If they were sure a asteroid were going to hit the earth

"Scott Hedrick" wrote in message
.. .
Uncountable telescopes in private hands. Not even possible to keep it a
secret.

The gubmint was able to keep an asteroid the size of Texas secret in
Armageddon!

Yet another factoid for my "Michael Bay is an artless hack" file.

Mark

"Mark Hanson" wrote in message
news:WJRrb.165024$e01.579447@attbi_s02...
"Hallerb" wrote in message
...
Do you think we would be told? Or would the adminstration keep it a
secret
to
prevent panic? Lets assume its a BIG one....

Uncountable telescopes in private hands. Not even possible to keep it a
secret.

BIG one, probably impossible. Big enough to do some real damage, it's quite
possible it would not be seen until to late.

Note some have only been detected AFTER they've passed by the Earth.
Anything on a direct course is going to be hard to pick out due to lack of
relative motion to the stars.


Mark

"Greg D. Moore \(Strider\)" wrote:
Note some have only been detected AFTER they've passed by the Earth.
Anything on a direct course is going to be hard to pick out due to lack of
relative motion to the stars.

hmm... In order to have a zero bearing rate, it will either have to
be *very* close, or traveling in a very unusual orbit.

IIRC the ones that worry the astronomers most is the retrograde ones,
as they are coming out of the suns glare.

D.
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Scott Ferrin wrote:




It's kindof like pulling the lever on a slot machine. Pretty easy to
get a buck or two but not to many pull the million dollar payouts. I
wonder what the odds on any given day of say a 10 gigaton impact? Or
a one megaton impact in a city of over 50,000? Any stataticians out
there?

It seems that the numbers are getting steadily revised downwards; I
don't think it was a coincidence that the "asteroid threat" and
protection plan suddenly appeared right after Reagan's Star Wars system
got canceled.
The aerospace firms wanted to get big bucks to make something, and a
asteroid stopper has the advantage that the odds it's going to get used
in any particular year are very small indeed. If it is used, then either
it works, and the companies that built it become heroes; or it doesn't
work, and the investigation into corporate fraud is then actually a
fairly small concern on the global scale of things. It's like somebody
sold me a lotion to wear that they guaranteed would prevent shark
attacks anytime I went swimming.....here in North Dakota.

Pat

In article ,
Scott Ferrin wrote:
wonder what the odds on any given day of say a 10 gigaton impact? Or
a one megaton impact in a city of over 50,000?

Really pretty unlikely. Impacts in the major-hydrogen-bomb class seem to
be once a century or less, on average, and even their effects are mostly
quite local. (The area of serious damage from Tunguska was about the size
of a large city.) Earth's surface is mostly water, and even most of the
land has quite low population densities. Cities cover only a very small
fraction of the planet.

The main risk to most cities is gigaton-plus impacts in oceans, because of
ensuing tsunamis. Those can be devastating to coastal cities even if the
impact itself is far away; tsunamis carry energy over long distances far
more efficiently than blast waves in air do.

...Only a year to design AND put the thing together so
things are going to be crude as in not extremely high tolerences...

This is basically just too short a time -- you can't debug the design,
even a fairly forgiving one, that quickly. You'd have to start with
hardware that was already developed or nearly so.

...So then you dust off the data for those 260" diameter
solid motors they tested (any idea how long to make the propellant?)
Slap some of those one something like Sea Dragon...

I think you have failed to grasp just how big Sea Dragon was supposed to
be. :-) Strap-ons of that size would increase its payload only a little.
(And the capability to build them is not something we could re-establish
quickly. Solids look easy but they are not; they are terribly sensitive
to even the tiniest flaws in those big masses of fuel.)

The idea being that you get the big nuclear warhead in just deep
enough that when it goes off it blows out the side using the ejected
fragments as reaction mass. If you just blow the thing on the
surface... well it probably wouldn't do much.

