X-43A/X-43B/X-43C/X-43D Hyper-X
![](x_planes/X-43.jpg) Specifications Company- MicroCraft and
The Boeing Company Type- Hypersonic screamjet.
Goals- Scramjet
demonstration vehicle.
Primary Testing Facility
Research- Over the Pacific Ocean Dimensions-
Span- 5 ft, 0 in; Length- 12 ft, 0 in Max Speed- Mach 7-10 Range- N/A Service Ceiling-
N/A Power Plant- N/A Thrust- N/A Weights-
Empty: 2,200 lbs Payload- None Flights-
3 Number of Prototypes Built- 3 (3
X-43A) Project Tenure- 2000-Present Project Status- Ongoing Information
The X-43 is an unmanned experimental hypersonic
aircraft design with multiple planned scale variations meant to test
different aspects of highly supersonic flight. It is part of NASA's
Hyper-X program.
A winged booster rocket with the X-43 itself at the
tip, called a "stack", is launched from a carrier plane. After the
booster rocket (a modified first stage of the Pegasus rocket) brings the
stack to the target speed and altitude, it is discarded, and the X-43
flies free using its own engine, a scramjet.
The initial version, the X-43A, was designed to
operate at speeds greater than Mach 7, about 5,400 mph (8,050 km/h) at
altitudes of 100,000 feet (30,000 m) or more. The X-43A is a single-use
vehicle and is designed to crash into the ocean without recovery. Three
of them have been built: the first was destroyed; the other two have
successfully flown, with the scramjet operating for approximately 10
seconds, followed by a 10 minute glide and intended crash.
The first flight in June 2001 failed when the stack
spun out of control about 11 seconds after the drop from the B-52
carrier plane. It was destroyed by the range safety officer, and it
crashed into the Pacific Ocean. NASA attributed the crash to several
inaccuracies in data modeling for this test, which led to an inadequate
control system for the particular Pegasus used.
The X-43A's successful second flight made it the
fastest free flying air-breathing aircraft in the world, though it was
preceded by an Australian HyShot as the first operating scramjet engine
flight. While still attached to its launching missile, the HyShot flew
in descending powered flight in 2002.
The third flight of a Boeing X-43A set a new speed
record of 12 144 km/h (7,546 mph), or Mach 9.8, on November 16, 2004. It
was boosted by a modified Pegasus rocket which was launched from a
Boeing B-52 at 13,157 meters (43,166 feet). After a free flight where
the scramjet operated for about ten seconds, the craft made a planned
crash into the Pacific ocean off the coast of southern California.
The most recent success in the X-plane series of
aircraft, the X-43 is part of NASA's Hyper-X program, involving the
American space agency and contractors such as Boeing, MicroCraft Inc,
Orbital Sciences Corporation and General Applied Science Laboratory (GASL).
MicroCraft Inc., now known as ATK GASL built the X-43A and its engine.
The Hyper-X Phase I is a NASA Aeronautics and Space
Technology Enterprise program being conducted jointly by the Langley
Research Center, Hampton, Virginia, and the Dryden Flight Research
Center, Edwards, California. Langley is the lead center and is
responsible for hypersonic technology development. Dryden is responsible
for flight research.
Phase I is a seven-year, approximately $230
million, program to flight-validate scramjet propulsion, hypersonic
aerodynamics and design methods.
The X-43A aircraft was a small unpiloted test
vehicle measuring just over 12 feet (3.7 m) in length. The vehicle was a
lifting body design, where the body of the aircraft provides a
significant amount of lift for flight, rather than relying on wings. The
aircraft weighed roughly 3,000 pounds or about 1,300 kilograms. The
X-43A was designed to be fully controllable in high-speed flight, even
when gliding without propulsion. However, the aircraft was not designed
to land and be recovered. Test vehicles crashed into the Pacific Ocean
when the test was over.
Traveling at Mach speeds produces a lot of heat due
to the compression shock waves involved in supersonic drag. At high Mach
speeds, heat can become so intense that metal portions of the airframe
melt. The X-43A compensated for this by cycling water behind the leading
edges of the aircraft, cooling those surfaces. In tests, the water
circulation was activated at about Mach 3. In the future, fuel may be
cycled through such areas instead, much like what is currently done in
many liquid-fuel rocket nozzles and high speed planes such as the SR-71.
The craft was created to develop and test an exotic
type of engine called a supersonic-combustion ramjet, or "scramjet," an
engine variation where external combustion takes place within air that
is flowing at supersonic speeds. The X-43A's developers designed the
aircraft's airframe to positively affect propulsion, just as it affects
aerodynamics: in this design, the forebody is a part of the intake
airflow, while the aft section functions as a nozzle.
