The Jet Fighter Laser Cannon

fahrbot-bot sends in a Register piece about DARPA issuing the penultimate contract for what is intended to be a jet-mounted laser cannon. The Reg outdoes itself in a BOTEC involving downsizing to shark scale. "The US military will shortly issue a brace of contracts for 'refrigerator sized' laser blaster cannons. One of the deals will see a full-power ground prototype built which will be the final stage prior to America's first raygun-equipped jet fighter. ... If it scales down far enough, this would seem to put handheld HELL-guns within an order of magnitude of the striking power offered by conventional small-arms. A 9mm pistol bullet has about 750 joules muzzle energy: a 5kg portable HELL-ray weapon would put out this much energy in a blast less than a second long. ... A dolphin can carry a human being weighing up to 100kg along for a ride. A thoroughbred shark in good training can surely match this. Thus, we seem to be looking at practicable head-[laser] output in the 20-kilowatt range."

Effect on humans?

[Singularity42]

I've never heard an analysis of effects on humans. Bullets are good a disrupting tissue, often causing death. A laser might deliver a cauterized burn, or blindness if in the right spot.

over one second?

[painandgreed]

We've been down this way back during the star wars days and trying to shoot down missiles. Any sort of energy that is released in the term of a second or so is useless against anything but stationary targets where you can assume you will hit the same point for that entire second. Bullets on the other hand expend their energy in a range of ten thousandths of a second. Until lasers or other beam weapons can deliver enough energy in a short enough amount of time similar to a bullet or supersonic missile, they simply will not make good weapons. Just make your missiles spin and any energy hitting them will be over a very large area. Similarly, the energy given for a 9mm hitting a human target that is moving around will be affected less than the firer of a 9mm who will probably absorb that energy over a shorter time and less area due to recoil.

Re:9mm?

[Shakrai]

Yeah, the Air Marshals use the .357 SIG, as does the Secret Service. The Coast Guard adopted it as well. I believe the FBI is still using the .40 S&W but I could be mistaken.

The 9mm is a joke. It's even worse for the military because they aren't allowed to use expanding ammunition. Buddy of mine who deployed in Iraq tells a story of an insurgent whom wasn't stopped in spite of the fact that he had absorbed no less than six center of mass hits from the M9. Makes you question the wisdom of the military abandoning the Model 1911, doesn't it?

Re:9mm?

[Rei]

Well, it's all irrelevant anyways, because if you want to compare damage, duration is just as important as energy. A one second laser pulse is nothing like a millisecond bullet impact. And furthermore, how the heck are you going to keep the beam on a single spot for a whole second, esp. at any sort of distance? Perhaps if you're talking stationary armor or something and you've got a tripod...

One of these cells may leave a nasty burn or blind you, but it's not going to kill you.

(Speaking of blinding: if serious lethal laser weapons ever do become common, that's going to be a new horror of war. Even the tangential reflections from any laser powerful enough to rapidly kill a person -- or worse, cut through armor -- are going to do catastrophic eye damage to everyone around them.)

Re:Effect on humans?

[smellsofbikes]

I can tell you from personal experience that high power lasers cause cauterized burns (in fact, if it's a big enough UV laser you get to watch your skin glow briefly: everything fluoresces and phosphoresces if you hit it with enough photons, I think) and causes blindness. Weird corollary: visible lasers are the nasty ones because they blow holes in the back of your eye, where we can't fix things. Most of the visible-wavelength laser PhD's I've worked with have had partial blindness in some area because they've cooked their retinas. However, IR and UV lasers, while seemingly more dangerous (because you can't see them and don't know you're being hit until it hurts/your vision goes fuzzy) are actually nicer since they primarily bake the front part of the eye, and we can repair that, either with corneal transplants or new intraocular lens implants. One of the PhD's I was working with on a massive UV laser had given himself DIY laser keratotomy: he'd flattened one cornea when a laser discharged a single pulse while his right eye was in the beampath. (It was one hell of a laser: we'd warm it up in the morning using a brick, because they're cheap and *anything* in front of a kilowatt laser is disposable so you might as well go with cheap.)

The fluorescence/phosphorescence was the most interesting thing to me. They're the same effect but different phenomena: you hit something really hard with a bunch of UV, and the surface -- the stuff that didn't get ablated -- is now covered in molecules with electrons blown up into higher orbitals. The ones that fall down immediately (within nanoseconds) are what produce fluorescence. The ones that have absorbed enough energy that they're in an orbital/spin combination that won't allow them to directly drop down to their original orbital, take a long time before they can do something like electron tunnelling to return to their orbital -- where by 'long time' I mean from a millisecond up to maybe six hours. So that's where you get actual glow-in-the-dark. I could put a notecard up in the beam and trigger a shot, and there'd be a nice yellow glow off the piece of paper for maybe half a second, and then the paper itself would be a moderate brown color. Next shot and it'd be gone. The individual shots were on the order of a microsecond long.

