How once-elusive laser weapons suddenly became a reality

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.

5kw output for 1kw input?

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’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.

Here's a YouTube video of a 500W laser cutting mirrors without any difficulty: https://www.youtube.com/watch?v=p-VlVmBZGI4

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.

if you're very reflective then the old technologies can do their thing. e.g. anything with a radar

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.

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.

Lasers still expand over time, and can expand more with lenses, so it isn't like hitting a laser pointer sized target.

Lasercoms has been around for decades.

I don't think they can yet..

Stepper motors and an active feedback loop most likely.

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

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.

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

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.

Using lasers to deliberately blind people is illegal:

https://en.wikipedia.org/wiki/Protocol_on_Blinding_Laser_Wea...

Everyone's going to have to wear really nice sunglasses into the battlefield.

They had actual scientist consultants on that movie and it shows. The proposed laser was based on real theory.

Love that film.

So classic. https://youtu.be/0ds0wYpc1eM

> 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.

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.