DARPA looking to kickstart raygun tech

Burn baby burn

Rayguns are, um, on fire lately, with the US Army dishing out early contracts in its monster truck laser cannon race, Boeing planning a rather unimpressive blaster-equipped Humvee and the famous American nuke-toasting jumbo jet continuing to make headlines. Now the Defence Advanced Research Projects Agency (DARPA), the Pentagon war-nerd bureau which loves nothing better than a long shot, has joined in.

In a solicitation (pdf) issued on Tuesday, the military boffins are looking for nothing less than "a Revolution in Fibre Lasers (RIFL)".

Fibre lasers are one of the types of solid-state laser, as opposed to chemically fuelled ones not usually seen as practical for mounting in anything but cargo planes. Fibre lasers generate a coherent beam using a specially made optical fibre, usually (in higher power applications) with cladding layers wrapped around the central core.

American arms giant Raytheon, working with the US forces and Sandia National Lab, told Wired magazine it has used a bundle of fibre lasers with a total strength of 20 kilowatts to explode mortar bombs very quickly in tests - so quickly that it might be possible to build a system that could shoot down enemy salvos in mid-air. Most raygun fanciers, though, reckon that 100kW is the minimum for a proper blaster cannon which would be fun to have.

Off-the-shelf combinable fibre laser amplifiers are currently limited to 200 watts each, according to DARPA: and it wants to push this up to 1kW to start with, then to 3KW in the next phase. That would mean a Raytheon/Sandia style bundle would scale up to 100kW or even 300kW, well into the proper-deathray range.

The DARPA chaps, though - perhaps upset by people calling them mad scientists - try to avoid talking about blaster guns too much. They say:

"High power fiber laser amplifiers that can be coherently combined will enable a broad spectrum of military applications ..."

Oh really. Such as?

Well, "...more effective [laser communications], target search and track, target identification..."

Come on, out with it. You know you want to.

Finally the boffins admit that what they're really after is "...ultimately, high power laser weapons".

They reckon that if RIFL achieves its goals it will be possible to make laser weapons that weigh less than 5kg per kilowatt of power.

Let's try out a few figures, then. An Accuracy International .50-calibre rifle - a massive brute, good for shooting through truck engines - weighs 15kg loaded. Instead of that you could carry a blaster weapon which might deliver 3 kilowatts to an enemy soldier. Depending on beam characteristics, atmosphere etc. that might be somewhat like pressing a steam iron against him. Nasty, but in the end you'd probably rather have the ordinary rifle.

Boeing's raygun-toting Humvee, though, could probably deliver full-on 100kW beams with this sort of gear - and so shoot down enemy shells or mortar bombs at light speed. The massive army-lorry blaster-cannon project - or naval warship installations - should be able to put out megawatts, and zap planes or missiles out of the sky as soon as they rose above the horizon - perhaps changing the whole game.

Still, it's important to remember that DARPA projects don't normally pan out.®

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