XF-108: MACH 3 Speed to Battle Soviet Bombers But Never Built
It was the height of the Cold War in the 1950s, and a vital part of the Soviet Union’s nuclear triad was large bombers that could deliver an astonishing nuclear payload to North America. The U.S. Air Force wanted an ultra-fast fighter to keep the supersonic Soviet strategic bombers from reaching the country. It settled on the XF-108 Rapier. The Air Force eventually passed on this powerful airplane because of the high costs and warfare had evolved away from airplane delivery of nuclear devices.
Could You Believe MACH 3 Speed Back in the 1950s?
But the high-altitude XF-108 would have been an excellent choice for a fighter. It was designed to have an internal rotary missile launcher to better eliminate the enemy bombers with its Falcon air-to-air missiles.
Talk about supersonic; the speed of the Rapier would have been a hair-raising MACH 3. This was like a missile or rocket with wings.
Ramjet Propulsion to Make It an Aerial Hot Rod
It all started in 1949 when the Air Force called for what would become the XF-108 concept.
In 1951, Republic Aviation responded to the request with an exciting proposal in 1951 for a ramjet-propelled interceptor that could hit three times the speed of sound and reach an altitude of 80,000 feet with a range of 1,000 nautical miles.
But this first attempt at what would become the experimental airplane was beyond the ability of engineers due to the technological advances that it required. The Republic Aviation model was canceled.
Wingman for Valkyrie Bomber
The Air Force was undeterred and still wanted this kind of “gee whiz” fighter. In 1955, the Air Force started a new program called the Long-range Interceptor, Experimental airplane. This time North American Aviation won the bid. North American had already been working on the XB-70 Valkyrie strategic bomber. The aerospace contractor felt they could take elements of the Valkyrie with its high speed and elevation and incorporate those features into the Long-range Interceptor. Both airplanes would have the General Electric YJ93 engines. North American thought the Rapier could even fly escort missions with the Valkyrie if everything went according to plan.
North American also wanted state-of-the-art sensors for the Rapier. This would have been one of the early pulse-doppler radars. The system could scan the entire area and easily pick out and lock on enemy fighters or bombers at long range. And I am talking serious long-range radar scans for the times – about 278,000 square miles each hour.
A Victim of Smaller Budgets
However, the technological advances needed to integrate all of the systems into one airplane were not possible then. This would cost serious money, and the Eisenhower administration saw defense as a place to make budget cuts and rely more on intercontinental ballistic missiles for the nuclear fight. Eisenhower balked because the Air Force’s request to buy 480 XF-108s would have set the branch back $4 billion ($33 billion in today’s dollars).
Emphasis Was on ICBMs
ICBMs were seen by both the Americans and Soviets as the place to invest serious money. Soviet supersonic bombers were believed to be the lesser threat. So, the XF-108 was discontinued in 1959. But the experimental plane’s design and attributes lived on in the future carrier-launched North American A-5 Vigilante bomber. The A-5 was never going to be as fast as that MACH 3 dream, but it served the navy well into the Vietnam era.
It’s too bad because such a fast fighter would have been able to outrun North Vietnamese surface-to-air missiles and win more dogfights than the slower F-105 Thunderchief. The XF-108 is an interesting case study on how engineers and designers were so ahead of their times.
If they could have reduced the price, the XF-108 may have been delivered in numbers.