BBC Future
Code Red

X-37B: Secrets of the US military spaceplane

About the author

Sharon is a 2012/13 fellow at the Woodrow Wilson International Center for Scholars in Washington DC, where she is working on a history of the Pentagon's Defense Advanced Research Projects Agency. Her writing on military science and technology has appeared in Nature, Discover, Slate, Wired, the Washington Post Magazine, and the Financial Times, among other publications. She is the co-author of A Nuclear Family Vacation: Travels in the World of Atomic Weaponry (Bloomsbury, 2008) and the author of Imaginary Weapons: A Journey Through the Pentagon's Scientific Underworld (Nations Books, 2006).

  • Classified data
    The X-37B Orbital Test Vehicle is a US Air Force unmanned, space plane whose purpose is shrouded by secrecy. (Copyright: US Air Force)
  • Rumour mill
    Since its first launch on 22 April 2010 speculation has been rife about its mission, with suggestions ranging from an anti-satellite weapon to a spy plane. (Copyright: Boeing)
  • Flight test
    The craft was originally developed by Nasa as the X-40 experimental craft. It was transferred to the military in 2004, when it became a classified project. (Copyright: Nasa)
  • Shuttle legacy
    From the front, it is easy to see that the X-37B also shares some common features with the space shuttle, including its thermal tiles. (Copyright Boeing)
  • Little brother
    It also has a similar aerodynamic shape and a cargo hold that can be used to take payloads into space, as well as return them to Earth. (Copyright Boeing)
  • Auto pilot
    However, the craft is just one-fourth of the size of the Shuttle and is designed to be able to de-orbit and land automatically. (Copyright: US Air Force)
  • Hands Free
    When the first X-37B touched down on 3 December 2010, it became the first US unmanned vehicle to return from space and land safely on its own. (Copyright Boeing)
  • Boost up
    The planes are launched in the nose cone of the huge Atlas 5 rocket, although it was originally designed to be launched from the cargo bay of the Shuttle. (Copyright Boeing)
  • Cruising altitude
    It is designed to operate in low-earth orbit, 180-800km (110 to 500 miles) above the Earth at a speed of around 28,000km/h (17,500mph).
  • Holding pattern
    Although the Air Force originally stated it was designed for missions up to 270 days, its most recent flight ended in June 2012 after 469 days. (Copyright: US Air Force)

HIDE CAPTION

As the US Air Force prepares for the third launch of its mysterious X-37B vehicle, BBC Future looks at what is known about the classified project.

In the early morning of 16 June, 2012, a top secret spaceplane made a picture perfect landing at the Vandenberg Air Force Base in California. To those unfamiliar with the vehicle, it might have looked roughly similar to the US space shuttle, the manned spacecraft that shuttled astronauts into space for three decades.

But this spaceplane, called the X-37B Orbital Test Vehicle, is very different. While it looks like a plane, is launched on a rocket, has a cargo bay and uses some of the same technology as the shuttle, such as thermal shielding to protect it during reentry, it is smaller and unmanned. It is designed to stay in orbit for months on end and can automatically land back on Earth. Perhaps more crucially, the Boeing-designed plane is operated by the US Air Force and its mission is a closely held secret, prompting a slew of speculation about its true purpose.

Since the first X-37B was launched in 2010, amateur satellite spotters have carefully followed the robotic spacecraft’s orbit, while those unconnected with the program have speculated that the plane could be anything from an anti-satellite weapon to so-called “on demand reconnaissance,” shorthand for a spy satellite that can be placed over any country in the world. Compounding the mystery was the launch of a second vehicle in 2011, which stayed in orbit for 469 days, long exceeding the Air Force’s stated maximum requirement of 270 days for the spaceplane.

Now, a third launch is slated for 11 December, according to an Air Force spokesperson, once again ramping up the rumour mill. So, what do we actually know about the plane?

Tactical response

Early reports focused on the X-37B’s seeming resemblance, at least in size and weight, to the X-20 Dynasoar (short for Dynamic Soarer), a 1950s-era hypersonic vehicle that was envisioned for a variety of military missions, including bombing and sabotaging enemy satellites. However, experts familiar with the X-37B programme emphasized that its technology is actually closer to the recently retired space shuttle (a fact reinforced by Boeings’ proposal for a crewed version of the vehicle known as the X-37C). The Air Force blandly described the role of the X-37B in a factsheet given to media as a "reliable, reusable, unmanned space test platform”.

The Air Force also says the mini-shuttle has two objectives: testing “reusable spacecraft technologies” and conducting “experiments which can be returned to, and examined, on Earth”. Again, this is similar to the stated aims of the space shuttle. But many forget that earlier craft also had a secret military role. Although ostensibly a civilian program, it conducted a series of missions from 1982-1992 on behalf of the National Reconnaissance Office, carrying a series of classified spy satellites.

Similarly, most outside experts now agree that it’s likely the robotic space plane is being used for some sort of secret reconnaissance. “I think the guess that makes most sense is quick-response tactical imaging, meaning hours to a couple of days from request to delivery,” says Allen Thomson, a former CIA analyst.

Thomson says it is also possible that it could have a more mundane but useful task, such as “maintaining up-to-date general purpose mapping imagery.” However, if that is the case, Thomson says that it could be a waste of money. “I think that the commercial satellites could and should do that cheaper and better than X-37B,” he says. It is a view backed by parts of the scientific community.

Indeed, the X-37B launches comes in the middle of a larger debate about the role of government-operated spy satellites, which have proven enormously costly but can provide some of the most advanced imagery, versus commercial satellite imagery. The US intelligence community recently slashed its budget for commercial imagery, indicating that it was going back to greater reliance on its own classified satellites.

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