New laser raygun tech: Our sharks kick the tyres

Raygun fans will be overjoyed today to hear that a major problem of energy weapons - the fact that they tend to be hugely more devastating to themselves and their users than they are to their targets - may soon be solved.

No, really. Even the very latest laser and high-powered microwave weapons have beam efficiencies well under 50 per cent. The rest of the energy is released inside the weapon, in the form of heat.

This means that one may very well generate an ass-whupping hundred-kilowatt or even megawatt-range beam capable of burning a blazing hole through armour plate or exploding an intercontinental missile or whatever; but you'll have inflicted twice as much potential destruction on yourself, as vast amounts of heat are released inside your raygun in a short space of time.

Measly ordinary-style machine guns and so on often have problems with heat buildup, but these can easily be dealt with using ordinary means such as air cooling, or simply firing shorter bursts. But a near-future raygun generates so much heat, so fast, that it simply can't be dumped into the surrounding air quickly enough. Nonetheless it has to be got rid of somehow in order to avoid melting (or exploding) the raygun itself.

The answer is a heat sink; but not just any old heat sink. A battle-strength war ray based on recent technology will be throwing out a beam of 100 kilowatts or more and needing to dump at least twice that over time.

Boffins at famous crazytech firm General Atomics - the company which gave us the killer robot, the electromagnetic aircraft-catapult and the "Blitzer" railgun - now say they've cracked the raygun hotness dump problem. They've come up with a relatively handy little 35kg unit which can store up to three megajoules of heat using "phase change", that is by "melting a wax-type phase change material".

“We are very pleased with its performance, which shows that it can store heat at an average rate of 230 kilowatts. To put it into perspective, it’s the equivalent of melting about 20 pounds of ice in 13 seconds,” says GA powersystems honcho Dr Paul Clark.

Whoa there. Let's just try to put that into terms we can all understand, rather than all this jibber-jabber about ice.

Let's assume an execution-pool shark equipped with a lightweight HELL-ray weapon, as discussed here. Take it that the laser shark, in a typical poolside energy weapon engagement, will need to fire say thirty blasts of 750-joule energy equivalent to the 9mm pistol bullets favoured by his adversaries, that is to say government operatives and their possible black clad SWAT-commando frogman allies, scantily-clad female sidekicks etc.

If the headmounted piscine directed-energy weapon has beam efficiency of one-third, 45 kilojoules of waste heat will need to be dumped in this scenario. A scaled down 17kg unit based on the General Atomics prototype would be capable of soaking this up in less than half a second. So far so good.

Now let's assume the shark switches to maximum 20 kW power and leaves the beam on, perhaps in order to perform some task such as slicing in half a government agent or scantily-clad female strapped down on a table.

Wasting heat at 40 kilowatts, the shark's lightweight heatsink will be brim-full in just under 40 seconds. Provided that the shark's boss doesn't indulge in any overly elaborate expository dialogue, gloating etc, it would seem that the phase-change unit should be up to the job, if not with any very large margin for error.

If the supervillain owner can't resist the temptation to describe his plans in detail, however, it may be necessary for the shark to temporarily deactivate the beam or risk an embarrassing cloud of steam beginning to emit from his heatsink - or possibly even a devastating in-pool explosion of molten "wax-type material".

It's plainly early days yet for this technology. ®