Boeing's unmanned spaceplane reprieved to perform original role as reusable long-duration test platform
Boeing's X-37 unmanned spaceplane will go into orbit after all. Designed to be released from the payload bay of a Space Shuttle, the winged X-37 was reduced to an atmospheric test programme and flown just once.
Now the US Air Force has announced plans for an X-37B orbital test vehicle (OTV), with the first launch - by Lockheed Martin Atlas V expendable booster - scheduled for 2008.
The X-37 began as a NASA programme to demonstrate reusable spaceplane technology, including autonomous re-entry and runway landing. Boeing's Phantom Works was awarded a cost-sharing contract in 1999 to develop the vehicle and, late that year, the US Air Force joined the project, intending to use the X-37 for in-orbit demonstration of spacecraft technologies.
After the Columbia Shuttle accident in 2003 the X-37 was redesigned for launch by expendable booster, but NASA's priorities changed and late in 2004, the programme was transferred to the US Defense Advanced Research Projects Agency and scaled back to atmospheric drop tests only.
The X-37 approach and landing test vehicle (ALTV) was carried under Scaled Composites' White Knight mothership and dropped only once, in April. It completed an autonomous landing, but then ran off the Mojave, California runway and damaged its nose gear.
"Reusable space vehicle technologies have advanced to the point where the next logical step is to conduct a demonstration with an orbital test vehicle based on theX-37 design," says the USAF.
News that the USAF Rapid Capabilities Office (RCO) intends using the X-37B as a reusable, long-duration test platform for spacecraft technologies revives plans to send the vehicle into low-Earth orbit and returns the programme to its original goals. The orbital vehicle, now in development at Boeing, will be used to test technologies in the space environment.
These will include guidance, navigation and control systems, high-temperature structures and seals, conformal reusable insulation, and lightweight electromechanical flight controls.
Experiments will be carried in the OTV's payload bay, then the 5,000kg (11,000lb) vehicle will be launched aboard an Atlas V and released to operate autonomously. "You could design something to extend itself out of the experiment bay, or have it on a retractable arm, or it could just stay inside the bay," says RCO programme manager Lt Col Kevin Walker.
Orbital experimentation is planned to begin after "a flight or two" to check out the OTV itself, says Walker. These will validate the X-37B's autonomous de-orbit capability and thermal-protection system, which were not part of the ALTV. NASA's X-37 orbital vehicle was never built, but its design is the starting point for the OTV, says the USAF.
Source: Flight International
