Re: meteors vs. missles

>Sorry, but a small asteriod/large meteor is *not* very visible. The only way
>to detect it is with active sensors as it won't have any emissions worth
>mentioning. You might say it is naturally stealthy. After all, it is just
>a falling rock. Nothing special about it except the fact that its orbit
>intersects that target's orbit at the time the target is there.

Actually, they are reasonably strong infrared sources.  For example, the
recent NASA IRAS (Infrared Astronomy Satellite) survey managed to detected
several comets in the outer solar system (i.e., where they are just icy
bodies of roughly kilometer size and have not developed a coma or tail)
using technology which is well behind our current state of the art (since
it had to be frozen years in advance of the launch).

Also, it seems perfectly reasonable to assume that systems with advanced TL
worlds will employ active sensors to monitor all local traffic and use
computers to flag any objects on non-ballistic trajectories
(i.e., accelerating) or with orbits which will carry them into high traffic
areas.

>And just what TL weapon can *destroy* a chunk of nickel-iron a mile or
>two in diameter? Breaking it up into pieces makes the problem *worse*
>not better. You have to completely destroy it or deflect its course.
>If you "break" it, the pieces will deliver just as much impact energy,
>and more of it will wind up in the atmosphere (and thus mess up your
>climate).

You are correct that breaking it up immediately outside the atmosphere will
do little, if any, good.  However, any weapon that breaks it up reasonably
violently (i.e., explosively) at a considerable distance will impart
sufficient transverse velocity to nearly all of the fragments so as to
make them miss the target entirely.  The basic point is that planets are
quite small objects on interplanetary scales and very easy to miss.  For
example, imparting a transverse velocity of only 1 km/s to an object
previously moving toward the center of the Earth as it crosses the Moon's
orbit (very close!) is about sufficient to cause it to miss entirely;
further away, even smaller deflection velocities will suffice.  For
basicly the same reasons, deflection of the whole incoming object is far
easier (less energetically demanding) than putting it on a collision
course in the first place.

>If we go for near-lightspeed projectiles, you won't be able to detect
>them in time to stop them. After all, at .9c, something a billion miles
>away will arrive less than 7 seconds after any possible detector message!
>A billion miles is roughly the diameter of Jupiter's orbit. And at .9c
>a projectile a few *meters* in diameter would be a world killer.

First of all, I make it to be more like 10 minutes than 7 seconds, but
in any case, you are now talking about a fundamentally different kind
of weapon.  Previously, we were discussing a weapon which derived its
energy primarily from its own mass and orbital velocities (i.e., basicly
the star's gravitational field) with the drive only supplying the
nudges needed to aim it at the target.  However, a .9c kinetic weapon
must derive nearly all of its energy from the drive itself which is
a very different situation.  If we control that much energy, there
will be many different ways to use it destructively.  For example, we can
use the drive itself (plus perhaps some stealth technology) as a missle.
The mass may be less but the velocity will be correspondingly increased
to deliver the same (actually more in the most reasonable case in which
the drive delivers a fixed thrust) kinetic energy.  Alternately, we
might be able to convert the drive's energy into an explosive form and
simply use it as a bomb.  Anyway, it is a whole different problem.

Ed Turner