Navy's New Laser Weapon: Hype Or Reality?

Lasrick writes: MIT's Subrata Ghoshroy deconstructs the Navy's recent claim of successful testing with the Laser Weapon System. It seems the test videos released to the press in December were nothing more than a dog-and-pony show with scaled-down expectations so as to appear successful: "When they couldn't get a laser lightweight enough to fit on a ship while still being powerful enough to burn through the metal skin of an incoming nuclear missile, they simply changed their goal to something akin to puncturing the side of an Iranian rubber dinghy." Ghoshroy is an entertaining writer and an old hand in the laser research industry. He gives a explanation here of the history of laser weapons, and how the search for combat-ready tech continues: 'At the end of the day, good beam quality and good SWAP—size, weight and power—still determine the success or failure of a given laser weapon, and we're just not anywhere near meeting all those requirements simultaneously.'

Comments

Re:The goal hasn't changed.

[Mr D from 63]

I'll add that maybe what is most impressive is not the laser power, but the control system required to keep the beam on a moving target at a mile away. The author seemed to miss that part of the technology.

oy

[anzha]

LaWS is rather unique. Its just a proof of concept test to see if what they will encounter when they put a laser weapon on a ship operationally. This is a step past what they are doing with the X-47b. However, there are no 'X Planes' for lasers, really. LaWS ought to be viewed from that POV. OTOH, HELLADS is a step or two (or more) further along the technology curve than LaWS. Under current Pentagon procurement law, we'll have a laser weapon for ships and/or aircraft by 2020. If we didn't have to go through the insanity of that system, we could have one in a couple years. 2nd, I used to work at HELSTF. I regularly watched pundits claim things we did /that/ day were impossible with the current technology or that there was an easy counter to what we'd done (as if we hadn't tested that first). Talking heads, even ones which have some background in a subject, ought to be taken with a grain of salt. In fact, the BoAS has an axe to grind. Opposition to SDI-like weapons is historical at this point and ought to be taken in that light. Likewise, anything put out there by a defense contractor ought to be taken with an equally large grain of salt, especially one of the beltway bandits.

Is that even correct ?

[aepervius]

If you have a reflectance of X% for the wavelength considered, that means 100-X% is absorbed. Granted I am not sure how the reflectance of materials is at short wavelength but the weapon considered are at long wavelength compared to visible (the weapon considered seems to be around 1 to 2 micrometer in the near infrared https://fas.org/sgp/crs/weapon...). Source cite a reflectance of 94% to 98% for that wavelength for some type of mirror (silver mirror among others).

At such a 50kW Laser at 95% reflectance would mean 5% absorbance or only 2.5 kW. That means to give the same amount energy at the same distance for the same surface you need 20 time the same time. Or put in another way if you need to give 10.000 Joule to ablate that surface , you would need 4 seconds exposition rather than 1/4 of a seconds for a non reflective surface.

So where do I make an error ? Where do you see that the mirror would quickly lose the ability to reflect compared to exposure time ? Keep in mind that in the case of a balistic projectile, you only need to make sure the laser do not pierce the skin long enough that targeting would be hard. I do not see why you keep telling reflectance has no impact on such laser. It certainly has an impact on how much kW will the target absorb.

Re:Is that even correct ?

[Anonymous Coward]

"X% reflectance" is a linear assumption. It suggests that you reflect X watt out of every 100 watt, and also X kilowatt out of every 100 kilowatt.

However, reflecting an electromagnetic wave is caused by currents in/near the reflecting surface. Metals reflect well because such currents encounter little resistance. But there's a limit to the current carrying capacity of metals. There are only a few free electrons per atom at best. If the incoming pulse is strong enough, the wave simply cannot be reflected. The current simply exceeds the current carrying capacity. Instead, the atoms of the metal ionize. That means the surface turns into a plasma, and a heated plasma at that. Plasma's absorb all that light instead of reflecting it. You just created a plasma torch on the metal surface.

Re:The goal hasn't changed.

[Anonymous Coward]

The author also misses what happens when you shine a 5kw+ laser back down the lens-path of an opponent's very expensive Electro-Optical system- you turn it into immediate junk. FLIR or TV or laser spot tracker on a surface ship, drone, helo or jet fighter, some schmuck looking through binoculars, IR/Heatseeking sensor on a missile, all become very permanently blind. And that in of itself is pretty useful. Not to mention since the tracking is so good, you could do fun things like setting a pilot inside a cockpit aflame.

Re:cover everything with mirrors

[The Grim Reefer]

Simply engineer a heat shield for the warhead that is ablative and outgasses enough to provide a protective layer around the object. The advantage of this over a mirror is that the laser's heat is carried away by the emitted gas.

For countries with MIVR'ed ICBM's, the dummy vehicles can be replaced with some sort of defensive weapon. In the case of Russia, you could have two warheads with four defensive vehicles per warhead on each ICBM, or the US could have 3 warheads with 3 defensive vehicles each per ICBM. Since they can be independently targeted, the defensive vehicles could arrive ahead of the warhead between the line of site of the laser and the trajectory of the active warhead. A nice thick cloud of opaque smoke could do the trick. And be cheaper than reflective/ablative armor.