3 ms·

Next: Drones are equipped with mirrors now. Your move!

ortusdux 2y ago
Spinning the drone also helps disperse the energy over a larger area. https://youtu.be/7JH1_ZKV7t4?si=QrvdFFipckU9fd_X&t=337 https://youtu.be/7JH1_ZKV7t4?si=QrvdFFipckU9fd_X&t=337
- tamimio 2y ago
  Cool concept! Probably not that useful for most payloads though like cameras or anything similar. Unless the base where the payload is attached to, is separate from the airframe.
XorNot 2y ago
Mirrors are not a defense against high power lasers. The mirror is not 100% efficient, and as soon as it warps or discolors, it absorbs more energy and promptly burns through. And yes, this is a problem for laser optics too: which is why these designs tend to use focused arrays of beams, cooling systems and/or parabolic mirrors (which also helps with divergence).
- tamimio 2y ago
  > The mirror is not 100% efficient That’s correct, but it will definitely require more time, which practically speaking, you won’t have, after all the mirror is made of thin sheet of metal, which requires an extremely high temperature to melt. I think beryllium -which is used already in military- make a good choice, plus the spinning drone as mentioned above would disperse the energy, making it harder to take down.
  - JumpCrisscross 2y ago
    > it will definitely require more time No, it won’t. Occlusive ablation and spinning make more sense, though that comes with other trade-offs.
  - jandrewrogers 2y ago
    Polished metal will not work at these power levels. It would need to be a dielectric mirror, which can only be tuned to be extremely reflective for a narrow range of wavelengths. The mirrors would cost more than the drone in many cases. Furthermore, the US has developed "white" lasers that don't have a specific wavelength to optimize for, they emit photons with a wide range of wavelengths specifically to defeat dielectric mirrors.
  - groby_b 2y ago
    > which requires an extremely high temperature to melt What do you think 4kW in a square centimeter generate? Spring air? Also, beryllium would be an odd choice because all you get is energy soaked up by ablation. No reflection whatsoever. How thick would you like to make that beryllium coating? If you assume one millimeter (which is a pretty chunky coating), you'd need about 1/10th of a second to ablate it. As for spinning... you do spin around an axis. And that axis is likely aligned with the direction of travel, otherwise you have interesting dynamic properties. Which means if you aim at the nose, you can spin all you want. It's not moving. If you miss the nose a bit, oh well, it'll take maybe 2 or 3 tenths of a second. Even if you're well into hypersonic speed range, that's not enough to get the missile on target. And drones... well, drones just limber along at speeds that make any rotations just a waste of engineering resources. You have time to heat up the whole thing. And fry an egg on it. Look, there are issues with DE weapons. But 50 years of research mean you're not discovering them from first principles while typing a HN comment.
    - tamimio 2y ago
      That’s all nice and sounds good in theory, but practically speaking, drones are always ahead. Assuming the laser is indeed effective, the drone was detected too, and the accuracy is spot on, good luck taking down a swarm that’s piloted by AI, all at the fraction of the cost compared to that defense system in place.
      - XorNot 2y ago
        That's a heckin' assumption you're injecting there. For a drone to fly a system of motors, batteries, sensors and microprocessors has to engage in a complex real-time process to maintain stability, navigate and acquire targets. Disrupt any of that, the drone falls out of the sky. Or goes off course. Or explodes. Punching through steel is useful when you're trying to shootdown dumb-fire artillery rounds which have to survive being fired under a 310MPa pressure and need to trigger an internal detonation. A drone with a camera will be blinded if it catches even a glancing reflection of a 50kW laser. And every bit of defense you add to that system is now increasing cost, weight and power requirements. How quickly can the laser track and engage a drone? It's light, so the time is limited solely by optics tracking speed - for all purposes impact is instantaneous. And the idea of "stealth" runs in direct opposition to all ideas of reflective coatings - since that does the exact opposite of what stealth materials do to defeat RADAR and LIDAR.
nirav72 2y ago
Might be be useful to burn out optical sensors on enemy vehicles or drones.

