From: rwallace@unix1.tcd.ie (russell wallace)
Subject: Re: Wreaking a habitat (was Re: Wrecking a Planet
Organization: Trinity College, Dublin
Date: Sat, 9 Jan 1993 00:16:30 GMT

In <1993Jan8.144835.281@linus.mitre.org> m23364@mwunix (James Meritt) writes:

>In article <rwallace.726452375@unix1.tcd.ie> rwallace@unix1.tcd.ie (russell wallace) writes:
>}In <1993Jan7.173125.20305@linus.mitre.org> m23364@mwunix (James Meritt) writes:
>}>Why bother with total destruction?  Have you considered the results of a
>}>number of 5 inch holes drilled through it by very fast gravel?
>}
>}As I explained in another article, a piece of gravel is not at all going
>}to drill a hole in a 1 billion ton O'Neill habitat.

>Why on earth would you use one piece of gravel?  Send a gigaton or so of
>rock towards it at a few percent of the speed of light.  I don't think
>that your "measures" would do much good against a few million foot-wide
>holes randomly scattered completely through the habitat...

?????!!!!!! A gigaton of rock travelling at a few percent of
lightspeed??? Well that would certainly dstroy a habitat! Anything can
be destroyed by a sufficiently massive attack. Why not postulate sending
100,000 gigantic interstellar battlecruisers instead? Probably cheaper
than your suggestion.

>}Plus, your attack carrier will have to get reasonably close to throw the
>}gravel. 

>Wrong.  The Oort belt, to pick a demonstratable rock-throwing region, is
>not close.

This is where the maneuvering ability comes in. You can hit a planet
from the Oort cloud. You can't hit a habitat from there, because it will
have moved a few hundred or thousand kilometres away from its previous
orbit by the time a projectile arrives, in a random direction. (For that
matter, a habitat being only a few kilometres across, you probably
couldn't hit such a small target from the Oort cloud anyway.)

>}>}Most importantly however, is that a space habitat can move. Not with
>}>}great agility, to be sure, but it means that a guided, powered missile
>}>}is needed, not simply throwing bombs on a precalculated ballistic
>}>}trajectory. 
>}>Unless you are advocating near continuous random changes in acceleration,
>}>it fits in much the same category as "planet" - except that the attack
>}>could come from any location in the universe, as opposed to less than
>}>half for a "moonbase".  There is something reassuring about being able to
>}>have your back against a few thousand miles of protective rock...
>}
>}Presumably the attackers of a planet will have the wit to time their
>}attack to hit the right side of the planet.  

>That's nice.  So you can cut the time in half, too...  An attack against a
>space platform could come at any time.

So what? A weapons systems costs the same amount to build, and nearly
the same to maintain, whether it is on alert 50% or 100% of the time.
Also you could send ships around the horizon to hit a moonbase, and the
defenders would have no warning. Just land a 0.5-gigaton device behind a
mountain a few kilometres away, and the base's defenses are useless
(unless they can fire through the mountain). Contrast this with a
habitat's 360-degree field of vision and fire.

>No comment on the problems associated with random sporatic acceleration?

>}>}Also a bomb to hit a habitat
>}>}will have to come within range of the habitat's own defensive armament,
>}
>}>So?  Tough to stop a rock...
>}
>}The habitat's defensive armament (which can be of almost any desired
>}size and power output) can simply vaporize the rock a long way away.

>Unfortunately, your saying so doesn't make it so.  If you have the
>power available to vaporize a planet, the "defense" question is irrelevant.
>A planetside base could have more available, through the same magic you
>are involking.

Vaporize a planet??? Who said anything about that? Just enough power to
vaporize missiles, bombs, spacecraft, and rocks small enough to be
carried by spacecraft. And a base on a planet with an atmosphere would
be unable to fire up through the atmosphere with any degree of
effectiveness.

>}>}which can be of almost any desired size and power output, with the
>}>}habitat's full power generating capacity available, and almost unlimited
>}>}heat sink capacity, and the population on hand to maintain it. As
>}
>}>heat sink, yes.  But terribly vulnerable radiators.  So to zap it, dump silver
>}>paint so that it coats the radiator.  And as for the "full power
>}>generating capacity", if it is environmental, you couldn't accelerate
>}>(read "move") and it could be closed down with black paint.  And if it
>}>is internal, so could the planetary base.  
>}
>}Who mentioned radiators? The heat sink for a fusion gun or whatever
>}could simply be the habitat's water reservoir. I think a 10,000-ton
>}water storage takn could soak up quite a lot of heat (with bleeder
>}valves in case the water got too hot).

>Wrong.  If your "beam" is enough to vaporize a few megatons of rock,

Megatons? Where are you going to get an attack carrier big enough to
throw megatons of rock? You can't throw them from the asteroid belt,
because the habitat would have dodged in the long lead time that range
would give it.

>with less than 1% of the beam even hitting the particles, you would
>boil your water away long before it worked.  If you happen to have an
>ocean available, or a river (read: planet) this might be a viable argument.
>As is, nope.

Why would less than 1% of the beam hit the particles? Unless you use
gravel, in which case the individual particles won't penetrate the
shell, in which case you must use such a huge quantity as to vaporize
the habitat by the total kinetic energy, in which case the thing becomes
unfeasibly expensive (see my comment above about the megaton of rock).
Also if you're on a planet with free water, it's also going to have an
atmosphere, thus rendering your weapons useless.


>Hmmm.  Thought - not only would you have to vaporize the rock, you would have 
>to divert the the vapor (photonic pressure).  Otherwise you would just wind
>up encasing the habitat in vapor-deposited material or STILL destroying
>it with the energy transferred - and again wiping it out.  Getting hit with 
>a cloud at those velocities would not be a terrific improvement...

Not unless the mass is sufficient to destroy the habitat by total
kinetic energy - see comments above. Also if you vaporize the rock far
enough away, the cloud will have mostly dissipated by that time. And the
impact of say 100 tons of vapor would not do any damage (unlike a 100
ton rock) because it would be too diffuse.

>}>}opposed to trying to defend a planet; the defences have to be in orbit,
>}>}which means they're separated from the population and industrial plants
>}>}which are on the ground.
>}
>}>Only if you are trying to defend the planet, and not just the "special"
>}>site.  Most folks I know really wouldn't care if a few cubic miles of the moon
>}>get peppered by gravel.  There is a LOT of turf that would count as a "miss".
>}
>}If an amount of nuclear explosives equivalent to a Dinosaur Killer hit
>}the Earth, that would cause a lot of inconvenience to everyone. Plus
>}that megatonnage aimed at say Europe would kill quite a lot of people.
>}Even not aimed at specific targets.

>And if it hit your habitat it would be vaporized.

Yes but as I explained, you can't use a bomb-plus-decoy attack on a
habitat because the habitat can dodge ballistic weapons given enough
time. Instead you must use either missiles (much more expensive) or
attack carriers (even more expensive). You could still do it, but the
cost of killing even one habitat would be huge, and there are thousands
more (assuming the same total population as would fit on a planet).

--
"To summarize the summary of the summary: people are a problem"
Russell Wallace, Trinity College, Dublin
rwallace@unix1.tcd.ie
Newsgroups: rec.arts.sf.science