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I'm really interested to see how the arms race changes with laser / directed energy weapons. I don't see ablative armor [1] discussed very much, even though it

I'm really interested to see how the arms race changes with laser / directed energy weapons. I don't see ablative armor [1] discussed very much, even though it seems like an obvious / hard to defeat countermeasure. The idea being that the target is covered with a material that turns to gas when hit by a laser - such as the ceramic tiles used on re-entering spacecraft - the idea of being the tile insulates the target from the heat damage and the smoke released by the laser hitting it both carries the laser's heat away and scatters the laser's light. You can imagine using fancy smoke generators (similar size/weight as the smoke grenade of today) that block all forms of light [2] further pushing smoke out of the surface for a larger protective bubble of scattering - perhaps activated when the ablative armor starts vaporizing and/or even being expelled through the armor's porous surface. Remember that missiles, jet drones, etc. may only take seconds to close the distance to engage your laser system, so you only need this protection to last that long. Also, energy weapons point both ways, and are very well painted targets - analogous to the "anti-radiation missiles" [3] that home-in on radar emissions to guide them to destroy enemy radars. In the ship example, a sticky smoke chemical targeted near the laser defense systems could blind or scatter them pretty effectively for hours before they could be cleared to make the systems combat operational again. Anyway - just some ideas from a non-professional military nerd. [1] https://en.wikipedia.org/wiki/Ablative_armor https://en.wikipedia.org/wiki/Ablative_armor [2] https://en.wikipedia.org/wiki/Smoke_screen https://en.wikipedia.org/wiki/Smoke_screen (Ctrl+F for"VIRSS") [3] https://en.wikipedia.org/wiki/Anti-radiation_missile https://en.wikipedia.org/wiki/Anti-radiation_missile

nradov 4y ago
Ablative armor is generally too heavy and bulky to be practical for use on aircraft or missiles. And it can't really work in combination with low-observable (stealth) airframe coatings.
rocqua 4y ago
It seems like the range downside due to diffraction and atmospheric dispersion of most lasers rules them out way before ablative armor becomes relevant. I could imagine close-in missle defense being some kind of exception, but if you can only cover a small area, then the 'high upfront cost, low cost per shot' tradeof stops being a good tradeof. As for anti radiation missles. The 'directed' part of a directed energy weapon should make that much harder. Besides, a laser like this probably isn't firing constantly, whilst a radar station is emmiting constantly.
jandrewrogers 4y ago
Ablative armor won’t help much. It creates enormous engineering challenges for endoatmospheric hypersonic missiles at energy levels orders of magnitude lower than what a laser will deliver. The amount of ablative armor required to slow these lasers would be infeasible on a practical weapon. Similarly, smoke wouldn’t even be a speed bump, since it would be instantly turned into plasma like the rest of the atmosphere. The base challenge on the receiving end is that it is very, very difficult to divert enough energy when the power levels are that high to limit damage. Based on the description of these laser, they are explicitly designed to defeat dielectric mirrors[0], which is the only vaguely plausible material that might survive a simple laser at these power levels. The original design target for the military lasers the US has been developing and refining for the last 40+ years is that they could deliver sufficient power on target such that no ordinary molecular material could withstand them as a matter of physics. That is a non-trivial objective but it looks like they’re starting to design practical systems that can approximately achieve that over some range. [0] https://en.wikipedia.org/wiki/Dielectric_mirror https://en.wikipedia.org/wiki/Dielectric_mirror
- jojobas 4y ago
  >instantly turned into plasma Is plasma itself not reflective enough?
  - nine_k 4y ago
    To the contrary, AFAIK plasma is very absorbing, very "black", despite its bright thermal radiation. It will heat up, an transfer the heat to anything next to it. It will of course diffuse the energy a little bit.
    - Trombone12 4y ago
      The plasma being warm is perfectly fine from the point of the weapon, as the weapon is moving and the plasma is not.
nine_k 4y ago
Usually you need your weapon to move much faster than the target. A rocket, like s Javelin or an NLAW, apparently moves fast enough to hit s tank or an APC. You don't necessarily need much-much faster, but it's important to pack a punch. But against a rocket you need a weapon that's much faster than a rocket. A laser (or a maser) reaches a rocket in negligible time, and may be very fast to retarget. A rocket can't have ablative armor on the side, it will be blown away instantly. Landing space capsules have an ablative cover on the bottom. Also, landing capsules only decelerate, so they can afford to carry much more mass for evaporation than a rocket that needs to accelerate and maneuver. The best a rocket can do us to become highly shiny. It's not as easy though to be shiny in a wider spectrum, from optical to deep IR or even sub-millimeter. I can imagine a multi-color ray gun :) So I think ray guns are going to be more widespread as anti-missile defense systems, to intercept incoming rockets, warheads, and even shells. At least one actually exists (in Israel), and works.
- consumer451 4y ago
  > So I think ray guns are going to be more widespread as anti-missile defense systems The issue as highlighted by the situation in UA is that the highest-tech weapons cannot be deployed to the front lines where they are needed, as they might fall into the enemy's hands and be reverse engineered. I am much more interested in hacked low-tech solutions. For example, walls of anti-air racing drone style quadcopters which can seek out an Iranian drone and just ram it. I am a little surprised that we have not seen these yet.
  - dsq 4y ago
    Laser defense is fundametally short range, so it's best use case is probably behind the front lines, to defend your air force bases and keep the air power active. Also to defend ships. Critical infrastructure such as fuel depots, power stations. Anything up to a few kilometers. This also means your lasers are connected to power lines. The best idea is to keep your rear echelons free from missile and drone harrassment, so you can focus your attention on the offensive. Drone swarms are an interesting idea as well.
Keysh 4y ago
Smoke screens are obviously not going to be useful as defenses for things like missiles, since the smoke immediately slows down when it collides with the air while the missile/projectile continues on at high speed. (It might be useful in space, where you'd be creating something like a comet's halo, which separates from the body on a much longer timescale.)

