space shuttle.

Fifty years ago in 1959, test pilot Scott Crossfield threw the switch to ignite the twin XLR-11 engines of his North American Aviation X-15 rocket plane and begin the storied test program's first powered flight.

It was a real kick in the pants.

"The drop from the B-52 carrier aircraft was pretty abrupt, and then when you lit that rocket a second or two later you definitely felt it,” said Joe Engle, another X-15 test pilot and member of the same exclusive fraternity of flyboys that included Crossfield and the eventual first man on the moon, Neil Armstrong. All took the X-15 to speeds and altitudes that extended the frontiers of flight.

The X-15 was a research scientist's dream. The experimental, rocket-boosted aircraft flew 199 flights with 12 different pilots at the controls from 1959 through 1968. It captured vital data on the effects of hypersonic flight on man and machine that proved invaluable to the nation's aeronautics researchers, including NASA and developers of the space shuttle.

"That first powered flight was a real milestone in a program that we still benefit from today," said Engle. Engle knows what he’s talking about. The Kansas native flew the X-15 for the U.S. Air Force 16 times from 1963 to 1965 and went on to command two missions of NASA's space shuttle.

Still an active pilot, the retired major general fondly recalled what it was like to fly the X-15 and how lessons learned then made possible the space shuttle program years later.

"It was a very busy airplane to fly, but it also was a beautiful airplane to fly; a very, very good solid flying vehicle. Particularly when you were subsonic, in the landing pattern— even at the lower supersonic speeds," Engle said.

Joe Engle standing in front of the X-15.Joe Engle during the X-15 program, which ran from 1959 through 1968. Three times Engle flew an X-15 higher than 50 miles, officially qualifying him for Air Force astronaut wings and providing him a brief moment for sightseeing at the edge of space.

"I didn't really have time to soak up the view in the X-15 like I did later when I flew the space shuttle," Engle said.