What would happen if an ICBM was hit by a 1.3 petawatt laser?

[MattRob]

In space... you'd need so much less power from the laser to defeat shielding (no atmospheric bloom), so I don't see that working.

Unless it's a ground-based system. Then you'd still have to shoot through the atmosphere.

Reactive armor, as with tanks, and then some means of correcting trajectory in a non-catastrophic manner seems to be the best defense...

Reactive armor against lasers? Hm. I guess that could work for the flash-point lasers. I hadn't thought of that... As for the long-burning lasers, not sure it would do much good, really. But given the almost total lack of other countermeasures I could understand.

There's a lot of debate on it, but I personally like wikipedia. It's almost the sum of all human knowledge quickly accessible, as for reliability, it does have citations. I said that b/c the Wiki article for the THEL has a nice list of possible countermeasures to LASER attacks. My first action when I'm trying to learn about something is Wikipedia, after all, there's really not much incentive or humor in changing some obscure scientific fact on there, and if you doubt something you can check it's source. Not sure how open other forumites are to it, but there's a sub-article for an Air Force laser program, lasers in general, and laser weapons.

My own idea I like is deploying a dust "cloud" of material where each particle is highly reflective, not just creating a bloom effect, but scattering light in every direction (like a water cloud appearing white from any direction).

...or so heavy that it would be cheaper to pour molten gold on our enemies.

That made me laugh, that's quotable. I get this idea when I see a lot of the advanced weapon systems they have in development. I think the best example would be "Fingers of God" - the uranium rods dropped from space. (Orbit? You can't "drop" something from orbit...)

 

[Nicodemus]

When I say in space, I mean in space, not orbit. As for ablative armor, the idea is:
1: Prevent destruction of the RV/Projectile/Missile
2: Formulated to maximize bloom: the more you burn, the less energy makes it to your target.
3: In the case of a high energy pulsed laser, it would be LESS effective; if the ablation is violent enough as you've pointed out, that would be enough to do the job of the laser.

The heart of ablative armor against a laser is to create the dust you mentioned, which requires either a TON of power to punch through, or a phased array that can change wavelengths on the fly. AFAIK, that last one doesn't exist yet, so it's a good way to achieve the former.

This is very distinct from ablative or reactive tank armor, which seeks to defeat through additional mass, or a counter-acting force.

The "fingers of god" idea is interesting, but while you CAN drop things from orbit with a little boost, you also have to LIFT those rods. The whole point is that you have this terrific mass of depleted uranium, or tungsten, but that's a FORTUNE to launch into space.

Frankly, it seems easier to use a massive ICBM if you want to level something that badly, and design it to carry "fingers". I gather that is something that's been explored, but in practice it's a political weapon. If you want to level a city, you don't need kinetic weaponry, or even nukes. It's cheap and relatively easy to firebomb a city, and dead is dead.

Now, if you make a land-based rail gun to launch orbital loads, or a sea-based version, I could see that being weaponized.

 

[yuiop]

It may be possible that "filament propagation" (See http://en.wikipedia.org/wiki/Filament_propagation) mat mitigate divergence problems in the atmosphere for laser beams with terawatt intensities.

Also see http://www.teramobile.org/publications/turbulence.pdf. However they seem to talking about applications in communications and lightning control rather than military applications. I guess for communication purposes you could keep the laser fixed on a given path, while for a military target the beam would have to track the object for a while and so the filament wave-guide will not stay in one place, limiting its effectiveness.

 

[Nicodemus]

It may be possible that "filament propagation" (See http://en.wikipedia.org/wiki/Filament_propagation) mat mitigate divergence problems in the atmosphere for laser beams with terawatt intensities.

Also see http://www.teramobile.org/publications/turbulence.pdf. However they seem to talking about applications in communications and lightning control rather than military applications. I guess for communication purposes you could keep the laser fixed on a given path, while for a military target the beam would have to track the object for a while and so the filament wave-guide will not stay in one place, limiting its effectiveness.

I can't see any reason why that wouldn't work, but until you linked to it, I'd only heard of it. I'm going to start that thread after all, but I think I'll make it more general: "Lasers At Improbable Energies: What Happens?" One thing: that could arguably go in a lot of catagories, but which one should I make it in?