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Tue, 31 Oct 89 03:23:12 -0500 (EST)
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Date: Tue, 31 Oct 89 03:22:49 -0500 (EST)
Subject: SPACE Digest V10 #178
SPACE Digest Volume 10 : Issue 178
Today's Topics:
Re: Asteroids as weapons of mass de
Re: Asteroids as weapons of mass destruction
Re: Exhaust velocity
Re: SPACE Digest V10 #160
Re: Asteroids via mass drivers
Re: Asteroids via mass drivers
Re: Space Shuttle SRB exhaust gas makeup.
how is Voyager gaining speed as it encounters Jupiter ?
Written 5:59 am Oct 23, 1989 by szabonj@ibmpa.UUCP (Nick Szabo):
> 3) We were only able to detect the asteroid that came within 2e6 km because
> it was _big_ and we were lucky. What are the statistical estimates for
> the number of asteroids per year between 10m and 1,000m across--which almost
> always go undetected at our current efforts-- that come within 2e6 km of
> Earth every year? Probably a large number, considering there are an
> estimated 100,000 asteroids >100m across with delta-v's closer than the
> lunar surface. Even an asteroid only 10m across could wipe out several
> acres of an urban area.
Does anyone know how large an asteroid must be (before entering the Earth's
atmosphere) in order to not burn up (as do many (most?) meteors)? How much
smaller would an asteroid (say a 100m one such as talked about in the previous
postings) be when it hit the earth's surface? Or can this be predicted to any
accuracy?
Erik A. Johnson
johnsone@uxh.cso.uiuc.edu
------------------------------
Date: 25 Oct 89 01:38:36 GMT
From: pacific.mps.ohio-state.edu!gem.mps.ohio-state.edu!ginosko!shadooby!mailrus!jarvis.csri.toronto.edu!utgpu!radio.astro!helios.physics!griffin@tut.cis.ohio-state.edu (Prof. A. Griffin)
Subject: Re: Asteroids as weapons of mass destruction
Disclaimer: I am NOT professor Griffin. If you use "F", please check the
attribution against the signature.
In article <2658@ibmpa.UUCP> szabonj@ibmpa.UUCP (Nick Szabo) writes:
>> Well, by my calculations, an object which is in a circular orbit at a
>>distance of 1 astronomical unit from the sun will, after applying .001 km/s
>>of delta-v, be in a slightly eccentric elliptical orbit. The maximum
>>deviation of the ellipse from the original circular path is 20000 km, which
>>which the original impact parameter would be about 2 000 000 km, which is
>>roughly the margin of miss we got on that asteroid a few months ago. What's
>>the best delta-v one could put on a 100m asteroid?
>> Based on this, I don't believe that a mass large enough to be dangerous
>>could be aimed to within 1000 km on the earth's surface
>
>1) We are talking about moving an asteroid, not the earth. What is the
>corresponding figure for a highly elliptical asteroid? The way you
>calculated it, the maximum deviation could be off by an order of
>magnitude.
>
Circular orbits are the hardest to shift, but the only ones I can
calculate without having to solve the differential equations :-).
Certainly, if you hit it at the right time, around the orbit of Mars, you
would get more than a tenfold deflection in position for the an elliptical
orbit.
>2) You did not take into account the possibility of using Venus, Mars or
>the Moon for gravity assist (even gravity assists at several million km can
>provide a small delta-v).
>
I would bet on the moon.
A question for the experts out there: would the exquisite aiming of the
Voyager probes have been possible if the maximum maneuvering acceleration
had been only 10^-4 m/s^2, which is the highest conceivable acceleration
for an asteroid missile (100m diameter sphere, propulsion of
200000 kg m/s^2).
>4) The terrorists can arrange for a delta-v greater than .001 km/s, if
>they really need to, with larger nuclear warheads.
>
>Now you might ask, why go to all the trouble of launching nukes way out
>in space when a city could just be nuked directly?
>
>a) Unlike smuggling nukes across borders, there is no risk of getting caught
>in foreign territory. Once you do it, you can ask for ransom without any
>possibility of the bomb being sniffed out and diffused.
>
>b) ditto if you launch an ICBM directly; it will be tracked, its source
>determined, and the perpetrators punished.
>
Put the bombs on the asteroid interceptor, fire it at the moon,
slingshot it around the moon for a straight-in approach to your target.
Easy to aim, lots of maneuvering acceleration, and the origin of the
missile is unknown. If you want to wait longer between launch and impact,
have it enter a parking orbit around the moon for a while.
>c) For the larger asteroids (100m+) the potential destruction is much
>greater. Entire continents could be wiped out, or even the whole planet,
>depending on how crazy the terrorists are.
>
I can't believe that terrorists who wanted to destroy the world could
get the technical support. The backers who provide thrusters for small
asteroids to bomb their enemies would balk at providing thrusters powerful
enough to throw a planetbuster.
>d) In the future, when we start asteroid mining, the temptation for mine
>workers, disgruntled about wages, conditions, or whatever, will be very great.
>
Only if they're self-sufficient. Blowing up your only source of food
isn't a great union negotiating tactic. If we had self-sufficient space
colonies, I really believe we would also have the early-warning ability to
see it coming.
>> All right, I've been making sweeping statements on a topic about which I
>>know very little.
>
>Same here. Same for 90% of the other stuff on the net. We're the first
>two to admit it. :-)
>
>I would be highly grateful for more rigorous calculations on this subject--
>it is important, but I'm afraid my math is lacking. :-(
>
Same here. I'm just recalling my undergraduate classical mechanics
stuff, since my field (condensed matter) doesn't give me much practice at
this.
>--
>--------------------------------------------
>Nick Szabo
>uunet!ibmsupt!szabonj
>These opinions are not related to Big Blue's
Well, I agree that asteroid diversion as a weapon is possible, but I
think it is unlikely. It presupposes equipment which could do as good a job
at lower risk of failure without bringing the asteroid into it. For
instance, it would be easier to put a base on the moon to throw rocks at
your target. Not only would you have a shorter interval between launch and
impact, and better targetting, but it would be reusable. I just hope no
bunch of environmentalists tries to ban asteroid diversion on the
grounds that it could be a "dangerous science".
--
Christopher Neufeld....Just a graduate student | "Scotty..now _would_
cneufeld@pro-generic.pnet01.crash | be a good time!"
griffin@helios.physics.utoronto.ca | - Pavel Chekov
"Don't edit reality for the sake of simplicity" |
------------------------------
Date: 25 Oct 89 02:01:04 GMT
From: cs.utexas.edu!ginosko!shadooby!mailrus!jarvis.csri.toronto.edu!utgpu!radio.astro!helios.physics!griffin@tut.cis.ohio-state.edu (Prof. A. Griffin)
Subject: Re: Exhaust velocity
Disclaimer: I am NOT professor Griffin. If you use "F", please check the
attribution against the signature.
In article <2639@ganymede.inmos.co.uk> conor@inmos.co.uk (Conor O'Neill) writes: