The US Navy's Laser Ray of DOOM!

[erik_t]

Someone_else, I suspect these lasers are meant to be installed on ships with all-electric propulsion: the main engines drive a generator that powers electric motors to move the ship. This is actually not new technology; the US Navy had a number of battleships and carriers with 'turboelectric' propulsion around the time of the First World War.

Yes, but the electric part of the system was really just a stand-in for reduction gears, completely disconnected from the rest of the ship. What is now in vogue (at least on paper) is integrated electric propulsion, where you can take full prime-mover power and redirect it as desired. That is new.

As for nukes for lasers, I rather doubt it. Naval nuclear plants don't have great power density at all, and the near-term chances of us building a new non-carrier, non-submarine nuclear ship seem quite remote.

[someone_else]

Lasers used for "burn a hole through that MF!" aren't touchy about uneven edges. The people designing such a weapon don't really care about the rest of the material around the beam path melting away. I believe they might even be happy about that.

Hehe, true, but the point is that the energy wasted to create "uneven edges" on enemy armor has to be subtracted from the laser's total energy output.
This means that the focus point (the "drill head", so to speak) receives less energy, and it takes very little to degrade its efficiency down to "crap".
This means that a moderately thick armor can simply ignore such lasers.

Still, you don't need to carry all that weight. The same principle allows whipple shields or even modern spaced armors to be very resistent to realistic laser cannons while also being reasonably light. To drill a hole big enough to let enough of the laser "cone" (not "laser beam", it is misleading) fit in to drill the second plate requires a huge lascannon (with a suitable power source). Or require the lascannon to waste time cutting circles in the first plate and then shooting in those circles to damage the second.

Note what Navy wants to put those lasers at: shooting down missiles (and maybe projectiles) shot at the ship.
Lasers aren't overly offensive weapons unless their output is truly mindboggling. And are shooting in a vacuum.

Yes, but the electric part of the system was really just a stand-in for reduction gears, completely disconnected from the rest of the ship. What is now in vogue (at least on paper) is integrated electric propulsion, where you can take full prime-mover power and redirect it as desired. That is new.

So that wasn't a novel idea. Hell, if they can pull off the trick correctly, they can get enough power to run dozens of lascannons like this baby by just redirecting power from one of the 2-4 engines. The death of missile warfare?

[Purple]

Hm, here is a hypothetical SF question. Could there be a situation where laser point defenses become so good that they can shoot down a missile in fight with something like 99% reliability but at the same time the laser beam lacks the capacity to shoot down something with even a little bit of armor like say an aircraft. Now, hypothetically if such a laser could be made light enough to be mounted on said aircraft could that be used as a plausible excuse in SF for a return to the age of close in dogfighting?

[Zaune]

Hm, here is a hypothetical SF question. Could there be a situation where laser point defenses become so good that they can shoot down a missile in fight with something like 99% reliability but at the same time the laser beam lacks the capacity to shoot down something with even a little bit of armor like say an aircraft. Now, hypothetically if such a laser could be made light enough to be mounted on said aircraft could that be used as a plausible excuse in SF for a return to the age of close in dogfighting?

Not particularly. Sci-fi writers who use the "advanced technology makes X obsolete" gimmick invariably fail to take into account the fact that as soon as some new innovation gives one side a tactical edge, the other side sets its R&D assets to work on countermeasures. As counter-missile defences get better we'll probably start seeing anti-shipping missiles programmed to fly random evasive patterns, or designed with a reduced radar cross-section and lower IR signature. It's even possible we'll see a seeker head designed specifically to home in on the source of point-defence laser emissions.

[Sarevok]

Missiles with thick layer of anti laser coating are going to be heavy, slow and fodder for older CIWS and naval SAMs.

Same for flying random patterns. It robs you of forward velocity and again makes it easier for enemy to intercept.

Low RCS missiles are going to be very slow. Stealth and high mach speeds don't go well togather.

Countermeasures don't come for free. Sometimes the performence hit from using countermeasures on a missile can make it no longer worthwhile to use.

[Simon_Jester]

Yes, but the electric part of the system was really just a stand-in for reduction gears, completely disconnected from the rest of the ship. What is now in vogue (at least on paper) is integrated electric propulsion, where you can take full prime-mover power and redirect it as desired. That is new.

So that wasn't a novel idea. Hell, if they can pull off the trick correctly, they can get enough power to run dozens of lascannons like this baby by just redirecting power from one of the 2-4 engines. The death of missile warfare?

Remember that real life isn't an SDN calc; you need to put more than 1 MW of power in to get 1 MW of laser beam out. There are also space constraints to factor in- the accelerator takes up a lot of space.

