The jet engine was still only a few years old when Chuck Yeager broke the sound barrier. Just a few years after that, NACA and the US Air Force were looking at what design was necessary for sustained supersonic flight. One such attempt was with the X-3 “Stiletto” beginning in 1952.
Built by Douglas Aircraft, the X-3 was part of a program where NACA and the USAF were trying to build and get test data from an aircraft and powerplant that could fly at sustained speeds over Mach 1. The goal for the X-3 was sustained flight at Mach 2. It never met that goal.
In fact, the aerodynamics and two underpowered Westinghouse J34 engines with afterburners could not even sustain Mach 1 in level flight. Despite this embarrassing failure, the aircraft was still flown over 50 times for research. It was the first aircraft to make significant use of titanium in its structure, it explored the use of low aspect ratio wings, and its very high takeoff and landing speeds it forced innovation in tire technology.
The X-3, despite not living up to its original goal, became important for future supersonic aircraft. Lockheed engineers studied the reams of data from the X-3 when they were designing the F-104 Starfighter.
Even more important, during one of its last flights the test pilot, Joseph Walker, was to fly at Mach 0.95 then roll to the left. When he did, the aircraft also pitched up and yawed. This phenomenon of transonic flight, called roll coupling, presented itself later in the flight. While in a dive, Walker accelerated to Mach 1.15 and rolled to the left again. Again, the aircraft pitched down and yawed. After fighting to regain control, Walker called it a day and landed the aircraft on the dry lake bed at Dryden.
The data collected on roll coupling was crucial to aerodynamics and aircraft controls advancement. The North American F-100 was experiencing a similar issue at the same time and NACA was able to conduct special research on this problem and find a solution to it.
The X-3 is pretty cool. Not just because it looks deadly, but because it shows that even when goals aren’t reached something can be learned. You see, failure is an option. Because it’s through failure that we learn.
[Image Credit: NASA]