight days, with
range closing to 7.7 million miles.  Finally, two low-altitude attacks
would occur in fast succession less than a day before impact, at 1.41
and 1.25 million miles.  The high-altitude interceptions would use
100MT bombs and would attempt to deflect Icarus.  The low-altitude
ones would have roughly twice the payload mass available, plus much
more precise guidance, and would use the most powerful bombs available
in an attempt to destroy as much of the asteroid and/or its fragments
as possible.  The estimate for all six missions was a 71% chance of
successful deflection, with most of the remaining possibilities
involving fragmentation plus destruction of at least some fragments.

>Anyway, this
>would only work if the object was small.

Icarus is about 700m across, which is actually pretty large for an
Earth-crossing asteroid.

>Also, has anyone addressed the problem of guiding such a device to the
>precise point at short notice?  What if the object is travelling
>retrograde?  A doubt you could lob a nuclear device at an asteroid/comet
>with sufficient accuracy.  Especially if we are talking combined
>velocities of >30 Km/s.

See the Project Icarus study for the gory details of how to do it with
mid-1960s technology at a closing velocity of about 40 km/s.  Not simple
but not impossibly hard.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 7 Nov 92 04:12:02 GMT
From: Jason D Corley <[e-mail]>
Subject: Viking Photos Shows Evidence of Marsquakes
Newsgroups: sci.space,sci.astro,alt.sci.planetary,sci.geo.geology

I thought that the Viking landers had picked up only
minimal Marsquake activities.  Has something changed?

I remember reading that only two, and those very slight,
earthquakes were recorded over the umpteen year run
of the Viking probes.

Could someone please explain the new data to me (an
ignorant physics/math undergrad?)

    Jason
    Ono-Sendai R&D

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

End of Space Digest Volume 15 : Issue 391
------------------------------