Naval Directed Energy Weapons

[HTV-3X]

Hi yall

Okay, now that the Navy has revealed the USS Ponce will be the testbed so to speak for their new laser, I was wondering yalls thoughts on this. I havent seen much specific details on the system.

What are they using for the fire control system/targeting? IMO thats gonna be the main hurdle for lasers is targeting. Though Im sure if they can build stabilizing systems to allow a 120mm tank gun to fire accurately over rough ground at 55mph it shouldnt be too much of a problem to stabilize the laser at sea I would think. Correct me if Im wrong here. Will they be using any type of stabilization mechanism on the LaWS?

I also wanted to clear some things up. I remember reading on here someone saying they had a "physics background" and that the problem with lasers is they follow the inverse square law requiring huge amounts of power for long distances and also are susceptible to atmospheric dispersion. Although Im sure thats not the opinion of everyone here, its not entirely true. Im not trying to insult anyones intelligence but lasers dont really follow the inverse square law in the traditional sense. In laymens terms, compare how a conventional blast fragmentation explosive disperses its energy evenly in a growing sphere. This is an example of the traditional inverse square law. Another example is a lightbulb, or a flashlight. A flashlight is the best comparison in this case. A laser beam looks nothing like a flashlight`s beam. This is because while the flashlight shines EM(Electromagnetic) radiation of many different wavelengths/frequencies, a lasers light is only at one specific wavelength. The effective range of a laser will be determined by the diameter of the mirror/lens/aperture and the wavelength. The inverse square law allows for no such things. The smallest spot can be determined by S = 1.2 R L / D, where S is spot size, R is range, L is wavelength, D is diameter of aperture. Granted, outside of the focus, the laser does start to disperse, but I doubt lasers will really be used outside of the focus range anyway. It is quite possible to build a laser which has an effective range of over 1 light-second, with a high frequency and large aperture. Its just not cheap.

Anyway, I was also thinking a microwave frequency laser would also be quite useful in damaging electronics. Which direction do yall think military lasers will take in the future? I honestly think an airborne laser could be very successful, not a physically damaging laser but one which damages/interferes with the electronics of other aircraft/targets.

Thanks

 

[StobieWan]

Laser physics gets complicated, and my brain is tiny so bear with, but as I understand it, if a laser formed a perfect beam with no divergence, and you were working outside the atmosphere, you would indeed see very little loss in transmitted power over a distance.

Unfortunately lasers don't form perfect beams, so what happens is that the beam remains the same size for a fair distance then it does begin to expand, which is why the laser targets on the moon are being hit by a laser spot several km across from a beam formed which is only a few mm wide.

Basically, at relatively short ranges, lasers (and to some extent other focussed light sources like searchlights,flashlights etc) don't follow the inverse square law, but over longer distances, the results average out to approximately the same values.

None of this is particularly relevant at the ranges and under the conditions in which lasers are deployed in atmosphere. Beam jitter and bleaching are more significant. Atmospheric bleaching can be reduced with the right wavelength of laser, but will remain a factor. Beam jitter from vibrations on the firing platform or the target end play much more of a part in reducing the efficiency of the weapon.

If you're after a soft kill EM device, look no further than the latest AESA radars which can often be focussed to disable enemy radars.

 

[My2Cents]

Laser are subject to lose of effectiveness from a number of mechanism and must be focused to achieve , but at the ranges contemplated beam divergence (spread) will not be significant.

