The program had strong political support from Senators Clinton P. Anderson and Margaret Chase Smith but was cancelled by President Richard Nixon in 1973.

During World War II, some scientists at the Manhattan Project's Los Alamos Laboratory where the first atomic bombs were designed, including Stan Ulam, Frederick Reines and Frederic de Hoffmann, speculated about the development of nuclear-powered rockets.

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.

[11] Bussard's study also attracted the attention of John von Neumann, who formed an ad hoc committee for nuclear propulsion of missiles.

Mark Mills, the assistant director at Livermore was its chairman, and its other members were Norris Bradbury from LASL; Edward Teller and Herbert York from Livermore; Abe Silverstein, the associate director of the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory, a federal agency that conducted aeronautical research; and Allen F. Donovan from Ramo-Wooldridge, an aerospace corporation.

[11] After hearing input on several designs, the Mills committee recommended in March 1955 that development proceed, with the aim of producing a nuclear rocket upper stage for an intercontinental ballistic missile (ICBM).

The deputy chairman of the United States Congress Joint Committee on Atomic Energy (JCAE), Anderson was close to von Neumann, Bradbury and Ulam.

[14] Project Rover was directed by an active duty United States Air Force (USAF) officer seconded to the AEC, Lieutenant Colonel Harold R. Schmidt.

He was answerable to another seconded USAF officer, Colonel Jack L. Armstrong, who was also in charge of Pluto and the Systems for Nuclear Auxiliary Power (SNAP) projects.

An efficient lightweight shield material was developed by the Aerojet Nuclear Systems Company from a mixture of boron carbide (B4C), aluminum and titanium hydride (TiH2), known as BATH after its components.

BATH was found to be strong, with a tensile strength of up to 190,000 kilopascals (28,000 psi), capable of withstanding high temperatures, and with superior radiation shielding properties.

Test Cell A consisted of a farm of hydrogen gas bottles and a concrete wall 1 meter (3 ft) thick to protect the electronic instrumentation from radiation produced by the reactor.

[20] The reactor maintenance and disassembly building (R-MAD) was in most respects a typical hot cell used by the nuclear industry, with thick concrete walls, lead glass viewing windows, and remote manipulation arms.

It demonstrated that the Soviet Union had the capability to deliver nuclear weapons over intercontinental distances, and contested cherished American notions of military, economic and technological superiority.

[47] Finger established branch offices at Albuquerque, New Mexico, (SNPO-A) to liaise with LASL, and in Cleveland, Ohio, (SNPO-C) to coordinate with the Lewis Research Center, which was activated in October 1961.

[54] In March 1961, President John F. Kennedy announced the cancellation of the aircraft nuclear propulsion project just as NASA's Plum Brook reactor was nearing completion,[57] and for a time it seemed that NERVA would soon follow.

"[60] The SNPO set an objective for NERVA of 99.7 percent reliability, meaning that the engine would fail to perform as designed no more than three times in every thousand starts.

[61] NASA delegated responsibility for RIFT to Wernher von Braun's Marshall Space Flight Center (MSFC) in Huntsville, Alabama.

[63] The December 1959 Silverstein Committee had defined the configuration of the Saturn launch vehicle,[64] including the use of liquid hydrogen as the fuel for the upper stages.

NERVA engines would be transported by road in shockproof, watertight containers, with the control rods locked in place and nuclear poison wires in the core.

[67] In March 1963, SNPO and MSFC commissioned Space Technology Laboratories (STL) to produce a report on what kind of nuclear rocket engine would be required for possible missions between 1975 and 1990.

The conclusion of this nine-volume report, which was delivered in March 1965, and of a follow-up study, was that these missions could be carried out with a 4,100 MW engine with a specific impulse of 825 seconds (8.09 km/s).

[23] The Kiwi program developed a series of non-flyable test nuclear engines, the primary focus being to improve the technology of hydrogen-cooled reactors.

The second test in the series, Kiwi B1B on 1 September 1962, resulted in extreme structural damage to the reactor, fuel module components being ejected as it was ramped up to full power.

He met privately with Kennedy, who agreed to request a supplemental appropriation for RIFT if a "quick fix" to the Kiwi vibration problem that Seaborg promised could be implemented.

Finger assembled a team of vibration specialists from other NASA centers, and along with staff from LASL, Aerojet and Westinghouse, conducted a series of "cold flow" reactor tests using fuel elements without fissionable material.

[98][99][100][101] Defending NERVA from its critics like Hornig, the chairman of the President's Science Advisory Committee (PSAC), required a series of bureaucratic and political battles as the rising cost of the Vietnam War put pressure on budgets.

[102] Klein, who had succeeded Finger as head of the SNPO in 1967, faced two hours of questioning on NERVA II before the House Committee on Science and Astronautics.

There was also of course the mission to Mars, which Klein diplomatically avoided mentioning,[105] knowing that, even in the wake of the Apollo 11 Moon landing, the idea was unpopular with Congress and the general public.

[123] The proposed rocket project was transferred to the Space Nuclear Thermal Propulsion (SNTP) program at the Air Force Phillips Laboratory in October 1991.