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.
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?
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?
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.
starlink doesn't, yet, all of the satellites so far are bent pipes. They're working on it however. It may not end up using lasers, but something in the E band RF for intersatellite links.
They have a couple birds up there with lasers. As I understand it, the unit price for the necessary actuators is too high right now to deploy thousands of them.
In a more regular appliance, the current Valve Lighthouse VR-tracking system works by sweeping lasers very precisely across a room and using the timing differences across the sensors on the HMD to triangulate its position in the room.
There is a good talk by one of the engineers who worked on the initial prototypes, and IIRC they both require and are able to achieve something like nm accuracy when they sweep the rotating masses with the lasers on them (That is, not only is the frequency very precisely controlled, the phase cannot drift either). With the help of some custom components they can do that for a hundred bucks.
I'm slightly hesitant to go into it for mostly ethical reasons, but military technology has always fascinated me if purely because of the toys they get to play with. The amount of gear even a World War 2 aircraft had by the end of still surprises me, i.e. The Mosquito had a primitive version of what we would now call a HUD displaying a radar horizon and a gunsight. Know-how and an unlimited budget go a very long way.
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.
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.
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.
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.
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.
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.
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.
Reflectivity of the target doesn’t matter. The specified power levels are high enough by design that a reflective surface will instantly be converted into plasma.
Even if you covered the target in dielectric mirrors specifically engineered for the wavelength of the laser, assuming such a thing was even feasible on a cost, weight, and functional basis for the target, you would have to keep them spotlessly clean in an operational military environment for them to be effective — an impossible task.
Hence why the military doesn’t concern itself with shiny targets. At the power levels they target, nothing real can be sufficiently shiny as a matter of practical physics.
I'm guessing the most effective anti-drone weapons are more akin to narrow beam EMP than thermal lasers.
Less because of any sort of reflective countermeasure and more because it takes way less power and precision to attack the delicate integrated electronics within a drone then it does it attack it's physical integrity.
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.
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?
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.
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.
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
Not to the same extent. Each element in a radar phased array has a wide angle of emission, and the overlap is necessary to produce the final aggregate steered beam. Lasers need to have as low dispersion as possible to be useful at range, so they can't do that. The project above used some other means of pointing for broad beam steering. The phase shifters are just such that each individual laser is closer to constructive vs destructive interference at the target surface.
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.)
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.
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.
> 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.
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.
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[ 3.3 ms ] story [ 60.3 ms ] threadBodie : 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.
Love that film.
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?
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.
There is a good talk by one of the engineers who worked on the initial prototypes, and IIRC they both require and are able to achieve something like nm accuracy when they sweep the rotating masses with the lasers on them (That is, not only is the frequency very precisely controlled, the phase cannot drift either). With the help of some custom components they can do that for a hundred bucks.
I'm slightly hesitant to go into it for mostly ethical reasons, but military technology has always fascinated me if purely because of the toys they get to play with. The amount of gear even a World War 2 aircraft had by the end of still surprises me, i.e. The Mosquito had a primitive version of what we would now call a HUD displaying a radar horizon and a gunsight. Know-how and an unlimited budget go a very long way.
https://en.wikipedia.org/wiki/Protocol_on_Blinding_Laser_Wea...
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.
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.
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.
Even if you covered the target in dielectric mirrors specifically engineered for the wavelength of the laser, assuming such a thing was even feasible on a cost, weight, and functional basis for the target, you would have to keep them spotlessly clean in an operational military environment for them to be effective — an impossible task.
Hence why the military doesn’t concern itself with shiny targets. At the power levels they target, nothing real can be sufficiently shiny as a matter of practical physics.
Less because of any sort of reflective countermeasure and more because it takes way less power and precision to attack the delicate integrated electronics within a drone then it does it attack it's physical integrity.
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
Slaughterbots: https://www.youtube.com/watch?v=9CO6M2HsoIA
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!
You can buy a 1.5kw laser cutter for $35K on Aliexpress.
https://aliexpress.com/item/4000063563337.html
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?
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
Seems this can do on order of 5 kw/kw output.
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.
Swarms of small drones lack the range to reach out as far a surface ships usually operate. And targeting is still a limiting factor.
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.
Where each light output adds to the overall intensity of the 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
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.