6 ms·

How once-elusive laser weapons suddenly became a reality

58 points by clouddrover 6y ago

hprotagonist 6y ago
Chris Knight : As you know, Mitch and I were working on the cyanide system. Well, earlier today it ate itself. But, these little set-backs are just what we need to take a giant step forward. Right, Kent? Needless to say, I was a little despondent about the meltdown, but then, in the midst of my preparations for hari kiri, it came to me. It is possible to synthesize excited bromide in an argon matrix. Yes, it's an excimer frozen in its excited state. Bodie : Th... That's impossible. Chris Knight : It's a chemical laser but in solid, not gaseous, form. Put simply, in deference to you, Kent, it's like lasing a stick of dynamite. As soon as we apply a field, we couple to a state that is radiatively coupled to the ground state. I figure we can extract at least ten to the twenty-first photons per cubic centimeter which will give one kilojoule per cubic centimeter at 600 nanometers, or, one megajoule per liter.
- aqme28 6y ago
  They had actual scientist consultants on that movie and it shows. The proposed laser was based on real theory. Love that film.
- deleted 6y ago
  [deleted]
- h2odragon 6y ago
  https://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator https://en.wikipedia.org/wiki/Explosively_pumped_flux_compre...
- siavosh 6y ago
  So classic. https://youtu.be/0ds0wYpc1eM https://youtu.be/0ds0wYpc1eM
mips_avatar 6y ago
It's really amazing how accurately these laser systems work. I was amazed that SpaceX Starlink uses lasers to communicate between nodes. How do they aim so accurately?
- exabrial 6y ago
  Stepper motors and an active feedback loop most likely.
  - thereisnospork 6y ago
    The positional accuracy of the motors aiming the lasers (relative to the satellite orientation) probably comes from optical encoders. I'd expect servos in an active loop as you mentioned, rather than steppers - which tend to settle at 1.8* increments. Either way I have no idea how they work out the firing solution for the comm lasers with sufficient accuracy. Hypothesizing: maybe they shoot multiple lasers, the main comm laser and a alignment pattern with auxiliary lasers which could be used for targeting feedback?
- stripline 6y ago
  I don't think they can yet..
- cma 6y ago
  Lasers still expand over time, and can expand more with lenses, so it isn't like hitting a laser pointer sized target.
  - TheSpiceIsLife 6y ago
    That's right. By the time the laser reaches the target receiver it could be covering an area of tens of meters, or grater, and still be usefully detected. Think about the tiny amount of energy emitted by a mobile phone transmitter and still able to he usefully detected by an antenna on a tower kilometres away.
- kevin_thibedeau 6y ago
the_only_law 6y ago
Even outside of weaponry, I see so many cool and innovative uses of lasers and optical technology these days. If I could redo everything, it’s certainly a field I’d consider.
ISL 6y ago
The next war will have new and unpleasant injuries so far largely unknown to the world.
- greesil 6y ago
  Everyone's going to have to wear really nice sunglasses into the battlefield.
  - YarickR2 6y ago
    And shiny armor
  - ISL 6y ago
    Bystanders will be blinded by specular reflections many miles from the battle.
- mikhailfranco 6y ago
  Using lasers to deliberately blind people is illegal: https://en.wikipedia.org/wiki/Protocol_on_Blinding_Laser_Weapons https://en.wikipedia.org/wiki/Protocol_on_Blinding_Laser_Wea...
  - 10000truths 6y ago
    International law is a gentleman’s agreement, not some divine regulatory framework. I assure you that such conventions will go out the window the moment they prove even mildly inconvenient to enforce.
  - ISL 6y ago
    Ah, true -- I'd forgotten about that. Even in the absence of blinding weapons, warfare and wounds will change completely when an overhead drone can target and burn a combatant in milliseconds. A quick and precise galvanometer may allow precisely-targeted strikes on tens of people in seconds. The combination of projectiles and directed-energy weapons will make defense and evasion much more difficult. David Drake tried to show us the depravity of wars of the past in his work, but it also highlighted the horror of wars to come.
jessaustin 6y ago
Just in time for deer season!
young_hopper 6y ago
