Nuclear propulsion

Last updated

Nuclear propulsion includes a wide variety of propulsion methods that fulfill the promise of the Atomic Age by using some form of nuclear reaction as their primary power source. The idea of using nuclear material for propulsion dates back to the beginning of the 20th century. In 1903 it was hypothesised that radioactive material, radium, might be a suitable fuel for engines to propel cars, boats, and planes. [1] H. G. Wells picked up this idea in his 1914 fiction work The World Set Free . [2]

Atomic Age period of history (1945–)

The Atomic Age, also known as the Atomic Era, is the period of history following the detonation of the first nuclear ("atomic") bomb, Trinity, on July 16, 1945, during World War II. Although nuclear chain reactions had been hypothesized in 1933 and the first artificial self-sustaining nuclear chain reaction had taken place in December 1942, the Trinity test and the ensuing bombings of Hiroshima and Nagasaki that ended World War II represented the first large-scale use of nuclear technology and ushered in profound changes in sociopolitical thinking and the course of technology development.

Nuclear reaction process in which two nuclei collide to produce one or more nuclides

In nuclear physics and nuclear chemistry, a nuclear reaction is semantically considered to be the process in which two nuclei, or else a nucleus of an atom and a subatomic particle from outside the atom, collide to produce one or more nuclides that are different from the nuclide(s) that began the process. Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. If a nucleus interacts with another nucleus or particle and they then separate without changing the nature of any nuclide, the process is simply referred to as a type of nuclear scattering, rather than a nuclear reaction.

Radium Chemical element with atomic number 88

Radium is a chemical element with symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) on exposure to air, forming a black surface layer of radium nitride (Ra3N2). All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1600 years and decays into radon gas (specifically the isotope radon-222). When radium decays, ionizing radiation is a product, which can excite fluorescent chemicals and cause radioluminescence.


Pressurised water reactors are the most common reactors used in ships and submarines. The pictorial diagram shows the operating principles. Primary coolant is in orange and the secondary coolant (steam and later feedwater) is in blue. PressurizedWaterReactor.gif
Pressurised water reactors are the most common reactors used in ships and submarines. The pictorial diagram shows the operating principles. Primary coolant is in orange and the secondary coolant (steam and later feedwater) is in blue.

Surface ships, submarines, and torpedoes

Nuclear-powered vessels are mainly military submarines, and aircraft carriers. Russia and America are the only countries that currently have nuclear-powered civilian surface ships, including icebreakers and Aircraft carriers. America currently (as of July 2018) has 11 Aircraft carriers in service, and all are powered by nuclear reactors. They use nuclear reactors as their power plants. For more detailed articles see:

Submarine Watercraft capable of independent operation underwater

A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term most commonly refers to a large, crewed vessel. It is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. The noun submarine evolved as a shortened form of submarine boat; by naval tradition, submarines are usually referred to as "boats" rather than as "ships", regardless of their size.

Aircraft carrier Warship that serves as a seagoing airbase

An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft. Typically, it is the capital ship of a fleet, as it allows a naval force to project air power worldwide without depending on local bases for staging aircraft operations. Carriers have evolved since their inception in the early twentieth century from wooden vessels used to deploy balloons to nuclear-powered warships that carry numerous fighters, strike aircraft, helicopters, and other types of aircraft. While heavier aircraft such as fixed-wing gunships and bombers have been launched from aircraft carriers, it is currently not possible to land them. By its diplomatic and tactical power, its mobility, its autonomy and the variety of its means, the aircraft carrier is often the centerpiece of modern combat fleets. Tactically or even strategically, it replaced the battleship in the role of flagship of a fleet. One of its great advantages is that, by sailing in international waters, it does not interfere with any territorial sovereignty and thus obviates the need for overflight authorizations from third party countries, reduce the times and transit distances of aircraft and therefore significantly increase the time of availability on the combat zone.

Icebreaker Special-purpose ship or boat capable of maneuvering through ice-covered water

An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller vessels, such as the icebreaking boats that were once used on the canals of the United Kingdom.

A Delta-class Nuclear-powered submarine. Delta-II class nuclear-powered ballistic missle submarine 3.jpg
A Delta-class Nuclear-powered submarine.