Spinning the drone also helps disperse the energy over a larger area. https://youtu.be/7JH1_ZKV7t4?si=QrvdFFipckU9fd_X&t=337 https://youtu.be/7JH1_ZKV7t4?si=QrvdFFipckU9fd_X&t=337

tamimio 2y ago
Cool concept! Probably not that useful for most payloads though like cameras or anything similar. Unless the base where the payload is attached to, is separate from the airframe.

XorNot 2y ago

Mirrors are not a defense against high power lasers. The mirror is not 100% efficient, and as soon as it warps or discolors, it absorbs more energy and promptly burns through. And yes, this is a problem for laser optics too: which is why these designs tend to use focused arrays of beams, cooling systems and/or parabolic mirrors (which also helps with divergence).

tamimio 2y ago
> The mirror is not 100% efficient That’s correct, but it will definitely require more time, which practically speaking, you won’t have, after all the mirror is made of thin sheet of metal, which requires an extremely high temperature to melt. I think beryllium -which is used already in military- make a good choice, plus the spinning drone as mentioned above would disperse the energy, making it harder to take down.
- JumpCrisscross 2y ago
  > it will definitely require more time No, it won’t. Occlusive ablation and spinning make more sense, though that comes with other trade-offs.
- jandrewrogers 2y ago
  Polished metal will not work at these power levels. It would need to be a dielectric mirror, which can only be tuned to be extremely reflective for a narrow range of wavelengths. The mirrors would cost more than the drone in many cases. Furthermore, the US has developed "white" lasers that don't have a specific wavelength to optimize for, they emit photons with a wide range of wavelengths specifically to defeat dielectric mirrors.
- groby_b 2y ago
  > which requires an extremely high temperature to melt What do you think 4kW in a square centimeter generate? Spring air? Also, beryllium would be an odd choice because all you get is energy soaked up by ablation. No reflection whatsoever. How thick would you like to make that beryllium coating? If you assume one millimeter (which is a pretty chunky coating), you'd need about 1/10th of a second to ablate it. As for spinning... you do spin around an axis. And that axis is likely aligned with the direction of travel, otherwise you have interesting dynamic properties. Which means if you aim at the nose, you can spin all you want. It's not moving. If you miss the nose a bit, oh well, it'll take maybe 2 or 3 tenths of a second. Even if you're well into hypersonic speed range, that's not enough to get the missile on target. And drones... well, drones just limber along at speeds that make any rotations just a waste of engineering resources. You have time to heat up the whole thing. And fry an egg on it. Look, there are issues with DE weapons. But 50 years of research mean you're not discovering them from first principles while typing a HN comment.
  - tamimio 2y ago
    That’s all nice and sounds good in theory, but practically speaking, drones are always ahead. Assuming the laser is indeed effective, the drone was detected too, and the accuracy is spot on, good luck taking down a swarm that’s piloted by AI, all at the fraction of the cost compared to that defense system in place.
    - XorNot 2y ago
      That's a heckin' assumption you're injecting there. For a drone to fly a system of motors, batteries, sensors and microprocessors has to engage in a complex real-time process to maintain stability, navigate and acquire targets. Disrupt any of that, the drone falls out of the sky. Or goes off course. Or explodes. Punching through steel is useful when you're trying to shootdown dumb-fire artillery rounds which have to survive being fired under a 310MPa pressure and need to trigger an internal detonation. A drone with a camera will be blinded if it catches even a glancing reflection of a 50kW laser. And every bit of defense you add to that system is now increasing cost, weight and power requirements. How quickly can the laser track and engage a drone? It's light, so the time is limited solely by optics tracking speed - for all purposes impact is instantaneous. And the idea of "stealth" runs in direct opposition to all ideas of reflective coatings - since that does the exact opposite of what stealth materials do to defeat RADAR and LIDAR.

nirav72 2y ago

Might be be useful to burn out optical sensors on enemy vehicles or drones.