I wonder how the efficacy of these laser-powered weapons systems is affected by how reflective the target is. It'd be a bummer if the military spent millions on this only to be foiled by a glossy paint finish.
- the_only_law 6y ago
  I’ve seen videos from guys building laser equipment and supposedly a powerful enough laser can punch through typical mirrors and specialized ones are required.
- carrolldunham 6y ago
  if you're very reflective then the old technologies can do their thing. e.g. anything with a radar
- nradov 6y ago
  Reflectivity doesn't matter in practice. No finish is sufficiently reflective and so the first part of the laser pulse burns it off and then the rest of the pulse gets through. An ablative heat shield can be more effective, although that adds weight and interferes with sensors. Spinning the target can also help a little by spreading the heat across a wider surface area.
  - shpx 6y ago
    What about shooting out a gas that’s dark in infrared between yourself and the laser?
    - jandrewrogers 6y ago
      Nope, same issue, it would absorb the energy and turn into a very low density plasma, blocking nothing. That is equivalent to very weak ablation shielding. In fact, using a high-power laser to punch a hole in the atmosphere, essentially creating a functional vacuum by superheating the atmosphere in the beam path, is an old school engineering trick for exotic systems. Though in those cases, they tune the laser so that it gets absorbed by the atmosphere (similar to the gas you are suggesting). The use case is roughly analogous to employing supercavitation on torpedos.
safog 6y ago
That link out to the China drone swarm video is pretty crazy. I hope we do live in boring times and don't have to deal with drone warfare wherever we live. https://www.thedrive.com/the-war-zone/37062/china-conducts-test-of-massive-suicide-drone-swarm-launched-from-a-box-on-a-truck https://www.thedrive.com/the-war-zone/37062/china-conducts-t... Drones in the recent war between Armenia and Azerbaijan. Some of the same Chinese suicide drones being used. https://en.wikipedia.org/wiki/2020_Nagorno-Karabakh_war https://en.wikipedia.org/wiki/2020_Nagorno-Karabakh_war Slaughterbots: https://www.youtube.com/watch?v=9CO6M2HsoIA https://www.youtube.com/watch?v=9CO6M2HsoIA
canada_dry 6y ago
> all sheet metal that's cut for home appliances and so forth, was starting to be cut by high-power fiber-lasers of the kilowatt-type power levels. Shame this tech has yet to trickle down to the home-hobbyist level. Having my 3D printer direct the end of a decently powered fiber laser cutting head would be a nice feature!
- bufferoverflow 6y ago
  It absolutely is available. It's just powerful lasers are very dangerous to your eyes, and you better really know what you're doing. You can buy a 1.5kw laser cutter for $35K on Aliexpress. https://aliexpress.com/item/4000063563337.html https://aliexpress.com/item/4000063563337.html
  - rtkwe 6y ago
    Available yes but it's still the realm of people with a good amount of disposable income such that they can drop 1-2k+ on a hobby.
- wolfretcrap 6y ago
  I bought CO2 laser for like $60 off eBay and it works fine with my 3d printer tho it will never be able to cut metal.
supernova87a 6y ago
Really impressive -- however last I recall reading about that breakthrough airborne platform laser (see photo in article), it involved dumping 2 huge tanks of chemicals together to produce a chemical fluorescence infrared laser pulse, wasn't it? Not as scalable that one I think. But the article emphasizes small lasers combined via fiber, ok. And yes the optics must be pretty impressive -- I wonder if adaptive optics (from astronomy) are used at these ranges and target sizes? And then, a puzzle I've always wished to have the knowledge to solve. Does a laser beam obey the 1/r^2 rule in intensity and area spread over distance? Of course it does, light waves intrinsically have that property I think. But how do you show it when it comes to a coherent beam that is always depicted as a focused pencil out into space forever?
- xyzzyz 6y ago
  If your beam is perfectly coherent, then its cross section has the same area regardless of the distance, so you should be getting full power. However, no beam is perfectly coherent, so it’s still O(1/r^2), and the better coherence, the smaller constant you have hidden in the big-O notation.
- ssivark 6y ago
