The U.S. Air Force plans to launch its X-37B prototype space plane for the third time from Cape Canaveral. Its mission is still a mystery.
The plane could carry out a range of missions, but in each case there are better, more efficient, and more cost-effective ways of accomplishing them, according to the Union of Concerned Scientists (UCS). And because it is an Air Force project and its details are classified, the plane has generated confusion, speculation and, in some cases, concern about its actual purpose.
In April 2010, the Air Force launched the first of two prototype space planes, which stayed in orbit for seven months. In March 2011, it launched the second prototype, which remained in orbit for more than a year. This launch will mark the first prototype’s return to space.
What distinguishes the space plane from other spacecraft is its ability to return from orbit and land on a runway. This capability requires extra structure, such as wings, landing gear, and heat shielding to withstand the rigors of re-entry, making it significantly heavier than comparable spacecraft that are not designed to return to Earth.
Because of this extra mass, the space plane is more difficult to maneuver in space and significantly more expensive to launch. According to a new UCS briefing paper, other spacecraft can carry payloads into orbit, maneuver in space, rendezvous with satellites, release multiple payloads, and return to Earth for tens of millions of dollars less than the space plane.
“The ability to return to Earth carries a high price,” says Laura Grego, a senior scientist with UCS’s Global Security Program. “Most space missions don’t require bringing a spacecraft back to Earth, and the space plane makes no sense for them. And if returning to Earth does make sense, spacecraft usually use parachutes, not wings and landing gear. Compared with those, the space plane will have a harder time carrying payloads into orbit, maneuvering in space, rendezvousing with satellites, and releasing multiple payloads.”
The Air Force has stated that the X-37B will allow it to carry out experiments in space over a long period of time and return them to Earth. Thus far, however, the Air Force has not provided any cost or capability analyses that compare the space plane with simpler spacecraft that return by parachuting to Earth rather than landing on a runway.
Given the Air Force’s reticence in discussing the rationale behind the space plane and the fact that it is a military program, other countries may infer that the X-37B has a specialized military purpose. But, according to Grego, the space plane does not make sense as a space weapon or a vehicle for deploying space weapons.