Nuclear-powered aircraft

A nuclear-powered aircraft is an aircraft whose power source is nuclear fission. Most designs use a nuclear reactor that heats compressed air inside a jet engine to provide thrust. Either a turbojet or a ramjet can be used, as with ordinary chemical propulsion. During the Cold War, the United States and Soviet Union researched nuclear-powered bomber aircraft, the greater endurance of which could enhance nuclear deterrence, but neither country created any such operational aircraft. The advent of ICBMs and nuclear submarines in the 1960s greatly diminished the strategic advantage of such aircraft, and respective projects were canceled. Likewise, proposals for supersonic nuclear-powered cruise missiles such as Project Pluto were never implemented. However, Russia developed a subsonic nuclear-powered cruise missile beginning in the 2010s, the 9M730 Burevestnik, as a strategic deterrent. Nuclear aircraft have several inadequately solved design problems, such as the need for heavy shielding to protect the crew and those on the ground from radiation, the release of fission products and neutron activation of nearby air, and crash-worthiness, particularly over water where moderation of neutrons can lead to a damaged reactor suffering a criticality accident.

U.S. programs

NEPA and ANP

In May 1946, the United States Army Air Forces started the Nuclear Energy for the Propulsion of Aircraft (NEPA) project, which conducted studies until the Aircraft Nuclear Propulsion (ANP) program replaced NEPA in 1951. The ANP program included provisions for studying two different types of nuclear-powered jet engines: General Electric's Direct Air Cycle and Pratt & Whitney's Indirect Air Cycle. ANP planned for Convair to modify two B-36s under the MX-1589 project. One of the B-36s, the NB-36H, was to be used for studying shielding requirements for an airborne reactor, while the other was to be the X-6; however, the program was canceled before the X-6 was completed. The first operation of a nuclear aircraft engine occurred on January 31, 1956 using a modified General Electric J47 turbojet engine. The Aircraft Nuclear Propulsion program was terminated by President Kennedy after his annual budget message to Congress in 1961. The Oak Ridge National Laboratory researched and developed nuclear aircraft engines. Two shielded reactors powered two General Electric J87 turbojet engines to nearly full thrust. Two experimental reactors, HTRE-2 with its turbojet engines intact, and HTRE-3 with its engines removed, are at the EBR-1 facility south of the Idaho National Laboratory.

The U.S. designed these engines for use in a new, specially designed nuclear bomber, the WS-125. Although President Eisenhower eventually terminated it by cutting NEPA and telling Congress that the program was not urgent, he backed a small program for developing high-temperature materials and high-performance reactors; that program was terminated early in the Kennedy administration.

Project Pluto

In 1957, the Air Force and the U.S. Atomic Energy Commission contracted with the Lawrence Radiation Laboratory to study the feasibility of applying heat from nuclear reactors to ramjet engines. This research became known as Project Pluto. This program was to provide engines for an unmanned cruise missile, called SLAM, for Supersonic Low Altitude Missile. The program succeeded in producing two test engines, which were operated on the ground. On May 14, 1961, the world's first nuclear ramjet engine, "Tory-IIA," mounted on a railroad car, roared to life for just a few seconds. On July 1, 1964, seven years and six months after it was born, "Project Pluto" was canceled.

Airships

There were several studies and proposals for nuclear-powered airships, starting with a 1954 study by F. W. Locke Jr. for US Navy. In 1957 Edwin J. Kirschner published the book The Zeppelin in the Atomic Age, which promoted the use of atomic airships. In 1959 Goodyear presented a plan for nuclear-powered airship for both military and commercial use. Several other proposals and papers were published during the next decades.

Soviet programs

Soviet nuclear bomber scare The 1 December 1958 issue of Aviation Week included an article, "Soviets Flight Testing Nuclear Bomber", that claimed that the Soviets had greatly progressed a nuclear aircraft program: "[a] nuclear-powered bomber is being flight tested in the Soviet Union. Completed about six months ago, this aircraft has been flying in the Moscow area for at least two months. It has been observed both in flight and on the ground by a wide variety of foreign observers from Communist and non-Communist countries." Unlike the US designs of the same era, which were purely experimental, the article noted that "The Soviet aircraft is a prototype of a design to perform a military mission as a continuous airborne alert warning system and missile launching platform." Photographs illustrated the article, along with technical diagrams on the proposed layout; these were so widely seen that one company produced a plastic model aircraft based on the diagrams in the article. An editorial on the topic accompanied the article. Concerns were soon expressed in Washington that "the Russians were from three to five years ahead of the US in the field of atomic aircraft engines and that they would move even further ahead unless the US pressed forward with its own program". These concerns caused continued but temporary funding of the US's own program. The aircraft in the photographs was later revealed to be the conventional Myasishchev M-50 Bounder, a medium-range strategic bomber that performed like the United States Air Force-operated B-58 Hustler. The design was considered a failure, never entered service, and was revealed to the public on Soviet Aviation Day in 1963 at Monino, putting the issue to rest.

Tupolev Tu-119

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