nradov 4y ago

Ablative armor is generally too heavy and bulky to be practical for use on aircraft or missiles. And it can't really work in combination with low-observable (stealth) airframe coatings.

rocqua 4y ago

It seems like the range downside due to diffraction and atmospheric dispersion of most lasers rules them out way before ablative armor becomes relevant. I could imagine close-in missle defense being some kind of exception, but if you can only cover a small area, then the 'high upfront cost, low cost per shot' tradeof stops being a good tradeof. As for anti radiation missles. The 'directed' part of a directed energy weapon should make that much harder. Besides, a laser like this probably isn't firing constantly, whilst a radar station is emmiting constantly.

jandrewrogers 4y ago

Ablative armor won’t help much. It creates enormous engineering challenges for endoatmospheric hypersonic missiles at energy levels orders of magnitude lower than what a laser will deliver. The amount of ablative armor required to slow these lasers would be infeasible on a practical weapon. Similarly, smoke wouldn’t even be a speed bump, since it would be instantly turned into plasma like the rest of the atmosphere. The base challenge on the receiving end is that it is very, very difficult to divert enough energy when the power levels are that high to limit damage. Based on the description of these laser, they are explicitly designed to defeat dielectric mirrors[0], which is the only vaguely plausible material that might survive a simple laser at these power levels. The original design target for the military lasers the US has been developing and refining for the last 40+ years is that they could deliver sufficient power on target such that no ordinary molecular material could withstand them as a matter of physics. That is a non-trivial objective but it looks like they’re starting to design practical systems that can approximately achieve that over some range. [0] https://en.wikipedia.org/wiki/Dielectric_mirror https://en.wikipedia.org/wiki/Dielectric_mirror

jojobas 4y ago
>instantly turned into plasma Is plasma itself not reflective enough?
- nine_k 4y ago
  To the contrary, AFAIK plasma is very absorbing, very "black", despite its bright thermal radiation. It will heat up, an transfer the heat to anything next to it. It will of course diffuse the energy a little bit.
  - Trombone12 4y ago
    The plasma being warm is perfectly fine from the point of the weapon, as the weapon is moving and the plasma is not.

nine_k 4y ago

Usually you need your weapon to move much faster than the target. A rocket, like s Javelin or an NLAW, apparently moves fast enough to hit s tank or an APC. You don't necessarily need much-much faster, but it's important to pack a punch. But against a rocket you need a weapon that's much faster than a rocket. A laser (or a maser) reaches a rocket in negligible time, and may be very fast to retarget. A rocket can't have ablative armor on the side, it will be blown away instantly. Landing space capsules have an ablative cover on the bottom. Also, landing capsules only decelerate, so they can afford to carry much more mass for evaporation than a rocket that needs to accelerate and maneuver. The best a rocket can do us to become highly shiny. It's not as easy though to be shiny in a wider spectrum, from optical to deep IR or even sub-millimeter. I can imagine a multi-color ray gun :) So I think ray guns are going to be more widespread as anti-missile defense systems, to intercept incoming rockets, warheads, and even shells. At least one actually exists (in Israel), and works.

consumer451 4y ago
> So I think ray guns are going to be more widespread as anti-missile defense systems The issue as highlighted by the situation in UA is that the highest-tech weapons cannot be deployed to the front lines where they are needed, as they might fall into the enemy's hands and be reverse engineered. I am much more interested in hacked low-tech solutions. For example, walls of anti-air racing drone style quadcopters which can seek out an Iranian drone and just ram it. I am a little surprised that we have not seen these yet.
- dsq 4y ago
  Laser defense is fundametally short range, so it's best use case is probably behind the front lines, to defend your air force bases and keep the air power active. Also to defend ships. Critical infrastructure such as fuel depots, power stations. Anything up to a few kilometers. This also means your lasers are connected to power lines. The best idea is to keep your rear echelons free from missile and drone harrassment, so you can focus your attention on the offensive. Drone swarms are an interesting idea as well.

Keysh 4y ago

Smoke screens are obviously not going to be useful as defenses for things like missiles, since the smoke immediately slows down when it collides with the air while the missile/projectile continues on at high speed. (It might be useful in space, where you'd be creating something like a comet's halo, which separates from the body on a much longer timescale.)