From: rwallace@unix1.tcd.ie (russell wallace)
Subject: Re: Wreaking a habitat (was Re: Wrecking a Planet
Organization: Trinity College, Dublin
Date: Wed, 13 Jan 1993 01:15:23 GMT

In <1993Jan12.141818.10637@linus.mitre.org> m23364@mwunix (James Meritt) writes:


>yawn.  This is getting old.  Russel does not apparently know what he is talking
>about.  Maybe this last time...

Polite, isn't he?

>}I'm assuming the attackers and the defenders have the same amount of
>}money to spend. For an attack on a planet, the attack is more
>}cost-effective, because the attackers can use cheap bombs and even
>}cheaper silvered-balloon decoys (or high-speed rocks if you prefer),
>}whereas the defenders must build orbital weapons platforms, which being
>}in orbit, are very expensive to build and maintain. On the other hand,
>}an attack on a habitat must use expensive guided missiles, whereas the
>}defenders can build guns relatively cheaply, because the guns are being
>}built and maintained right next to the population and industry.

>Wrong.  Read closely: There is no need to attack a planet.  There is no need
>to defend a planet.  Most of the planet is nothing but filler of little to
>no consequence.  The people and their direct support are all that need
>protecting.

If the planet has a biosphere, that also needs protecting. If it hasn't,
the attackers have to go to the trouble of aiming at the actual
population centres, which unlike a habitat, can't dodge, even slowly.
Turn a moonbase into a crater 5 miles wide (with a 0.5-gigaton bomb,
accompanied by a few thousand silvered-balloon decoys) and anyone not
wearing 2 million sunblock is going to have a really bad day.

>}>You cannot maneuver a gigaton habitat outside of a cloud of incoming
>}>gravel without absurd energy and reaaction masses available.  You are
>}>calling upon magic of an order not far below a gigaton of rock at a few
>}>percent of c.  
>}
>}You only need to impart a delta-vee of 1 m/sec to get the habitat
>}kilometres out of the way within a couple of hours (less than the time
>}an attack from the asteroid belt, let alone the Oort cloud, will take to
>}arrive). 1 m/sec is a *very* long way from the tens of km/sec people
>}have been casually talking about chucking kilotons of rock around at. I
>}leave as an exercise to the reader the difference in energy between
>}moving a habitat at 1 m/sec and moving a comparable mass at relativistic
>}speeds.

>A kilometer out of the way of what?  A cloud of gravel would not have a sharp
>border, and would be dispersed much wider than a delta-v of a habitat
>could avoid.  For instance, aim an asteroid at the habitat.  You could use
>more powerful engines than the habitat has to start it (magical arm waving
>like yours).  Blow it apart.  You now would have a "cone of death" as shrapnel
>spreads.  Do this a dozen times - asteroids are plentiful.  Your habitat
>is now out of gas (reaction mass).  Poke a hole through it in a few
>thousand places.  Tear apart the radiator.  No large air pockets.  No
>power.  No acceleration possible.  Can you say "dead"?

How? You're no longer talking about bombs, missiles or other dangerous
projectiles, even high-speed rocks. You're talking about a very thin
cloud of dust and gravel, which will present almost no threat, mainly
because almost all of it will miss. To create which, you have gone to
enormous expensive, what with very powerful engines, fuel tanks,
defensive armament, detectors, life support for crew to operate and
maintain the whole shebang, escape pods for them (which will likely be
shot down by the habitat as they leave the protection of the asteroid,
so you won't get many volunteers for the next mission). Sure, the
population of the habitat have gone to even greater expense to defend
themselves, but they haven't just self-destructed all this expensive
equipment to no purpose!

(Note: there will probably be fragments of the asteroid large enough to
be a potential threat. Such tiny fraction of these as happen to end up
on collision course with the habitat can easily be vaporized before they
hit.)

>}>Not into offense/defense systems, are you.  Wrong.  For an example,
>}>look at the maintenance costs of an aircraft carrier during flight
>}>ops and one in mothballs.
>}
>}Absolutely. Consider in old-time naval war, the fact that a battery of
>                         ^^^^^^^^^^^^^^^^^ - consider present-time may be closer

I am considering present time. Have you read my comments about the
relative costs of the habitat's defense armament versus the weapons
needed to attack it?

>Yawn.  Why bother with the guy that is shielded from you by an entire
>mountain?  The mountain IS shielding.  The habitat is ALWAYS exposed.

The mountain will shield against the guns of the moonbase. It won't
shield against the gigaton-range bomb that the attacks of the moonbase
can bring up with impunity.

>}>You are postulating detection systems for the habitat, while precluding them
>}>from the planetary system.  Consistency, please.
>}
>}OK, let the defenders of the moon base have detectors that can pick up
>}an incoming attack on the other side of a mountain, perhaps by
>}distributing the detectors, or putting them in orbit. What good will
>}that do them, when the attackers are on the other side of a mountain,
>}which the defenders' guns cannot fire through? On the other hand, the
>}attackers only have to detonate a big enough bomb on the other side of
>}that mountain for the shock wave to wipe out the base. Space is lousy
>}for transmitting shock waves, but solid ground is wonderful for the
>}purpose.

>If the defenders cannot shoot through the mountain, neither can the
>attackers.  And that "big enough bomb" is just more of your magic.
>Have you honestly never heard of recon?  Antisurface defense has LONG
>been worked out.

A gigaton-range bomb is not "magic", unless you think there is some
mysterious limit on how large a bomb can be built (which would be
surprising, coming from someone who thinks billion-ton asteroids can be
tossed around so cheaply that the operation can be done dozens of
times). Again, the attackers don't have to shoot through the mountain,
they just have to blow up the entire area. And I already postulated that
the defenders had recon, and therefore knew exactly what was going on -
my question is what are they going to do about it?

>}What has that got to do with anything? (I'm assuming that the people on
>}the habitat will have the wit not to do your job for you by accidentally
>}colliding with an asteroid :-)). I repeat, how are you going to throw
>}the megatons of rock at the habitat from an adequately close range,
>}without using an attack carrier (being a ship carrying a rail gun or
>}equivalent device capable of accelerating large masses of rock to very
>}high speeds)?

>Read above - with the same magic engines you propose.

Read above - with appropriately huge expense. And the occupants of the
habitat aren't planning to destroy their "magic engines" in a suicide
attack.

>Are you really this stupid?

Leaving aside the issue under discussion, I find your tone entirely
inappropriate for a public newsgroup. If you insist on throwing personal
insults, please send email and we can call each other names without
wasting everyone else's time reading them.

>A cosmic ray is nothing but a very small
>particle.  A chip of paint has blasted craters in the shuttle.  Yes, it
>WOULD.  An impact with a relative velocity of .....oh, say 170,000 MPH
>(doable now) would do quite well.  Face it - we're better at making bullets
>than shields.

A small crater is simply not going to do significant damage to something
the size of a space habitat. So it makes a dent in the outer shell - so
what? Actually, a layer of foam plastic would probably vaporize the
particle before it hit the outer shell, so the kinetic energy would be
harmlessly dissipated in boiling away small amounts of material.

>}I don't happen to be a 1 billion ton space habitat :-). And consider the
>}total mass of air that was involved in the Siberian impact. How are you
>}going to throw that mass of material at the target habitat?

>The same way that the rock was thrown at Siberia.

With, as I've pointed out, plenty of time for the habitat to dodge, even
at its low acceleration. Unless you mount expensive engines on the
asteroid, and expensive weaponry to protect the engines.

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