The B-29 mothership shuddered, and pilot Neil Armstrong, flying the airplane from the co-pilot's seat, glimpsed a bullet-shaped propeller hub shoot past the cockpit. He looked over and saw that the number four propeller had disintegrated.

Armstrong, along with pilot Stan Butchart, reacted coolly, testing the bomber's controls. Butchart's were gone, but Armstrong still had some flight control linkage, so together they prepared the aircraft for an emergency landing. They had been trying unsuccessfully for some time to feather the number four propeller. Seconds before the disintegration, they had jettisoned the D-558-II Skyrocket research aircraft with pilot Jack McKay aboard to land early, due to a stuck valve on the Skyrocket, as well as the large workload the propeller problem presented. McKay landed the Skyrocket safely on the dry lakebed below.

This hair-raising moment in 1956 over California's Mojave Desert, and others experienced later in space, footnote the illustrious career of Neil Armstrong, the first man to walk on the moon.

Before joining NASA's astronaut corps, Armstrong served as a research pilot at the NASA High Speed Flight Station, now NASA's Dryden Flight Research Center, located on Edwards Air Force Base in California, from 1955-1962.

The first airplane Armstrong flew at NASA Dryden was a World War II-vintage P-51 Mustang fighter. He learned the ropes of airborne data collection in this aircraft, performing many flights to hone his techniques. Early on, flying the station's modified B-29 mothership aircraft, he launched more than 100 X-plane missions.

Armstrong's primary responsibility at NASA Dryden was as an engineer. Program development, devising simulations, and looking at the problems of flight while trying to figure out solutions took a great deal of time.

"It was a wonderful time period and it was very satisfying work," Armstrong said during an interview with Stephen Ambrose and Douglas Brinkley for the NASA Johnson Space Center's oral history program in 2001.

He remembered the planning for hypersonic flight, faster than five times the speed of sound, leading up to the X-15 program.

"In those days space flight was not generally regarded as a realistic objective, and it was a bit pie-in-the-sky. So although we were working toward that end, it was not something that we acknowledged much publicly," Armstrong said.

Armstrong flew seven flights in the famed X-15, including the first flight of the third X-15, before continuing the journey that led him to the moon.

Leaving NASA Dryden and the flight research community to join the space program was a trade-off.

"It wasn't an easy decision," Armstrong reflected. "I was flying the X-15 and I had the understanding or belief that if I continued, I would be the chief pilot of that project. I was also working on the Dyna-Soar, and that was still a paper airplane, but was a possibility."

"I always felt that the risks that we had in the space side of the program were probably less than we had back in flying at Edwards or the general flight test community," said Armstrong. "The reason is that when we were out exploring the frontiers, we were out at the edges of the flight envelope all the time, testing limits. We had less technical insurance, less minds looking, less backup programs, less other analysis going on."

That most famous small step Armstrong made on the moon 35 years ago on July 20, 1969 followed the pattern of his flying boots on the tarmac at Dryden years earlier, where the abilities and temperament that suited him for space exploration were validated time and again.

Continuing to be a voice supporting America's space program, Armstrong sees value in NASA's new Vision for Space Exploration.

"Our president has introduced a new initiative with renewed emphasis on exploration of our solar system and expansion of the human frontiers. This proposal has substantial merit and promise," Armstrong says.