[Zaune]

True enough, but there's things you can do to cut down RCS without going for expensive radar-absorbent materials or screwing up the aerodynamics too badly, and it's not necessary to make a missile anywhere near as stealthy as a fighter or even a UCAV; the objective isn't to maximise the chances of every missile finding its target so much as to ensure that at least one does.

[someone_else]

Could there be a situation where laser point defenses become so good that they can shoot down a missile in fight with something like 99% reliability but at the same time the laser beam lacks the capacity to shoot down something with even a little bit of armor like say an aircraft.

Definetly possible that lasers could become the Missile's bane, although I doubt aircraft could carry anti-laser armor, since it would be either too dense or too bulky. They also have too much exposed parts that cannot be armored (like radar).

Now, hypothetically if such a laser could be made light enough to be mounted on said aircraft could that be used as a plausible excuse in SF for a return to the age of close in dogfighting?

No. Evading photons is stupid no matter how you look at it. Once they have a sensor lock on you, no matter how evasive you maneuver, they will keep shooting at you and hit with a never-seen-before godlike accuracy. The battle becomes a game of "who kills the enemy sensors first?" or the always fun "eyeball frying contest" where the lasers try to scorch each other's optics.

Same for flying random patterns. It robs you of forward velocity and again makes it easier for enemy to intercept.

Agreed on this. Although since lasers are line-of-sight weapons, flying very low (truly low) or even through not-so-dense stuff like treetops or going underwater ala cavitation torpedo in the final approach would work.

But as you said, these redesigns and additions don't come for free. Missiles with any decent range are pretty expensive already, even if they are made of tinfoil.

The usual way to overcome lasers is the Macross Missile Massacre. You throw at them n times more missiles than normal and hope to saturate the defences. Costs rise by n, of course.

Remember that real life isn't an SDN calc; you need to put more than 1 MW of power in to get 1 MW of laser beam out. There are also space constraints to factor in- the accelerator takes up a lot of space.

Yup, I was eyeballing. But I didn't get too far wrong, as I said above, one of the four gas turbines of an Arleigh burke can deliver 20 Mw of mechanical power, I know electrical motors are very efficient, more than 90%, and double as generators with similar efficiency. So you have somewhat like 19 Mw plus pocket change reaching your 500 kw laser. The baby will have at worst 20% efficiency so it should suck around 2.5 Mw. That's still around seven of those things powered by just one of the four main engines.

And space contstraints are somewhat lessened by the fact that the laser engine (the thing producing the laser light) can be placed where you want, and the laser light will be moved around the ship through tubes with mirrors at the ends up to the turrets, that are just big optic arrays.
(and you cannot really do any different, since the laser engine is usually too heavy, frail and unwieldy to be bolted on a weapon mount)

Having mutiple optic arrays also lessens each laser engine's downtime, since while Turret 1 is killing missile A, Turret 2 is tracking Missile B, and switching the laser light from Turret 1 to Turret 2 is just flipping a mirror in the tubes, way faster than waiting turret 1 to reaquire another missile. So you can shoot on more targets from the same "weapon barrel" in less time. Just what you need for a PDS.

[GrandMasterTerwynn]

Hm, here is a hypothetical SF question. Could there be a situation where laser point defenses become so good that they can shoot down a missile in fight with something like 99% reliability but at the same time the laser beam lacks the capacity to shoot down something with even a little bit of armor like say an aircraft. Now, hypothetically if such a laser could be made light enough to be mounted on said aircraft could that be used as a plausible excuse in SF for a return to the age of close in dogfighting?

No. If CIWS ever got that good, we'd just build more attack subs and shoot at surface ships where the lasers don't shine. Or build more torpedo bombers. Or launch more missiles. After all the superstructure of a surface ship is a busy place. You can't put lasers everywhere, since they'd start to get in the way of niceties like radar and communications. Worse, these lasers will be power-hungry, since the efficiency of a laser is appalling, and it takes a non-trivial period of time to burn through the missile's skin and touch off something important.

On an aircraft, it's even worse. They're high-vibration environments, and there aren't a lot of places to put a weaponized laser aboard a fighter jet (you'd end up sticking it in a streamlined pod.) And since this pod must be aerodynamic, the beam will only come out of the nose or tail of the pod. When you throw in the dwell-time required to intercept a missile with a laser beam; the solution simply becomes . . . use more missiles fired from tag-teaming aircraft, since the fighter jet must turn towards an incoming missile to hit it.