  1/r^2 comes from the fact that space is three dimensional. No amount of beam collimating can change that (unless we have some fundamental breakthrough/change in our understanding of physics). Better beam coherence could keep improving on the solid angle, which is the multiplicative coefficient to the (asymptotic) scaling behavior.
- jasonwatkinspdx 6y ago
  I've been following this topic as a curiosity. I'm not totally certain but I think the LM systems don't have adaptive optics. But DARPA had a program where they were making something analogous to a phased array out of fiber lasers, where each individual laser had its own independent lens, and a phase shifter is used on each to align all the beams in real time so they're all mutually coherent. The phase shifter is tuned in real time by reflection back along each beam line from the target, split off with a beam splitter to some sort of sensor. They stopped talking about it after like 2 years, which maybe means it was a flop or maybe they took it secret. Who knows. If you're curious this is the name to google: https://www.darpa.mil/program/excalibur https://www.darpa.mil/program/excalibur
akimball 6y ago
Commercial product links would be nice
jccooper 6y ago
So one of the other problems with high power lasers is cooling the lasing mechanism. A recent novel solution to that is to have a liquid with the same refractive index and to circulate it (with no turbulence) through passages within the lasing mechanism. That way it can be cooled very thoroughly without interfering with the light generation. (Probably the coolant doesn't contribute, but maybe it does.) Seems this can do on order of 5 kw/kw output.
- bufferoverflow 6y ago
  5kw output for 1kw input?
  - jccooper 6y ago
    Sorry, typo. Should be kg/kw
- jasonwatkinspdx 6y ago
  Fiber lasers are relatively easy to cool due to their high surface area. A 20kw industrial one is about a cubic meter box and just air cooled.
AtlasBarfed 6y ago
These laser weapons conveniently keep the Navy funded and their sitting duck surface fleet in the budget. I'm skeptical a laser can defend against supersonic antiship missiles and ICBMs. Furthermore, the future battlefield will be owned by swarms of drone weaponry, these lasers probably can't fire frequently enough to defend against those.
- nradov 6y ago
  This first generation of defensive lasers isn't really intended to counter missiles. The Navy already has the SM-3 / SM-6 for that. Lasers are a cheaper, quicker way to defend against lower end threats. Swarms of small drones lack the range to reach out as far a surface ships usually operate. And targeting is still a limiting factor.
- DuskStar 6y ago
  > I'm skeptical a laser can defend against supersonic antiship missiles and ICBMs. I don't think lasers are meant to counter high-end threats like hypersonic missiles or MRBM/ICBM reentry vehicles. Not yet, at least. That can be done with SAMs - trading a $Xmm missile for a $Ymm missile is acceptable. (Trading that missile for a $Zk drone is not) > these lasers probably can't fire frequently enough to defend against those. This comes down to "dwell time to kill" and "duty cycle". Assuming 1s and 10%, you've got 6 kills/minute steady state. (Or 9 kills against a swarm incoming at 200kph with an engagement range of 5km) If the laser could do 50% for 2 minutes before taking 10 to cool down, though, it could handle 45 in that same scenario. And considering that commercial fiber lasers have duty cycles in the 50+% range sustained, I don't think this is unreasonable.
blackrock 6y ago
So they finally made a weapons grade laser work, by bundling together a bunch of fiber optics cables. Where each light output adds to the overall intensity of the laser.
mikewarot 6y ago
The gas dynamic laser has been capable of operating as a megawatt CO2 laser for decades. https://en.wikipedia.org/wiki/Gas_dynamic_laser https://en.wikipedia.org/wiki/Gas_dynamic_laser The technology was invented in 1967 and the patent granted in 1974 https://patents.google.com/patent/US3801927 https://patents.google.com/patent/US3801927 I can't find the reference offhand (Google isn't what it was), but the idea was to use the population inversion present in the exhaust of a jet fighter as a megawatt CO2 laser.
Held_der_Arbeit 6y ago
I wonder how easy it would be to make an automatic chemical laser emplacement good for single use?