I think you have failed to grasp just how powerful a big bomb is. :-)
There is not a lot of difference between burying it a few meters and
detonating it on the surface. Besides, it is not clear that you want a
surface burst -- you may get a better propulsive effect by setting it off
at a modest altitude, where its X-ray flux can reach and vaporize a larger
area of surface. (It is *gas* you want for efficient propulsion, not
fragments.)
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

In article ,
Pat Flannery wrote:
It seems that the numbers are getting steadily revised downwards; I
don't think it was a coincidence that the "asteroid threat" and
protection plan suddenly appeared right after Reagan's Star Wars system
got canceled.

While the threat undoubtedly got played up a bit by people with axes to
grind, the numbers came from the astronomers, who are not noted for their
huge military contracts.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

On Thu, 13 Nov 2003 03:31:35 -0600, Pat Flannery
wrote:



Scott Ferrin wrote:




It's kindof like pulling the lever on a slot machine. Pretty easy to
get a buck or two but not to many pull the million dollar payouts. I
wonder what the odds on any given day of say a 10 gigaton impact? Or
a one megaton impact in a city of over 50,000? Any stataticians out
there?

It seems that the numbers are getting steadily revised downwards; I
don't think it was a coincidence that the "asteroid threat" and
protection plan suddenly appeared right after Reagan's Star Wars system
got canceled.
The aerospace firms wanted to get big bucks to make something, and a
asteroid stopper has the advantage that the odds it's going to get used
in any particular year are very small indeed. If it is used, then either
it works, and the companies that built it become heroes; or it doesn't
work, and the investigation into corporate fraud is then actually a
fairly small concern on the global scale of things. It's like somebody
sold me a lotion to wear that they guaranteed would prevent shark
attacks anytime I went swimming.....here in North Dakota.

Pat


The thing I find interesting is that they say there are sizable
impacts on a yearly basis but they all seem to fall in the ocean ;-)

This is basically just too short a time -- you can't debug the design,
even a fairly forgiving one, that quickly. You'd have to start with
hardware that was already developed or nearly so.


At this point though it's "do we try and maybe fail or do we not try
at all?"





...So then you dust off the data for those 260" diameter
solid motors they tested (any idea how long to make the propellant?)
Slap some of those one something like Sea Dragon...

I think you have failed to grasp just how big Sea Dragon was supposed to
be. :-) Strap-ons of that size would increase its payload only a little.

Yeah. IIRC Sea Dragon's liftoff thrust was suppose to be something
like 72 million. I'm pretty sure even full length 260s were under
ten. I figured it would be easier than the 325s or 380s they were
kicking around back then :-)



(And the capability to build them is not something we could re-establish
quickly. Solids look easy but they are not; they are terribly sensitive
to even the tiniest flaws in those big masses of fuel.)

It would probably be easier then to just make the liquid engine
bigger.



The idea being that you get the big nuclear warhead in just deep
enough that when it goes off it blows out the side using the ejected
fragments as reaction mass. If you just blow the thing on the
surface... well it probably wouldn't do much.

I think you have failed to grasp just how powerful a big bomb is. :-)

I was looking at some of the underground detonations back in the day.
Even the biggest one (5 Mt) was contained and it was just in dirt.
(even still it was pretty amazing. Over a mile down. Check out the
11 Mb file here http://arcticcircle.uconn.edu/SEEJ/amchitka/)



There is not a lot of difference between burying it a few meters and
detonating it on the surface.


I was thinking more along the lines of several hundred feet :-).
Granted a 30 foot diameter shaped charge is nothing to sneeze at but I
doubt it's beyond current technology. Two of them in tandem would
get you three hundred feet in. Follow that with a long slim nuclear
weapon that was tough enough to to survive a few lateral bounces and
it could get most of the way to the bottom before going off.


Besides, it is not clear that you want a
surface burst -- you may get a better propulsive effect by setting it off
at a modest altitude, where its X-ray flux can reach and vaporize a larger
area of surface.

