HOME

TheInfoList



OR:

The Aircraft Nuclear Propulsion (ANP) program and the preceding Nuclear Energy for the Propulsion of Aircraft (NEPA) project worked to develop a nuclear propulsion system for aircraft. The
United States Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...
initiated Project NEPA on May 28, 1946. NEPA operated until May 1951, when the project was transferred to the joint Atomic Energy Commission (AEC)/USAF ANP. The USAF pursued two different systems for nuclear-powered jet engines, the Direct Air Cycle concept, which was developed by
General Electric General Electric Company (GE) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston. Over the year ...
, and Indirect Air Cycle, which was assigned to
Pratt & Whitney Pratt & Whitney is an American aerospace manufacturer with global service operations. It is a subsidiary of RTX Corporation (formerly Raytheon Technologies). Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially ...
. The program was intended to develop and test the Convair X-6, but was canceled in 1961 before that aircraft was built. The total cost of the program from 1946 to 1961 was about $1 billion.


Types


Direct air cycle

Direct cycle nuclear engines resemble a conventional
jet engine A jet engine is a type of reaction engine, discharging a fast-moving jet (fluid), jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition may include Rocket engine, rocket, Pump-jet, water jet, and ...
without
combustion chamber A combustion chamber is part of an internal combustion engine in which the air–fuel ratio, fuel/air mix is burned. For steam engines, the term has also been used for an extension of the Firebox (steam engine), firebox which is used to allow a mo ...
s. The air gained from the compressor section is sent to a plenum that directs the air into the nuclear reactor core. An exchange takes place where the reactor is cooled, but it then heats up the same air and sends it to another plenum. The second plenum directs the air through a turbine (powering the compressor), then out the exhaust, providing thrust. The end result is that instead of using jet fuel, an aircraft could rely on the heat from nuclear reactions for power. The General Electric program, which was based at
Evendale, Ohio Evendale (pronounced ) is a village in Hamilton County, Ohio, United States, within the Cincinnati metropolitan area. The population was 2,669 at the 2020 census. Geography According to the United States Census Bureau, the village has a tota ...
, was pursued because of its advantages in simplicity, reliability, suitability and quick start ability. Conventional jet engine
compressor A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Many compressors can be staged, that is, the gas is compressed several times in steps o ...
and
turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical ...
sections were used, with the compressed air run through the reactor to be heated by it before being exhausted through the turbine.


Indirect air cycle

Indirect cycling involves thermal exchange outside of the core with compressor air being sent to a
heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...
. The nuclear reactor core would heat up pressurized water or liquid metal and send it to the heat exchanger as well. That hot liquid would be cooled by the air; the air would be heated by the liquid, sent through a turbine (powering the compressor), then out the exhaust, providing thrust. The indirect air cycle program was assigned to Pratt & Whitney, at a facility near
Middletown, Connecticut Middletown is a city in Middlesex County, Connecticut, United States. Located along the Connecticut River, in the central part of the state, 16 miles (25.749504 km) south of Hartford, Connecticut, Hartford. Middletown is the largest city in the L ...
. This concept would have produced far less radioactive pollution. One or two loops of liquid metal would carry the heat from the reactor to the engine. This program involved a great deal of research and development of many light-weight systems suitable for use in aircraft, such as heat exchangers, liquid-metal turbopumps and
radiator A radiator is a heat exchanger used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics. A radiator is always a ...
s. The Indirect Cycle program never came anywhere near producing flight-ready hardware.