58 points by clouddrover 6y ago

Chris Knight : As you know, Mitch and I were working on the cyanide system. Well, earlier today it ate itself. But, these little set-backs are just what we need to take a giant step forward. Right, Kent? Needless to say, I was a little despondent about the meltdown, but then, in the midst of my preparations for hari kiri, it came to me. It is possible to synthesize excited bromide in an argon matrix. Yes, it's an excimer frozen in its excited state. Bodie : Th... That's impossible. Chris Knight : It's a chemical laser but in solid, not gaseous, form. Put simply, in deference to you, Kent, it's like lasing a stick of dynamite. As soon as we apply a field, we couple to a state that is radiatively coupled to the ground state. I figure we can extract at least ten to the twenty-first photons per cubic centimeter which will give one kilojoule per cubic centimeter at 600 nanometers, or, one megajoule per liter.

aqme28 6y ago
They had actual scientist consultants on that movie and it shows. The proposed laser was based on real theory. Love that film.
deleted 6y ago
[deleted]
h2odragon 6y ago
https://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator https://en.wikipedia.org/wiki/Explosively_pumped_flux_compre...
siavosh 6y ago
So classic. https://youtu.be/0ds0wYpc1eM https://youtu.be/0ds0wYpc1eM

mips_avatar 6y ago

It's really amazing how accurately these laser systems work. I was amazed that SpaceX Starlink uses lasers to communicate between nodes. How do they aim so accurately?

exabrial 6y ago
Stepper motors and an active feedback loop most likely.
- thereisnospork 6y ago
  The positional accuracy of the motors aiming the lasers (relative to the satellite orientation) probably comes from optical encoders. I'd expect servos in an active loop as you mentioned, rather than steppers - which tend to settle at 1.8* increments. Either way I have no idea how they work out the firing solution for the comm lasers with sufficient accuracy. Hypothesizing: maybe they shoot multiple lasers, the main comm laser and a alignment pattern with auxiliary lasers which could be used for targeting feedback?
stripline 6y ago
I don't think they can yet..
cma 6y ago
Lasers still expand over time, and can expand more with lenses, so it isn't like hitting a laser pointer sized target.
- TheSpiceIsLife 6y ago
  That's right. By the time the laser reaches the target receiver it could be covering an area of tens of meters, or grater, and still be usefully detected. Think about the tiny amount of energy emitted by a mobile phone transmitter and still able to he usefully detected by an antenna on a tower kilometres away.
kevin_thibedeau 6y ago

the_only_law 6y ago

Even outside of weaponry, I see so many cool and innovative uses of lasers and optical technology these days. If I could redo everything, it’s certainly a field I’d consider.

ISL 6y ago

The next war will have new and unpleasant injuries so far largely unknown to the world.

greesil 6y ago
Everyone's going to have to wear really nice sunglasses into the battlefield.
- YarickR2 6y ago
  And shiny armor
- ISL 6y ago
  Bystanders will be blinded by specular reflections many miles from the battle.
mikhailfranco 6y ago
Using lasers to deliberately blind people is illegal: https://en.wikipedia.org/wiki/Protocol_on_Blinding_Laser_Weapons https://en.wikipedia.org/wiki/Protocol_on_Blinding_Laser_Wea...
- 10000truths 6y ago
  International law is a gentleman’s agreement, not some divine regulatory framework. I assure you that such conventions will go out the window the moment they prove even mildly inconvenient to enforce.
- ISL 6y ago
  Ah, true -- I'd forgotten about that. Even in the absence of blinding weapons, warfare and wounds will change completely when an overhead drone can target and burn a combatant in milliseconds. A quick and precise galvanometer may allow precisely-targeted strikes on tens of people in seconds. The combination of projectiles and directed-energy weapons will make defense and evasion much more difficult. David Drake tried to show us the depravity of wars of the past in his work, but it also highlighted the horror of wars to come.

jessaustin 6y ago

Just in time for deer season!

