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X-38
Update: On April 29, 2002, NASA announced the cancellation of the
X-38 program due to budget pressures associated with the international
space station. The X-38 was two years short of completing its flight test
phase.
Engineers at NASA's Dryden Flight Research Center,
Edwards, Calif., and the Johnson Space Center, (JSC) Houston, Texas, were
flight-testing the X-38, a prototype spacecraft that could have become the
first new human spacecraft built in the past two decades that travels to and
from orbit. The vehicle was being developed at a fraction of the cost of
past human space vehicles. The goal was to take advantage of available
equipment, and already developed technology for as much as 80 percent of the
spacecraft's design.
Using available technology and off-the-shelf equipment
significantly reduces cost. The original estimates to build a capsule-type
crew return vehicle (CRV) were more than $2 billion in total development
cost. According to NASA project officials, the X-38 concept and four
operational vehicles will to be built for approximately one quarter of the
original $2 billion cost.
Current Status
Full-scale, unpiloted "captive carry" flight tests began
at Dryden in July 1997 in which the vehicle remained attached to the NASA
B-52 aircraft. Unpiloted free-flight drop tests from the B-52 began in March
1998.
Project Goals
The immediate goal of the innovative X-38 project, was to
develop the technology for a prototype emergency CRV, or lifeboat, for the
ISS. The project also intended to develop a crew return vehicle design that
could be modified for other uses, such as a possible joint U.S. and
international human spacecraft that could be launched on the French Ariane 5
booster.
In the early years of the International Space Station, a
Russian Soyuz spacecraft was be attached to the station as a CRV. But, as
the size of the crew aboard the station increases, a return vehicle that can
accommodate up to six passengers would be needed. The X-38 design used a
lifting body concept originally developed by the Air Force's X-24A project
in the mid-1970's. After the deorbit engine module is jettisoned, the X-38
would glide from orbit unpowered like the Space Shuttle and then use a
steerable, parafoil parachute, a technology recently developed by the Army,
for its final descent to landing. Its landing gear would consist of skids
rather than wheels.
Technology
Off-the-shelf technology doesn't mean it is old
technology. Many of the technologies used in the X-38 had never before been
applied to a human spacecraft.
The X-38 flight computer is commercial equipment that is
currently used in aircraft, and the flight software operating system is a
commercial system already in use in many aerospace applications. The video
equipment on the atmospheric vehicles is existing equipment, some of which
has already flown on the Space Shuttle for other NASA experiments. The
electromechanical actuators that are used on the X-38 come from a previous
joint NASA, Air Force, and Navy research and development project.
An existing special coating developed by NASA was to be
used on the X-38 thermal tiles to make them more durable than the tiles used
on the Space Shuttle. The X-38's primary navigational equipment, the
Inertial Navigation System/Global Positioning System, is a unit already in
use on Navy fighters.
Future Plans
Although the design could one day be modified for other
uses such as a crew transport vehicle, the X-38 would strictly be used as a
CRV. It was baselined with only enough life support supplies to last about
nine hours flying free of the space station in orbit. The spacecraft's
landing would be totally automated, although the crew would be able to
switch to backup systems, control the orientation in orbit, pick a deorbit
site, and steer the parafoil, if necessary. The X-38 CRV had a nitrogen
gas-fueled attitude control system and used a bank of batteries for power.
The spacecraft was to be 28.5 feet long, 14.5 feet wide, and weigh about
16,000 pounds.
X-38 three view
An, in-house development study of the X-38 concept began
at JSC in early 1995. In the summer of 1995, early flight tests were
conducted of the parafoil concept by dropping platforms with a parafoil from
an aircraft at the Army's Yuma Proving Ground, Yuma, Arizona. In early 1996
a contract was awarded to Scaled Composites, Inc., of Mojave, Calif. to
build three full-scale atmospheric test airframes. The first vehicle
airframe was delivered to JSC in September 1996, where it was outfitted with
avionics, computer systems, and other hardware in preparation for the flight
tests at Dryden. A second vehicle was delivered to JSC in December 1996.
Team Approach
Some 200 people were working on the project at Johnson,
Dryden, and the Langley Research Center in Hampton, Va. This was the first
time a prototype vehicle has been built-up in-house at JSC, rather than by a
contractor; an approach that has many advantages. By building up the
vehicles in-house, engineers had a better understanding of the problems
contractors experience when they build vehicles for NASA. JSC's X-38 team
will have a detailed set of requirements for the contractor to use to
construct the CRVs for the ISS. This type of hands-on work was done by the
National Advisory Committee on Aeronautics (NACA), NASA's predecessor,
before the space age began. Dryden conducted model flights in 1995. The 1/6
scale-model of the CRV spacecraft using a parafoil parachute system was
flown 13 times. The results showed that the vehicle had good flight control
characteristics and also demonstrated good slideout characteristics
Resources
-
Project's Cancellation Irks NASA, by Mark
Carreau, Houston Chronicle, June 9, 2002.
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