Experimental reactors and projects


Aircraft Reactor Experiment

The United States Aircraft Reactor Experiment (ARE) was a 2.5 MWth
thermal A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...
-spectrum
nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...
experiment designed to attain a high
power density Power density, defined as the amount of power (the time rate of energy transfer) per unit volume, is a critical parameter used across a spectrum of scientific and engineering disciplines. This metric, typically denoted in watts per cubic meter ...
and high output temperature for use as an engine in a nuclear-powered bomber aircraft. The advantage of a nuclear-powered aircraft over a conventionally-powered aircraft is that it could remain airborne orders of magnitude longer and provide an effective nuclear strategic deterrent to a nuclear-armed
Soviet The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
adversary. The ARE was the first
molten salt reactor A molten-salt reactor (MSR) is a class of nuclear fission reactor in which the primary nuclear reactor coolant and/or the fuel is a mixture of molten salt with a fissile material. Two research MSRs operated in the United States in the mid-20th ...
(MSR) to be built and operated. It used the molten fluoride salt NaFZrF4UF4 (53–41–6 mol%) as
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...
, was moderated by a hexagonal-configuration beryllium oxide (BeO), and had a peak temperature of 860 °C. A redundant liquid
sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
coolant system was used to cool the moderator and reflector materials. A secondary
helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...
gas coolant loop was circulated around the primary coolant to transfer heat to a water radiator where heat output was dumped to atmosphere. Reactivity control rods were installed and it was found that the control rods did not determine the output power of the ARE; rather, the power demand did, which affected the outlet and inlet temperatures because of the negative temperature coefficient of reactivity. The ARE was operated at power for 221 hours up to a peak of 2.5 MWth.MegaZone (1997)
"Aircraft Nuclear Propulsion – Politics"
Retrieved January 16, 2016.


MX-1589 project

On September 5, 1951, the USAF awarded
Convair Convair, previously Consolidated Vultee Aircraft Corporation, was an American aircraft-manufacturing company that later expanded into rockets and spacecraft. The company was formed in 1943 by the merger of Consolidated Aircraft and Vultee ...
a contract to fly a nuclear reactor on board a modified
Convair B-36 Peacemaker The Convair B-36 "Peacemaker" is a strategic bomber built by Convair and operated by the United States Air Force (USAF) from 1949 to 1959. The B-36 is the largest mass-produced piston-engined aircraft ever built, although it was exceeded in spa ...
under the MX-1589 project of the ANP program. The NB-36H Nuclear Test Aircraft (NTA) was to study shielding requirements for an airborne reactor, to determine whether a nuclear aircraft was feasible. This was the only known airborne reactor experiment by the U.S. with an operational nuclear reactor on board. The NTA flew a total of 47 times testing the reactor over West Texas and Southern New Mexico. The reactor, named the Aircraft Shield Test Reactor (ASTR), was operational but did not power the aircraft; the primary purpose of the flight program was testing the effectiveness of the shielding. Based on the results of the NTA, the X-6 and the entire nuclear aircraft program was abandoned in 1961.


Heat Transfer Reactor Experiments

As part of the AEC/USAF ANP program, in 1956 modified General Electric J47s were first operated on nuclear power using a reactor test assembly known as Heat Transfer Reactor Experiment 1 (HTRE-1). HTRE-1, which used vertically-oriented control rods, was reconfigured with a removable core to become HTRE-2 for additional testing. HTRE-3 was built separately to test horizontally-oriented control rods as appropriate for use in an airframe. The decommissioned HTRE-2 and HTRE-3 reactors and test assemblies can be viewed by the public in the
Experimental Breeder Reactor I Experimental Breeder Reactor I (EBR-I) is a decommissioned research reactor and U.S. National Historic Landmark located in the desert about southeast of Arco, Idaho. It was the world's first breeder reactor. At 1:50 p.m. on December 2 ...
parking lot at
Idaho National Laboratory Idaho National Laboratory (INL) is one of the national laboratories of the United States Department of Energy and is managed by the Battelle Energy Alliance. Historically, the lab has been involved with nuclear research, although the labora ...
.


