X-51 Waverider Makes Historic Hypersonic Flight
An X-51A Waverider flight-test vehicle successfully made the
longest supersonic combustion ramjet-powered hypersonic flight May
26 off the southern California Pacific coast. The more than 200
second burn by the X-51's air breathing scramjet engine accelerated
the vehicle to Mach 5. The previous longest scramjet burn in a
flight test was 12 seconds in a NASA X-43.
Air Force officials called the test, the first of four planned,
an unqualified success. The flight is considered the first use of a
practical hydrocarbon fueled scramjet in flight.
"We ... have accomplished most of our test points on the X-51A's
very first hypersonic mission," said Charlie Brink, a X-51A program
manager with the Air Force Research Laboratory at Wright-Patterson
Air Force Base, Ohio. "We equate this leap in engine technology as
equivalent to the post-World War II jump from propeller-driven
aircraft to jet engines."
The X-51 launched at about 1000 PDT from Edwards AFB, carried
under the left wing of an Air Force Flight Test Center B-52
Stratofortress. Then, flying at 50,000 feet over the Point Mugu
Naval Air Warfare Center Sea Range, it was released. Four seconds
later an Army Tactical Missile solid rocket booster accelerated the
X-51 to about Mach 4.8 mach before it and a connecting interstage
were jettisoned. The launch and separation were normal, Mr.
Four X-51A cruisers have been built for the Air Force and the
(Defense Advanced Research Projects Agency) by industry partners
Pratt & Whitney Rocketdyne and Boeing. Air Force officials
intend to fly the three remaining X-51A flight test vehicles this
fall, Mr. Brink said. Air Force officials currently plan to fly
each on virtually identical flight profiles, building knowledge
from each successive flight.
Hypersonic flight, normally defined as beginning at Mach 5, five
times speed of sound, presents unique technical challenges with
heat and pressure, which make conventional turbine engines
impractical. Program officials said producing thrust with a
scramjet has been compared to lighting a match in a hurricane and
keeping it burning.
"This first flight was the culmination of a six-year effort by a
small, but very talented AFRL, DARPA and industry development
team," Mr. Brink said. "Now we will go back and really scrutinize
our data. No test is perfect, and I'm sure we will find anomalies
that we will need to address before the next flight. But anyone
will tell you that we learn just as much, if not more, when we
encounter a glitch."
Mr. Brink noted while development of the X-51A's engine and the
test program are complex, controlling costs has been a key
objective. The team has incorporated or adapted existing proven
technologies and elected from the outset not to build recovery
systems in the flight test vehicles, in an effort to control costs
and focus funding on the vehicle's fuel-cooled scramjet engine,
which was developed by Pratt & Whitney Rocketdyne.
Mr. Brink said he believes the X-51A program will provide
knowledge required to develop the game changing technologies needed
for future access to space and hypersonic weapon applications.