Technology in Sci-Fi, Discussion #2: Nuclear Fusion

Several of my recent Science Saturday posts have mentioned developments in the pursuit of nuclear fusion. Today we’ll take a closer look at what fusion really is, how we could use it, and speculate at whether or not it’s really possible.

What is Fusion?

Fusion is a nuclear reaction where two smaller atomic nuclei fuse together to form a larger, heavier nucleus. This reaction releases a large amount of energy, but can only occur at extremely high temperatures. In nature, it is found at the centers of stars, where the pressure and temperature is high enough to support the reaction. Here on Earth, we have been unable to harness Fusion for our own use (with the exception of hydrogen bombs, which is a topic for another day.)

Is Fusion Different Than Fission?

Yes. In a way, fusion is the exact opposite of fission, which is what makes it desirable for use as a source of energy. While fission reactors produce a lot of energy, they require unstable materials (uranium or plutonium isotopes) in order to work, and yield waste that is still radioactive. Fusion on the other hand, does not require radioactive materials in order for the reaction to take place, and is therefore inherently much safer. For example, the Sun takes hydrogen atoms and fuses them into slightly larger helium atoms. Neither of these elements are considered very dangerous here on Earth when compared to Plutonium-239. Fusion materials are also much more abundant on Earth than fissile ones.

How Could We Use It?

To find a myriad of possible uses for fusion, you’d have to look no further than science-fiction. From the impulse drive engines of space ships in Star Trek, to the power for Mjolnir armor in Halo, fusion provides a clean and convenient source of energy for things that are otherwise difficult to power. Master Chief would have a hard time walking in his armor if he had to carry around an enormous battery rather than the tiny on board fusion pack. Fusion has been speculated about in sci-fi for a very long time, and with good reason. It’s theoretically sound science that would be invaluable to us, but far enough off to allow writers to let their imaginations run wild, showing us its uses eons into the future, and in the farthest reaches of the universe.

The possible applications for fusion energy are, perhaps not limitless, but inordinately numerous. If fusion were viable now, it would fill our immediate need for abundant, clean electrical energy. Looking ahead to the future, it might power something as small as a car, or drive the engines of spacecraft that’ll allow us to explore our solar system. Perhaps one day it will power starships that will send us to other star systems, all the processes that build them, and all the systems that are present on them.

What’s Holding Us Back?

Right now, the biggest obstacle we face in creating stable fusion reactors is the reaction temperature. Nuclei without electrons have a positive charge and repel each other, similarly to how the like ends of a magnet repel. To initiate fusion, the nuclei must be brought close enough together in spite of the repellent charges. This requires that the reactor core be heated to enormous temperatures, depending on which atoms are being fused. As a general rule, larger atoms require a higher core temperature. For example, a deuterium-tritium reactor, (theoretically the easiest to achieve and then scale on Earth) requires a core temperature of over 100,000,000 degrees Kelvin. That’s quite hot. Achieving these temperatures, and cooling the machines that contain the reaction, has proven to be an enormously difficult task.

For any updates on the pursuit of fusion reactors, and for other interesting scientific discoveries, stop by The Cluttered Desk every Saturday for Science Saturday posts. Don’t be left behind!

Until next time,

-Sal