LOS ANGELES (AP) — An unmanned Air Force space plane steered itself to a landing early Saturday at a California military base, capping a 15-month clandestine mission.
The spacecraft, which was launched from Cape Canaveral Air Force Station
in Florida in March 2011, conducted in-orbit experiments during the
mission, officials said. It was the second such autonomous landing at
the Vandenberg Air Force Base, 130 miles northwest of Los Angeles. In 2010, an identical unmanned spacecraft returned to Earth after seven months and 91 million miles in orbit.
The
latest homecoming was set in motion when the stubby-winged robotic
X-37B fired its engine to slip out of orbit, then pierced through the
atmosphere and glided down the runway like an airplane.
"With the retirement of the Space Shuttle fleet, the X-37B OTV program brings a singular capability to space technology development," said Lt. Col. Tom McIntyre, the X-37B's program manager. "The return capability allows the Air Force
to test new technologies without the same risk commitment faced by
other programs. We're proud of the entire team's successful efforts to
bring this mission to an outstanding conclusion."
With the second
X-37B on the ground, the Air Force planned to launch the first one again
in the fall. An exact date has not been set.
The twin X-37B
vehicles are part of a military program testing robotically controlled
reusable spacecraft technologies. Though the Air Force has emphasized
the goal is to test the space plane itself, there's a classified payload on board — a detail that has led to much speculation about the mission's ultimate purpose.
Some
amateur trackers think the craft carried an experimental spy satellite
sensor judging by its low orbit and inclination, suggesting
reconnaissance or intelligence gathering rather than communications.
Harvard
astrophysicist Jonathan McDowell, who runs Jonathan's Space Report,
which tracks the world's space launches and satellites, said it's
possible it was testing some form of new imaging.
The latest X-37B
was boosted into orbit atop an Atlas 5 rocket. It was designed to stay
aloft for nine months, but the Air Force wanted to test its endurance.
After determining the space plane was performing well, the military
decided in December to extend the mission.
Little has been said
publicly about the second X-37B flight and operations. At a budget
hearing before the Senate Armed Services subcommittee in March, William
Shelton, head of the Air Force Space Command, made a passing mention.
That
the second X-37B has stayed longer in space than the first shows "the
flexibility of this unique system," he told lawmakers.
Defense analysts are divided over its usefulness.
Joan
Johnson-Freese, professor of national security affairs at the Naval War
College, said such a craft could give the U.S. "eyes" over conflict
regions faster than a satellite.
"Having a vehicle with a broad range of capabilities that can get into space quickly is a very good thing," she said.
Yousaf
Butt, a nuclear physicist and scientific consultant for the Federation
of American Scientists, thinks the capabilities of the X-37B could be
done more cheaply with a disposable spacecraft.
"I believe one of the reasons that the mission is still around is institutional inertia," he said.
The
arc of the X-37 program spans back to 1999 and has changed hands
several times. Originally a NASA project, the space agency in 2004
transferred it to the Pentagon's research and development arm, DARPA,
and then to the secretive Air Force Rapid Capabilities Office. Hundreds
of millions of dollars have been poured into development, but the
current total spent remains a secret.
Built by Boeing Government
Space Systems, a unit of the company's satellite manufacturing area, the
11,000-pound space plane stands 9 1/2 feet tall and is just over 29
feet long, with a wingspan of less than 15 feet. It possesses two angled
tail fins rather than a single vertical stabilizer. Once in orbit, it
has solar panels that unfurl to charge batteries for electrical power.
McDowell
of the Jonathan's Space Report sees a downside. He noted it'll be tough
for the Air Force to send up such planes on short notice if it has to
rely on the Atlas V rocket, which requires lengthy preparations.
"The
requirement to go on Atlas V is a problem; they may need to look at a
new launch vehicle that would be ready to go more quickly," he said.
___
Online:
X-37B fact sheet: http://www.af.mil/information/factsheets/factsheet.asp?fsID=16639
Vandenberg AFB: http://www.vandenberg.af.mil
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