Project Rover was a United States project to develop a nuclear-thermal rocket that ran from 1955 to 1973 at the Los Alamos Scientific Laboratory (LASL). It began as a United States Air Force project to develop a nuclear-powered upper stage for an intercontinental ballistic missile (ICBM). The project was transferred to NASA in 1958 after the Sputnik crisis triggered the Space Race. It was managed by the Space Nuclear Propulsion Office (SNPO), a joint agency of the Atomic Energy Commission (AEC), and NASA. Project Rover became part of NASA's Nuclear Engine for Rocket Vehicle Application (NERVA) project and henceforth dealt with the research into nuclear rocket reactor design, while NERVA involved the overall development and deployment of nuclear rocket engines, and the planning for space missions. Nuclear reactors for Project Rover were built at LASL Technical Area 18 (TA-18), also known as the Pajarito Canyon Site. They were tested there at very low power and then shipped to Area 25 (known as Jackass Flats) at the AEC's Nevada Test Site. Testing of fuel elements and other materials science was done by the LASL N-Division at TA-46 using various ovens and later a custom test reactor, the Nuclear Furnace. Project Rover resulted in the development of three reactor types: Kiwi (1955 to 1964), Phoebus (1964 to 1969), and Pewee (1969 to 1972). Kiwi and Phoebus were large reactors, while Pewee was much smaller, conforming to the smaller budget available after 1968. The reactors were fueled by highly enriched uranium, with liquid hydrogen used as both a rocket propellant and reactor coolant. Nuclear graphite and beryllium were used as neutron moderators and neutron reflectors. The engines were controlled by drums with graphite or beryllium on one side and boron (a nuclear poison) on the other, and the energy level adjusted by rotating the drums. Because hydrogen also acts as a moderator, increasing the flow of propellant also increased reactor power without the need to adjust the drums. Project Rover tests demonstrated that nuclear rocket engines could be shut down and restarted many times without difficulty, and could be clustered if more thrust was desired. Their specific impulse (efficiency) was roughly double that of chemical rockets. The nuclear rocket enjoyed strong political support from the influential chairman of the United States Congress Joint Committee on Atomic Energy, Senator Clinton P. Anderson from New Mexico (where LASL was located), and his allies, Senators Howard Cannon from Nevada and Margaret Chase Smith from Maine. This enabled it to survive multiple cancellation attempts that became ever more serious in the cost cutting that prevailed as the Vietnam War escalated and after the space race ended with the Apollo 11 Moon landing. Projects Rover and NERVA were canceled over their objection in January 1973, and none of the reactors ever flew.
Beginnings
Early concepts During World War II, some scientists at the Manhattan Project's Los Alamos Laboratory, including Stan Ulam, Frederick Reines and Frederic de Hoffmann, speculated about the development of nuclear-powered rockets, and in 1947, Ulam and Cornelius Joseph "C. J." Everett wrote a paper in which they considered using atomic bombs as a means of rocket propulsion. This became the basis for Project Orion. In December 1945, Theodore von Karman and Hsue-Shen Tsien wrote a report for the United States Army Air Forces. While they agreed that it was not yet practical, Tsien speculated that nuclear-powered rockets might one day be powerful enough to launch satellites into orbit. In 1947, North American Aviation's Aerophysics Laboratory published a large paper surveying many of the problems involved in using nuclear reactors to power airplanes and rockets. The study was specifically aimed at an aircraft with a range of 16,000 kilometers (10,000 mi) and a payload of 3,600 kilograms (8,000 lb), and covered turbopumps, structure, tankage, aerodynamics and nuclear reactor design. They concluded that hydrogen was best as a propellant and that graphite would be the best neutron moderator, but assumed an operating temperature of 3,150 °C (5,700 °F), which was beyond the capabilities of available materials. The conclusion was that nuclear-powered rockets were not yet practical. The public revelation of atomic energy at the end of the war generated a great deal of speculation, and in the United Kingdom, Val Cleaver, the chief engineer of the rocket division at De Havilland, and Leslie Shepard, a nuclear physicist at the University of Cambridge, independently considered the problem of nuclear rocket propulsion. They became collaborators, and in a series of papers published in the Journal of the British Interplanetary Society in 1948 and 1949, they outlined the design of a nuclear-powered rocket with a solid-core graphite heat exchanger. They reluctantly concluded that nuclear rockets were essential for deep space exploration, but not yet technically feasible.
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