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