Civilian maritime use

Nuclear marine propulsion propulsion system for marine vessels utilizing a nuclear powerplant

Nuclear marine propulsion is propulsion of a ship or submarine with heat provided by a nuclear power plant. The power plant heats water to produce steam for a turbine used to turn the ship's propeller through a gearbox or through an electric generator and motor. Naval nuclear propulsion is used specifically within naval warships such as supercarriers. A small number of experimental civil nuclear ships have been built.

Military maritime use

A nuclear navy, or nuclear-powered navy, refers to the portion of a navy consisting of naval ships powered by nuclear marine propulsion. The concept was revolutionary for naval warfare when first proposed. Prior to nuclear power, submarines were powered by diesel engines and could only submerge through the use of batteries. In order for these submarines to run their diesel engines and charge their batteries they would have to surface or snorkel. The use of nuclear power allowed these submarines to become true submersibles and unlike their conventional counterparts, they became limited only by crew endurance and supplies.

Soviet naval reactors have been used to power both military and civilian vessels, including:

A nuclear submarine is a submarine powered by a nuclear reactor. The performance advantages of nuclear submarines over "conventional" submarines are considerable. Nuclear propulsion, being completely independent of air, frees the submarine from the need to surface frequently, as is necessary for conventional submarines. The large amount of power generated by a nuclear reactor allows nuclear submarines to operate at high speed for long periods of time; and the long interval between refuelings grants a range virtually unlimited, making the only limits on voyage times being imposed by such factors as the need to restock food or other consumables.


Russia's Channel One Television news broadcast a picture and details of a nuclear-powered torpedo called Status-6 on about 12 November 2015. The torpedo was stated as having a range of up to 10,000 km, a cruising speed of 100 knots, and operational depth of up to 1000 metres below the surface. The torpedo carried a 100-megaton nuclear warhead. [3]

One of the suggestions emerging in the summer of 1958 from the first meeting of the scientific advisory group that became JASON was for "a nuclear-powered torpedo that could roam the seas almost indefinitely". [4]

JASON is an independent group of elite scientists which advises the United States government on matters of science and technology, mostly of a sensitive nature. The group was first created as a way to get a younger generation of scientists—that is, not the older Los Alamos and MIT Radiation Laboratory alumni—involved in advising the government. It was established in 1960 and has somewhere between 30 and 60 members. Its work first gained public notoriety as the source of the Vietnam War's McNamara Line electronic barrier. Although most of its research is military-focused, JASON also produced early work on the science of global warming and acid rain. Current unclassified research interests include health informatics, cyberwarfare, and renewable energy.

Aircraft and missiles

A picture of an Aircraft Nuclear Propulsion system, known as HTRE-3(Heat Transfer Reactor Experiment no. 3). The central EBR-1 based reactor took the place of chemical fuel combustion to heat the air. The reactor rapidly raised the temperature via an air heat exchanger and powered the dual J47 engines in a number of ground tests. HTRE-3.jpg
A picture of an Aircraft Nuclear Propulsion system, known as HTRE-3(Heat Transfer Reactor Experiment no. 3). The central EBR-1 based reactor took the place of chemical fuel combustion to heat the air. The reactor rapidly raised the temperature via an air heat exchanger and powered the dual J47 engines in a number of ground tests.

Research into nuclear-powered aircraft was pursued during the Cold War by the United States and the Soviet Union as they would presumably allow a country to keep nuclear bombers in the air for extremely long periods of time, a useful tactic for nuclear deterrence. Neither country created any operational nuclear aircraft. One design problem, never adequately solved, was the need for heavy shielding to protect the crew from radiation sickness. Since the advent of ICBMs in the 1960s the tactical advantage of such aircraft was greatly diminished and respective projects were cancelled. Because the technology was inherently dangerous it was not considered in non-military contexts. Nuclear-powered missiles were also researched and discounted during the same period.




Many types of nuclear propulsion have been proposed, and some of them (e.g. NERVA) tested for spacecraft applications.

