More about the Air Force's mysterious X-37B space plane.
Though based in many ways on the shuttle-the only operational orbital space plane in the world-the X-37B showcases plenty of innovation. The shuttle uses hydraulic lines to power the control surfaces on its wings and tail, but the X-37B takes advantage of small, powerful electromechanical actuators instead, eliminating the weight of fluid and hoses. In lieu of the ceramic tiles used on the shuttle, the X-37B's leading edges and nose cap are made of an easily shaped composite material that NASA developed when the space agency ran the experimental craft's development, before the military took charge of it in 2004.
The stubby 15-foot wingspan also echoes the shuttle's design, but unlike the larger craft, which has one tall vertical stabilizer, the X-37B has a V-tail with two ruddervators, a combination of a rudder and an elevator. David Hamilton, the director of the Air Force Rapid Capabilities Office, explains that the shorter V-tails are easier to package in a fairing, something that's not a concern for the shuttle. Those V-tails also help guide the X-37B through its 40-degree, nose-high re-entry, while a speed brake along the upper centerline helps it slow down as it prepares to land. Since the X-37B is unmanned, it does not need hardware to maintain a pressurized compartment for a crew and does not have to carry supplies for an extended manned mission.
The X-37B's simplicity and small size are part of what makes it appealing to the military. "There was always this issue with the space shuttle that you were sending up this enormous truck no matter what you were launching into space," says Mark Lewis, the former chief scientist for the Air Force. "There are times you want the Mack truck and times you want the Volkswagen Beetle. Unfortunately, with the shuttle, you were forced to fly the Mack truck."
The key to cheaper, more accessible space travel is more frequent space travel. This is a Good Thing.