Ian Allen

Former astronaut Ed Lu thinks the biggest threat to our existence is up in the air. Way up in the air. His nonprofit, the B612 Foundation, wants to set up a defense perimeter around the planet. Not against aliens, but against asteroids—life–eradicating space rocks like the one that killed the Cretaceous dinosaurs. The first step? Completing a space telescope called Sentinel, equipped with optics to search the skies for threatening objects, scheduled for launch in 2018. Funded largely by private donors like Googler Peter Norvig and Reddit CEO Yishan Wong, the setup has a pretty light budget—just a few hundred million dollars to save whole cities from destruction.

What got you so interested in asteroids?

I spent six months aboard the International Space Station. From there, you notice a stark difference between the moon and the Earth: The moon is covered in craters. But Earth has craters too—you just can’t see them, because they’re underneath the oceans. So anybody who knows anything about space and probability knows that this is something you have to solve. Nothing else matters at all if you’re going to get wiped out. Since 2000, there have been eight impacts roughly the size of Hiroshima or larger, and the fact that asteroids hit Earth somewhat randomly means you’re basically on borrowed time. You don’t know when the next one’s gonna happen.

I would have thought NASA was already on top of that.

We—meaning all of humanity—have found about 10,000 of these asteroids, mostly supported by NASA. They’ve got a telescope already up there called Neowise. It was recently reactivated to study the reflectivity of near-Earth asteroids. It’s not optimized to find a great number of them—only about 50 per year for a couple of years. Sentinel will find 200,000 in its first year. And there are about a million of them out there large enough to destroy a major city. So we have a long way to go, and that’s what Sentinel is going to do. We’re trying to protect Earth, not do scientific studies on asteroids. And while it is true that the great majority of those would not be harmful because they explode at high altitude over unpopulated areas, not all of Earth is unpopulated.

How does Sentinel work?

Asteroids are dark—almost black or charcoal-colored. They don’t reflect a lot of light. So Sentinel is going to scan the sky in infrared, and rescan about an hour later, then do that again the next day, and then repeat that every 26 days. That infrared imaging detector, incidentally, which is the heart and soul of this thing, is only about the size of a sheet of paper. By looking at multiple images, Sentinel can measure the velocities of these asteroids down to a millimeter per second, which is amazing. Then you can calculate their trajectories to know if any of them are going to hit us.

And how fast are they going, exactly?

Typically an asteroid is moving at roughly the same speed as Earth. Earth moves at about 65,000 miles per hour. That’s about 1.6 million miles per day, right? So in one month it’ll travel nearly 50 million miles.

And if they are going to hit us, then what?

That’s the easy part. You only need to change an asteroid’s speed by about a millimeter per second to prevent a collision. So we just run into the asteroid with a small spacecraft.

That doesn’t sound so easy.

The difficult part is seeing a business model: When you find something that’s going to hit Earth, how do you monetize that? Do you make people pay for the data? That’s why we’re doing this as a nonprofit. The other challenge is human nature—people bury their heads in the sand. Did New Orleans know that the next major hurricane would destroy that city? Yup. Did they fix the levees? Nope.