Boeing X-37: US Air Force Launches Unmanned Space Plane

A secretive United States Air Force space plane is on a fourth trip into orbit.

As with the previous flights, the Air Force revealed few details about what the unmanned X-37B spacecraft, which resembles a smaller version of NASA’s retired space shuttles, will be doing.

“The test mission furthers the development of the concept of operations for reusable space vehicles, and fine-tunes technical parameters for an affordable, reusable space vehicle,” said Capt. Christopher M. Hoyler, a spokesman for the Air Force.

Boeing has built two X-37B spacecraft for the Air Force. The first launched in April 2010, setting off speculation over the vessel’s purposes. Some suggested that the craft had something to do with space weapons, which the Pentagon denied. It landed in December that year. The second orbiter was sent up from March 2011 to June 2012. The first craft made a second flight, launching in December 2012 and returning 674 days later, in October 2014.

The Air Force was not saying which of the two was packed inside an Atlas 5 rocket on the launchpad at Cape Canaveral, Fla.

“We are excited about our fourth X-37B mission,” Randy Walden, the director of the Air Force Rapid Capabilities Office, said in a statement released last month. “With the demonstrated success of the first three missions, we’re able to shift our focus from initial checkouts of the vehicle to testing of experimental payloads.”

The rocket lifted off Wednesday morning.

One of the experiments the Air Force has talked about is an improved version of an electric thruster. Unlike conventional thrusters employing chemical reactions, electric thrusters are more efficient, accelerating charged ions through electric fields.

Electric thrusters are common on commercial satellites, but the Air Force needs more powerful propulsion. Aerojet Rocketdyne has built thrusters for three military satellites that run at 5 kilowatts, or about four times the power of those on commercial satellites. The thruster on the X-37B is a modified version, intended to improve performance, although it still generates less than a tenth of a pound of thrust. “But it does it very, very efficiently from a fuel standpoint,” said Fred C. Wilson, director of business development at Aerojet Rocketdyne. “It’s a higher-power, higher-performance device.”

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Sasha Perkins

Administrative Assistant and Journalist at the Pluto Daily since 2012.