Here's the problem with that. Surpisingly little of the surface would
get vaporized. Back when they were doing testing to figure the
erosion on the push plate on Project Orion they discovered that the
erosion would be negligable and that something as simple as a very
thin coat of oil would eliminate it altogether.



(It is *gas* you want for efficient propulsion, not
fragments.)

F=ma. Trying to vaporize the surface would result in very little "m"
and most of the "a" would not be directly away from the astroid. In a
subsurface burst the "m" would be very high and the "a" would not be
insignificant and the majority of it would be directed perpendicular
to the impact (the hole cut by the shaped charges would direct the
blast).


Granted these are big ideas but it's an attempt to figure out how to
use current technology to move a LOT of weight.

In article ,
Scott Ferrin wrote:
I think you have failed to grasp just how powerful a big bomb is. :-)

I was looking at some of the underground detonations back in the day.
Even the biggest one (5 Mt) was contained...

By the standards of asteroid moving, 5 MT is still a pretty small bomb.
The MIT "Project Icarus" study specified 100-MT bombs, and they would have
preferred more -- that was just the largest bomb they thought could be
put together on 16 months' notice in the late 60s.

Besides, it is not clear that you want a
surface burst -- you may get a better propulsive effect by setting it off
at a modest altitude, where its X-ray flux can reach and vaporize a larger
area of surface.

Here's the problem with that. Surpisingly little of the surface would
get vaporized. Back when they were doing testing to figure the
erosion on the push plate on Project Orion they discovered that the
erosion would be negligable...

Orion wasn't using bare bombs -- they were planning to absorb most of the
X-ray pulse in the reaction mass wrapped around the bomb proper. What hit
the pusher plate was hot plasma, not X-rays. (Indeed, the fact that they
were talking about surface erosion tells you that! The X-ray pulse is too
penetrating to stop at the surface; it deposits most of its energy a few
centimeters *inside* whatever it hits.)

(It is *gas* you want for efficient propulsion, not fragments.)

F=ma. Trying to vaporize the surface would result in very little "m"
and most of the "a" would not be directly away from the astroid.

Actually, it would be, simply because there's no other place for the gas
to go. If you heat material at one point -- say, with a surface burst --
then yes, it does expand more or less in a hemisphere. But if you heat
material over a wide area of the surface, it expands outward as a sheet of
gas, and the only major losses are at the edges; the gas in the middle has
nowhere to go except directly away, because it has other gas on all sides.

In a subsurface burst the "m" would be very high...

However, much of that energy will go to heating that large mass, which
contributes nothing at all to propulsion. It's only expanding gas which
pushes things. You are better off having the expanding gas push the
asteroid directly, rather than relying on it to push pieces away from
the asteroid.

(Other things being equal, the latter *is* preferable, because you get the
most momentum from a given amount of energy by using the energy to push a
large mass away at low speed. But other things are not equal.)

...and the majority of it would be directed perpendicular
to the impact (the hole cut by the shaped charges would direct the blast).

Uh, no, some of the blast may squirt out the hole -- as hot gas -- but
there will be no particular tendency for the hole to direct the expansion
of rocks pushed by the blast.

Granted these are big ideas but it's an attempt to figure out how to
use current technology to move a LOT of weight.

People have looked at this before. Above-surface blasts generally look
best, especially if you are unsure of the structural integrity of the
asteroid. (Even the metallic asteroids aren't necessarily single pieces.)
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

Scott Ferrin wrote:


The thing I find interesting is that they say there are sizable
impacts on a yearly basis but they all seem to fall in the ocean ;-)


There are lots of bolides though on a yearly basis; we didn't take into
account that a lot of meteors explode in midair (particularly the
carbonaceous chondrites) in the original figures. Mind you, a big one
exploding over your head isn't going to be any fun- if Tunguska is
anything to go by.

Pat