asteroid impact
Onno Meyer
kind of rock) passing the earth with ... million miles distance.
The paper said that a rock that would hit the earth could be deflected
with nuclear arms.
I always thought this is science fiction. Any comments?
--
* Onno Meyer - Kastanienallee 40 - 2900 Oldenburg - Deutschland *
* e-mail: Onno....@arbi.informatik.uni-oldenburg.de *
* Mathe-Student, und auch etwas Informatik... *
Erick Singley
hit- though small chunks would 'burn up' faster due to the larger surface area
of smaller chunks. Then we'd have radio-active bits of dust coming down too
(donno if that's hype or truth). Still better than what they conjecture
happened to Siberia those many decades ago. (Didn't some humungo rock hit there
and knock down trees for miles?). Messy either way- atomic bombs don't
'disintegrate' things- but might 'knock off course'. Hard to say.
Though not my field. :)
Erick
russell wallace
>I read a newspaper notice concerning an asteroid (or some other
>kind of rock) passing the earth with ... million miles distance.
>The paper said that a rock that would hit the earth could be deflected
>with nuclear arms.
>I always thought this is science fiction. Any comments?
Such an object could in principle be deflected or disintegrated by
nuclear explosives, though this would be a nontrivial engineering
project. It woud depend on factors such as, how early we spotted the
object, how big it was, and how quickly we managed to get a spacecraft
out to it (therefore how far away it is from Earth by the time the
spacecraft carrying the bombs reaches it).
--
"To summarize the summary of the summary: people are a problem"
Russell Wallace, Trinity College, Dublin
rwal...@unix1.tcd.ie
Stefano Pagiola
Arthur C. Clarke on precisely this topic.
--
-
Stefano Pagiola
Food Research Institute, Stanford University
spag...@frinext.stanford.edu (NeXTMail encouraged)
Dani Zweig
>The paper said that a rock that would hit the earth could be deflected
>with nuclear arms.
>I always thought this is science fiction. Any comments?
It *is* science fiction, but that doesn't mean that it's not feasible.
sd...@cas.org
>I read a newspaper notice concerning an asteroid (or some other
>kind of rock) passing the earth with ... million miles distance.
>The paper said that a rock that would hit the earth could be deflected
>with nuclear arms.
>I always thought this is science fiction. Any comments?
>--
NASA did some studies on deflecting large rocks away from earth
impact many moons ago - very preliminary stuff, as I recall.
The idea was you could change the course of a rock enough
to keep it from hitting the earth if you hit it far enough away
with a big enough bomb. The idea resurfaced when the speculation
about dinosaur extinction being caused by a meteor impact
hit the popular press. I have no idea if there is any funding
for any ongoing studies now, but it would probably work *if*
you hit the rock far enough out and *if* it didn't just break
up into a lot of medium sized rocks. The real problem is detecting
it and accurately determining its course far enough away to
get the intercept started.
We've had some very near misses in the past - one provoked a lot of
UFO sightings plus some neat movie film back in the 60's as a big
rock grazed the atmosphere - long smoke trail - would have made a big
hole if it had come in, but fortunately it went away.
******************************************************************************
Renegade academician. They're a dangerous breed when they go feral,
academics are...a chemist, too.
-(James P. Blaylock in "Lord Kelvin's Machine")
My organization hasn't agreed with any of my opinions so far, and
I doubt they'll start now.
Stanley "Ya nee speon" Roberts
timothy c huesman
on the success of 'aiming' a missile from earth. When Halley'd comet
made its last pass, there was plenty of warning and they MISSED with
flybys. Hmm as one gets old the memory fades. The comet was other
than Halley's...not that it matters much, they still missed. I'd
put a better chance of success from a space-launched missile or
'placed' nukes set in place by people in a vehicle matching velocities
with said asteroid.
--
Doc Pan t...@mik.uky.edu Tim Huesman
sd...@cas.org
Nick Szabo
>kind of rock) passing the earth with ... million miles distance.
This would be Toutatis. It's about 1/2 the diameter, or 1/8 the
mass of the dinosaur killer. It's been said that if that asteroid
had killed off only 99% of the individual plants and animals, it
wouldn't even have shown up in the fossil record.
