Exploring hypersonic history
by Paul Raveling,
  Publication anticipated in Village Life in El Dorado Hills, January, 2005

History presents not just a record of the past, but a wealth of stories to interpret and learn from. In November I indulged my own focus in aviation and space history with a field trip to the eastern states. Highlights were long talks with Bob White and Neil Armstrong, each a distinguished research pilot who flew the rocket-powered X-15. Filling out the trip were archive searches at the National Air and Space Museum, NASA headquarters, and the Air Force Museum.

X-15 art by Stan Sokes, NASA EC94-42909-1The X-15 research program was one of the "giant leaps" of the twentieth century, acknowledged by the first X-15's residence in NASM's Milestones of Flight Gallery. North American Aviation's three X-15s made 199 research flights from 1959 through 1968, advancing both aviation and space technology. They pushed the world speed record up from Mach 3.2 to Mach 6.7 -- 6.7 times the speed of sound -- and raised the altitude record from 126,200 to 354,200 feet, about 67 miles. They were the first to test aerodynamic heating in winged reentry from space, with parts of the X-15's skin glowing red hot at 1,200 degrees F. Beneficiaries of their research included Apollo moon flights and the Space Shuttle.

Heavily instrumented X-15s collected masses of flight test data at hypersonic speeds, logging more time over Mach 4 than any winged vehicle until the Space Shuttle. They pioneered hypersonic stability and control, human factors, and flight in the vacuum of space. They tested the first 3-axis inertial guidance in a manned craft. X-15s carried experiments to the edge of space; one was an early star tracker, developing technology for celestial navigation in Apollo. 

Bob White is Air Force Major General Robert M. White, Retired.  During X-15 flight envelope expansion he became the first pilot to fly faster than Mach 4, then Mach 5, then Mach 6. He was the first of eight X-15 pilots to qualify for astronaut wings, setting a record of 314,750 feet in 1962. Four decades later that official world record as a winged aircraft still stands.Robert M. White

In General White's own words, "My flights to 217,000 feet and 314,750 feet were very dramatic in revealing the earth's curvature ... at my highest altitude I could turn my head through a 180º arc and wow! - the earth is really round. At my peak altitude I was roughly over the Arizona/California border in the area of Las Vegas ...  Looking to my left I felt I could spit into the Gulf of California.  Looking to my right I felt I could toss a dime into San Francisco Bay."

General White had a long and distinguished career in Air Force aviation. His later career included command of the Air Force Flight Test Center at Edwards Air Force Base and heading program management to develop the F-15 fighter. Most biographic summaries say he was shot down over southern Germany in 1945, but that's only a shadow of the story.

In truth he was finishing low altitude pursuit of a Messerschmitt 109, close on its tail while gunning it down. Debris from the Me-109 flew back and hit his his P-51 Mustang, yielding a flood of oil from his engine that instantly covered the canopy. He quickly jettisoned the canopy and tried to climb, realizing that the engine would soon seize.  He exited with a standard Mustang bailout, diving over the right wing and hurtling just under the horizontal stabilizer. Pulling the rip cord as soon as he was clear, his feet hit tree tops just as the parachute popped open.

Neil ArmstrongNeil Armstrong had a classic adventure in an X-15 flight, producing a research result that changed reentry planning for both the X-15 and the Space Shuttle. In performing a planned pullup maneuver on reentry he skipped off the atmosphere, zooming back into air so thin that it's effectively space. He shot past Edwards AFB at just over 100,000 feet and Mach 3, unable turn back for lack of air to generate aerodynamic force. As the X-15 finally dropped into denser air Armstrong established a 3 G turn but still overshot by 45 miles, overflying Pasadena before heading back toward Rogers Dry Lake. He stretched his glide to the max, dropping no less than 9,000 feet per minute, and barely made it.  A chase pilot reported his clearance from the joshua trees at the edge of the lakebed as "about 100 feet -- on either side".

All twelve X-15 pilots were engineers, and Neil Armstrong is one of those who was an engineer first, a research pilot second. He constantly  contributed to ground-bound engineering as well as to flight test, starting with the X-1B rocket plane in the early 1950s.  A later example was preflight analysis of Apollo's drogue parachute, which would open at supersonic speed after reentry. An engineer's first thoughts are "Won't that produce a chaotic pattern of shock waves impinging on the flexible airfoil? Will it work???" Armstrong's analysis showed it was safe, helping to clear Apollo for flight.

Robert White and Neil Armstrong are among those who made the fifties and sixties a time in air and space history that carried us across new frontiers.  It was a time when we rapidly expanded our scientific knowledge of "what is" and resoundingly pushed our horizons  to engineer "what can be".  This forward-looking spirit can serve us well in reaching for more "giant leaps for mankind".

Send questions and comments on the SierraFoot X-15 web pages to Paul Raveling.
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