[erik_t]

Remember that real life isn't an SDN calc; you need to put more than 1 MW of power in to get 1 MW of laser beam out. There are also space constraints to factor in- the accelerator takes up a lot of space.

Yup, I was eyeballing. But I didn't get too far wrong, as I said above, one of the four gas turbines of an Arleigh burke can deliver 20 Mw of mechanical power, I know electrical motors are very efficient, more than 90%, and double as generators with similar efficiency. So you have somewhat like 19 Mw plus pocket change reaching your 500 kw laser. The baby will have at worst 20% efficiency so it should suck around 2.5 Mw. That's still around seven of those things powered by just one of the four main engines.

And space contstraints are somewhat lessened by the fact that the laser engine (the thing producing the laser light) can be placed where you want, and the laser light will be moved around the ship through tubes with mirrors at the ends up to the turrets, that are just big optic arrays.
(and you cannot really do any different, since the laser engine is usually too heavy, frail and unwieldy to be bolted on a weapon mount)

Having mutiple optic arrays also lessens each laser engine's downtime, since while Turret 1 is killing missile A, Turret 2 is tracking Missile B, and switching the laser light from Turret 1 to Turret 2 is just flipping a mirror in the tubes, way faster than waiting turret 1 to reaquire another missile. So you can shoot on more targets from the same "weapon barrel" in less time. Just what you need for a PDS. [/quote]
Waste heat will, presumably, be handled by magic

So will perfect pointing. So will this thing I heard of called "fog".

[Simon_Jester]

Now, hypothetically if such a laser could be made light enough to be mounted on said aircraft could that be used as a plausible excuse in SF for a return to the age of close in dogfighting?

No. Evading photons is stupid no matter how you look at it. Once they have a sensor lock on you, no matter how evasive you maneuver, they will keep shooting at you and hit with a never-seen-before godlike accuracy. The battle becomes a game of "who kills the enemy sensors first?" or the always fun "eyeball frying contest" where the lasers try to scorch each other's optics.

The only context in which anything even vaguely like dogfighting with lasers becomes possible is if you've got soft-SF spaceships fighting each other at light-second ranges.

Remember that real life isn't an SDN calc; you need to put more than 1 MW of power in to get 1 MW of laser beam out. There are also space constraints to factor in- the accelerator takes up a lot of space.

Yup, I was eyeballing. But I didn't get too far wrong, as I said above, one of the four gas turbines of an Arleigh burke can deliver 20 Mw of mechanical power, I know electrical motors are very efficient, more than 90%, and double as generators with similar efficiency. So you have somewhat like 19 Mw plus pocket change reaching your 500 kw laser. The baby will have at worst 20% efficiency so it should suck around 2.5 Mw. That's still around seven of those things powered by just one of the four main engines.[/quote]"At worst 20% efficiency" my foot; they're putting 200 kW into the electron gun alone to get 14 kW out of the laser. That's not factoring in the power consumption of the magnets (necessary component of the electron beamline), targeting radars (necessary component if you're going to aim this sucker), cooling systems (necessary component if this sucker isn't going to burn itself out in short order)... yeah. I'd say 10% efficiency is optimistic, probably extremely overoptimistic, when the weapon system is taken into consideration.

(note: "watt" is abbreviated "W" not "w")

No. If CIWS ever got that good, we'd just build more attack subs and shoot at surface ships where the lasers don't shine. Or build more torpedo bombers. Or launch more missiles. After all the superstructure of a surface ship is a busy place. You can't put lasers everywhere, since they'd start to get in the way of niceties like radar and communications. Worse, these lasers will be power-hungry, since the efficiency of a laser is appalling, and it takes a non-trivial period of time to burn through the missile's skin and touch off something important.

On an aircraft, it's even worse. They're high-vibration environments, and there aren't a lot of places to put a weaponized laser aboard a fighter jet (you'd end up sticking it in a streamlined pod.) And since this pod must be aerodynamic, the beam will only come out of the nose or tail of the pod. When you throw in the dwell-time required to intercept a missile with a laser beam; the solution simply becomes . . . use more missiles fired from tag-teaming aircraft, since the fighter jet must turn towards an incoming missile to hit it.

Or away from it; rear-firing lasers as opposed to forward-firing might actually become quite attractive for aircraft defense on fighters, especially if you can combine them with missiles like the latest Sidewinder that can acquire and hit targets behind the aircraft. That maximizes the time you have to shoot down an enemy missile launch, maximizes the number of missiles you can shoot down before one hits you, and allows you to shoot back at them by dropping the missiles and having them spin round to engage the aircraft chasing you.

At least, I think that works...