The engine of the X-43A was primarily fueled with
hydrogen. In the successful test, about two pounds (or roughly one
kilogram) of the fuel was used. However, because hydrogen poses certain
difficulties in storage, transport, and even production, further X-43
versions were planned to use more commonly available hydrocarbon fuels
instead. Unlike rockets, scramjet-powered vehicles do not carry oxygen
onboard for fueling the engine. Removing the need to carry oxygen
significantly reduces the vehicle's size and weight. In the future, such
lighter vehicles could bring heavier payloads into space or carry
payloads of the same weight much more efficiently.
Scramjets only operate at hypersonic speeds in the
range of Mach 6 or higher, so rockets or other jet engines are required
to initially boost scramjet-powered aircraft to this base velocity. In
the case of the X-43A, the aircraft was accelerated to high speed with a
Pegasus rocket launched from a converted B-52 Stratofortress bomber. The
combined X-43A/Pegasus vehicle was referred to as the "stack" by the
program's team members.
The engines in the X-43A test vehicles were
specifically designed for a certain speed range, only able to compress
and ignite the fuel-air mixture when the incoming airflow is moving as
expected. The first two X-43A aircraft were intended for flight at
approximately Mach 7, while the third flew at approximately Mach 10.
The first X-43A test on June 2, 2001 failed because
the Pegasus booster lost control about 13 seconds after it was released
from the B-52 carrier. The rocket experienced a control oscillation as
it went transonic, eventually leading to the failure of the rocket's
starboard elevon. This caused the rocket to deviate significantly from
the planned course, so the stack was destroyed by onboard explosives as
a safety precaution. An investigation into the incident stated that
imprecise information about the capabilities of the rocket as well as
its flight environment contributed to the accident, though no single
factor could ultimately be blamed for the failure.
In the second test, the Pegasus fired successfully
and released the test vehicle at an altitude of about 95,000 feet. After
separation, the engine's air intake was opened, the engine ignited, and
the aircraft then accelerated away from the rocket. Fuel was flowing to
the engine for eleven seconds, a time in which the aircraft traveled
more than 15 miles (24 km). After burnout, controllers were still able
to maneuver the vehicle and manipulate the flight controls for several
minutes as the aircraft was slowed down by wind resistance and took a
long dive into the Pacific. Peak speed was at burnout of the Pegasus but
the scramjet engine did accelerate the vehicle in climbing flight, after
a small drop in speed following separation.
NASA flew a third version of the X-43A on November
16, 2004, achieving a speed of approximately Mach 10 and further testing
the ability of the vehicle to withstand the heat loads involved.
Other X-43 vehicles were designed, but as of
November 2004 appear to have been suspended. They were expected to have
the same basic body design as the X-43A, though the aircraft were
expected to be moderately to significantly larger in size.
X-43B
The next letter down the list, the X-43B, was
expected to be a full-size vehicle, incorporating a turbine-based
combined cycle (TBCC) engine or a rocket-based combined cycle (RBCC)
ISTAR engine. Jet turbines or rockets would initially propel the vehicle
to supersonic speed. A ramjet might take over starting at Mach 2.5, with
the engine converting to a scramjet configuration at approximately Mach
5.
X-43C
The X-43C would have been somewhat larger than the
X-43A and was expected to test the viability of hydrocarbon fuel,
possibly with the HyTech engine. While most scramjet designs have used
hydrogen for fuel, HyTech runs with conventional kerosene-type
hydrocarbon fuels, which are more practical for support of operational
vehicles. The building of a full-scale engine was planned which would
use its own fuel for cooling. The engine cooling system would have acted
as a chemical reactor by breaking long-chain hydrocarbons into
short-chain hydrocarbons for a rapid burn.
The X-43C was indefinitely suspended in March 2004.
The linked story reports the project's indefinite suspension and the
appearance of Rear Admiral (RADM) Craig Steidle before a House Space and
Aeronautics subcommittee hearing on March 18, 2004.
According to a special feature article by Daryl
Stephenson in the August 2005 online issue of Boeing Frontiers the X-43C
appears to be funded through 2005. "Thanks to a funding request of $25
million for NASA sponsored by U.S. Rep. Jim Talent (R-Mo.), work on the
X-43C program will continue through 2005."
X-43D
The X-43D would have been almost identical to the
X-43A, but expanding the speed envelope to approximately Mach 15.
After the X-43 tests in 2004, NASA Dryden engineers
said that they expected all of their efforts to cumulate into a Two
Stage To Orbit Manned Vehicle in about 20 years. The scientists
expressed much doubt that there would ever be a Single Stage to Orbit
manned vehicle like the National Aerospace Plane (NASP), also known as
the "Orient Express", that would takeoff from an ordinary airport
runway.
** Information provided by Wikipedia ** |