U.S. Air Force to Test X-37B Orbital Test Vehicle
The X-37B is shown above after landing at 1:16 a.m. Pacific time on December 3, 2010, concluding its more than 220-day experimental test mission. It was launched from Cape Canaveral Air Force Station, Fla., on April 22. Photo: Boeing
"The X-37B is an important step in the effort to make space access more routine, affordable, and responsive," said David Hamilton Jr., the Air Force Rapid Capabilities office director. "The technologies and concepts of employment that are proven by the Orbital Test Vehicle will be folded into development programs that will provide capabilities for our warfighters in the future."
The OTV will demonstrate a number of advanced technologies; some have already been tested on modern spacecraft but have not been used on reusable vehicles. These include thermal protection systems, utilizing advanced ceramic tiles made of silica, expected to better isolate the vehicle from heat developed through reentry, these tiles are also expected to better withstand ablation and not absorb moisture, enhancing the vehicle's ability to launch under weather conditions that would have restricted current Shuttle operations. The OTV also uses advanced power sources based on solar array powered lithium-ion batteries, replacing the hydrogen-oxygen fuel cells used on the Space Shuttle. Other experiments to be performed on board involve the new avionics systems, guidance, navigation and control, systems, high temperature structures and seals.
A vehicle like the X-47B is designed to carry out extended space missions of up to 270 days (the spacecraft landed on December 3, 2010 50 days short of that target), providing a flexible platform offering the air force rapid access to space, deploying multiple small satellites into orbit in quick succession. According to Payton, the Air Force hopes for turnaround time similar to the SR-71 Blackbird – several days or few weeks, rather than months required for refurbishing the Space Shuttle for space missions. Eventually, the Air Force plans to operate a fleet of reusable spacecraft - Boeing is already producing the next X-47B, to be delivered next year.
Although the X-37B represents a new generation of spacecraft, it is based on a design dating back to the mid- 1990s, at the time when NASA explored several concepts reusable space vehicles but hasn't flown any of them to space. Among these programs were the X-33, X-34, and X-37 vehicles. All have flown in the atmosphere in captive and free flight experiments but were not launched into orbit. The OTV is the first vehicle since NASA's shuttle orbiter that has the ability to return experiments to Earth for further inspection and analysis.
NASA's original X-37 program began in l999 and ran until September 2004 when NASA transferred the program to DARPA. NASA envisioned building two vehicles, an Approach and Landing Test Vehicle, or ALTV, and an Orbital Vehicle. The ALTV validated flight dynamics and extended the flight envelope beyond the low speed/low altitude tests conducted by NASA from 1998 through 2001 on the X-40A, a sub-scale version of the X-37 developed by Air Force Research Labs. DARPA completed the ALTV portion of the X-37 program in September 2006 by successfully executing a series of captive carry and free flight tests. NASA's X-37 Orbital Vehicle was never built: but its design was the starting point for the Air Force's X-37B Orbital Test Vehicle program.
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The X-37B landed at Vandenberg AFB on December 3, 2010, concluding its more than 220-day experimental test mission. Photo: Boeing