Pratt & Whitney Aircraft Reactor-1

On February 5, 1957, another reactor was made critical at the Critical Experiments Facility of the Oak Ridge National Laboratory (ORNL) as part of the circulating-fuel reactor program of the
Pratt & Whitney Pratt & Whitney is an American aerospace manufacturer with global service operations. It is a subsidiary of RTX Corporation (formerly Raytheon Technologies). Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially ...
Aircraft Company (PWAC). This was called the PWAR-1, the Pratt & Whitney Aircraft Reactor-1. The purpose of the experiment was to experimentally verify the theoretically predicted nuclear properties of a PWAC reactor. The experiment was only run briefly; by the end of February 1957 all data had been taken and disassembly had begun. The experiment was run at essentially zero nuclear power. The operating temperature was held constant at approximately , which corresponds closely to the design operating temperature of the PWAR-l moderator; this temperature was maintained by external heaters. Like the 2.5 MWt ARE, the PWAR-1 used NaF-ZrF4-UF4 as the primary fuel and coolant.


Cancellation

Technological competition with the Soviet Union (as represented by the launch of
Sputnik 1 Sputnik 1 (, , ''Satellite 1''), sometimes referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program ...
), and continued strong support from the Air Force allowed the program to continue, despite divided leadership between the DOD and the AEC. Numerous test facilities were funded and constructed through the 1950s and 1960–61 in order to produce a flight-worthy nuclear power unit, including one at the
Oak Ridge National Laboratory Oak Ridge National Laboratory (ORNL) is a federally funded research and development centers, federally funded research and development center in Oak Ridge, Tennessee, United States. Founded in 1943, the laboratory is sponsored by the United Sta ...
(ORNL). While the ARE successfully demonstrated operation of a MSR concept, the program was canceled by President Kennedy on March 26, 1961, citing the high cost with no flight-worthy reactor having been produced up to that point – "15 years and about $1 billion have been devoted to the attempted development of a nuclear-powered aircraft; but the possibility of achieving a militarily useful aircraft in the foreseeable future is still very remote". Also contributing to the cancellation was that the first
intercontinental ballistic missile An intercontinental ballistic missile (ICBM) is a ballistic missile with a range (aeronautics), range greater than , primarily designed for nuclear weapons delivery (delivering one or more Thermonuclear weapon, thermonuclear warheads). Conven ...
s entered into active service in September 1959 which all but eliminated the need for a nuclear-powered aircraft as a strategic deterrent. Nevertheless, the results of the ARE program prompted scientists and engineers at ORNL to submit a preliminary design proposal to the Atomic Energy Commission for a 30 MWth experimental MSR to explore MSR as a civilian power station concept. The result of the proposal was direction from the Atomic Energy Commission for ORNL to design, construct, and operate the Molten-Salt Reactor Experiment (MSRE).Robertson, R. C., et al. (January 1965)
MSRE Design and Operations Report Part I description of reactor design"
Oak Ridge National Laboratory. ORNL-TM-728. pp. 3–6. Retrieved December 1, 2015.


See also

* List of nuclear-powered aircraft * Georgia Nuclear Aircraft Laboratory * WS-125, 1955 USAF requirement for nuclear powered bomber *
NERVA Nerva (; born Marcus Cocceius Nerva; 8 November 30 – 27 January 98) was a Roman emperor from 96 to 98. Nerva became emperor when aged almost 66, after a lifetime of imperial service under Nero and the succeeding rulers of the Flavian dynast ...
* Project Pluto to develop nuclear powered ramjet engines for use in cruise missiles * Project Rover to develop a nuclear thermal rocket * Tupolev Tu-95LAL


References


External links

* . * . * . * . * with illustrations on the subject of using an atomic reactor to power an aircraft. * .
SOVİET TOP SECRET NUCLEAR AIRPLANE M-60 Akademi Portal
by Akademi Portal web site (in English)
COMPREHENSHIVE TECHNICAL REPORT GE DIRECT AIR CYCLE AIRCRAFT NUCLEAR PROPULSION PROGRAM
(in English)
“Flyable” Reactors & Neutron Coupling
(in English) *
Declassified Aircraft Nuclear Propulsion Program: Manned Aircraft Progress Report 1956-1958
{{Authority control Nuclear-powered aircraft Science experiments 1946 establishments in the United States 1961 disestablishments Atomic tourism Projects of the United States Air Force