A Russian Air Force MiG-31K jet carries the
high-precision hypersonic missile Kh-47M2 Kinzhal during the Victory Day
military parade. (Pavel Golovkin/AP)
WASHINGTON — In 1959, the U.S. Air
Force and Navy partnered with NASA to fly a piloted hypersonic test aircraft,
the X-15, for the first time.
During that flight, the high-speed
vehicle designed to travel at speeds of at least Mach 5 was dropped from under
the wing of a B-52 bomber flying over the Mojave Desert in Southern California.
Pilot Scott Crossfield carried the aircraft to an altitude of 52,341 feet and
reached a peak speed of Mach 2.11.
The flight kicked off a robust testing
effort, and over the next nine years, three X-15 aircraft flew 199 times. The
program eventually surpassed performance targets and achieved what is still the
nation’s the fastest piloted hypersonic flight at Mach 6.72, or 4,520 miles per
hour. Though it ended in 1968, discoveries from the program continue to inform
the government’s hypersonic vehicle research.
In a 1964 report detailing the
program’s accomplishments, NASA researcher Wendell Stillwell wrote: “As long as
Earth’s atmosphere exists, wherever men fly that fast, they will be traveling
in a region whose secrets the X-15 was first to probe.”
More than a half century later, the
X-15 remains the Defense Department’s most rigorous hypersonic testing endeavor
— a testament to the program’s success, but also a result of periods of
restrained investment in high-speed vehicle research. Whereas in the 1960s the
X-15 flew an average of one airborne test every 18 days, today the department
only supports about a dozen hypersonic flight tests in a good year.
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