Hello all, and welcome to this week’s (not time travel) edition of Science Fiction Problems. I’ve been sitting on this one for a while now and had to shoo Dr. Melton away from it lest he encroach upon my sacred territory, but now I will finally address that oh-so-often used sciencey space weapon, the laser. In this episode I will be describing just how the things allegedly work, and highlighting some emerging technology that will rapidly make lasers a viable weapon in current-generation warfare. No, you did not misread that last sentence, but don’t get too excited- we’re still a ways away from beam-swords and blaster cannons. In my next post I’ll get into how laser weapons are used (and misused), and how realism and fantasy can be balanced to make them cool and believable.
Light Amplification by Stimulated Emission of Radiation
In case you didn’t catch it, that’s what “LASER” actually stands for. Actually, to be more accurate, lasers that generate their own light for the process would operate with “Light Oscillation by Stimulated Emission of Radiation”, but the acronym “LOSER” is not quite as catchy. We’ve probably all played with a laser pointer at one time or another, and it may have occurred to some that the little dot they generate seems something like the dot from a flashlight when you shine it close to a surface. Both lasers and flashlights focus light into a beam, but of course lasers are much more highly focused- but how is this? Well, obviously there are differences, but they operate on the same basic principles of quantum physics (Einstein again).
Light as Particles or Waves (Both/And?)
Light is a peculiar thing to model mathematically. In some cases, light seems to act in waves, as in radio or microwaves, and some cases, more like particles, as in gamma radiation. For lasers, it is easiest to imagine light as particles, like grains of sand, which travel in a straight line from the source. With flashlights, the light particles are emitted and reflected as well as possible to force them all in one direction- the further out from the source, the more spread out the paths of the particles become, and the beam spreads. With lasers, instead of focusing them, the light particles are emitted into a tube-like chamber and reflected back and forth (or “oscillated”) between two reflective surfaces. As the chamber fills with bouncing particles, a large amount of them find their way through a hole in the center of one and pour out in a straight beam. Because the light particles fly out only once they are traveling in the same direction, the beam is very tight and focused.
If you’ve ever used a powerful hand-held spotlight, when you put your hand in front of the lens, you can almost
burn yourself from the heat. Now imagine if all of this heat was focused into one little dot, sometimes only a few nanometers in diameter, and you can get an idea of how lasers can be used to cut through things as hard as steel or diamonds. The cutting action comes from the energy of the light particles transferring to the surface, converting into heat, so if all of that energy is focused into one tiny point, it starts to burn, melt, or vaporize the material away.
So, pretty cool what we’ve managed to figure out here, but there’s one major problem that keeps us from building Death Star-class super-weapons: all that energy has to come from somewhere. It takes a significant amount of energy to carve up quarter-inch stainless steel, but what about several feet of armor plating? You can hook up some nuclear generators into your death ray if it’s mounted on top of a military compound or aircraft carrier, but as of yet we have no practical way to generate that much power for laser weapons mounted on aircraft or armored vehicles. Part of the problem is that most of the energy that is used for the laser is actually coaxed out of some kind of electron-rich material (be it solid, liquid, or gas), and so there is a certain inefficiency in the process, not to mention all the heat generated to deal with. Fortunately, we now have the FEL laser.
The Free Electron Laser
This is a neat trick that gets a lot more bang for the energy buck than the typical setup, using electromagnets to yank a bunch more electrons from the laser’s medium. What this means is that it’s now possible to generate a much higher amount of energy in a laser, and so it takes less power to emit a more powerful beam. It’s also much more stable and easier to control, so the beam can be tweaked depending on the application and need, making lasers a much more flexible option as a weapon. Watch this short Youtube video if you want more information; it’s pretty neat seeing how it works. The way the Office of Naval Research presents it, they plan to stick these high-powered, super-efficient lasers on aircraft carriers to shoot down incoming missiles (and potentially enemy aircraft- note the shot down helicopter from the video). This technology also has a ton of industry applications, but more important to us science-fiction fans, this is a huge step towards practical, effective laser weapons. Pretty soon the navy will have railgun-toting battleships and impervious missile-hacking laser defenses- how cool is that!?
Alright, I think I covered that well enough- next week I’ll get into how science fiction has treated (or mistreated) this staple technology, and give my advice for how it can be handled realistically while not sacrificing the coolness factor.
Until then, what are your favorite lasers in science fiction? Does it bother anyone else when books, movies, or tv shows fall back on the inexplicable Star Wars-style blaster weapons?