On Feb 8, 6:56=A0am, MacFrag...@[EMAIL PROTECTED]
wrote:
> > You can have a mirror which reflects exactly one or two specific
> > frequencies extremely well, but no mirror will be extremely
> > reflective across a broad range of frequencies. =A0
> > Against infrared
> > to visible to near UV lasers, I actually think the best defense
> > may be to let the light through. =A0Diamond-like carbon is very
> > tough and very transparent.<snip>
> That's interesting, diamond ****ps. So that would require that any
> desired quantity of this carbon modification can be created
> industrially (at low cost). The side effect would be that diamonds
> would be treated just by their economic value, which will be low.
> They'd be a dime a dozen. Reminds me of this classic SF story where
> humans and aliens trade in a greenhouse for a machine that produces
> gold. <g>
High quality large diamonds may still be expensive and hard to
produce. However, it is plausible that diamonds will be
relatively easy to produce.
> Anyway, that would amount to quite some mass. You say "thick shell",
> so how thick, 10cm? Since in the diamond modification, the density of
> carbon is 3.5g/ccm, a square metre would be 350kg, i.e. 0.35 tons (per
> 10cm thickness). I suppose you need real behemoths to lug that around.
> But the idea is certainly interesting.
It depends on the level of threat, and how much protection is
desired. 10+cm "feels" about right, but it all depends on what
you're defending against. And yes, this is heavy stuff.
> Two problems I see with that:
> a) the molten aluminum will expand, so the question is, where will it
> go if it is sandwiched between layers of diamond carbon?
You don't sandwich it directly, but rather you have two concentric
shells with a gap.
> b) if the laser heats up the aluminum sufficiently (>1300K?), it will
> convey the heat to the diamond and may turn it into graphite.
Yes, that can be a problem. It may be possible to mitigate
this effect by filling the gap with a gas. That'll help cool down
va****ized aluminum before it hits the carbon layer.
> But I'd really like to know what ****p sizes and m***** you are talking
> about. ^^
I tend to think in terms of laser-****ps that are on the order of
1,000 to 10,000 tons, and on the order of 100m to 1,000m long.
These would be escorted by solar power drones which are
perhaps 1-100 tons each, and 10m-100m across.
> >=A0This is because wavelengths as small or smaller than the size of
atoms=
see the smoothest
> > of all possible mirrors as bumpy.
> In that light, wouldn't a low-wavelength beam like that go straight
> through the target without doing much damage? Sorry if the question
> sounds naive.
If the wavelength is sufficiently small, yes. Small wavelength
photons tend to penetrate matter deeply. Hard X-rays could
penetrate through several cm of solid armor, so a foil
target (like a solar reflector) would only absorb a fraction
of the beam. Given how flimsy such a foil target would be,
it would still suffer heavy damage, of course. High energy
gamma rays could penetrate through many meters, so
depositing sufficient energy on the target can be a problem.
Thus, even if you have the technology to generate a high
energy gamma ray laser, it might not make for a desirable
weapon. Note that it is HARD to make a gamma ray laser.
We don't know how to do it, although it MIGHT be possible
if there's some weird way to make positronium lase. If
positronium can lase, then you may be able to make a
high efficiency gamma ray laser using a linac to accelerate
electrons and positrons. The resulting beam could be very
narrow and have practically no spread at all. But it would
have severe overpenetration issues.
> > X-ray lasers could be rather compact and 300,000km would actually
> > be short range for them.
> Focus-wise maybe, but at that distance you will still have 2 seconds
> lag. Hitting a 300 metre ****p must be sort of like hitting a 1mm(!)
> target at 1000m distance with a rifle (bullet travel time ~2s for
> special long-range ammo like the Grendel). A target trying to evade.
It's more like trying to hit a target with a continuous bombardment
of a machinegun. The chances of each particular "photon bullet"
hitting are low. But you can shoot tens of thousands of bullets
per second. It's actually more like a continuous "cutting beam"
rather than a stream of bullets. If you get lucky, you slice through
the target. If you don't, then you just keep on hosing away.
> And an x-ray laser must produce enormous amount of waste heat, so you
> get only a few shots before the damn thing overheats.
A practical X-ray laser weapon needs to be able to continuously
reject the waste heat. Otherwise, you end up with a ton of hardware
sitting around going to waste waiting for the rest of the system to
cool down. I assume as a baseline a beam which is 10MW at
the target, 20MW at the muzzle, and 60MW at the plug (solar
panels). The waste heat is conveniently distributed along the
electron accelerator elements, requiring only about 2m wide
radiators (which may actually match up roughly with the size
of the microwave generator hardware). Basically, the thing can
continuously shoot all day and never overheat.
> But nevertheless: what effect would kinetic slugs have on this diamond-
> carbon armour?
Against kinetic impactors, diamond-like carbon blocks are as
good as any alternative solid armor materials. However, the
most efficient defenses against kinetic impactors are layered.
Ideally, you have layers of thin sheets, and/or a cloud of small
particles. When an impactor hits such a "whipple ****eld"
defense, the successive layers convert the impactor into an
ever expanding field of smaller bits of debris. As a result,
the impact is thinned out until ultimately the bits of debris
are small enough to get stopped entirely.
Such a whipple ****eld is more vulnerable to laser damage,
though. So the armor design is going to depend on the
nature of the threat. Since the laser threat is likely
continuous while the kinetic threat will likely come in
discrete waves, one good compromise is to have a standing
defense of solid armor blocks along with a last ditch kinetic
defense involving projecting clouds of particles in the way
of the incoming. Such clouds will only provide a defense
for a short time, but this is okay if the threat is only momentary.
Isaac Kuo
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