Very early on in the Cold War, the U.S. Air Force practically mandated a “penetrating escort” jet that could, along with the B-29 and B-50, keep strategic bombers company en route to their targets at the very heart of Soviet territory. But this jet would have to be supersonic, have a combat radius of 900 to 1,500 miles, and have the flexibility to strike ground targets. Enter the Lockheed XF-90, a jet that would achieve legendary status not from its combat prowess, but from the incredible toughness it would demonstrate.
The XF-90 was designed at Lockheed’s Skunk Works, under chief designer Kelly Johnson. First of all, Johnson had looked at a delta-wing configuration; this would have avoided the straight-winged F-80 Shooting Star’s undesirable aerodynamic characteristics but would have paid for this with poor low-speed performance. From there, he went through sixty-five different concepts to swept wings, which delayed the onset of shockwaves at high Mach.
This XF-90 had a needlenose design, with 35-degree swept wings and a vertical tail stabilizer that could move back and forth. It was powered by side-mounted Westinghouse J34 turbojets, with the first afterburners ever used on an Air Force aircraft. This allowed the pilot to inject fuel directly into the jet pipe for added bursts of speed at the cost of fuel efficiency. The jet was armed with six 20-millimeter M39 cannons mounted under the nose; wingtip fuel pods extended its range to a projected 2,300 miles.
Knowing that the era of supersonic flight was new, Johnson’s team over-engineered the XF-90 using high-strength 75T aluminum alloy, making it as tough as a “bridge girder.” This created one of the biggest and heaviest single-seat fighters of its time, weighing nine tons empty. The skin of the XF-90 could hold up to twelve times the force of gravity, evidence of its strength..
Two prototypes were made by Lockheed: the XF-90 number 46-687 and an afterburning J34-WE-15 powerplant XF-90A #46-688. The first XF-90 flew on 3 June 1949, piloted by test pilot Tony Levier. The J34 engines were underpowered, and the jet proved slower than the Air Force’s F-86 Sabre while requiring long takeoff and landing distances. The afterburner-equipped XF-90A flew at a maximum level speed of only 665 miles per hour, earning it the unflattering nickname “the big-breasted turkey.”
The August 1950 fly-off was conducted between the XF-90 and the McDonnell Douglas XF-88 Voodoo. The XF-90 lost the competition, and soon after the outbreak of the Korean War, with its new requirements for tactical air power, the whole long-range escort fighter project would be scrapped by the Air Force. The XF-88 would develop into the F-101 Voodoo, itself seeing extensive action during the Vietnam War.
Though the XF-90 never saw combat, it won some celebrity in the Blackhawks comic book series as the aircraft of choice for the titular squadron of ace pilots. Reality was far less glamorous. In 1952, XF-90 46-687 was dispatched to the NACA testing facility in Cleveland, Ohio, where its tough frame was subjected to stress tests until it was destroyed.
The XF-90A had an even more dismal fate. It was sent to the Frenchman’s Flat test range in Nevada to see how well-parked aircraft could stand up to nuclear blasts. On 15 April 1952, a 1-kiloton Mark 4 nuclear bomb was dropped by a B-50 bomber half a mile from the XF-90A. The jet was cracked but in one piece; it needed 106 hours of repairs. Another test a week later with a 33-kiloton nuke caused even greater damage, especially to the nose. Finally, on 1 May, a 19-kiloton bomb blew up the XF-90, ripping off its tail and landing gear; its wings were warped.
The irradiated hulk was taken to Nevada Area 11 and left until scientist Robert Friedrich spotted it from the air in the late 1980s. In 2001, experts dismantled the jet, cleaned it up, and shipped it to the U.S. Air Force Museum in Dayton, Ohio, where it is still stored in its nuke-blasted state.
While not successful as a design in its own right, experience with the XF-90 helped me gain experience with jets having after-burning engines, ejection seats, and Fowler flaps. Indeed, today, the Air Force’s sixth-generation stealth jet plans are a little different from where the original concept of the XF-90 began, to be a “Penetrating Counter-Air” fighter to escort deep stealthy bombers over enemy airspace.