Toutatis will approach earth this December, in 2000, and 2004. The positions
of the 2000 and 2004 flybies will not be well known until after December
due to earth's perturbations which enhance the uncertainty. According to
a very crude calculation based on current uncertainties, you have five times
the chance of being killed by Toutatis in 2000 as you have of being killed
in an airline crash that year.
>The paper said that a rock that would hit the earth could be deflected
>with nuclear arms.
A couple problems. First, our warning time is less than 8 years.
Second, asteroids may be rubble piles rather than one big rock.
A nuclear bomb would disperse the pieces, but not deflect them
to any signficant degree. I doubt we could launch the nuclear
energy needed to actually vaporize the asteroid, or at least
pulverize it into harmless-sized chunks. In general, though, we just
don't have enough information about the various types of asteroids
to know how to deflect them.
A couple projects if funded could remedy our ignorance.
These projects would cost only $70 million apiece, or in total
1/10 of 1% -- one-one-thousandth -- the cost of NASA's space
station. The first is Spacewatch, to find and track all dangerous
earth-approaching asteroids. The second would be a survey to use big
telescopes and spectroscopy to determine the composition of these bodies.
These projects are also critical to getting raw materials from these
asteroids in the future, so we kill two birds with one stone (so to speak :-)
--
Nick Szabo sz...@techboook.com
Hold Your Nose: vote Republocrat //////// Breathe Free: vote Libertarian
Aaron Wigley [Wigs]
currently a discussion of this right now there.
The Wigs of Oz,
Aaron Wigley
Richard Clark x4971
What do you mean by missed? There have been no attempts to impact or land a
probe on a cometary nucleus thusfar although such have been discussed.
The Europeans were careful NOT to fly Giotto to close to Halley--they hoped
it might survive the encounter.
There was some uncertainty about the exact location of the nucleus. This was
important both for camera pointing and for getting the probe as close as
possible while maintaining a reasonable probability of survival. The properties
of dust particles in the coma was also a bit uncertain.
Occasionally asteroids occult stars. Plans for groundbased observations of
these events start out with a lot of slop in the ground path. Continuing
astrometric measurements of cataloged asteriods allows the 'discovery' of
an upcomming event with 1-2 years advanced notice. Ground path errors are
on the order of continental. The occultation circumstances are refined as
the event nears until a couple of weeks before the big night (when the star
and asteroid can be photographed on the same plate) the uncertainty is down
to perhapse 100-200 km. This is as good as it gets with ground based optical
observations.
This is the uncertainty of the relative positions on the sky of the star and
the main belt asteroid. If the object were important enough to want the range
it might be determined from radar, someone else will have to take that one:
How far out can we get returns from a 10, 20, 100 km rock? snowball? Don't
need anything fancy like the radar studies of Venus' surface, just range and
v.
Of course a comet has that pesky coma which conceals the actual nucleus.
Our comet killer has to fly into a fog bank to find the nucleus on its own
and home in. Halley's nucleus wasn't detected photographically until Giotto
was within 1000 km or so. Of course it could have been detected by radar at
considerably greater distance but Giotto wasn't so equiped.
We would know the orbit of the Hammer better on the pre perihelion portion
than post perihelion because the active nucleus causes lots of non
gravitational perturbations. In any case suppose tha panic criterion is
achieved and General Sagan presses the button. The actual intercept is
a simpler than what's invisioned for the SDI kinetic kill vehicles.
Encounter velocity between probe and comet could be something like 50-60
km/s since we don't have the propulsion systems to do the intercept out
more than a few e6 km. Even with 3 months warning we can't intercept out as
far as 1.5 au (mars' orbit). So the probe's radar picks up the nucleus at
50000 km and has 10 minutes to home in. Since JPL is working with NORAD on
this one the cross range error shouldn't be over 100-500 km (the nucleus is
already quite active even if its pre perihelion so the opaque coma makes
radar necessary for terminal guidance--optical navigation during the day
prior to encounter doesn't help that much). If we can scale up a Brilliant
Pebble to carry a nuke on a short interplanetary mission it should be quite
simple to make the kill. There won't be much chance to go for the deflection
by optimal placement of the nuke but disruption of a comet nucleus should
be fairly easy.