1. Focus –The beam emitter on the ship is quite large, probably around 1m in diameter. This is necessary to manage the heat in beam generation system. Basically if the beam power density (watts/cm2) is high enough to damage the target, then if the beam were the same at the beam generator it would destroy it. The optical system in the beam is supposed to reduce the size of the laser spot at the target no more than a couple cm in diameter, increasing the energy density to the point where it is destructive. If the beam is out of focus it will cease to be effective.
2. Atmospheric absorption – The molecules that make up the air absorb part of the laser beam, reducing its power, particularly if the frequency of the laser matches a resonant frequency of the molecule, which is also the frequency that a laser using that molecule as the lasing medium will operate at. As a result gas dynamic lasers that have been evaluated as lasers tend to exotic materials that are not present in the atmosphere at detectable levels, for example the COIL used iodine. Solid state lasers can be almost any frequency, but that frequency is fixed at the time of manufacture. Free Electron Lasers are continuously tunable. The absorbed process also supplies the energy driving …
3. Atmospheric distortion and blooming – The atmosphere distorts the beam and changes the path (distortion) and focus (blooming) continuously, driven by its flows both normal and driven by the heat absorbed from the beam. An example of this process can be seen by looking across a flat plain or body of water on a very hot day.
4. Target movement – Current laser weapons are continuous output devices and take time to deposit enough energy to damage the target. A better description of the damage mechanism would be a heat ray, not the pulse weapons in science fiction and fantasy.

Focusing the beam and compensating for distortion and blooming is the job of the adaptive optics package on a laser weapon. The adaptive optics track the target and use feedback from thermal sensors to keep the beam on the target spot. It is likely that the adaptive optics can supply a degree or 2 of steering. The mount itself is adapted from a stabilized gun, so combining the mount and optics the ship motion is probably not a factor

 

[tatra]

If you're after a soft kill EM device, look no further than the latest AESA radars which can often be focussed to disable enemy radars.

You mean "fry" the radar of the launch platform, or of a missile?

 

[StobieWan]

You mean "fry" the radar of the launch platform, or of a missile?

Primarily the launch platform as far as I understand it - the EF/18 Growler has some sort of a soft kill capability touted and it's definitely in the brief for F35 - I'd imagine flooding the smaller and lower powered seeker for an AIM120 or similar class would be easier but you'd have less time usually, given that the seeker is usually off for a lot of the flight time.

I'm sure someone who knows what they're talking about can chip in

 

[HTV-3X]

Laser physics gets complicated, and my brain is tiny so bear with, but as I understand it, if a laser formed a perfect beam with no divergence, and you were working outside the atmosphere, you would indeed see very little loss in transmitted power over a distance.

Unfortunately lasers don't form perfect beams, so what happens is that the beam remains the same size for a fair distance then it does begin to expand, which is why the laser targets on the moon are being hit by a laser spot several km across from a beam formed which is only a few mm wide.

Basically, at relatively short ranges, lasers (and to some extent other focussed light sources like searchlights,flashlights etc) don't follow the inverse square law, but over longer distances, the results average out to approximately the same values.

None of this is particularly relevant at the ranges and under the conditions in which lasers are deployed in atmosphere. Beam jitter and bleaching are more significant. Atmospheric bleaching can be reduced with the right wavelength of laser, but will remain a factor. Beam jitter from vibrations on the firing platform or the target end play much more of a part in reducing the efficiency of the weapon.

If you're after a soft kill EM device, look no further than the latest AESA radars which can often be focussed to disable enemy radars.

You took the words right out of my mouth. Thats precisely what I was trying to say. Theyre not going to be even trying to hit anything outside the focus range. And it really depends on how you want to focus it. IMO a respectable weaponized laser though will be able to focus at widely varying distances very rapidly, similar to a camera. I would think 100km maximum would suffice for ASuW seeing as how youll be limited to the horizon anyway and it will most likely be used for AA defensive purposes.



Also, I thought I remembered hearing that some AESA radars had the capability but wasnt positive. Thanks for clearing that up. If its not all classified, may I ask what they are actually capable of in terms of effects? And have they been used in anger in that role? Also, what would it take to harden(if possible) the target from such effects?

 

[HTV-3X]

Laser are subject to lose of effectiveness from a number of mechanism and must be focused to achieve , but at the ranges contemplated beam divergence (spread) will not be significant.

