When the engines of a 19-story Atlas V ignite in April at Cape Canaveral Air Force Station in Florida, the liftoff will look like any other for the workhorse launch vehicle. After about 4 minutes, the engines will cut off and the rocket;s first stage will fall away, freeing the second stage to boost the upper section of the rocket into low Earth orbit.
Away from prying eyes, the mission will cease to be ordinary. A few seconds after the second stage fires, the fairing, a protective shroud that surrounds the cargo at the rocket’s tip, will split in half, revealing the classified payload: a 29-foot-long delta-wing spacecraft called the X-37B Orbital Test Vehicle. It might look like a miniature version of the space shuttle, but this spacecraft is unmanned, and instead of NASA, the U.S. Air Force is operating it. The moment the X-37B emerges from the shroud will mark the fulfillment of a dream the Department of Defense has been pursuing for nearly 50 years: the orbital flight of a military vehicle that combines an airplane’s agility with a spacecraft’s capacity to travel in orbit at 5 miles per second.
At the end of its maiden trip, which could last days or even weeks, the X-37B will glide to Earth under robotic control without the benefit of engines. Instead, it will rely on flight-control surfaces in the tail to steer it through a fiery re-entry, during which the nose and leading edges of the wings must resist 3000-degree-Fahrenheit temperatures. The flight will end in secrecy with a 230-mph touchdown on an isolated runway at an Air Force base in California, most likely Vandenberg. If all goes well, the X-37B will be the first unmanned space plane to complete an orbital mission.
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.
Full story: Behind the Air Force’s and NASA’s X-37B Space Plane – Popularmechanics.com