The standard situation in which interception of an Earth threatening object
is actually feasible is when it is noticed that a recently discovered Earth
Crosser will come uncomfortably close in June of 2265. In this case the
deflection of a moderate size solid rock is quite possible. There is even
room to get fancy and assure that it WILL impact the moon! What a show that
would be!
Richard Clark
rcl...@lpl.arizona.edu
Erik Max Francis
> I read a newspaper notice concerning an asteroid (or some other
> kind of rock) passing the earth with ... million miles distance.
> The paper said that a rock that would hit the earth could be deflected
> with nuclear arms.
This certainly would work, if we got there in time and in full enough
force. Just detonate a nuclear warhead in the right place, and it will
alter the path of rock, hopefully to miss the Earth. (Shattering into a
million pieces would be a very bad idea. Instead of having a
trillion-tonne mass slam into the Earth, you have a million million-tonne
masses pepper the Earth, creating _real_ damage.)
The key is you have to get there early enough and have enough time to
analyze the situation well enough to detonate the warhead at the right
position on the rock, so that it gives maximal push but doesn't cause any
calving.
As I understand it, the present problem is with near-Earth asteroids.
These are mostly tiny little asteroids that are zipping around right
around our neighborhood. Somewhat recently, a very small one passed
between the Earth and the Moon -- that's less than 400 000 km. Our
problem right now is with spotting it. If I recall, we discovered this
particular body only a few days before aphelion, closest approach. If
that had been less than the Earth's radius, then it would have hit and we
couldn't have done anything about it.
At the present time it would difficult to deflect an object, but we could
do it if we had sufficient time warning. How long? A month? Three
weeks?
----------
Erik Max Francis Omnia quia sunt, lumina sunt. Coming soon: UNIVERSE _ | _
USmail: 1070 Oakmont Dr. #1 San Jose CA 95117 ICBM: 37 20 N 121 53 W _>|<_
UUCP: ..!apple!uuwest!max Usenet: m...@west.darkside.com 464E4F5244 |
Bill Higgins-- Beam Jockey
> In article <1992Oct8.1...@arbi.Informatik.Uni-Oldenburg.DE> Onno....@arbi.informatik.uni-oldenburg.de (Onno Meyer) writes:
>>I read a newspaper notice concerning an asteroid (or some other
>>kind of rock) passing the earth with ... million miles distance.
>>with nuclear arms.
>
>
> A couple projects if funded could remedy our ignorance.
> These projects would cost only $70 million apiece, or in total
> 1/10 of 1% -- one-one-thousandth -- the cost of NASA's space
> station. The first is Spacewatch, to find and track all dangerous
> earth-approaching asteroids. The second would be a survey to use big
> telescopes and spectroscopy to determine the composition of these bodies.
> These projects are also critical to getting raw materials from these
> asteroids in the future, so we kill two birds with one stone (so to speak :-)
People seriously interested in these questions will want to get hold
of *The Spaceguard Survey: Report of the NASA International
Near-Earth-Object Detection Workshop*. The group was chaired by David
Morrison of the University of Hawaii. It met a number of times during
1991, and the report was released earlier this year. I believe copies
can be obtained from NASA Headquarters in Washington; start by asking
the Public Affairs Office, NASA Headquarters, 600 Independence Avenue,
Washington, DC 20546 (202)453-1549. To quote from the press release:
> The NASA-sponsored Near-Earth-Object Detection Workshop
>judged asteroids with diameters 1 km or larger the most
>dangerous objects in terms of potential for causing catastrophic
>global effects on Earth. Impacts of such asteroids are extremely
>rare and can be detected with current ground-based technology,
>most likely decades in advance of any collision.
Later, in January 1992, Los Alamos National Laboratory hosted a
Near-Earth-Object Interception Workshop. This group worked on the
question of how to *prevent* asteroid collisions. Their report isn't
out yet, having run into both political and budgetary problems (they
ran out of money to pay their editor).