[someone_else]

Waste heat will, presumably, be handled by magic

Well, the navy's geeks are the ones claiming that such laser will work. And frankly, sea water is a good radiator.

So will perfect pointing.

A different weapon doesn't make your sensors more accurate. But a laser is much more accurate than a (non-guided) bullet.

So will this thing I heard of called "fog".

Yup. Fog or smoke make you invulnerable to lasers.

"At worst 20% efficiency" my foot; they're putting 200 kW into the electron gun alone to get 14 kW out of the laser.

Uh, read kW instead of kV. Big difference. Spanking myself.

[Simon_Jester]

Waste heat will, presumably, be handled by magic

Well, the navy's geeks are the ones claiming that such laser will work. And frankly, sea water is a good radiator.

They're not the ones thinking they can stack half a dozen of the things on a ship. You are.

That is what makes waste heat a problem- it's not that it can't be dealt with, it's that cooling systems consume power and the limits of your cooling systems impose practical limits on the performance of your hardware. This is a major problem with modern military radars, for instance- they have megawatt range outputs, but it's entirely possible to fry the radar set using them carelessly.

[erik_t]

Waste heat will, presumably, be handled by magic

Well, the navy's geeks are the ones claiming that such laser will work. And frankly, sea water is a good radiator.

The problem is getting the heat out of the laser itself, not rejecting it from the ship overall. This is like saying your CPU shouldn't need a fan because your floor is cold.

So will perfect pointing.

A different weapon doesn't make your sensors more accurate. But a laser is much more accurate than a (non-guided) bullet.

A laser does not have intrinsic accuracy. It has intrinsic precision. A 1m beam subtends an angle of only about 20 seconds of arc at 10km. If you point off the target by a minute of arc, he won't much care. This is not a trivial matter. Ten arcseconds is the sort of number you hear in legit astronomical duty (PDF warning).

So will this thing I heard of called "fog".

Yup. Fog or smoke make you invulnerable to lasers.

I'm not sure if you're being sarcastic. Shipborne radar has nowhere near the angular resolution required to direct a laser at appreciable range, which is why laser pointing is an optical business (note the pod atop YAL-1). Even if it weren't, heavy fog can reach densities on the order of 0.5g/m^3. A 1m beam 10km long would pass through 4kg of water, and boiling this water would require on the order of 9MJ. This is... a buttload of energy. I don't know the exact propagation challenges associated with cloud/fog burn-through but I would expect it to be within an order of magnitude of this number.



Lasers are absolutely going to go to sea and be useful in a big way, but there are some very serious challenges associated with their use and I very much doubt we will ever see them replace guns and missiles entirely.

[someone_else]

The problem is getting the heat out of the laser itself, not rejecting it from the ship overall. This is like saying your CPU shouldn't need a fan because your floor is cold.

Yeah, I know that . I "just" thought this laser was a 500 kW thing since I'm a moron that can't read properly the article in the OP. And I assumed that "cooling the beast" was a problem already figured out by them.

I'm not sure if you're being sarcastic.

I act flippantly but I wasn't kidding . I know about smoke and moderately moist moving air doing all kinds of dirty tricks on lasers, like thermal blooming that ends up defocusing the beam (so you end up shining a laser spotlight) or circulating enough to partially regenerate the stuff you are burning away with each pulse, and also what you said.
In my first post in this thread I also said

Lasers aren't overly offensive weapons unless their output is truly mindboggling. And are shooting in a vacuum.

In following posts I tend to forget that (bolded) detail.

[Sea Skimmer]

And space contstraints are somewhat lessened by the fact that the laser engine (the thing producing the laser light) can be placed where you want, and the laser light will be moved around the ship through tubes with mirrors at the ends up to the turrets, that are just big optic arrays.
(and you cannot really do any different, since the laser engine is usually too heavy, frail and unwieldy to be bolted on a weapon mount)

I doubt longitudinal flexing of the hull will allow your laser engine to be all that much more remote from the beam directors then some position directly under it between the same frames. Modularity would also heavily favor installation in the superstructure, but that's not a deal breaker. Ideally the whole laser installation would lift out in pieces using one overhead crane position.

[erik_t]

I want to interject that a quote up there got all screwball-y, and that's actually quoting someone_else (in more ways than one!).

[Sidewinder]

God knows, Wired has run enough "TECHnology TECHniques of the FUTURE will SAVE us!" articles. They make Tom Clancy look like a Luddite! If making a "Laser Ray of DOOM!" was as easy as the magazine suggested, wouldn't the Navy already have laser-armed battlecruisers to make mincemeat of the People's Liberation Army Navy (or whoever was the Villain of the Week)?