Nuclear pulse propulsion

Nuclear thermal rocket

Bimodal Nuclear Thermal Rockets - conduct nuclear fission reactions similar to those employed at nuclear power plants including submarines. The energy is used to heat the liquid hydrogen propellant. The vehicle depicted is the "Copernicus" an upper stage assembly being designed for the Space Launch System (2010). Bimodal Nuclear Thermal Rocket.jpg
Bimodal Nuclear Thermal Rockets - conduct nuclear fission reactions similar to those employed at nuclear power plants including submarines. The energy is used to heat the liquid hydrogen propellant. The vehicle depicted is the "Copernicus" an upper stage assembly being designed for the Space Launch System (2010).


Direct nuclear

Nuclear electric

Russian Federal Space Agency development

Anatolij Perminov, head of the Russian Federal Space Agency, announced[ when? ] that it is going to develop a nuclear-powered spacecraft for deep space travel. [9] [10] Preliminary design was done by 2013, and 9 more years are planned for development (in space assembly). The price is set at 17 billion rubles (600 million dollars). [11] The nuclear propulsion would have mega-watt class, [12] [13] provided necessary funding, Roscosmos Head stated.

This system would consist of a space nuclear power and a matrix of ion engines. "...Hot inert gas temperature of 1500 °C from the reactor turns turbines. The turbine turns the generator and compressor, which circulates the working fluid in a closed circuit. The working fluid is cooled in the radiator. The generator produces electricity for the same ion (plasma) engine..." [14] [ not in citation given ]

According to him, the propulsion will be able to support human mission to Mars, with cosmonauts staying on the Red planet for 30 days. This journey to Mars with nuclear propulsion and a steady acceleration would take six weeks, instead of eight months by using chemical propulsion – assuming thrust of 300 times higher than that of chemical propulsion. [15] [16]



The idea of making cars that used radioactive material, radium, for fuel dates back to at least 1903. Analysis of the concept in 1937 indicated that the driver of such a vehicle might need a 50-ton lead barrier to shield them from radiation. [17]

In 1941 Dr R M Langer, a Caltech physicist, espoused the idea of a car powered by uranium-235 in the January edition of Popular Mechanics . He was followed by William Bushnell Stout, designer of the Stout Scarab and former Society of Engineers president, on 7 August 1945 in the New York Times . The problem of shielding the reactor continued to render the idea impractical. [18] In December 1945, a John Wilson of London, announced he had created an atomic car. This created considerable interest. The Minister of Fuel and Power along with a large press contingent turned out to view it. The car did not show and Wilson claimed that it had been sabotaged. A later court case found that he was a fraud and there was no nuclear-powered car. [19] [20]

Despite the shielding problem, through the late 1940s and early 1950s debate continued around the possibility of nuclear-powered cars. The development of nuclear-powered submarines and ships, and experiments to develop a nuclear-powered aircraft at that time kept the idea alive. [21] Russian papers in the mid-1950s reported the development of a nuclear-powered car by Professor V P Romadin, but again shielding proved to be a problem. [22] It was claimed that its laboratories had overcome the shielding problem with a new alloy that absorbed the rays. [23]

In 1958 at the height of the 1950s American automobile culture there were at least four theoretical nuclear-powered concept cars proposed, the American Ford Nucleon and Studebaker Packard Astral, as well as the French Simca Fulgur designed by Robert Opron [24] [25] and the Arbel Symétric. Apart from these concept models, none were built and no automotive nuclear power plants ever made. Chrysler engineer C R Lewis had discounted the idea in 1957 because of estimates that an 80,000 lb (36,000 kg) engine would be required by a 3,000 lb (1,400 kg) car. His view was that an efficient means of storing energy was required for nuclear power to be practical. [26] Despite this, Chrysler's stylists in 1958 drew up some possible designs.

In 1959 it was reported that Goodyear Tire and Rubber Company had developed a new rubber compound that was light and absorbed radiation, obviating the need for heavy shielding. A reporter at the time considered it might make nuclear-powered cars and aircraft a possibility. [27]

Ford made another potentially nuclear-powered model in 1962 for the Seattle World's Fair, the Ford Seattle-ite XXI. [28] [29] This also never went beyond the initial concept.

