High Flight: Really, Really High Flight

Q: How high do you have to fly to be considered an astronaut?

Hint – you have to fly into space. So, where does “space” begin?

A. According to the Federation Aeronautique Internationale (FAI), space begins at the Karman Line, which is 100 kilometers or roughly 62 miles above sea level.  At this height the air is too thin to give a vehicle sufficient aerodynamic lift to maintain altitude. In order to stay aloft at that level a vehicle must be traveling at orbital speed.

The barrier is named for Hungarian-American astrophysicist Theodore von Karman (1881-1963), who made the calculations that establish the limits of aerodynamic atmospheric lift.

Von Karman, called “Father of Supersonic Flight,” left Hungary at the end of World War I and returned to Aachen, Germany to head the Aeronautical Institute. He designed and built the first wind tunnels at Aachen. In 1926, he built the first ones in California.  He was offered the post of director of the Aeronautical Laboratory at Caltech in 1930. The rise of the Nazis in Germany troubled him, so he accepted the offer and became a U.S. citizen in 1936.  In 1941, he co-founded Aerojet General to develop rocket engines for the U.S. military, and he was a principal mover of the creation of Caltech's Jet Propulsion Laboratory (JPL). In 1945, he co-developed America's first high-altitude sounding rocket, the WAC Corporal.

The FAI states that if you’ve gone beyond the Karman Barrier, you’ve made it to space and you are an astronaut.

But here’s the rest of the story. The U.S. Air Force has always maintained that space begins 12 miles lower, at 50 miles above sea level.  That made for long-delayed recognition, as astronauts, of a number of brave test pilots of the X-15.

My contemporaries will doubtless remember the exploits of the X-15, an experimental rocket-powered aircraft/spaceplane that set speed and altitude records in the early 1960s. The X-15 reached the edge of outer space and returned with valuable data used in aircraft and spacecraft design. As of 2012, it still holds the official world record for the fastest speed ever reached by a manned rocket-powered aircraft.

During the X-15 program, 13 different flights by eight pilots, five military and three civilian, met the USAF spaceflight criteria by exceeding the altitude of 50 miles (80 km).  But of all the X-15 missions, only two flights (by the same pilot) exceeded 100 kilometers (62.1 mi, 328,084 ft.) in altitude and qualified as space flights per the FAI definition.

All of the pilots qualified as astronauts by military standards, and the Air Force pilots received USAF astronaut wings.  But NASA, apparently worried about ruffling the FAI's feathers, did not accord similar recognition to the civilian pilots. The agency hemmed and hawed about it for almost 40 years.

Finally, in 2005, the three civilian pilots - Bill Dana, John McKay and Joseph Walker, were awarded NASA astronaut wings - 35 years after the last X-15 flight. McKay’s and Walker’s wings were, unfortunately, awarded posthumously.

Congratulations, at long last, to those three gentlemen. And remember, as our old television favorite Major Mudd would say, “I’ll Be Blasting You!”