#Project MX-1589

[historyofguns]

The article discusses the Convair NB-36H, a nuclear-powered bomber developed during the Cold War by the United States Air Force and the Atomic Energy Commission. Post-World War II, nuclear power was seen as a miracle energy source, leading to its consideration for military applications beyond submarines and supercarriers, like bombers. The NB-36H was a modified Convair B-36 Peacemaker, equipped with an air-cooled nuclear reactor, although the reactor never powered the aircraft in flight. Despite extensive research, including 47 test flights, the program was deemed too costly and risky, ultimately scrapped, as missile advancements reduced the need for such bombers. This endeavor reflects Cold War era technological ambitions and challenges in nuclear propulsion development.

[usafphantom2]

Ronnie Bell Following

Convair NB-36H

Convair NB-36H in flight. Note the radiation warning symbol on the tail. (U.S. Air Force photo)The NB-36H (originally designated XB-36H) was used in the studies and testing of an airborne nuclear reactor. The reactor to be carried aloft was not to be used for aircraft propulsion but primarily for determining many unknown factors pertaining to the effects of nuclear reaction. The NB-36H, named "The Crusader," flew 47 times during the mid-1950s.

Project MX-1589 was carried under two Air Force contracts -- one pertaining to research and development of an airframe and one for the construction of what became the Nuclear Aircraft Research Facility operated by Convair-Fort Worth for the Air Force.

The project was classified until late 1955 when the Department of Defense revealed the existence of the B-36 testbed for an airborne atomic reactor. The nose section of the aircraft had to be completely redesigned and resulted in one of the first uses of a full-scale working mock-up. The nose section mock-up included a hydraulic design feature providing simulation of aircraft take-off position, and detail design of the crew compartment interior duplicating actual aircraft conditions of ventilation, color scheming and other crew comfort and safety factors never before involved in airframe construction.

The XB-36H carried a crew of five: pilot, copilot, flight engineer, and two nuclear engineers. All crew members were located in the forward section of the aircraft while the atomic reactor was located aft. The greenhouse nose of a production B-36H was replaced by a more conventional cockpit arrangement. The new nose section was slightly shorter than the original and the nose landing gear was moved six inches forward to allow for a crew entrance/escape hatch just behind the nose landing gear.

On Labor Day (Sept. 1) 1952, Carswell Air Force Base was struck by a tornado and several aircraft were damaged. These aircraft were returned to Convair for major repairs. In the group was airplane No. 242 (S/N 51-5712), which had lost the nose section of the fuselage. Convair proposed that this airplane be used for the nuclear program, with the damaged nose section forward of Station 5 to be replaced with the nose section and crew compartment then being designed as a mock-up. The proposal was agreed to by the Air Force.

The size of the crew compartment was determined by the total allowable weight of the nose section of a B-36H airplane. In order to lessen the indoctrination, which would otherwise be necessary, the pilot and co-pilot stations were held as closely as possible to the arrangement of the standard B-36. The nuclear engineer stations were designed to incorporate the necessary instrumentation for the reactor operation. Engine scanning normally performed by crew members from the rear of the conventional B-36, had to be taken over by television cameras in the test aircraft. The placement of the television set presented another problem. The set had to be located where the flight engineer could readily see it. Although space was not available at the flight engineer's station, there was room in the overhead area between the nuclear engineers' stations within easy viewing distance of the flight engineer.

The color treatment and lighting arrangement of the interior surfaces were designed to help eliminate as much eye fatigue as possible. A gray color scheme used in the nuclear and flight engineers' compartments, proved unfavorable for the pilot and co-pilot stations. Exterior light passing through the yellow windshield turned the light gray into an unfavorable color. By using lavender, in the pilot and co-pilot compartment, and illusion of gray is achieved.

Type Number built/

converted Remarks

NB-36H 1 (cv) Airborne testbed for a nuclear reactor

TECHNICAL NOTES:

Armament: None

Engines: Six Pratt & Whitney R-4360-53 radials of 3,800 hp each (takeoff power) and four General Electric J47-GE-19 turbojets of 5,200 lbs. thrust each

Maximum speed: Approx. 420 mph at 47,000 ft.

Cruising speed: 235 mph

Service ceiling: Approx. 47,000 ft.

Span: 230 ft. 0 in.