In 2009, for the hundredth anniversary of General Motors' acquisition of Cadillac, Loren Kulesus created concept art depicting a car powered by thorium. [30]


The Chrysler TV-8 was an experimental concept tank designed by Chrysler in the 1950s. The tank was intended to be a nuclear-powered medium tank capable of land and amphibious warfare. The design was never mass-produced. [31] The Mars rover Curiosity is powered by a radioisotope thermoelectric generator (RTG), like the successful Viking 1 and Viking 2 Mars landers in 1976. [32] [33]

See also

Related Research Articles

Interstellar travel term used for hypothetical manned or unmanned travel between stars

Interstellar travel is the term used for crewed or uncrewed travel between stars or planetary systems. Interstellar travel will be much more difficult than interplanetary spaceflight; the distances between the planets in the Solar System are less than 30 astronomical units (AU)—whereas the distances between stars are typically hundreds of thousands of AU, and usually expressed in light-years. Because of the vastness of those distances, interstellar travel would require a high percentage of the speed of light; huge travel time, lasting from decades to millennia or longer; or a combination of both.

Nuclear thermal rocket form of rocket propulsion

A nuclear thermal rocket is a proposed spacecraft propulsion technology. In a nuclear thermal rocket a working fluid, usually liquid hydrogen, is heated to a high temperature in a nuclear reactor, and then expands through a rocket nozzle to create thrust. This kind of thermal rocket, the nuclear reactor's energy replaces the chemical energy of the propellant's reactive chemicals in a chemical rocket. The thermal heater / inert propellant paradigm as opposed to the reactive propellants of chemical rockets turns out to produce a superior effective exhaust velocity, and therefore a superior propulsive efficiency, with specific impulses on the order of twice that of chemical engines. The overall gross lift-off mass of a nuclear rocket is about half that of a chemical rocket, and hence when used as an upper stage it roughly doubles or triples the payload carried to orbit.

In a Nuclear Electric Rocket, nuclear thermal energy is changed into electrical energy that is used to power one of the electrical propulsion technologies. Technically the powerplant is nuclear, not the propulsion system, but the terminology is standard. A number of heat-to-electricity schemes have been proposed: Rankine cycle, Brayton cycle, Stirling cycle, thermoelectric, pyroelectric, thermophotovoltaic, thermionic and magnetohydrodynamic type thermoelectric materials.

A nuclear salt-water rocket (NSWR) is a theoretical type of nuclear thermal rocket which was designed by Robert Zubrin. In place of traditional chemical propellant, such as that in a chemical rocket, the rocket would be fueled by salts of plutonium or 20 percent enriched uranium. The solution would be contained in a bundle of pipes coated in boron carbide. Through a combination of the coating and space between the pipes, the contents would not reach critical mass until the solution is pumped into a reaction chamber, thus reaching a critical mass, and being expelled through a nozzle to generate thrust.

In a traditional nuclear photonic rocket, an onboard nuclear reactor would generate such high temperatures that the blackbody radiation from the reactor would provide significant thrust. The disadvantage is that it takes a lot of power to generate a small amount of thrust this way, so acceleration is very low. The photon radiators would most likely be constructed using graphite or tungsten. Photonic rockets are technologically feasible, but rather impractical with current technology based on an onboard nuclear power source. However, the recent development of Photonic Laser Thruster (PLT), the Beamed Laser Propulsion (BLP) with photon recycling, promises to overcome these issues by separating the nuclear power source and the spacecraft and by increasing the thrust to nuclear power ratio by orders of magnitude.

A fusion rocket is a theoretical design for a rocket driven by fusion propulsion which could provide efficient and long-term acceleration in space without the need to carry a large fuel supply. The design relies on the development of fusion power technology beyond current capabilities, and the construction of rockets much larger and more complex than any current spacecraft. A smaller and lighter fusion reactor might be possible in the future when more sophisticated methods have been devised to control magnetic confinement and prevent plasma instabilities. Inertial fusion could provide a lighter and more compact alternative, as might a fusion engine based on an FRC.

Bussard ramjet

The Bussard ramjet is a theoretical method of spacecraft propulsion proposed in 1960 by the physicist Robert W. Bussard, popularized by Poul Anderson's novel Tau Zero, Larry Niven in his Known Space series of books, Vernor Vinge in his Zones of Thought series, and referred to by Carl Sagan in the television series and book Cosmos.

