Project Pluto

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For the World War II Pipeline Under The Ocean project, see Operation Pluto.

Project Pluto was a United States government program to develop nuclear powered ramjet engines for use in cruise missiles. Two experimental engines were tested at the United States Department of Energy Nevada Test Site (NTS) in 1961 and 1964.


On January 1, 1957, the U.S. Air Force and the U.S. Atomic Energy Commission selected the Lawrence Livermore National Laboratory's (LLNL) predecessor, the Lawrence Radiation Laboratory, to study the feasibility of applying heat from nuclear reactors to ramjet engines. This research became known as "Project Pluto". The work was directed by Dr. Ted Merkle, leader of the laboratory's R-Division.

The "Tory-IIC" prototype

Originally carried out at Livermore, California, the work was moved to new facilities constructed for $1.2 million on 8 square miles (21 km2) of Jackass Flats at the NTS, known as Site 401. The complex consisted of 6 miles (10 km) of roads, critical assembly building, control building, assembly and shop buildings, and utilities. Also required for the construction was 25 miles (40 km) of oil well casing which was necessary to store the approximately 1,000,000 pounds (450,000 kg) of pressurized air used to simulate ramjet flight conditions for Pluto.

The principle behind the nuclear ramjet was relatively simple: motion of the vehicle pushed air in through the front of the vehicle (ram effect), a nuclear reactor heated the air, and then the hot air expanded at high speed out through a nozzle at the back, providing thrust.


The success of this project would depend upon a series of technological advances in metallurgy and materials science. Pneumatic motors necessary to control the reactor in flight had to operate while red-hot and in the presence of intense radiation. The need to maintain supersonic speed at low altitude and in all kinds of weather meant the reactor, code named "Tory", had to survive high temperatures and conditions that would melt the metals used in most jet and rocket engines. Ceramic fuel elements would have to be used; the contract to manufacture the 500,000 pencil-sized elements was given to the Coors Porcelain Company.


On May 14, 1961, the world's first nuclear ramjet engine, "Tory-IIA", mounted on a railroad car, roared to life for a few seconds. Three years later, "Tory-IIC" was run for five minutes at full power. Despite these and other successful tests the Pentagon, sponsor of the "Pluto project", had second thoughts. The weapon was considered "too provocative",[1] and it was believed that it would compel the Soviets to construct a similar device, against which there was no known defense. Intercontinental ballistic missile technology had proven to be more easily developed than previously thought, reducing the need for such highly capable cruise missiles. On July 1, 1964, seven years and six months after it was started, "Project Pluto" was canceled.

See also[edit]


  1. ^ "Muscle in Mothballs". Retrieved 2014-07-21. 
  • Initial text taken from a public domain document at DOE

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