Short overviews of both workshops, authored by some of their
participants, appeared in the May/June 1992 issue of *Mercury*, the
magazine of the Astronomical Society of the Pacific. They were
accompanied by an article by Fran Smith of the *San Jose Mercury
News*, "A Collision over Collisions: A Tale of Astronomy and
Politics."
According to Smith's account, Morrison persuaded Congressional
committees "that you didn't have to be a nut or a tabloid editor to
contemplate cosmic collisions." Thus NASA's FY 1991 authorization
bill included a requirement to report to Congress on the asteroid
hazard; that's how these two workshops got started.
Smith describes a disagreement between Morrison and John Rather,
assistant director for space technology at NASA Headquarters, and a
member of the SDI community before he came to NASA. Morrison's group
emphasized large objects, bigger than a kilometer in diameter, which
could cause regional or global cataclysm-- but which are eminently
detectable in ground-based telescopes. Rather's group, which included
weapons physicists from Livermore and Los Alamos, was more interested
in objects 4 to 20 meters across-- hard to find with telescopes, but
more common, and easier to destroy or deflect with SDI-derived
technology plus nuclear weapons.
Names of such prominent SDI advocates as Edward Teller, Lowell Wood,
Roderick Hyde, and Gregory Canavan appear in the article, but it's not
clear to me who among them were actually involved with the
"Interception" workshop (Canavan was). "Several months ago, after
several astronomers got their hands on a near-final draft calling for
`star-wars' technology and nuclear bombs," Smith writes, "they angrily
demanded that NASA revise these recommendations-- or drop their names
from the report." She does not name these people, but long-time
opponents of SDI like Louis Friedman and John Pike are among the
members of Morrison's workshop.
My impression, from Smith's article, is that a number of specialists
in asteroid astronomy believe that organizing a search for possible
collisions is a good idea, but is difficult enough to sell without
getting connected to a weapons-development project. Odds are that if
the search finds a large asteroid or comet due to collide with the
Earth, there will be years or decades of warning. One could bet that
there would be plenty of time to develop a defense *after* such
detection. Yet it might make sense to have collision-defense
development proceed in parallel with the search, at least at a modest
level.
In the same issue of *Mercury*, Gregory Canavan and Johndale Solem of
Los Alamos write in their summary, "Interception of Near-Earth
Objects:" "The premiums for such insurance vary. A few million
dollars per year could support observations and theory on detection
and interception. A few tens of millions per year could provide
research on the technologies for interception, the dedicated
instruments needed to search for large Earth-threatening NEOs, and
research on the sensors needed to detect smaller asteroids at the
ranges desired. A few hundred million dollars could develop and test
the robotic spacecraft missions needed to characterize NEOs of all
sizes. Unfortunately, confusion over the relative priorities of
detection and interception has thus far delayed action on either,
although preliminary estimates indicate that either would justify the
research."
O~~* /_) ' / / /_/ ' , , ' ,_ _ \|/
- ~ -~~~~~~~~~~~/_) / / / / / / (_) (_) / / / _\~~~~~~~~~~~zap!
/ \ (_) (_) / | \
| | Bill Higgins Fermi National Accelerator Laboratory
\ / Bitnet: HIG...@FNAL.BITNET
- - Internet: HIG...@FNAL.FNAL.GOV
~ SPAN/Hepnet: 43011::HIGGINS
Charlie Stross
In article <1992Oct11....@techbook.com> sz...@techbook.com (Nick Szabo) writes:
>
>Toutatis will approach earth this December, in 2000, and 2004. The positions
>of the 2000 and 2004 flybies will not be well known until after December
>due to earth's perturbations which enhance the uncertainty. According to
>a very crude calculation based on current uncertainties, you have five times
>the chance of being killed by Toutatis in 2000 as you have of being killed
>in an airline crash that year.
>
>>The paper said that a rock that would hit the earth could be deflected
>>with nuclear arms.
>
>A couple problems. First, our warning time is less than 8 years.
>Second, asteroids may be rubble piles rather than one big rock.
>A nuclear bomb would disperse the pieces, but not deflect them
>to any signficant degree. I doubt we could launch the nuclear
>energy needed to actually vaporize the asteroid, or at least
>pulverize it into harmless-sized chunks. In general, though, we just
>don't have enough information about the various types of asteroids
>to know how to deflect them.
