this post was submitted on 22 Jan 2024
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Laser defense systems are short range and anything traveling between mach 6 and mach 10 is going to be extremely difficult to hit by the time the weapon is in range. Some tactical nukes might be slower and more vulnerable, but laser defense weapons are better used on slower things like drones, rockets or even artillery shells and morters, for now.
Lasers have been used to shoot down satellites before, by both the US and China. Those shows were not really about satellites, they were about hitting long range targets moving at above "mach 10".
The effectiveness of a laser system, is neither about speed nor range, but about exposure time of the target. They need more time than a high velocity explosive to disable a target, and they need it to stay in line of sight for that time... but once they get that, nothing can beat the speed of light.
Drones, are more likely to be able to hide until the last moment, but a strong enough beam may not need much time to disable one... yet any explosives attached, might still reach their target. Shells and mortars are a mixed bag, they may offer longer exposure, but not necessarily enough to get disabled before impact. Rockets can be turned into falling balls of scrap, but also become ballistic explosives. High maneuverability airplanes and missiles can be a serious challenge, particularly if they fly low enough to stay out of sight. Ships would make great targets, if it wasn't that they're massive heat sinks, and usually equipped with something capable of shooting back along the laser beam to wherever it's coming from.
Where lasers outshine themselves, is at targets with low angular speeds, long line of sight times, following a predictable trajectory, which can't shoot back. That includes trees, blimps, satellites... and ICBMs.
If Russia doesn't have some serious lasers under the sleeve, and nothing indicates towards that, then MAD is broken and using Russia as an ICBM testing ground becomes viable, for at least the US and China.
I get what you are saying, but exposure time is directly related to speed and range in the context of the laser systems I was referring to. I'll explain below and try to call out my own knowledge gaps as well.
I knew we had satellite killers, but I didn't think those were practical enough to be deployed in an effective capacity yet. If there are, that would be neat.
For the smaller systems, I am only aware of the Israeli laser systems used to supplement their "iron dome" and some of the ones the US has on their ships. Both of those, I thought, only had an max effective range of about 2km, but only because of average atmospheric conditions. (And maybe even beam dispersion or something? That is a guess.) 2km @ mach 6 is 2 seconds of exposure time provided that the target acquired in advance.
It just makes more sense that those two laser systems are used to supplement a larger defense strategy. My mistake if I implied that they would completely solve any issues and not have consequences. Sure, the rocket, morter or whatever may not hit its primary target, but anything else could be considered a secondary target, I suppose.
(If I said anything stupid, just call me out. I like discussions about these kinds of things.)
In 1997, the US tested "illuminating a satellite" with a laser:
https://www.flightglobal.com/anti-satellite-laser-test-is-successful/17857.article
...achieving up to 10s continuous illumination against a US spy satellite at low power. That was 30 years ago, and it was already a given that firing that same laser at full power would have melted the satellite, even though the beam was 2m wide.
Modern lasers can get tighter and more powerful beams, the main issues are power usage and overheating. Something like the lasers at the NIF, can achieve fusion... or could be targeted somewhere else, if properly cooled down.
In 2023, China is claimed to have achieved enhanced cooling for continuous laser firing:
https://asiatimes.com/2023/08/china-claims-laser-weapon-gain-on-us-space-dominance/
...the title is obvious BS, in light of the 1997 US tests, but it makes one think the US likely has had something very similar for quite some time already.
Smaller systems have a smaller range, because... well, they're smaller. Fitting a laser system onto a ship, has some space, weight, and power limitations. Iron Dome ones are fitted to ground vehicles... and yet:
https://en.m.wikipedia.org/wiki/Iron_Beam
That's gonna hurt.
The thing about ICBMs, is that they may enter the atmosphere at hypersonic speeds... but there lies the key: "enter the atmosphere"
https://en.m.wikipedia.org/wiki/Ballistic_missile
The trajectory of an ICBM takes it out of the atmosphere, up to 4500Km, where it is well visible from the ground. Even moving at up to 8Km/s on reentry, that gives several minutes for a laser to hit them, and up to a minute during atmospheric descent itself.
Missiles like the Iskander, reach an altitude of 50Km at 2Km/s... which again gives about a minute since detection, for a laser to burn one to a crisp. Not to mention conventional missile interceptors, launched from close to its target, can easily hit one too (interceptor speed is irrelevant, when the attacker is basically aiming at them).
Now, you're right about atmospheric conditions, and the beam can only be collimated so much (although some amazing progress is being made on that front too), and the longer the beam has to travel through atmosphere, the more it gets scattered.
Still, at current power levels, having several of these laser systems spread over a country would make it essentially immune to ICBMs, very hard to hit with semi-ballistic missiles, and leaves low flying drones and missiles as a best option to ever reach a specific target... which means flying in thicker layers of atmosphere, increasing propellant consumption and reducing their range.
Paired with conventional countermeasures against rockets and mortars, it makes for a pretty decent defense system. The US has also shown interest in acquiring some Iron Dome to complement its Patriot systems, which would seem like a winning combo.
Overall, right now it looks like in a total nuclear WW3 scenario, only missiles launched from subs would stand any chance at reaching any targets, and even that would remain to be seen. That's definitely a far cry from a 1960s MAD scenario... which makes it somewhat more scary, because someone might think the outcome could be actually acceptable.
Laser systems are far more effective in space than on the ground. (still plenty effective, but you need very powerful lasers to destroy a spread of warheads on time)
The tests were done with ground based lasers, in 1997. Once they've proven the ability to go through the atmosphere, it means they can go any additional distance. Check the specs for the thing:
https://en.m.wikipedia.org/wiki/MIRACL
That was 40+ years ago... but the satellite test was done 17 years later, and it was claimed to have damaged the laser, even though it was operating at low power. Right now the Iron Dome is working on getting their "short range" lasers upgraded from 100kW to 300kW plus a multi-target capability, and China is boasting about a new cooling system that will allow them to fire continuously.
How powerful, and firing for how long, and/or how many lasers at once, does it take, to take out how many warheads falling for how long?
I bet someone has the right numbers for that, and if their installed capabilities are larger than the maximum number of simultaneous warheads they can expect, the effect is that ICBMs stop being a threat. Combined with the fact that lasers are perfect for hitting flimsy drones, it makes sense to have a lot of them installed.
PS: it gets slightly more complicated with something like a FOBS, but I wonder if a reflector satellite could be used against that.