Key point: The XF-90 was a tough little plane.
In 1945, the U.S. Army Air Force issued a requirement for a “penetrating escort” jet that could accompany comparatively ponderous B-29 and B-50 strategic bombers all the way to targets over the Soviet Union. It wanted that jet to be capable of supersonic speeds, boast a combat radius of 900 to 1,500 miles, and for the sake of versatility, also be capable of hitting ground targets.
The Air Force’s first operational jet, the Lockheed F-80 Shooting Star, was a reliable workhorse but its straight-winged configuration limited its potential at high speeds. Kelly Johnson, chief designer at Lockheed’s innovative Skunk Works facility in California, initially thought to overcome this limitation with a delta-wing configuration, but this would have degraded lift and thus low-speed performance. He iterated through sixty-five different concepts before settling on using swept-wings, which delay the formation of shockwaves at high speeds.
The needle-nose XF-90 retained the basic contours of the F-80, but with a pointed needle-nose, 35-degree swept wings and horizontal tail stabilizer, and a vertical tail stabilizer that could move forward and backward.
The jet’s side-mounted Westinghouse J34 turbojets would eventually include the Air Force’s first afterburners, which allow pilots to inject fuel straight into the jet pipe for bursts of added speed, though at a cost to fuel efficiency. Six 20-millimeter M39 cannons mounted in two rows under the nose would serve for armament, while wingtip fuel pods extended the XF-90’s range to a projected 2,300 miles.
As Chuck Yeager only achieved the first manned supersonic flight on October 14, 1947, Johnson’s team could only hypothesize that supersonic speeds would impose extreme stress on the airframe. This led them to over-compensate by using extremely high-strength 75T aluminum alloy instead of the standard 25T.