Everything We Know About X-37B, the Air Force's Mysterious Space Drone

The US Air Force's mini robotic space plane, called the X-37B, is reportedly coming home today after spending 22 months orbiting Earth. The question today, as it was when it launched is, what the heck was it doing up there?

If you haven't heard of it, the X-37B looks exactly like NASA's retired space shuttles, except it's about one-quarter the size, and it's unmanned. Its mission, like its budget, is completely classified, which has led to plenty of conspiracy theories and speculation about the plane's possible use not simply as a spy plane but as a space weapon or something of that sort.

The only information the Air Force has ever volunteered about the Boeing-made vehicle's mission is that it's testing "reusable spacecraft technologies for America's future in space and operating experiments which can be returned to, and examined, on Earth."

So, umm, we're not learning all that much there.

Image: USAF

More than two years ago, I attended a stuffy, Washington, DC breakfast with General William Shelton, who served as head of Air Force Space Command from January 2011 until August of this year.

Shelton was in charge of the project, and the vast majority of questions (including my own) were aimed at learning something—anything—about the X-37B, which at the time had been in orbit for only a few months (it would land later in 2012, and then took off again on a third mission).

"We've had a successful mission and we're very happy with its performance," Shelton said at the time. "That vehicle is performing a great service."

He described the plane as "spectacular," and "game-changing," but refused to elaborate further. Even its budget is completely classified.

"I think there's a good reason to keep [the budget] as quiet as we possibly can," Shelton told me. "If you reveal budgets, you sometimes reveal the capabilities, the amount of technology inserted into a program. It's a good, strategic national security decision."

The Air Force ain't telling us much, but Shelton was pretty damn excited about the thing, while remaining as vague as humanly possible.

But it's hard to keep a space project completely secret, because, well, you can see what it's doing with a good telescope. Some who have been following its orbit and believe that it's trying to spy on China's Tiangong-1 space station, an idea that has been vehemently disputed by observers, such as longtime space journalist James Oberg.

"The American plane's orbit is at a steep angle with respect to that of the Chinese space station," Oberg wrote. "When the two vehicles pass, they do so at speeds of up to 8000 meters per second, making it practically impossible for one to gather intelligence on the other."

Oberg went on to note that X-37B was originally launched before Tiangong-1.

Others have noted that the drone's orbit takes it over North Korea, Iran, Pakistan, Afghanistan, and China.

If the plane is outfitted with even the latest known existing spy satellite camera technology, it could be capable of watching those places with detailed accuracy, and through smoke, haze, fog, and perhaps more.

The Air Force, for its part, is standing by its original explanation that simple spaceflight technologies are being tested.

"Technologies being tested in the program include advanced guidance, navigation and control, thermal protection systems, avionics, high temperature structures and seals, conformal reusable insulation, lightweight electromechanical flight systems, and autonomous orbital flight, re-entry and landing," it said in a statement announcing that it'd be landing.

As useless as that statement is ("avionics" certainly is a bit broad, no?), it's probably the best we'll hear on the record for quite some time.

In any case, we almost certainly haven't seen the last of the X-37B. While Boeing and the Air Force have been silent on plans for their plane, last week NASA confirmed long-known plans for the X-37B program to use the Space Shuttle program's old hangars at Kennedy Space Center in Florida, and that those hangars will be used for "processing spacecraft." The hangers' painted blue doors already tout it as "Home of the X-37B" to passing tour buses.