young_hopper 6y ago

I wonder how the efficacy of these laser-powered weapons systems is affected by how reflective the target is. It'd be a bummer if the military spent millions on this only to be foiled by a glossy paint finish.

the_only_law 6y ago
I’ve seen videos from guys building laser equipment and supposedly a powerful enough laser can punch through typical mirrors and specialized ones are required.
carrolldunham 6y ago
if you're very reflective then the old technologies can do their thing. e.g. anything with a radar
nradov 6y ago
Reflectivity doesn't matter in practice. No finish is sufficiently reflective and so the first part of the laser pulse burns it off and then the rest of the pulse gets through. An ablative heat shield can be more effective, although that adds weight and interferes with sensors. Spinning the target can also help a little by spreading the heat across a wider surface area.
- shpx 6y ago
  What about shooting out a gas that’s dark in infrared between yourself and the laser?
  - jandrewrogers 6y ago
    Nope, same issue, it would absorb the energy and turn into a very low density plasma, blocking nothing. That is equivalent to very weak ablation shielding. In fact, using a high-power laser to punch a hole in the atmosphere, essentially creating a functional vacuum by superheating the atmosphere in the beam path, is an old school engineering trick for exotic systems. Though in those cases, they tune the laser so that it gets absorbed by the atmosphere (similar to the gas you are suggesting). The use case is roughly analogous to employing supercavitation on torpedos.

safog 6y ago

That link out to the China drone swarm video is pretty crazy. I hope we do live in boring times and don't have to deal with drone warfare wherever we live. https://www.thedrive.com/the-war-zone/37062/china-conducts-test-of-massive-suicide-drone-swarm-launched-from-a-box-on-a-truck https://www.thedrive.com/the-war-zone/37062/china-conducts-t... Drones in the recent war between Armenia and Azerbaijan. Some of the same Chinese suicide drones being used. https://en.wikipedia.org/wiki/2020_Nagorno-Karabakh_war https://en.wikipedia.org/wiki/2020_Nagorno-Karabakh_war Slaughterbots: https://www.youtube.com/watch?v=9CO6M2HsoIA https://www.youtube.com/watch?v=9CO6M2HsoIA

canada_dry 6y ago

> all sheet metal that's cut for home appliances and so forth, was starting to be cut by high-power fiber-lasers of the kilowatt-type power levels. Shame this tech has yet to trickle down to the home-hobbyist level. Having my 3D printer direct the end of a decently powered fiber laser cutting head would be a nice feature!

bufferoverflow 6y ago
It absolutely is available. It's just powerful lasers are very dangerous to your eyes, and you better really know what you're doing. You can buy a 1.5kw laser cutter for $35K on Aliexpress. https://aliexpress.com/item/4000063563337.html https://aliexpress.com/item/4000063563337.html
- rtkwe 6y ago
  Available yes but it's still the realm of people with a good amount of disposable income such that they can drop 1-2k+ on a hobby.
wolfretcrap 6y ago
I bought CO2 laser for like $60 off eBay and it works fine with my 3d printer tho it will never be able to cut metal.

supernova87a 6y ago

Really impressive -- however last I recall reading about that breakthrough airborne platform laser (see photo in article), it involved dumping 2 huge tanks of chemicals together to produce a chemical fluorescence infrared laser pulse, wasn't it? Not as scalable that one I think. But the article emphasizes small lasers combined via fiber, ok. And yes the optics must be pretty impressive -- I wonder if adaptive optics (from astronomy) are used at these ranges and target sizes? And then, a puzzle I've always wished to have the knowledge to solve. Does a laser beam obey the 1/r^2 rule in intensity and area spread over distance? Of course it does, light waves intrinsically have that property I think. But how do you show it when it comes to a coherent beam that is always depicted as a focused pencil out into space forever?

