What if an aircraft could fly for an indefinite amounts of time, maybe even for weeks or months? This was a question under much investigation during the Cold War, and a race of its own was under way during the 1950’s and 60’s between the Soviet Union and United States. Both the United States and the Soviet Union dreamed of a bomber that could stay in the air for months at time, constantly close to the enemy and ready for attack. A post Cold-War Russian account of this period remembered the the intelligence they had received regarding a successful American test flight of a B-36 bomber with a nuclear reactor on board. Despite the seemingly successful engineering operations from these test flights, an American nuclear powered aircraft never flew. From 1955 to 1957, the Air Force flew two modified B-36 bomber aircraft 47 times testing huge amounts of radiation shielding while carrying a three-megawatt test reactor in the back of the plane. However, the reactors never actually powered the engines, as engineers realized test flights would be necessary to to experiment with the massive dilemmas involved with a nuclear powered flight. Although extensive progress in this field was achieved by both the United States and Soviet Union, neither were able to overcome the technologies challenges without sacrificing the speed, maneuverability or environmental cost of the aircraft. The three largest problems with the technology were creating an environmentally friendly engine, shielding radiation from the reactor, and managing disaster if the plane was the crash. If these three problems are solved, a nuclear powered aircraft may be seen in the future.
The original American design behind the nuclear powered jet engine, was actually surprising simple. Using the same principles as the “once through reactor” cooling system, nuclear jet engines would pass cold air through the reactor, quickly expanding it and shooting it back out the other end. This simple process of expanding air through a chamber was thought to created the necessary thrust to propel the aircraft. However, it was quickly realized that thrust would not be the primary problem with this kind of reactor. The engine would face the same problem’s of the “once through” cooling system, as any leakage from the reactor would spit irradiated materials out of the engine, causing environmental catastrophe. Eventually a new kind of engine was proposed, where the air would not pass directly through the reactor, but close to it. General Electric successfully completed the development of this engine, however failed to generate the necessary thrust before President Eisenhower heavily cut funding to the project stating it to be “overly ambitious”.
The Second problem with nuclear powered flight regards the large amount of radiation that fire out of the engine, damaging the DNA of a crew. In order for a crew to safely operate a nuclear reactor on board, huge amounts of shielding must be place. The problem with shielding is that denser the material, the better a job of blocking radiation it will do. Lead being one of the most dense metals, was often used for reactors on the ground, however it was extremely heavy. An aircraft would certainly not be able to carry the amount of lead found on a power station on the ground. The method for shielding used on the B-36 test flights was a distributed system. Instead of housing all lead around the reactor, the distributed system placed some shielding around the reactor while placing most of it in the walls of the rooms where the crew spent most of their time. However after testing the B-36 design, it became apparent that the problem of shielding the interior of the aircraft from the reactor’s radiation was too great.
The third problem of a nuclear aircraft goes without saying, if the plane crashes environmental catastrophe will be large. During the B-36 test flights, the Air Force took extreme precaution given this risk. Along side ever single test flight, were two crews flying at the same speed, ready to secure a crash sight if it were to happen. Their job was to be ready to land at any moment and seal off the crash with large tarps to prevent the spread of irradiated material. Luckily, the crews never had to take action.
Ultimately, the annoyance of and inefficiency of inflight refueling combined with the nuclear hype of the mid 20th century pushed this project to heights. The success of conventionally powered long-range aircraft and the development of ICBMs weakened the case for trying to obtain nuclear propulsion of aircraft.