To get a second opinion, I called up Rhett Allain – a physics professor at Southeastern Louisiana University who's written extensively about Death Stars. He's done the sums on how many people you'd need to crew one, and also how it would be resupplied. He's even analysed the explosions of both Death Stars in the Star Wars movies.
He had a better idea than lead for protecting the inhabitants of the Death Star from radiation: water. "You're going to use the water anyway," he said. "Bring it up and then use that as shielding." Water, it transpires, is one of the most effective radiation shields of all – as long as you can keep it in place. With a space station large enough to have its own gravity, that might not be a problem.
That's construction materials and water supply solved, and food would be easy enough to supply with existing hydroponics technology. The next concern is power. In the canonical Star Wars universe, the Death Star is powered by a "hypermatter reactor" with an output equivalent to several stars. We don't have that technology, so let's look at what we do have.
Solar isn't an option, because while the shiny black/blue colour scheme of solar panels would look suitably Imperial, spheres have pretty small surface areas. As Allain explains: "As you get really, really big, your surface area to volume ratio is crazy and you don't have enough energy on the surface to power the whole thing." Plus, we're planning to cover the whole thing with water anyway.
Instead he proposes nuclear power. "Fusion or fission, probably fusion would be best. If you could get a fusion reactor in there, that would be good." But that brings its own problems, says Nergaard, most of which revolve around the fact that putting nuclear material into spacecraft is currently illegal under international law.
"We're not allowed to transport radioactive materials into space," he explains. "There are waivers – When the early Mars missions took place, and Voyager, nobody really cared about it so much. But now… I think the last one that went up with nuclear power like that was Cassini, and I don't know if the Americans have launched anything since then with nuclear power. The Europeans certainly haven't."
I idly wonder if asteroid mining could be a solution to that problem – and ask Nergaard if that's feasible. "Well, I'm not an astrogeologist or anything like that. But I've never heard that being discussed – getting plutonium out of asteroids," he says. "It's a good idea!"
