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• ... the ... If the RKV is not moving near-c, then yes...but why would you? You can acheive the same effect for many orders of magnitude less effort using
Message 1 of 39 , Mar 1, 2007
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--- In sfconsim-l@yahoogroups.com, "Jonathan" <linguofreak@...> wrote:

> --- In sfconsim-l@yahoogroups.com, "mechdan" <mechdan@> wrote:

> > Note that it is HARD to get a physical projectile up
> > to relativistic velocities. You can't accelerate a
> > projectile too quickly or it will melt/vaporize in
> > the process. If you accelerate the projectile gently
> > enough that it can reject the heat buildup, then
> > you're talking about acceleration runs on the order of
> > an AU in length taking maybe a day just to get the
> > projectile up to speed.

> > [Snip]

> > Thus, you may need to use near-c projectiles if
> > you're going relativistic at all. Near-c projectiles
> > take a lot more energy than, say, 10%c projectiles.
> > However, you have a chance to catch the enemy
> > unawares so the enemy doesn't have a chance to throw
> > up a defensive screen. The problem? How do you
> > spend days or weeks of high energy acceleration
> > that the enemy doesn't notice? Well, if you
> > launch the projectiles from a different star system,
> > then you have a chance. The enemy will see your
> > launch, but the projectiles can tack against the
> > interstellar medium with a magsail in order to
> > keep the enemy guessing about which direction the
> > projectile is coming from. Without a good
> > estimate of which direction the projectile is
> > coming from, the enemy needs to put up a much
> > larger defense screen.

> Couldn't you just hit an RKV with a swarm of smaller RKV's coming
the
> other way?

If the RKV is not moving near-c, then yes...but
why would you? You can acheive the same effect
for many orders of magnitude less effort using
"slow" defensive projectiles.

If the RKV is moving near-c, then no. You don't
have enough reaction time to do it.

> The attacking missile may be able to change course with a
> magsail, but it still has to head for its target at some point, and
> the more it deviates the longer it will take to reach the target
and
> the more time the target will have to defend itself.

The problem is that the speed of light limits
how much time you have between when you see the
magsail veer around and when it arrives.

What you see is a few days or weeks of the magsails
being accelerated at the home system, and then at
the last minute you see the sails tacking wildly
against the ISM. If you weren't perfectly aware
of the compression effect of looking at near-c
movement toward you, it could look like the magsail
was moving sideways at FTL speeds. In the last
few seconds, the magsails turns inward to hit you
(or maybe some other target...you don't know until
it's too late exactly who is being targetted).

It's maybe in the last few seconds that you can
make a good estimate of where the incoming is coming
from and you (and every other potential target)
can try and throw up a defense. This isn't enough
time to launch RKVs (that takes hours, at least).

You could fire relativistic particle beams which
can meet the RKVs at a decent standoff distance,
but these won't have enough mass--the impact will
result in a very narrow conical spread of debris
which still hits you.

Isaac Kuo
• ... debris ... We don t have a good idea of how much macroscopic interstellar debris there is, although it s apparently not very much because we can see so
Message 39 of 39 , Mar 3, 2007
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--- In sfconsim-l@yahoogroups.com, "Jonathan" <linguofreak@...> wrote:

> Though I do wonder, what are the chances of your RKV suddenly
> blundering straight into a comet or other piece of natural space
debris
> that it did not have time to see or avoid?

We don't have a good idea of how much macroscopic
interstellar debris there is, although it's apparently
not very much because we can see so far.

Within our solar system, at least, space is
astronomically empty of macroscopic debris.
We don't know if our solar system is in any way
typical, of course. Hmm...maybe the answer to the
Fermi paradox is that virtually all star systems
have all sorts of space debris making spaceflight
all but impossible for alien civilizations...

Regardless, you don't have to rely just on naturally
occuring space debris when you can make an artificial
defensive debris field.

Isaac Kuo
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