Variable Specific Impulse Magnetoplasma Rocket concept for an advanced propulsion rocket engine

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an electrothermal thruster under development for possible use in spacecraft propulsion. It uses radio waves to ionize and heat a propellant. Then a magnetic field accelerates the resulting plasma to generate thrust. It is one of several types of spacecraft electric propulsion systems.

Nuclear pulse propulsion

Nuclear pulse propulsion or external pulsed plasma propulsion, is a hypothetical method of spacecraft propulsion that uses nuclear explosions for thrust. It was first developed as Project Orion by DARPA, after a suggestion by Stanislaw Ulam in 1947. Newer designs using inertial confinement fusion have been the baseline for most post-Orion designs, including Project Daedalus and Project Longshot.

Radioisotope thermoelectric generator electrical generator that converts heat released by radioactive decay into electricity by the Seebeck effect

A radioisotope thermoelectric generator is an electrical generator that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This generator has no moving parts.

Robert W. Bussard was an American physicist who worked primarily in nuclear fusion energy research. He was the recipient of the Schreiber-Spence Achievement Award for STAIF-2004. He was also a fellow of the International Academy of Astronautics and held a Ph.D. from Princeton University.

Project Orion (nuclear propulsion)

Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft. Early versions of this vehicle were proposed to take off from the ground with significant associated nuclear fallout; later versions were presented for use only in space. Six tests were launched.

Project Prometheus NASA project to develop nuclear-powered systems for long-duration space missions

Project Prometheus/Project Promethian was established in 2003 by NASA to develop nuclear-powered systems for long-duration space missions. This was NASA's first serious foray into nuclear spacecraft propulsion since the cancellation of the SNTP project in 1995. The project was cancelled in 2005. Its budget shrank from $252.6 million in 2005 to only $100 million in 2006, $90 million of which was for closeout costs on cancelled contracts.


The Nuclear Engine for Rocket Vehicle Application (NERVA) was a U.S. nuclear thermal rocket engine development program that ran for roughly two decades. NERVA was a joint effort of the U.S. Atomic Energy Commission (AEC) and NASA, managed by the Space Nuclear Propulsion Office (SNPO) until both the program and the office ended at the end of 1972.

Project Longshot

Project Longshot was a conceptual interstellar spacecraft design. It would have been an unmanned probe, intended to fly to and enter orbit around Alpha Centauri B powered by nuclear pulse propulsion.

Interstellar probe spaceprobe that can travel out of the Solar System

An interstellar probe is a space probe that has left—or is expected to leave—the Solar System and enter interstellar space, which is typically defined as the region beyond the heliopause. It also refers to probes capable of reaching other star systems.

Project Rover was an American project to develop a nuclear thermal rocket. The program ran at the Los Alamos Scientific Laboratory from 1955 through 1972 and involved the Atomic Energy Commission, and NASA. The project was managed by the Space Nuclear Propulsion Office.

Gas core reactor rockets are a conceptual type of rocket that is propelled by the exhausted coolant of a gaseous fission reactor. The nuclear fission reactor core may be either a gas or plasma. They may be capable of creating specific impulses of 3,000–5,000 s and thrust which is enough for relatively fast interplanetary travel. Heat transfer to the working fluid (propellant) is by thermal radiation, mostly in the ultraviolet, given off by the fission gas at a working temperature of around 25,000 °C.

A thermal rocket is a rocket engine that uses a propellant that is externally heated before being passed through a nozzle, as opposed to undergoing a chemical reaction as in a chemical rocket.

Nuclear power in space

Nuclear power in space is the use of nuclear power in outer space, typically either small fission systems or radioactive decay for electricity or heat. Another use is for scientific observation, as in a Mössbauer spectrometer. One common type is a radioisotope thermoelectric generator, which has been used on many space probes and on manned lunar missions, and another is small fission reactors for Earth observation satellites such as the TOPAZ nuclear reactor. A radioisotope heater unit provides heat from radioactive decay of a material and can potentially produce heat for decades.


