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The U.S. Air Force’s Secret Spaceplane Touches Down After Two Years in Orbit

11 May 2017


The X-37B under service on the runway.The X-37B under service on the runway.Last weekend the U.S. Air Force’s experimental X-37B spaceplane landed at the Shuttle Landing Facility at Kennedy Space Center in Merritt Island, Fla. The event culminated nearly two years of flight time for the experimental unmanned aircraft, as the X-37B was boosted into orbit on May 20, 2015 to conduct research on — well, nobody really knows for sure.

The actual mission objectives of the X-37B are strictly classified, and the Air Force has offered little insight other than to confirm that this two-year-long flight was not a trial of an anticipated space-based weapons platform. The official stance, per the Air Force, is that the X-37B is meant to demonstrate potential reusable space technologies for the Air Force, including avionics, flight, navigation, propulsion, thermal and reentry systems.

The X-37 originally started out as a NASA program in 1999, who hoped to be able to launch the X-37 from the cargo bay of the original Space Shuttles. The intent was for the X-37 to service orbiting satellites. Since the X-37 started life as a well-publicized NASA program, the Air Force talks openly about the existence of the spaceplane itself, even if they don’t address its missions.

What raises eyebrows about the X-37B program is the extensive flight times of the spaceplane across four separate missions.

  • OTV-1 (April 2010 – December 2010): 224 days, 9 hours
  • OTV-2 (March 2011 – June 2012): 468 days, 14 hours
  • OTV-3 (December 2010 – October 2014); 674 days, 22 hours
  • OTV-4 (May 2015 – May 2017): 717 days, 20 hours

The Air Force ordered two X-37s from Boeing, who also designed the X-37’s predecessor, the X-40. Between the two X-37B aircraft, a total of 2,086 days — or more than 5 years and 8 months — have been spent in low Earth orbit. Originally, Boeing specified that the X-37 would have an operational orbital time of just 270 days.


The curtains of secrecy that surround the X-37 were drawn when the Defense Advanced Research Projects Agency (DARPA) assumed the project from NASA in 2004, after the space agency’s priorities changed. The Air Force, who were investors in the original NASA project, announced their own spinoff in 2006, dubbed the X-37B. DARPA’s X-37 program has quieted down, while the Air Force’s continues to soar.

The classified nature of the program obviously fuels a lot of military, aerospace and political speculation. With a small cargo bay that measures just 28 square feet, and a wingspan under 15 feet, it’s unlikely that current X-37s are outfitted with space-based weapons. Arguments that the X-37 is used to spy on Russian and Chinese military assets and satellites are also canon.

But the truth is that the X-37B probably doesn’t have much or anything to hide. Over time, certain details have leaked about the project. At least one X-37B is outfitted with EmDrive, a theoretical type of thruster that could power craft on long voyages through space with little propellant. The most recently-flown X-37B was powered by Hall-effect thrusters and carried 100 material samples for NASA to test their spaceworthiness.

Perhaps more details will emerge when OTV-5 launches via Atlas V rocket sometime later this year. Until then, at least, the X-37 will remain a mystery.



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