He earned his Bachelor of Arts degree in physics from Washington and Jefferson College in 1942, before entering the United States Army Air Forces.

Walker earned the Distinguished Flying Cross once, awarded by General Nathan Twining in July 1944, and the Air Medal with seven oak leaf clusters.

[citation needed] After World War II, Walker separated from the Army Air Forces and joined the National Advisory Committee for Aeronautics (NACA) Aircraft Engine Research Laboratory in Cleveland, Ohio, as an experimental physicist.

Flights 90 and 91 made Walker the first human to make multiple spaceflights according to the FAI definition of greater than 100 km (62 mi).

Neil Armstrong later flew this craft many times in preparation for the spaceflight of Apollo 11 – the first human landing on the Moon – including crashing it once and barely escaping from it with his ejection seat.

[13] At an altitude of about 25,000 ft (7.6 km)[14] Walker's Starfighter was one of five aircraft in a tight group formation for a General Electric publicity photo when his F-104 drifted into contact with the XB-70's right wingtip.

The F-104 flipped over, and, rolling inverted, passed over the top of the XB-70, striking both its vertical stabilizers and its left wing in the process, and exploded, killing Walker.

[N 2] The Valkyrie entered an uncontrollable spin and crashed into the ground north of Barstow, California, killing co-pilot Carl Cross.

Its pilot, Alvin White, one of Walker's colleagues from the Man In Space Soonest program, ejected and was the sole survivor.

The USAF summary report of the accident investigation stated that, given the position of the F-104 relative to the XB-70, the F-104 pilot would not have been able to see the XB-70's wing, except by uncomfortably looking back over his left shoulder.

The report concluded that from that position, without appropriate sight cues, Walker was unable to properly perceive his motion relative to the Valkyrie, leading to his aircraft drifting into contact with the XB-70's wing.

Because the formation flight and photo were unauthorized, the careers of several Air Force colonels ended as a result of this aviation accident.