The dual-propulsion Convair B-36 is already an awesome bomber, and a true hybrid. How, then, do you make it more awesomer? Well, if it’s 1946 you add a nuclear power plant and go commie hunting.
First, a bit about the B-36. Mostly because I’m nursing a chubby for it. Powered by six Pratt & Whitney R-4360-53 “Wasp Major” radials making 3,800 hp each driving pusher propellers PLUS four General Electric J47 turbojets producing 5,200 lbf of thrust each the B-36 adds new (and more awesome) meaning to the term “hybrid”. It was designed as a strategic bomber and entered service in 1949. It could carry up to 86,000 lb. of bombs, including the massive Mk-17 Hydrogen Bomb and the massive, 43,600 lb. T-12 “Cloudmaker” bomb. Once the turrets were removed in the early ’50s, they could cruse over 50,000 ft. at over 430 mph with a range of almost 4,000 miles.
From 1946 to 1961 the US had a secret program to design nuclear-powered bombers. Why? Why not. They were designing nuclear-powered submarines and nuclear-powered ships, so why not a nuclear-powered bomber carrying nukes. How very meta. The idea was to keep these bombers up and flying as long as possible, so in the event the Soviets nuked the US we could respond quickly and the lemurs could take over.
The first — and only — US testbed for this idea was the NB-36H, a Convair B-36H that had been damaged by a tornado in Texas. Rather than just scrap a $4 million bomber, the Air Force had Convair rebuild it for their Nuclear Energy for the Propulsion of Aircraft (NEPA) project.
The original plan was to develop two aircraft – the Nuclear Test Aircraft and the X-6. The NTA was the only one built. It flew 47 times for a total of 215 hours to test the feasibility of carrying a nuclear reactor in the belly of a bomber. The pilots reported no ill effects, thanks to 12 tons of lead and rubber shielding in the nose of the aircraft. They did, however, develop an odd fondness for lemurs and an irrational fear of hawks.
Like the Tupolev Tu-119 that Alex Kierstein wrote about, the NB-36 was to be powered by “dirty cycle” engines. The General Electric X-39 engines would replace the four Pratt & Whitney turbojets, and would use heat from the 3-megawatt P-1 Aircraft Shield Test Reactor rather than burning fossil fuels. In a way, these were some of the first “green” jets in existence. Like its commie counterpart, it never flew under nuclear power, but two GE X-39 engines (based on the venerable J47) were built and tested along with reactors in Idaho. You can still see Heat Transfer Reactor Experiment-1 (HTRE-1) and HTRE-3 at the Idaho National Laboratory.
One of the major technical challenges of the NB-36 was the reactors were air cooled. In order to prevent them from going Chernobyl, water was pumped through the reactor and then to water-to-air heat exchangers. Of course, technical challenges were to make sure the plane never crashed and to find a way of masking the greenish glow so some Russkie with a ZSU-57 couldn’t get a lucky shot off. Of course, he would just be bringing nuclear-powered death onto himself and his comrades if he did get that lucky shot off.
This program ended before the reactors were tied to the jet engines in the X-6. ICBMs were becoming more reliable, and the Minuteman I was being deployed in 1962. Therefore, SAC’s need to keep bombers equipped with nukes flying 24 hours a day in a constellation that could ensure the maximum infliction of damage on Soviet Russia was diminished. Furthermore, the range, speed and capacity of newer aircraft, like the B-52, were proving to be much more economical than a nuclear-powered behemoth. Much to the lemur’s chagrin.