1. Focus –The beam emitter on the ship is quite large, probably around 1m in diameter. This is necessary to manage the heat in beam generation system. Basically if the beam power density (watts/cm2) is high enough to damage the target, then if the beam were the same at the beam generator it would destroy it. The optical system in the beam is supposed to reduce the size of the laser spot at the target no more than a couple cm in diameter, increasing the energy density to the point where it is destructive. If the beam is out of focus it will cease to be effective.
2. Atmospheric absorption – The molecules that make up the air absorb part of the laser beam, reducing its power, particularly if the frequency of the laser matches a resonant frequency of the molecule, which is also the frequency that a laser using that molecule as the lasing medium will operate at. As a result gas dynamic lasers that have been evaluated as lasers tend to exotic materials that are not present in the atmosphere at detectable levels, for example the COIL used iodine. Solid state lasers can be almost any frequency, but that frequency is fixed at the time of manufacture. Free Electron Lasers are continuously tunable. The absorbed process also supplies the energy driving …
3. Atmospheric distortion and blooming – The atmosphere distorts the beam and changes the path (distortion) and focus (blooming) continuously, driven by its flows both normal and driven by the heat absorbed from the beam. An example of this process can be seen by looking across a flat plain or body of water on a very hot day.
4. Target movement – Current laser weapons are continuous output devices and take time to deposit enough energy to damage the target. A better description of the damage mechanism would be a heat ray, not the pulse weapons in science fiction and fantasy.

Focusing the beam and compensating for distortion and blooming is the job of the adaptive optics package on a laser weapon. The adaptive optics track the target and use feedback from thermal sensors to keep the beam on the target spot. It is likely that the adaptive optics can supply a degree or 2 of steering. The mount itself is adapted from a stabilized gun, so combining the mount and optics the ship motion is probably not a factor

Yes sir, by the way, how is the FEL doing as far as funding and development at the moment? Also, Im not sure what the engineering hurdles would be, but I would think thermal blooming could be solved by instead using very short high power pulses instead of continuous. Because hot air takes time to expand into low density air, so if the pulse is done before the air expands, it will not be affected. What is your opinion on the difficulty of instead engineering it for very short pulses 2cents? Why did they just not design that way in the first place? It seems like it would be much more effective, because not only would blooming be out the way, but instead of just massively heating the target, you would get an explosion like effect from the material vaporizing.

 

[RobWilliams]

I would think 100km maximum would suffice for ASuW seeing as how youll be limited to the horizon anyway and it will most likely be used for AA defensive purposes.

This is something that has been covered elsewhere, i'll link the calculator + associated chart (courtesy of FormerDirtDart)

Distance to the Horizon Calculator

To get even close to 100km distance, the laser would need to be close to 1km up in the sky due to the nature of it being a laser.

Not to mention that by the time you get within 100km of another vessel you're going to be within range of a conventional surface launched AShM anyway.

IMO DE weapons will remain in the AD use for a while.

 

[HTV-3X]

This is something that has been covered elsewhere, i'll link the calculator + associated chart (courtesy of FormerDirtDart)


To get even close to 100km distance, the laser would need to be close to 1km up in the sky due to the nature of it being a laser.

Not to mention that by the time you get within 100km of another vessel you're going to be within range of a conventional surface launched AShM anyway.

IMO DE weapons will remain in the AD use for a while.

Nice, wow. I had no idea the horizon was so close. I was always under the impression the horizon was around 20mi out at average man height. No idea where 20mi came from lol. Thanks for that one.

 

[HTV-3X]

Wow, thanks for the chart. I had no idea the horizon was so close. Puts into perspective how difficult it truly is to intercept a sea-skimming missile and how little time you would have, much more so if its moving at mach-many.

Does anyone know how the Navy`s FEL is doing currently? I heard that it may have been cancelled?

Another interesting one I see DARPA is currently working on is a scalable Phased Array Laser.

Edit: What exactly is "doppler beam sharpening" and approximately how sharp/thin can a modern AESA radar`s beam get? Are we talking on the verge of a laser beam or something more akin to a flashlight or??? Approximately how much divergence will there be with such a beam; again, are we talking laser beam divergence?