Length: 162 ft. 1 in. (as B-36H, the NB-36H was slightly shorter)

Height: 46 ft. 8 in.

Weight: 357,500 lbs. (maximum gross weight)

Crew: Five (pilot, copilot, flight engineer and two nuclear engineers)

Serial number: 51-5712 (originally B-36H-20-CF)

Via Flickr

[kesslersymbolic]

It has been tried before, and some issues you mention:

"With the right shielding, the radiation exposure from flying par l'atome would be dominated by the cosmic rays that normally come from flying."

That's what the MX-1589 project tested and found that they couldn't sufficiently shield the reactor. in theory it's still sorta possible, and that experiment was looking at a reactor in the fuselage as opposed to a direct-air style engine. Direct air is basically just take a jet engine and replace the burner with a reactor core, so putting them out on the wings could reduce radiation exposure... though air is a bit crap as a mediator so not sure it quite solves it.

But yeahh my vibe is it's mostly the that it's not the engineering challenge but instead the political concerns which aren't quite addressed by "simply don't crash" and "nuclear proliferation laws don't exist if you're fast enough" which would kill the idea

OK, so nuclear-powered aircraft, while extremely cool, are Not A Good Idea (the inherent cost, need for shielding and attendant weight, difficulty of servicing the reactor in any situation besides routine maintenance, and dangerous dispersion of fission products in the event of a crash all recommend against it even in a world without eg NRC certification). But—bear with me—would it actually be Worse For The Environment than the status quo of aircraft burning fossil kerosene? I don't think the answer is Obviously Yes Duh! Every transcontinental plane flight melts 3m² of arctic sea ice. Kerosene is a carcinogen, thanks largely to the aromatics in refined petroleum. With the right shielding, the radiation exposure from flying par l'atome would be dominated by the cosmic rays that normally come from flying.

Even minute leaks of radionuclides would be easy to detect, both inside the aircraft and out—moreso than other safety-critical leaks like those of the hydraulic or fuel lines.

Anything short of a hull loss of the aircraft is unlikely to produce a radiotoxic dispersion event, assuming the aircraft is at all sanely designed. In a configuration similar to the Air Force's project, air would be ducted from the turbofans through heat exchangers near the reactor, so even a bird strike would not be a radionuclide/toxin dispersion event. There is absolutely no reason to pipe radioactive material from the vicinity of the reactor, well within the hull of the aircraft, anywhere else.

It would surprise me if a crash (rare, if we ignore the 737 MAX) killed more people from the radiotoxicity of dispersed radionuclides than from the things that normally kill people in plane crashes. Besides which, keep in mind that the molten salt that would almost certainly be used as coolant would have all the fuel and fission products in solution. A properly functioning airborne molten salt reactor would have in-situ reprocessing of actinides (if you wanted to prioritize service flexibility and medium-lived isotope elimination) or on-the-ground reprocessing (if you wanted to prioritize mechanical simplicity). In either case, the mid-lived fission products would be minimal. Cleaning up a crash site would be…not easy, but not necessarily much harder compared with how we deal with crashes now. The scattered nuclear remnants, unlike with Chernobyl, would be fairly well localized and could be robotically isolated, processed and buried in geological storage. It would be fairly straightforward to verify decontamination of an accident site with radiation monitoring.

The biggest concern I'd have would be suicide hijackings, but this has gotten a lot harder since 9/11 thanks to airport security and the hardening of cockpit doors against forced entry. Even if you assume this kind of hijacking would happen, it's hard for me to come up with a worst case scenario for one that's obviously worse than eg probability-weighted material/bodily damages over global warming contributions from aviation.

Also—how deadly Chernobyl and Fukushima actually were qua radiotoxicity is vastly overstated in the popular imagination; UN thinks about 6k people have ultimately died from exposure to radioactive toxins at Chernobyl, while several sources think no one died from exposure to Fukushima.

You're possibly looking at a mechanically simpler bird than our extant aircraft.

Also: this doesn't bear on the enviro question, but...

Think of the power and range at your disposal! Mach 5 baybeeee!!!! New York to Tokyo in 3 hours!* No refueling for months!

---

Note: i am a random internet person and not a nuclear plane doctor I filmed this on a closed course please do not attempt this experiment at home nuclear passenger jets are not a good idea

★at least at altitude and assuming eg Boom Aerospace actually have figured out a solution to the noise problem!