Laser vs Missile

[Dr Strangelove]

Originally posted by Kuciwalker


It's coherence, not cohesion, and you can't "weaken" the coherence. The light stays coherent even as the beam widens.

Yes, but the beam was de-focused by passing it through the telescope's optics so I'm certain that the beam's photons diverged at a greater angle than they would have had they not been passed through the telescope's optics. I recall hearing about this experiment. NASA initially thought they could simply aim the laser at the mirror array, but found that their aim wasn't so great. Later someone thought of shining the laser through the telescope. That made the beam much larger thereby making hitting the array easier.

[Straybow]

Originally posted by Kuciwalker

But there is still no way that the matter will absorb all that energy, and most of it is going out the other side of the ship.

Coming back to this, the energy of the laser will go pretty much anywhere but the other side of the ship. If you look at the kinematics you'll see a lot of the energy actually escapes with the vaporized hull material, back towards the source of the beam.

It doesn't go "back towards the source" it goes every direction available. Do you think this is like a pot boiling on the stove or something?

"Energy escapes with the vaporized hull" = explosion, which is what the attacker wants.

[Straybow]

You guys have no concept of vector motion, do you?

[Kuciwalker]

It doesn't go "back towards the source" it goes every direction available. Do you think this is like a pot boiling on the stove or something?

Laser hits armor. Surface of armor in a certain area vaporizes. The vaporized armor expands in all directions. It immediately runs into the rest of the ship in one direction, transferring energy and momentum. Assuming the net momentum of the system changes very little with the laser impact (a good assumption), the kinematic equations guarantee that the energy transferred to the vaporized armor travelling away from the ship is greater than the energy of the ship + vaporized armor that impacted with it.

m1*v1 + m2*v2 ~= 0
(m1*v1^2 + m2*v2^2)/2 = E > 0
m1 < m2

therefore E2 = m2*v2^2 / 2 < m1*v1^2 = E1.

Trivial.

I am, of course, assuming the laser hits normal to the surface of the armor. If it doesn't, most of the energy doesn't go "back towards the laser" but merely "away from the ship".

[Zkribbler]

So, you have a laser?
I have a mirror.