The Convair WS-125A, the nuclear-powered bomber hybrid of B-58 and XB-70 that never was

The Convair WS-125A, the nuclear-powered bomber hybrid of B-58 and XB-70 that never was

By Dario Leone
Jul 3 2024
Sponsored by: Mortons Books
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The Convair WS-125A

In October 1954, the USAF put out requirements for two supersonic bombers, the WS-110A and the WS- 125A. These were intended as replacements for the Boeing B-52; while that aircraft had only just started entering service, at the time it was expected that obsolescence would come fast and that by 1965 an entirely new bomber would be needed.

As told by Scott Lowther in his book US Supersonic Bomber Projects 2, both the WS-110A and WS-125A were to be supersonic strategic bombers, the main difference being that the WS-110A was to be chemically powered with the WS-125A being nuclear powered. Both were to have the speed of the B-58 and the payload of the B-52.

The Strategic Air Command did not truly want two very different aircraft to replace the B-52, but it was felt that systems developed for the less technically aggressive (and thus safer and cheaper) WS-110A could be applied to the WS-125A. In the end, Boeing, Douglas. Martin and North American decided to pursue the WS- 110A, the competition for which resulted in the North American Aviation XB-70, while Convair and Lockheed went after – and received contracts for – the WS-125A.

The WS-125A was required to cruise at Mach 0.9 and have a mission radius of 11,000 nautical miles of which 1,000 nautical miles was to be at Mach 2 and 60,000ft altitude, Lockheed and Convair both put forward several conceptual designs, though detailed descriptions of them remain unavailable at this time.

A cross between the B-58 and the XB-70

In late 1956 Convair designed a WS-125A – the Model 25 – that appeared as a cross between the B-58 and the XB-70. Minimal information is currently available on it beyond a layout diagram. A modified delta wing was married to a very long fuselage and a conventional tail unit. Four nuclear turbojet engines – two General Electric AC-110s- were contained in a pack underneath the rear fuselage, fed by wing root inlets. Additional engines were in individual pods under the wings; these were chemically fuelled, used for takeoff and high-speed dash but powered down during subsonic cruise.

The wingtips had different leading and trailing edge sweeps than the main wing, and were supposed to be able to fold down in much the same way as the B-70 wingtips. The cockpit canopy was surprisingly large with a number of individual panes. This probably indicates that the crew compartment was a heavily shielded pod within the fuselage. In order to give the pilots a fair view, the external windscreens would have to be quite large. An “Advanced Model 25” was said to have a folding nose to improve pilot visibility during landing, but that feature does not seem to be present in this layout.

Quite a bit larger than the B-58

As shown in the diagram, the Convair WS-125A was quite a bit larger than the B-58 but shared many configuration similarities. Shown here specifically is the proposed B-58 Model Improved, which used not only similar folding wingtips but also used cockpit canopies of remarkably similar appearance. It seems quite possible that the same designers worked on both concepts.

The extreme range available to the WS-125A meant that even though its bases would be doubtless known to the Soviets, the direction the bombers would come in from would not. The bombers would not need to take a fuel-conserving direct course, but could instead follow a dog-leg pattern far from Soviet air defences. The bombers could then penetrate Soviet airspace from many unpredictable and difficult to intercept vectors.

The need to expend chemical fuel for the high-speed dash was a limiting factor, as was crew fatigue and radiation dosage. But given the likelihood that these bombers would only be used in the event of all-out thermonuclear war, the crews would doubtless have been considered expendable. The nuclear engines could be used as purely chemical- fuel burners, with the reactor safely shut down; this would greatly restrict the range and duration of the aircraft, but it would permit radiation-free training and ferrying flights.

US Supersonic Bomber Projects 2 is published by Mortons Books and is available to order here.

The Convair WS-125A, the nuclear-powered bomber hybrid of B-58 and XB-70 that never was
Convair WS-125A

Photo credit: U.S. Air Force and Mortons Books


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Dario Leone

Dario Leone

Dario Leone is an aviation, defense and military writer. He is the Founder and Editor of “The Aviation Geek Club” one of the world’s most read military aviation blogs. His writing has appeared in The National Interest and other news media. He has reported from Europe and flown Super Puma and Cougar helicopters with the Swiss Air Force.
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