October 19, 2021

I, Science

The science magazine of Imperial College

Think lightsabres are only possible in a galaxy far, far away? If we replace the photons with plasma, they may not be so out of reach...


When Walt Disney purchased the Star Wars franchise in late 2012, I saw it as the perfect excuse to whittle away nearly 18 hours of my life re-watching both trilogies.

In addition to the incredible graphics of Episodes 1-3 and the warm feelings of nostalgia I felt watching Episodes 4-6, I was struck dumb by the lightsabre in a way I never had been as a child.

Science has helped humanity make intense and formidable advancements by way of weapons technology, but decimating an enemy with a beam of light still seemed like the stuff of science fiction.


In ‘real life’, Darth Vader would destroy the entire Death Star if he switched on his lightsabre while inside the space station.


That’s because (in its LucasFilm form) it is. The design of the lightsaber is flawed for several reasons. First, the light laser blade would have to be around 6,650ºC to ensure it would be hot enough to cut through any material. This means the lightsaber would need to pack an incredibly powerful energy source in its handle to achieve such levels of heat energy (Added challenge: the handle measures about half a foot.)

Moreover, in theory, there is no limit to the power a laser lightsaber can contain, so the more energy you pump into a lightsaber, the stronger it would become. A light laser beam is just a flow of photons, which are massless particles; therefore, the exceptionally energetic beam of light released from the device would go on forever, shooting out of the handle at the speed of light and destroying everything in its path. (Note: avoid fighting indoors!)

To add further complications, in a fight between two people wielding lightsabers, these massless beams wouldn’t be able to make contact because light can’t be solidified into a blade. The beams would also be invisible if you were fighting an opponent in a lighted area, so you’d have to challenge your partner to a duel in the dark.

After looking at the lightsaber from this point of view, I was tempted to say “Into the garbage shoot, flyboy!”

But, what would happen if we widened our imagination?

I started pouring through the Internet to see what scientists have to say about the technology, when I came across Dr Michio Kaku, an American theoretical physicist who could be the father of the modern-day lightsabre.

Dr Kaku created an elegant design for a lightsabre that actually might actually be possible to build and operate in the next few decades (he explains all in this rather cool video).

His idea? Use plasma.

Plasma is the fourth state of matter. It is a hot, ionised gas made up of free-floating positively charged ions and negatively charged electrons.

Dr Kaku’s ‘lightsabre’ would suck in air through the handle and, using a very powerful energy source, convert the oxygen into a plasma state. The blade of the weapon would be made up of a retractable telescopic ceramic rod; the only material with the potential of surviving the high temperatures inherent in a lightsabre. The plasma would flow through the inside of the heat-resistant rod and into holes drilled into the surface.

I was impressed by Dr Kaku’s design because it seems very simplistic while still staying relatively true to the design of the lightsabre from the Star Wars movies. The only thought racing through my head was: how would you power it?

It turns out that Dr Kaku thought of this too. According to his calculations, it would take nearly 50 MW to heat the plasma up to 6,650 ºC. That’s around the amount of power consumed by a small city.

According to Dr Kaku, carbon nanotubes, which are symmetrical strings of strong, carbon atoms, could be the answer to the lightsabre’s energy needs. These carbon structures are tiny. Very tiny. They’re about 20,000 times smaller than a hair on your head, making it possible to cram trillions upon trillions of these carbon nanotubes in the handle of the sabre.

In addition to being small, these structures also have unique properties. Though carbon is not normally able to conduct electricity, scientists have found that, on the nano-scale, carbon nanotubes actually can conduct electricity. In fact, they would be able to do so at a rate that is 1,000 times more efficient than copper. The only issue with Dr Kaku’s battery is that carbon nanotubes are still a heavily researched, but underdeveloped field of science, in terms of practical applications.

So, plasma-based lightsabres may not be the solution you were hoping for, but they do at least have the possibility of being constructed for real in our galaxy – as opposed to one that is far, far away.

IMAGES: Arbyreed, flickr.