The U.S. Air Force’s X-37B space plane concluded its third mission Friday, streaking through the atmosphere over the Pacific Ocean and gliding to an automated landing on a runway at Vandenberg Air Force Base, Calif., after spending a record 675 days in orbit.
Touchdown on Vandenberg’s Runway 12 occurred at 1624 GMT (12:24 p.m. EDT; 9:24 a.m. PDT) Friday, according to an Air Force press release.
“The 30th Space Wing and our mission partners, Air Force Rapid Capabilities Office, Boeing, and our base support contractors, have put countless hours of hard work into preparing for this landing and today we were able to see the culmination of that dedication,” said Col. Keith Balts, 30th Space Wing commander, in an Air Force statement.
The unpiloted reusable space plane — called the Orbital Test Vehicle by the Air Force — conducted on-orbit experiments during its mission, officials said.
The Boeing-built X-37B launched on the Orbital Test Vehicle 3, or OTV 3, mission from Cape Canaveral on Dec. 11, 2012, aboard a United Launch Alliance Atlas 5 rocket.
The flight shattered the X-37B’s officially stated orbital lifetime of 270 days, but Air Force officials offered no explanation for the mission’s long duration.
Details on its activities in space have been kept secret by the Air Force, but some analysts speculate the winged spaceship could test next-generation surveillance, communications and intelligence-gathering instruments, deploy small satellites, or demonstrate new materials for use in future military programs.
“The X-37B program performs risk reduction, experimentation and concept of operations development for reusable space vehicle technologies,” the Air Force said in a press release.
“I’m extremely proud of our team for coming together to execute this third safe and successful landing,” Balts said. “Everyone from our on console space operators to our airfield managers and civil engineers take pride in this unique mission and exemplify excellence during its execution.”
With the successful landing of the X-37B Friday, the program’s three missions have accumulated 1,368 days in orbit.
“The landing of OTV-3 marks a hallmark event for the program,” said the X-37B program manager, who was not named by the Air Force. “The mission is our longest to date and we’re pleased with the incremental progress we’ve seen in our testing of the reusable space plane. The dedication and hard work by the entire team has made us extremely proud.”
The Air Force’s two earlier X-37B missions landed in June 2012 and December 2010 after 224 days and 469 days in orbit.
A fourth X-37B mission is scheduled for launch from Cape Canaveral in 2015, the Air Force said.
The military space plane can stay in orbit much longer than NASA’s space shuttle, which was limited to missions lasting a few weeks because it generated electricity with fuel cells consuming finite oxygen and hydrogen. The X-37B is powered by solar energy.
The space plane that landed Friday also flew on the program’s first space mission in 2010. Air Force and Boeing engineers refurbished the spacecraft and launched it again two years after it landed.
Resembling a miniature space shuttle, the X-37B space plane takes off on top of a conventional launch vehicle, deploys solar panels to generate electricity in orbit, then returns to Earth like a glider for an automated landing on a runway.
After closing its payload bay doors and retracting its solar array, the space plane fired its main thruster in a ground-commanded de-orbit burn to drop out of orbit and fall back into the atmosphere Friday.
It is designed to weather blazing temperatures with a shield of thermal blankets and ceramic tiles. The lifting body space plane approached the California coastline on autopilot and touched down on Vandenberg’s runway at nearly 300 mph.
With a wingspan of nearly 15 feet and a height of 9.5 feet, the X-37B is about one-fourth the size of a space shuttle orbiter. Its cargo hold is about the size of a pickup truck bed.
According to a Boeing fact sheet, the X-37B weighs about 11,000 pounds fully fueled for launch. It is made of composite structures, and its heat shield is made reusable insulation blankets and silica thermal protection tiles tougher than the tiles flown on the space shuttle.
Fitted with wings lined with heat-resistant ceramic tiles at the leading edge, the X-37B can withstand fiery-hot temperatures of re-entry. An on-board GPS navigation system is programmed to guide the automated spaceship toward the runway, and a three-piece landing gear is supposed to lower from the craft’s belly just before touchdown.
The space plane’s cost is kept under wraps by the military, which runs the X-37B program from the Air Force Rapid Capabilities Office managed by the service’s top leaders in the Pentagon.
Without an explanation of the X-37B’s mission, national security analysts, conspiracy theorists and space enthusiasts have speculated on the space plane’s activities in orbit.
“The space plane program inspires speculation in part because its purpose, its budget and most of its details are kept secret. And in part because while the technology is intriguing, few missions are especially suited to a long-duration, elegantly-returning spacecraft with low on-orbit maneuverability and small payload — most space missions can be done cheaper or better using existing technology,” wrote Laura Grego, a senior scientist at the Union of Concerned Scientists.
The X-37B program had its roots at NASA, which started the space plane project in 1999 before handing it over to DARPA, the Pentagon’s research and development arm, in 2004. The Air Force took charge of the X-37B in 2006 and launched its first space mission in 2010.
“Its history of being kicked between NASA, DARPA and the Air Force, and then getting funded in the classified realm inspires skepticism whether the program would survive if it had to compete for funding in the light of day,” Grego wrote.
Whatever the program’s cost, it’s not clear how the Air Force justifies it, Grego said.
“One mission that seems to be frequently suggested is a maneuvering sensor to look at ‘hot spots’ on Earth,” Grego wrote. “The space plane may be able to do that. But the problem is that the ability to maneuver and the ability to return to earth work at cross purposes Returning to earth requires massive landing gear and heat shielding, which is like putting rocks in your backpack when you’re trying to be agile. It’s not well-suited — this mission could be done much better and cheaper using other platforms.
“And there is nothing stealthy about this craft. It is easily observed from the ground and because of all the extra mass must be launched on a large rocket (Atlas 5),” Grego wrote. “So while the space plane may be carrying advanced sensors to orbit so that they can be tested and returned, roving or stealthy sensors are not a good missions for it.”
The X-37B was the first U.S.-built spacecraft to return to Earth and land on a runway completely on autopilot.
“The X-37B program does seem to be exploring a bit of parameter space that is uncharted — long-ish duration orbiting then returning to Earth, and is developing cutting edge materials and technologies for return and autonomous landing,” Grego wrote. “These are interesting technologies, but returning to Earth using valet parking … isn’t a mission, it’s a technology. Why classified, though?”
“Which is really the interesting point. It’s a well-resourced classified military program, so will generate plenty of raised eyebrows and interest in similar technologies in other countries. Is it worth it? We have yet to hear anything approaching a convincing argument.”
But the military plans to keep the program going.
The Air Force could move the X-37B’s home base to NASA’s Kennedy Space Center in Florida as soon as next year.
Boeing is overseeing modifications to two decommissioned space shuttle hangers at KSC, aiming to complete the work by December, NASA said in a statement last week.
An Air Force spokesperson said in July that the X-37B’s fourth mission — scheduled for liftoff in 2015 — could return to Earth at the space center’s Shuttle Landing Facility and tow over to one of the hangers for refurbishment for another launch from nearby Cape Canaveral Air Force Station.