The golden age of (fill in item of your choice) is thirteen.
I first read that phrase in reference to science fiction, but it works for quite an array of things. Certainly the music of our youth is the music we will always prefer, although that may come to us a couple of years after thirteen. It certainly works for automobiles and aircraft.
For me that golden age revolves around the F-104 and the X-15.
The entire focus of Edwards AFB, including most of the X-craft, was to fly higher and faster. The higher part caused problems with loss of control as the atmosphere thinned. The faster part brought about heating problems from atmospheric friction. Both lines of research culminated in the X-15.
The X-15 was first contracted in 1954. Early in its development, a follow-up aircraft to be called X-15B was considered. It was to be launched atop a Navaho missile in order to reach into space. NASA dropped the idea in favor of the Mercury program. The Air Force followed up with the proposed X-20, but that too was cancelled after Mercury became successful. Actual flight into orbit by a winged craft would not occur until the first Space Shuttle launch.
The first X-15 flight took place in 1959 and it was still flying nine years later, less than a year before the first moon landing. Like the earlier X-planes, the X-15 was dropped from a larger plane, in this case a converted B-52 bomber. Rather like a two stage rocket, this piggybacking allowed the X-15 a head start. The first 8.5 miles of altitude and 500 mph of speed came out the the B-52’s fuel tank, leaving the X-15’s fuel supply intact for the final push.
During that near decade, there were almost 200 flights. Thirteen of those flights went above 50 miles. The maximum speed reached in level flight was 4,520 mph.
The Air Force awards astronaut wings for flights above 50 miles – international rules do not agree. Two of those thirteen flights went above 100 kilometers. The Federation Aeronautique Internationale counts 100 kilometers as the edge of space, making Joseph Walker officially the thirteenth man in space. (Also the fourteenth.) One of those who gained Air Force astronauts wings was Joe Engle who later flew the Space Shuttle. Neil Armstrong flew the X-15 seven times, but never above fifty miles. He had to settle for a consolation prize on July 20, 1969 when he landed on the moon.
To successfully fly at such altitudes requires a series of small rocket motors strategically placed around the spacecraft to control attitude when the rudder, elevator, and ailerons have nothing to work against.
On high speed flights by the rebuilt X-15A-2, an ablative coating was sprayed onto the surface of the aircraft to protect it from overheating due to atmospheric friction, an issue that the SR-71 and the Space Shuttle would also have to face.
For my generation, the X-15 was the ultimate, and it looked the part. It’s pilots flew to the edge of space; they were not blown there in a capsule on top of a converted ICBM. Mercury and Gemini were wonderful. I followed them religiously. But the X-20, proposed descendant of the X-15, riding on top of a Titan missile would have done it with more class. And it would have landed under the pilot’s control, not on the end of a parachute in the middle of the ocean.
Scott Crossfield, the X-15’s designer and first pilot said it was one of the few aircraft that caused grown men to cry upon its retirement.