  1. Some practical uses of radium rays, The Republic, Sunday, September 13, 1903
  2. The new source of energy, The World Set Free, H G Wells, Collins, London and Glasgow, 1956 edition, page 55
  3. Russia reveals giant nuclear torpedo in state TV 'leak', BBC news, 12 November 2015 - retrieved 27 November 2015
  4. Science Magazine, 29 November 1991, p.1284
  5. Thornton, G; Blumbeg, B. (January 1961). "Aircraft Nuclear Propulsion Heat Transfer Reactor Experiments Fulfill Test Goals". Nucleonics. McGraw-Hill. 19 (1). ISSN   0096-6207.
  6. Norris, Guy (14 October 2014). "False Starts For Aviation's Atomic Age". Aviation Week. Retrieved 17 October 2014.
  7. Gady, Franz-Stefan (2 March 2018). "Russia Reveals 'Unstoppable' Nuclear-Powered Cruise Missile". The Diplomat. Retrieved 26 March 2018.
  8. Contact: Gynelle C. Steele (July 15, 2005). "F-22 Raptor Stealth". NASA Glenn's Research & Technology. Retrieved 2009-07-08.
  9. Russian Space Agency Announces Plans to Build Nuclear-Powered Deep Space Rocket
  10. Russia And US To Discuss Nuke-Powered Spaceship Project
  11. Russians to ride a nuclear-powered spacecraft to Mars // 2009
  12. Page, Lewis (5 April 2011). "Russia, NASA to hold talks on nuclear-powered spacecraft. Muscovites have the balls but not the money". The Register. Retrieved 26 December 2013.
  13. "Interview: Academician Anatoly Koroteyev An Inside Look at Russia's Nuclear Power Propulsion System" (PDF). 21st CENTURY. Fall/Winter 2012-2013. Retrieved 26 December 2013.Check date values in: |date= (help)
  14. (in Russian) Academician Anatoly Koroteev: "Nuclear power can provide a qualitative leap in the development of space"
  15. Space Propulsion for Martian Mission may be Developed in 6-9 Years
  16. Russia Leads Nuclear Space Race After U.S. Drops Out
  17. The Science Review, Issues 1-12, University of Melbourne Science Club, Melbourne University, 1937, page 22
  18. Automobile Quarterly, Volume 31 Number 1, 1992, pages 14-29
  19. First Atomic Car "sabotaged", Townsville Daily Bulletin, Queensland, Australia, Monday 3 December 1945 page 2
  20. "Atomic Car" hoax - Elderly inventor gets goal sentence, Cairns Post, Queensland Australia, Monday 22 July 1946, page 3
  21. "Benson Ford poses challenge on atomic powered automobiles". The Brooklyn Daily Eagle. October 2, 1951. p. 3. Retrieved June 4, 2015 via Open Access logo PLoS transparent.svg
  22. Reading Eagle, Sunday, February 20, 1955, page 8
  23. Atom-powered Automobile Claimed Russian, The victoria Advocate, Victoria, Texas, Sunday, January 30, 1955, page 7
  24. "Radioactive cars of the twentieth century" . Retrieved 26 April 2012.
  25. "Une anticipation Simca : la "fulgur"" (in French). Retrieved 26 April 2012.
  26. Hearst Magazines (April 1957). "The Atom powered carPopular Mechanics". Popular Mechanics. Hearst Magazines. p. 141.
  27. Advent of Atom Powered Plane Speeded, Ray Cromley, The Victoria Advocate, Victoria, Texas, Wednesday, June 24, 1959, page 4
  28. Hanlon, Mike. "Ford Seattle-ite: one of history's most significant concept cars". Retrieved 26 April 2012.
  29. "1962 Ford Seattle-ite XXI" . Retrieved 26 April 2012.
  30. WTF? Cadillac World Thorium Fuel Concept?
  31. Hunnicutt 1990, p. 36.
  32. "Multi-Mission Radioisotope Thermoelectric Generator" (PDF). NASA/JPL. January 1, 2008. Archived from the original (PDF) on August 13, 2012. Retrieved August 6, 2012.
  33. "Mars Exploration: Radioisotope Power and Heating for Mars Surface Exploration" (PDF). NASA/JPL. April 18, 2006. Retrieved September 7, 2009.

Further reading