How to build a death ray — a new book looks at attempts to make the ultimate weapon

The death ray has been a staple of science fiction forever. It appeared in H.G. Wells's The War of the Worlds in 1897, Buck Rogers serials in the 1930s, and of course brightly-coloured beams of energy are the preferred weapon in every modern science fiction movie. And just ask the citizens of Alderaan in the first Star Wars movie how destructive a death ray can be. Oh right. You can't. They were all vaporized by the Death Star.

But perhaps we can be thankful that the death ray has been conspicuously absent in the real world. Like flying cars and teleporters, it seems to be a technology that can only exist in fiction.

Or maybe not. In fact, since the invention of the laser in 1960, there have been those who have sought to find a way to make the laser weapons of science fiction a reality. 

In a new book called Lasers, Death Rays and the Long, Strange Quest for the Ultimate Weapon, science writer and laser expert Jeff Hecht traces the history and the surprising present of the death ray. Here's part of his conversation with Quirks & Quarks host Bob McDonald:

This interview has been edited for length and clarity.

Bob McDonald: I mentioned that the laser was invented in 1960. But in your book, you trace the origins of the death ray back a couple of thousand years before that to Ancient Greece. Tell me about that.

Jeff Hecht: There's an enchanting legend that goes back to 2000 years ago when Archimedes, the legendary Greek scientist and engineer, supposedly got a group of soldiers to get their shields all polished up and use those shields to focus the sunlight onto Roman ships in the harbor of Syracuse that were besieging the city. The legend says that they focused so much energy on the ships that they were able to make them catch fire. MythBusters tried and they said, "Nah, you can't do it." MIT tried as well and said it works.

BM: But that at least is still taking light energy and using it as a weapon, whether it worked or not. Was there anything between Archimedes and 1960 when the actual laser was invented?

JH: H.G. Wells in 1896 published The War Of The Worlds, which had the Martian heat gun, and there were all kinds of new rays and radiation being discovered at this time. This was about the time X-rays were discovered, radio waves had been discovered shortly before, and there were other reports, some of them entirely mistaken, of other new kinds of radiation. So people started thinking of maybe there are new weapons that can be made. And as the world sort of spiraled down into World War One, people began to wonder, "Can we make something to shoot down these airplanes?" That became called a death ray. Somehow, I think it was from a reporter trying to describe someone trying to invent something like this, he called it a death ray, and the term picked up and the laser was invented in 1960.

BM: How soon did people start to think about turning it into a weapon?

JH:The idea of the laser as a weapon came before the first laser existed. Gordon Gould who was had been working in a lab with Charles Towne, who had earlier invented the microwave maser, which was sort of the father of the whole laser idea. Gould came up with the idea of making an optical version and he went to work for a small military contractor and they decided that they can get the Pentagon to pay for this. They went into DARPA, which was then brand new and had been founded to find some way to defend against Soviet nuclear missiles, and the director of DARPA told Congress we will look for anything, we'll even look for a death ray. Maybe that will be the ultimate weapon. So in January of 1959, Gould walks into DARPA and says, "Hey, I can build this laser" and the colonels jumped up and down in excitement. Gould had asked for $300,000 to start the research. They gave him a million.

BM: Once the laser was actually invented and the idea that maybe it could be a military death ray, what were the biggest challenges that the military faced in trying to do that?

JH: It was to get enough power out of it, because some of the first lasers were bright flashes of light that didn't burn holes in anything, so they needed a more powerful type of laser. There were a couple of guys at the Avco-Everett Research Laboratory who started thinking about what can you do to make a much more powerful laser. One of them was a rocket scientist, and he starts thinking maybe we can make something like a rocket engine to be a laser. Their idea is simple: you burn a chemical fuel, say kerosene, and you're making carbon dioxide that you spray.. out through nozzles, so you've got hard carbon dioxide molecules that can emit infrared light and you put mirrors on the two sides and you get this tremendous amount of power with this rocket engine. So maybe you make a gigawatt of power. And they said, "Well, maybe we can make a megawatt, a tenth of one percent of the energy in a rocket engine." That's still enough, if you get that little bit of light all lined up in a beam, that you could burn holes in things and shoot down Russian missiles if everything went well. They soon got up to tens of thousands of watts and super secret clearance for what they called the gas dynamic laser. All of a sudden, the Pentagon got real interested again because now they had enough power to start shooting things.

BM: So the idea behind the rocket engine laser is that you pump a huge amount of energy like a rocket engine into it and then you get a little bit of laser light out, but that laser light is still useful but it's a very inefficient system?

JH: Yes, it's inefficient. One thousandth of the energy comes out in the laser beam, if it all works as neatly and nicely as you want.

BM: But how do you turn that into something that's a practical weapon?

JH: Well, the Air Force decided to try. They put one of these things into a 707. This is about the early 1970s, and it's a very big laser and you don't get very much fuel into the plane and the plane sort of jiggles a little bit as it's flying. So it's kind of hard to stabilize anything. But eventually, they kind of managed to shoot down a few targets, but it took them about 10 years, and by then, the joke was that the laser was so big and so cumbersome that the only militarily useful thing you could do would be to drop it from the airplane onto the enemy.

BM: It is kind of odd to think about a rocket engine on an airplane that's not being used for thrust and is being used to power a laser instead.

JH:That was also one of the problems that they had because the thrust they made from the rocket engine was pushing the plane around.

BM: So perhaps we shouldn't be thinking of lasers as death rays, we should be thinking about them as more useful technology for things like eye surgery, checking out at the supermarket, running CDs, communication.

JH: In a sense, it's funny that the laser industry has always been a little appalled by the image of the laser as a death ray because the laser industry is really interested in making laser machine tools to cut sheet metal, surgery, sensing, all kinds of things where the ways lasers are used are to help people.