One interesting question occurs to me. The Earth actually sweeps
up a helluvalot of garbage every day without major problems;
indeed, the effect of a gigatonne or ten of rock would probably be
minimal *if* it was evenly distributed over the entire frontal
area of the planet.
Surely the logical strategy for dealing with anything short of a
humongous planetoid would be to gravitationally disrupt it with
a sub-surface blast, then zero in on the biggest fragments
and gravitationally disrupt _them_? If it was a choice between
a single multi-gigatonne equivalent dinosaur zapper and a
shotgun blast of kilotonne range detonations along with some
assorted crud, I'd go for the `several small impacts' option.
(Although it's worth bearing the square-cube law in mind ...
big blasts are not proportionately more devestating than
small blasts, which is why nobody bothers much with nukes that
deliver more than 250 Kt (city-buster) or 400 Kt (silo-buster)
any more.)
>A couple projects if funded could remedy our ignorance.
>These projects would cost only $70 million apiece, or in total
>1/10 of 1% -- one-one-thousandth -- the cost of NASA's space
>station. The first is Spacewatch, to find and track all dangerous
>earth-approaching asteroids. The second would be a survey to use big
>telescopes and spectroscopy to determine the composition of these bodies.
>These projects are also critical to getting raw materials from these
>asteroids in the future, so we kill two birds with one stone (so to speak :-)
Two excellent ideas ...
--
Charlie Stross aka char...@scol.sco.com ..... UNIX oriented text mangler
WARNING: The opinions voiced in the preceding electronic document are the
product of a warped mind. Take two before meals.
James Davis Nicoll
>
>One interesting question occurs to me. The Earth actually sweeps
>up a helluvalot of garbage every day without major problems;
>indeed, the effect of a gigatonne or ten of rock would probably be
>minimal *if* it was evenly distributed over the entire frontal
>area of the planet.
You want to spread it over time aswell as area. A 2km
rockmight mass 10**12 kg; at 30km/s that's 4.5x10**20 J. Spread
over 2.6x10**14 m**2, that's 1.7x10**6 J/m**2, or about the equivalent
of 20 minutes of sunlight. I don't know what percentage of the kinetic
energy of the rock would reach the surface, but I could see flashburns
easily, and perhaps widespread incindiary effects if the impacts are
not spread over time.
>Surely the logical strategy for dealing with anything short of a
>humongous planetoid would be to gravitationally disrupt it with
^^^^^^^^^^^^^^^^^^^^^^^^
>a sub-surface blast, then zero in on the biggest fragments
>and gravitationally disrupt _them_?
^^^^^^^^^^^^^^^^^^^^^^^
How?
James Nicoll
Steinn Sigurdsson
Some people are really going to hate me for this, but here goes
anyway...
A recent IAU circular reports that the best current fit for orbit
for comet Swift-Tuttle is for close approach next time around,
late summer 2126 AD. The comet is the parent comet of the Perseids,
it's very high inclination and eccentricity, looks like an Oort
cloud body that was deflected to its current short period orbit
by a close Earth approach (we were guesstimating 10 Earth radii
at first close approach N orbits ago) it is thus self-selected for
close Earth approach. Now, the orbit is uncertain due to
non-gravitational effects and won't be well determined until the comet
is well past this perihelion, the errors allow for a Earth impact
on August 14 2126 - with very low a priori probability -
speed relative to Earth is high at close approach, figure 40km/sec +,
maybe about 50 km/sec. Mass is unknown but it's hefty (anyone know
current best estimate?).
So, what would you do about it?
| Steinn Sigurdsson |I saw two shooting stars last night |
| Lick Observatory |I wished on them but they were only satellites |
| ste...@lick.ucsc.edu |Is it wrong to wish on space hardware? |
| "standard disclaimer" |I wish, I wish, I wish you'd care - B.B. 1983 |
Bill Higgins-- Beam Jockey
> A recent IAU circular reports that the best current fit for orbit
> for comet Swift-Tuttle is for close approach next time around,
> non-gravitational effects and won't be well determined until the comet
> is well past this perihelion, the errors allow for a Earth impact
> on August 14 2126 - with very low a priori probability -
> speed relative to Earth is high at close approach, figure 40km/sec +,
> maybe about 50 km/sec. Mass is unknown but it's hefty (anyone know
> current best estimate?).
