CBS NEWS
By Leonard David Space.com
December 6, 2013, 8:00 AM
This NASA Marshall Space Flight Center image shows on-orbit functions for the reusable X-37 space plane.
NASA/MSFC
The U.S. Air Force's mysterious X-37B space plane is nearing a
major milestone — one year of travel in Earth orbit, performing duties
in support of long-term space objectives.
The unmanned
X-37B spacecraft —
flying a mission known as Orbital Test Vehicle 3 (OTV-3) — launched
into space atop an Atlas 5 rocket from Florida’s Cape Canaveral Air
Force Station on Dec. 11, 2012. What payloads the space plane is toting
and the overall mission goals on its confidential cruise are classified.
But it is known that the OTV-3 mission signals a milestone for the X-37B program. [
See photos from Air Force's 3rd mystery flight of the X-37B space plane]
This
same vehicle was flown on the X-37B program's inaugural flight back in
2010. That OTV-1 mission lasted nearly 225 days in orbit, gliding back
to Earth on autopilot over the Pacific Ocean and touching down at
Vandenberg Air Force Base in California.
An OTV-2 mission, which used a different X-37B
space plane,
was lofted in 2011. That vehicle flew for 469 days, more than doubling
its sister ship’s space stay, concluding its mission by also making a
Vandenberg landing.
Altitude changes
A
global network of skywatchers has been keeping an eye on the robotic
space plane's movements during its three flights to date. Some veteran
observers, like skywatcher Kevin Fetter of Brockville, Ontario in
Canada, have even captured
video of the X-37B space plane in the night sky.
"All
three OTV missions maneuvered to change altitude at least once between
launch and landing. Between maneuvers, they made frequent small thruster
firings to counteract the effects of atmospheric drag, to maintain a
nearly constant altitude," said Ted Molczan of Toronto, a leader in the
worldwide community of satellite trackers.
Taking a look at the
military space plane's past flights and the present-day mission, Molczan
told SPACE.com that OTV-1 occupied a half-dozen different orbital
altitudes during its 225-day mission. OTV-2 occupied two different
orbital altitudes during its days aloft, accomplished by a series of
small thruster firings over a seven-week period. [
Photos: Spotting Satellites & Spaceships from Earth]
"
OTV-3,
as of day 343 in flight, has occupied two different orbital altitudes,
accomplished using standard Hohmann transfer maneuvers about 11 weeks
after launch," Molczan said in a Nov. 22 email.
Lifting-body design
The
two known X-37B space planes have been built for the Air Force by
Boeing Government Space Systems, with flights conducted under the
auspices of the Air Force’s Rapid Capabilities Office.
The 11,000-pound (4,990 kilograms) X-37B is one-fourth the size of an orbiter in the now-retired NASA
space shuttle fleet but relies upon the same type of lifting-body design.
The
vehicle is 29 feet (8.8 meters) long and nearly 15 feet (4.5 m) wide
and has a payload bay that measures 7 feet (2.1 meters) long and 4 feet
(1.2 meters) wide. Traveling in low-Earth orbit, the space plane
operates from 110 miles (177 kilometers) to 500 miles (805 km) in
altitude.
Next-generation technology
According
to a Boeing fact sheet, each space plane is built with lightweight
composite structures, rather than traditional aluminum. A new generation
of high-temperature leading-edge tiles for the wings is utilized,
distinct from the space shuttle’s carbon leading-edge segments.
The
X-37B is outfitted with toughened uni-piece fibrous insulation
impregnated silica tiles, which are significantly more durable than the
first-generation tiles used by the space shuttle. Advanced conformal
reusable insulation blankets are used for the first time on the X-37B.
The
Boeing fact sheet also points out that avionics on an X-37B are
designed to automate all de-orbit and landing functions. Additionally,
there are no hydraulics onboard the winged vehicle; flight controls and
brakes use electromechanical actuation.
Air Force mission control
Mission
control for OTV flights are handled by the 3rd Space Experimentation
Squadron at Schriever Air Force Base in Colorado. This unit is billed as
the Air Force Space Command’s premier organization for space-based
demonstrations, pathfinders and experiment testing, gathering
information on objects high above Earth and carrying out other
intelligence-gathering duties.
While details are scant about the
X-37B program,
a little light on the project may be shed during the National Space
Club'’s 57th Annual Robert H. Goddard Memorial Dinner, to be held next
March in Washington, D.C.
Slated to receive the General Bernard
Schriever Award at the event is Major Joshua Chumley, USAF, Commander,
Operating Location Alpha, 3d Space Experimentation Squadron, U.S. Air
Force Space Command.
Chumley is on tap to pick up the prestigious
award "for leading a selectively manned team responsible for operation
of the United States’ first unmanned, autonomous, reusable space plane —
the Orbital Test Vehicle, or X-37B," according to a National Space Club
press release.
Landing location?
Although
there’s no official word how long the OTV-3 mission will go, there has
been some talk that this craft may not land at California’s Vandenberg
Air Force Base.
The Air Force has been evaluating auto-piloting
the vehicle down at the space shuttle landing strip at NASA's Kennedy
Space Center, next door to its Cape Canaveral departure site.
Making
use of former space shuttle infrastructure is viewed as a possible
cost-cutting measure for the program, officials have said.
Leonard
David has been reporting on the space industry for more than five
decades. He is former director of research for the National Commission
on Space and is co-author of Buzz Aldrin's new book "Mission to Mars –
My Vision for Space Exploration" published by National Geographic.
Follow us @Spacedotcom, Facebook or Google+. Originally published on SPACE.com.
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