The U.S. Air Force says the second planned mission of the X-37B Orbital Test Vehicle (OTV) will “expand the operating envelope” of the autonomous space vehicle, potentially increasing the orbital cross-range and capability of landing in stronger crosswinds.
Richard McKinney, Air Force undersecretary for space programs, says the second test X-37B—OTV-2—is being prepared in Boeing’s California space facilities for transfer “soon” to Cape Canaveral AFS, Fla. From there it will be launched on an Atlas V in the March-April 2011 time period.
Lt. Col. Troy Giese, X-37B program manager from the Air Force Rapid Capabilities Office (Afrco), which manages the X-37B program, says OTV-2’s mission will focus on “expanding the operating envelope of what its capabilities are. This time, we put more restrictions on landing winds and on orbiting cross-range. We picked an orbit that was well within its ability to get back to Vandenberg Air Force Base,” he adds. The next flight may have a more exaggerated orbit to test the cross-range recovery characteristics and may end up with an attempted recovery in more marginal weather.
McKinney and Giese commented on the Air Force plans for OTV-2 following the successful autonomous landing and recovery of OTV-1 at Vandenberg in the early hours of Dec. 3 after a 244-day mission.
But the landing, which was the first successful runway recovery of an autonomous space vehicle since the 1988 demonstration launch and landing of the former Soviet Union’s Buran unmanned space shuttle, was not without incident. McKinney says the vehicle’s left main landing gear tire blew out on touchdown—a mishap not easily spotted in initial photos released by the Air Force. However program officials say the fact the X-37B continued to roll down the runway centerline without deviation following the blowout of the 300-psi. dinner-plate-size tire is a testament to the integrity of its control system.
Shreds of ruptured tire caused some damage to the belly of the vehicle, which also was pitted in several places by unidentified space debris. “Where it came from we don’t know,” McKinney says, adding that initial inspections have revealed damage in “about seven” places to the thermal protection tiles and vehicle body. However, McKinney says evidence of impacts and tire burst does not diminish the overall performance of the vehicle or its test accomplishments over an almost eight-month space mission. “The purpose of this particular mission was the vehicle,” he adds.
Stressing the use of the OTV as a test platform, McKinney downplays the possible role of the X-37B itself as a reusable vehicle for responsive space roles. “It’s a test vehicle. We want to be able to put objects in to space and test them out, and exercise them.” As such, OTV “does not replace the other [responsive space] capabilities such as TacSat, but it gives us another dimension. We have the ability to research technologies, do experiments in space and return them to Earth. That’s a capability that’s been severely limited in the past. We have a very serious and important business in providing national security space capability, and our ability to examine those technologies before deployment is a big sought-after capability.”
OTV-1 primarily was aimed at checking out vehicle systems and design features, with a secondary emphasis on the more advanced sensor technology likely to feature more prominently in follow-up missions. Vehicle technology test targets for OTV-1 included advanced guidance, navigation and control; thermal protection systems; avionics; high-temperature structures and seals; conformal reusable insulation, and lightweight electromechanical flight systems. Giese says the flight also was a successful test of the vehicle’s ability to open its payload doors and deploy a solar array that provided onboard power for the duration of the mission.
On command, the X-37B autonomously folded the array, closed the doors (which contain radiator panels to dissipate heat into space), commenced a reentry burn, and performed a series of S-turns to bleed off energy like the space shuttle during its descent through the atmosphere. The entire flight profile in the “end game” was autonomous, Giese says, adding that, by design, “there was no way to take over the vehicle, although the 30th Space Wing [at Vandenberg] do have a way to terminate the flight.”
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