
At the onset of the Cold War era, America was confronted with a formidable issue: how could its bombers not only get inside enemy lines deep enough but also remain intact under the fast-growing threats of speedy fighters, long-range missiles, and nuclear war? A possible solution that came up was ‘penetration fighter’ – a single jet that could escort bombers, wipe out enemy fighters, and land back at base safely.

Lockheed brought this challenge home with the XF-90, designed at the famous Skunk Works by Kelly Johnson and Willis Hawkins. The XF-90 was a spectacular idea that drew its lineaments from the P-80 Shooting Star.

It was fitted with 35-degree swept wings, Fowler flaps, leading-edge slats, and a distinct afterburner and tip tank integration. Just the tail surfaces of the plane could move at several angles as the rest of the aircraft showed the developers’ innovative approach.

However, with all the amazing engineering that was put into it, the device was weighed down by its own airframe made from 75ST aluminum, which was not only stronger but significantly heavier than the usual alloys. As a result, the XF-90 was extremely rugged, capable of absorbing the most severe impacts, such as the explosions of nuclear bombs, but at the same time, it was squeezing the energy out of its two Westinghouse J34 turbojets to the maximum.

According to the calculations, the aircraft could speed up to 665 mph, fly as far as 2300 miles, and ascend to 39000 feet. Nevertheless, the jet found it very hard to live up to the Air Force’s expectations in real-life scenarios. The flight tests revealed that it was only when the aircraft was in a dive that it could go beyond the speed of sound.

For even the most everyday sort of takeoff, rocket-assisted boosters were necessary. In comparison to rivals like the McDonnell XF-88 and North American YF-93, the XF-90 seemed lethargic, clunky, and lacking power. The Air Force, after some time, decided to go with the XF-88, which meant not only the penetration fighter’s enthusiasm but also its financing would vanish pretty fast.

The XF-90, however, did not accept being the weakest link in the chain and instead became the toughest among all jets. One of the prototypes experienced the most brutal stress test at the National Advisory Committee for Aeronautics, while another was used for nuclear bomb tests at the Nevada test location.

The outcomes were beyond expectations. Minor fractures were the only damage done by a one-kiloton explosion, the crash of the nose without a massive fire was the effect of a 33-kiloton blast, and when the tail was detached by the 19-kiloton explosion, the aircraft was still relatively unharmed. The engineers figured it would take just 106 hours of work to turn the jet around after the first explosion so that it could take off again.

Decades later, the radiation-damaged remains from the XF-90 were dug out, recovered, cleaned up, and displayed at the United States Air Force National Museum in Dayton, Ohio, as a rare witness to a plane having not one but three nuclear detonations and coming out alive.

The XF-90 didn’t get to active service and missed its original target; however, it has not been forgotten and will always be remembered in the annals of aviation as one of those that left a deep footprint behind them.

Its radical designs had a role in the emergence of the future fighter jets, the F-104 Starfighter among them, thus showing that even a so-called failed aircraft can be a driver of technological fronts and a hardy survivor when subjected to the most severe conditions.