The X-15′s First Glide

Crossfield stands in front of the X-15. Credit: The Scott Crossfield Foundation online

It was a chilly morning on June 8, 1959 when Scott Crossfield climbed into the cockpit of the X-15 rocket aircraft. By 8:30, he was airborne, and the aircraft  was nestled under the wing of the larger B-52 launch plane. Pilots Captain Charles Bock and Captain Jack Allavie kept a steady conversation with Crossfield about the X-15’s status. The B-52 was scheduled to launch the X-15 that morning at 8:40. More men than just the three in the air hoped nothing would prevent Crossfield making this maiden voyage. 

As the first free flight of the X-15, the mission had a modest flight plan. Crossfield, the prime pilot for the program’s checkout flights, wouldn’t ignite the X-15’s rocket engine so wouldn’t push the aircraft’s speed and altitude limits. Instead, this was a relatively simple gliding flight. Once the B-52 launched the X-15, the smaller aircraft would fall like a slightly aerodynamic stone; its stubby 22.36 foot wingspan provided minimal lift for its 49.5 foot body. Crossfield would have enough control to guide the unlikely glider to a smooth runway landing. North American Aviation engineer Harrison Storms, the company that built the small aircraft, half joked that only a stone falls faster than the X-15.

The X-15 shortly after launch. Credit: NASA

June 8 wasn’t the first time Crossfield tried to put the X-15 through its paces. On January 1, the pilot had sat in the cockpit and ‘flown’ the X-15 while it remained mated to the B-52. It was a useful exercise that taught him about the aircraft’s handling qualities, but it wasn’t as good as a free flight. He’d attempted free flights since, but never got to the point of actually separating from the B-52. Just days earlier he’d been in the X-15 cockpit ready to fly when he saw smoke filling the small cabin. The flight was cancelled before the launch plane even left the ground. It turned out to be an innocuous problem attributed to an overheated ventilation fan motor in the cockpit.

On June 8, everything finally looked good. But just before launch Crossfield reported a failure of the aircraft’s pitch damper. The X-15 had a “self-adaptive” damping system, an automatic gain changer that maintained the pilot’s desired dynamic response characteristics over a wide range of dynamic pressures. In short, it increased the X-15’s smooth handling as it flew through the thin upper atmosphere and back through the thicker air on its way down. Since Crossfield wouldn’t be flying through extreme atmospheric pressures, he elected to proceed with the flight in spite of the malfunction.

The X-15 (foreground) and F-104 chase plane come in for a landing. Credit: NASA

Once the B-52 reached a speed of Mach 0.79 and an altitude of 37,500 feet, it’s pilots launched the X-15. Separation was clean, and Crossfield immediately rolled to the right with a bank angle of about 30 degrees. To slow his speed before landing, he traced out wide arcs over the runway.

But as he began to even out the steep angle of his glide in preparation for landing, he ran into problems. The faulty pitch damper caused the X-15 to begin a series of increasingly wild pitching motions. It’s nose began moving up then down. Crossfield reacted by trying to manually dampen motions, but his pilot instincts made things worse. Every move he made against the aircraft’s oscillations added to their intensity until the pilot-induced oscillations were clearly visible from the ground as Crossfield approached the runway. His skill overpowered the oscillations, and he maintained sufficient control over the X-15 to make a safe, though hard, landing.

Scott Crossfield sits in a thermal-vacuum chamber during tests of a prototype XMC-2 pressure suit. Production versions of this suit were used for thirty-six early X-15 flights. Photo Credit: Boeing

The X-15 ended its first free flight four minutes and 56 seconds after launch at 8:43:36 that morning. It landed traveling 173 miles per hour then rolled out for 3,900 feet while turning very slightly to the right before coming to a stop. The forward landing gear under the aircraft’s nose sustained such significant damage that it was sent back to NAA’s facility in Los Angeles for repairs. The contractor not only fixed the landing gear, but the modified the control system as well. Increasing the control rate response solved the problem.

While the aircraft emerged from the flight a little worse for the wear, Crossfield was unscathed and program on the whole was bolstered by the successful first flight. This was the first of 14 flights for Corssfield who had taken a job as test pilot working with NAA just so he could be the first to fly the X-15.

Suggested Reading

My articles about the X-15 as a space plane, the X-15 as a research aircraft, and the support crews on hand for X-15 flights.

Video of the first glide flight on YouTube.

Robert Godwin. X-15: the NASA mission reports, incorporating files from the USAF: Collector’s Guide Publishing. 2000.

Milton O. Thompson. At the edge of space: the X-15 flight program: Smithsonian Inst Pr. 1992.

Milton O.Thompson. Flying Without Wings: NASA lifting bodies and the birth of the space shuttle. Washington: Smithsonian Institution Press. 1999.

Richard Tregaskis. X-15 Diary: The Story of America’s First Space Ship. Bison Books. 2004.

Dennis R. Jenkins. Hypersonics Before the Shuttle: A Concise History of the X-15 Research Airplane. Monographs in Aerospace History, NASA. 2000.

Comments

  1. Stu Young says

    Amy, I’ve said it before – but I continue to wonder: where do you find some of these photos?! The one of Scott Crossfield in front of the X-15 is one I haven’t seen before – and it’s such high resolution! It’ll make a great reference photo for my X-15 modeling project (which I intend to get around to, someday…).

    -Stu

  2. rickl says

    Those photos looked familiar, so I dug out my old copy of the book “Man In Space”, part of the “Science Service” series of books my parents bought for me when I was a child back in the 1960s.

    There is a similar photo of the X-15 which must have been taken that same day. The angle is different, but the fence in the background is identical. Later in the book, there is a color photo of Scott Crossfield in the test chamber.

    While I never became a scientist or engineer, those books instilled in me a lifelong love of science and technology of all kinds.

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