# Here's How We Could Build A Death Star, According To NASA

The Death Star can only work as a long-term investment. It is the ultimate weapon after all. LucasArts/Disney.

For all you boys and girls who dream of one day ruling the galaxy with a tremendous weapon of mass destruction, NASA has some suggestions for you. The trick is to mine asteroids and use the material to construct the Death Star directly in space.

In a video on Wired, Brian Muirhead, chief engineer at NASA’s Jet Propulsion Laboratory, illustrates how the Asteroid Redirect Mission will look at the feasibility of asteroid mining, and although the mission doesn’t exactly show you how to build a Death Star, it will do something nobody has done before. In 2023, a probe will capture a boulder and carry it into lunar orbit, where a group of astronauts will later visit to mine some of the asteroid material.

But is Muirhead right about using asteroids? Could we start building a mega structure around Earth in 2016? Let's take a quick look at the calculations involved.

According to Wookieepedia, the first Death Star has a radius of 60 kilometers (37 miles), which corresponds to a volume of about 904,000 cubic kilometers (217,000 cubic miles). Finding the mass of such an object is quite difficult, as we don’t exactly know the internal structure, the building materials used, etc.

To simplify this problem, we imagined that the Death Star would be built similarly to an aircraft carrier, so we used the USS Ranger, which has a density of 210 kilograms (460 pounds) per cubic meter. This gives us a mass of 190 trillion tonnes (187 trillion US tons).

Now, a medium-small asteroid is on paper the perfect candidate: It is about the right mass and it is rich in iron and carbon (to make steel), as well as other material that can be used in the construction. But is it cheaper mining the material on Earth and sending it to space, or to directly mine asteroids?

Sending stuff into space costs about \$20,000 (£13,000) per kilogram, so assembling the Death Star would cost us \$40,000 billion billion dollars (we're not converting that to £). That's about a billion times more expensive than all the Earth’s economies combined.

The boulder that the Asteroid Redirect Mission will capture is about 450,000 kilograms (500 tons) and the mission will cost \$2.6 billions (£1.7 billion). This is the cost of retrieval, so let’s assume that the mining cost is equivalent. If the asteroid is completely mined, the material would cost \$10,400 (£6,900) per kilogram. Of course, it's unlikely to have 100 percent of any particular metal, so the prices are likely to be a bit skewed. On paper though, it's possibly comparable.

But don’t wave your lightsabers in celebration just yet. There are many unknown variables when it comes to mining asteroids, which could easily increase the price of materials. On Earth, only one in 5,000 to 10,000 prospected mines goes into production, and the chances of mining an asteroid might be just as dire. But hey, when it comes to asteroids, never tell us the odds.

[H/T: Wired]