>
> So, what would you do about it?
Assuming more observations refined the predicted orbit, and it still
told us the comet is going to hit?
I would begin an intensive research and development program to figure
out how to divert and/or destroy a big comet.
But I wouldn't start my program until 2095. No point in tackling the
problem with obsolete technology.
(What I'm doing about it *now* is trying to get a copy of the Los
Alamos workshop report, which I described in an earlier posting.
Unfortunately, it's not written yet, and it doesn't look like it will
*get* written any time soon. :-( )
Steinn Sigurdsson
In article <STEINLY.92...@topaz.ucsc.edu>, ste...@topaz.ucsc.edu (Steinn Sigurdsson) writes:
> A recent IAU circular reports that the best current fit for orbit
> for comet Swift-Tuttle is for close approach next time around,
> late summer 2126 AD. [...] Now, the orbit is uncertain due to
> non-gravitational effects and won't be well determined until the comet
> is well past this perihelion, the errors allow for a Earth impact
> on August 14 2126 - with very low a priori probability -
> speed relative to Earth is high at close approach, figure 40km/sec +,
> maybe about 50 km/sec. Mass is unknown but it's hefty (anyone know
> current best estimate?).
>
> So, what would you do about it?
Assuming more observations refined the predicted orbit, and it still
told us the comet is going to hit?
I would begin an intensive research and development program to figure
out how to divert and/or destroy a big comet.
But I wouldn't start my program until 2095. No point in tackling the
problem with obsolete technology.
Hmm, first priority is to refine the orbit which means following
towards aphelion as far as possible - currently it will be tracked
to 3-5 AU, maybe out to 10AU if serious scopes are allocated,
aphelion is at 50AU and that's where orbit uncertainties are
amplified, something tells me it would be a very bad idea
to lose track of CS-T on this orbit - it was 17 days late
this time around, 15 days late next time and we're in trouble.
(What I'm doing about it *now* is trying to get a copy of the Los
Alamos workshop report, which I described in an earlier posting.
Unfortunately, it's not written yet, and it doesn't look like it will
*get* written any time soon. :-( )
Swift-Tuttle arguable presents a very serious long term problem.
In its current orbit it has a probability of order 0.5+ to hit in
the next 10**7 years, the orbit is orthogonal to the plane of the
Earth's orbit and goes nowhere near any other planet - immediate
conclusion is that the Earth deflected it into its current orbit
from a long period orbit down from the Oort cloud. Delta v of 3-5 km/s
was necessary, so off the cuff it came within 5-10 Earth radii first
time around. Problem is nothing will systematicall perturb it away
from us and outgassing is random walking it around Earth's orbit,
the probability of collision at each pass is selected to be
disproportionately high and unlike most short period comets Jupiter
is not going to perturb it away from us. It is almost certain to
hit eventually.
Now, relative speed at close approach is just about 50 km/s
(orbit is slightly retrograde), but deflecting it is not a long term
solution, it is easiest to deflect it along the orbit trajectory,
but that still leaves it on Earth crossing orbit and a threat,
a small deflection away from Earth orbit can save us on any one
orbit but unless Delta v is large, order 5-10 km/s, outgassing and
Earth perturbations can still put it back in Earth collision orbit.
There is a small chance the comet will be deflected into a longer
period orbit by a close Earth encounter but all that does is delay
collision (unless something in the Oort cloud then knocks it away
- prob 0) as it will _still_ be in Earth crossing orbit.
Now, S-T's size is uncertain, as I recall 10 km diameter
is more of a civilization killer than a dinosaur killer, but it really
does look like we're looking at a major long term problem.
BTW 1:10,000 odds of collision in 134 years are very poor
odds, be a hell of a Perseids display though :-)
* Steinn Sigurdsson Lick Observatory *
* ste...@lick.ucsc.edu "standard disclaimer" *
* The laws of gravity are very,very strict *
* And you're just bending them for your own benefit - B.B. 1988*