How to make a lightsaber (in theory)

Ever dreamed of being a Jedi? Armed with an elegant weapon for a more civilised age, many of us have fantasised about cutting a bright green (or blue) swathe across a galaxy far, far away. Disney even released a patent in 2018 for one such device, although ‘Sword device with retractable, internally illuminated blade,’ doesn’t quite evoke images of cutting through blast doors or droid armour.

That begs the question on this Star Wars Day: is it actually possible to build a lightsaber, and if so, how far away from holding it in our hands and whistling ‘Duel of Fates’ are we? The answer might surprise you —but first, we’ll have to set out exactly what we mean when we say lightsaber and learn some science on the way.

So what would you need to make a lightsaber as we know it?

There are six fundamental boxes a lightsaber must tick: it must light up and glow when in use, it must be able to cut through an object, it must be retractable, it must make a trademark whooshing noise, you must be able to cross them in a fight, and most importantly, it must obey the rule of cool. The bad news is that not all of these are possible at once — yet — but the good news is that all of them are already possible individually — at least, in theory.

Whilst we don’t have access to Kyber Crystals in our galaxy, the laws of physics make more than a fine substitute. The first problem to tackle is the light and cutting edge, and for that, we can utilise the physical principle of laminar flow. This is when all the components in a gas or fluid are moving in the exact same direction without colliding into one another, a little like when you use a shower head. 

This then allows us to use any kind of fluid fuel-oxidiser mix to make a single, high-intensity beam of cutting power. Whilst we may be tempted to use a rocket-grade propellant and fuel, the reality is that something simple like the liquid propane used in BBQs is more than enough. With these ingredients; BBQ fuel, and a laminar flow jet, the task simply becomes one of tuning the fuel mix and valves to get a retractable blade. For the iconic whoosh, it’s a matter of building a circuit with a speaker and accelerometer to make the famed sound of a lightsaber when it’s swung.

Yoda's gorgeous green lightsaber

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