I’m very excited about seeing Rogue One: A Star Wars Story, which tells the tale summarised in the original Star Wars’ opening crawl. This is the story of how the rebels stole the plans to the original “Death Star” -a space station the size of a small moon with a weapon powerful enough to destroy a planet.

By Martin Archer, Space Plasma Physicist, Queen Mary University of London

If we could get our hands on those plans, could we build a similar fortress? I decided to try and work out some aspects of how a Death Star might actually work. In Star Wars lore, the 120km (75-mile) diameter space station was made from quadanium steel (a fictional metal alloy) and crewed by 2m Imperial personnel, including officers, Stormtroopers and TIE pilots.

So would it possible in the real world? Let’s not worry about the vast quantities of raw materials required. For example, at current production rates of steel it would take 182 times the current age of the universe to accrue enough. I’m more concerned conceptually with how to power such a colossal battle station and how to generate gravity for everyone on board. It turns out our conventional technologies might not cut it.

The International Space Station requires about 0.75W of power for every m³ of the space station. These are provided by eight solar arrays, 112 feet (34m) long by 39 feet (12m) wide. Even if we had 100% efficient solar panels covering the much larger Death Star, we’d still be a factor of 45 times short of the ISS’s power requirements per unit volume. Not to mention that power would severely diminish if we took the space station further away from the sun.

You might think we could learn lessons from the sci-fi classic 2001 A Space Odyssey in terms of the gravity and just spin the Death Star to create artificial gravity via centrifugal forces. To replicate the gravity on Earth (9.81 metres per second squared or 1 g), the station would only need to revolve once every 3.5 minutes, which doesn’t sound too absurd.

But there was a reason the station was ring-shaped in 2001. The centrifugal force is proportional to the radius of your circular path. As you travel either towards the centre of the station or towards the poles, this radius decreases meaning the artificial gravity would start to vanish. If indeed gravity was created this way, it calls into question the Death Star’s spherical design.

Dyson sphere

Perhaps the clue was in the name the whole time. What if at the heart of the Death Star is an artificial star? Surely that would solve the gravity problem? This makes the station something of a Dyson sphere, the sort of technological megastructure physicist Freeman Dyson imagined advanced civilisations might be able to build to harness all the energy from their stars. However, Dyson spheres of the rigid shell variety usually run into problems from being under immense stresses due to the gravitational forces. Even if the sphere isn’t ripped apart by this, just a small push certainly would be enough to send the structure crashing into its star.

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