Interesting factoid that I wish I didn't know: fluorine gas smells somewhat like Elmer's Glue. Deep UV lasers often use fluorine as an excimer and when you have to replace the cavity mirrors, no matter how many times you purge it with argon, there's still some fluorine in there when you finally open it up. Gack *cough*.

Re:9mm?

[photon317]

Mostly they did it for stupid reasons, if you really read up the informed sources on these things.

The truth is 9mm is every bit as capable across a broad range of handgun scenarios that LE are likely to face as any other reasonable semi-auto cartridge (.40, .45, .357Sig), assuming one makes the correct ammo choices (on that point I'll concede: correct ammo choices matter more in 9mm than they do in .45, but not by a huge amount). Add to that the 9mm's lower perceived recoil, faster followup shots, and larger round counts in the same physical magazine size, and the 9mm looks quite good. That's why most of the world's militaries, including the US, and all NATO and UN types, have standardized on 9mm. Operator skill and unpredictable situational factors will make far more difference than any you can find between the calibers in any case, so the whole argument is really just a religious debate.

Back to the point about the fed branches though. The FBI originally tested the 10mm Auto to replace 9mm. The 10mm Auto actually *is* arguably a superior round to everything mentioned above in terms of "incapacitate in as few shots as possible". That is, of course, if you're willing to make the tradeoffs in mag capacity, ammo/gun weight, and extreme recoil. Once they had mostly settled on 10mm Auto, they did some testing with agents, and found that many (mostly females - it's in the reports, I'm not trying to be sexist here) simply could not handle the 10mm recoil and would not use it. So S&W came up with a "10mm short", which became the .40 we know today, as a compromise package that would be "like the 10mm (at least in diameter)" but lower recoil. It's basically a 10mm Auto that's been cut down with a lot less powder behind it.

And like all irrational "compromise" solutions of that sort, it's a complete practical failure. All objective testing indicates at best it's on par with its 9mm and .45 cousins (certainly nothing like the original 10mm), and arguably you're better off with one of those two. It just takes generations for people to admit those kinds of mistakes and move past them when you've got industry giants and federal government branches involved.

Re:The Future

[EdIII]

Basically we can boil your argument down to "people are too fucking cheap and stupid".

I totally agree. If it were not for concerns about government totalitarianism I would wholly support a 100% public transportation system in which only licensed, heavily regulated, and *REGULARLY TESTED* operators could use any transportation equipment in a public space.

The average person just does not have the responsibility and skill to be operating motor vehicles next to other average people. The real problem is that you are also mixing the slow, stupid, and inconsiderate with the fast, reckless, and homicidal. Not a good idea.

Ohh, and I totally include myself in the list of people that should not be driving on the roads. I am easily just a few months away from going Road Warrior on the rest of your asses out there. The moment one of you idiots starts doing 20mph less than the speed limit in the fast lane, I am *severely* tested in my ability to not drive your ass off the road with a well placed "bump".

I honestly don't know how much longer I can hold out.

Re:9mm?

[Zantetsuken]

Personally, this is why the Saiga exists - upscale an AK47 into a 12 gauge semi-automatic (full auto for Gov't/Military) shotgun.

http://en.wikipedia.org/wiki/Saiga-12 [wikipedia.org]
http://www.youtube.com/watch?v=-jPI5j3jjqo&feature=player_embedded [youtube.com]

Even with a 10 shell box magazine, load that with slugs. Assuming you're military with authorization to do so, get one with a short barrel, maybe an assault grip, and you'd have a helluva semi-auto hand-cannon or super high caliber smg...

As to so many people yelping about the Desert Eagle, it has the potential to *occasionally* look kinda cool, but if you're really needing a high caliber pistol, you'd be going with a revolver anyway. A revolver basically can't jam, and can use much higher and uncommon rounds that any other handgun design would not be able to handle the stresses of firing.

re:over one second?

[Anonymous Coward]

I worked on a laser system that was designed to shoot down rockets and mortars. I can tell you that there's enough energy put onto the target to melt through inch thick or thicker rocket/mortar casings easily within the time of flight.

As to the spinning, that's actually better. When a laser is melting metal, the melted part gets in the way of the beam. On non-spinning targets you actually have to wiggle the beam a bit to counteract that problem. If the missile spins, then you just keep it on the target and you melt a nice ring through it.

I see two problems with the laser in the article though
1) too weak, 150 Kw isn't really weapons grade
2) lasers melt, they don't explode, so you have to have very precise targeting to put energy on something that goes boom, otherwise you just melt divots.

Re:9mm?

[KibibyteBrain]

All it would have to do is heat up the fuel tanks to combustion. It may not even have to do that, the thermals on jet fighter engines are insane. The exhaust leaves at far greater than the melting temperature of the alloy the engines are made out of. Therefore all sorts of tricks like laminar airflow cooling are used. However, an external source of heat into the system could totally mess up those cooling techniques...