xyzzyz 6y ago
If your beam is perfectly coherent, then its cross section has the same area regardless of the distance, so you should be getting full power. However, no beam is perfectly coherent, so it’s still O(1/r^2), and the better coherence, the smaller constant you have hidden in the big-O notation.
ssivark 6y ago
1/r^2 comes from the fact that space is three dimensional. No amount of beam collimating can change that (unless we have some fundamental breakthrough/change in our understanding of physics). Better beam coherence could keep improving on the solid angle, which is the multiplicative coefficient to the (asymptotic) scaling behavior.
jasonwatkinspdx 6y ago
I've been following this topic as a curiosity. I'm not totally certain but I think the LM systems don't have adaptive optics. But DARPA had a program where they were making something analogous to a phased array out of fiber lasers, where each individual laser had its own independent lens, and a phase shifter is used on each to align all the beams in real time so they're all mutually coherent. The phase shifter is tuned in real time by reflection back along each beam line from the target, split off with a beam splitter to some sort of sensor. They stopped talking about it after like 2 years, which maybe means it was a flop or maybe they took it secret. Who knows. If you're curious this is the name to google: https://www.darpa.mil/program/excalibur https://www.darpa.mil/program/excalibur

akimball 6y ago

Commercial product links would be nice

jccooper 6y ago

So one of the other problems with high power lasers is cooling the lasing mechanism. A recent novel solution to that is to have a liquid with the same refractive index and to circulate it (with no turbulence) through passages within the lasing mechanism. That way it can be cooled very thoroughly without interfering with the light generation. (Probably the coolant doesn't contribute, but maybe it does.) Seems this can do on order of 5 kw/kw output.

bufferoverflow 6y ago
5kw output for 1kw input?
- jccooper 6y ago
  Sorry, typo. Should be kg/kw
jasonwatkinspdx 6y ago
Fiber lasers are relatively easy to cool due to their high surface area. A 20kw industrial one is about a cubic meter box and just air cooled.

AtlasBarfed 6y ago

These laser weapons conveniently keep the Navy funded and their sitting duck surface fleet in the budget. I'm skeptical a laser can defend against supersonic antiship missiles and ICBMs. Furthermore, the future battlefield will be owned by swarms of drone weaponry, these lasers probably can't fire frequently enough to defend against those.

nradov 6y ago
This first generation of defensive lasers isn't really intended to counter missiles. The Navy already has the SM-3 / SM-6 for that. Lasers are a cheaper, quicker way to defend against lower end threats. Swarms of small drones lack the range to reach out as far a surface ships usually operate. And targeting is still a limiting factor.
DuskStar 6y ago
> I'm skeptical a laser can defend against supersonic antiship missiles and ICBMs. I don't think lasers are meant to counter high-end threats like hypersonic missiles or MRBM/ICBM reentry vehicles. Not yet, at least. That can be done with SAMs - trading a $Xmm missile for a $Ymm missile is acceptable. (Trading that missile for a $Zk drone is not) > these lasers probably can't fire frequently enough to defend against those. This comes down to "dwell time to kill" and "duty cycle". Assuming 1s and 10%, you've got 6 kills/minute steady state. (Or 9 kills against a swarm incoming at 200kph with an engagement range of 5km) If the laser could do 50% for 2 minutes before taking 10 to cool down, though, it could handle 45 in that same scenario. And considering that commercial fiber lasers have duty cycles in the 50+% range sustained, I don't think this is unreasonable.

blackrock 6y ago

So they finally made a weapons grade laser work, by bundling together a bunch of fiber optics cables. Where each light output adds to the overall intensity of the laser.

mikewarot 6y ago

The gas dynamic laser has been capable of operating as a megawatt CO2 laser for decades. https://en.wikipedia.org/wiki/Gas_dynamic_laser https://en.wikipedia.org/wiki/Gas_dynamic_laser The technology was invented in 1967 and the patent granted in 1974 https://patents.google.com/patent/US3801927 https://patents.google.com/patent/US3801927 I can't find the reference offhand (Google isn't what it was), but the idea was to use the population inversion present in the exhaust of a jet fighter as a megawatt CO2 laser.

Held_der_Arbeit 6y ago

I wonder how easy it would be to make an automatic chemical laser emplacement good for single use?