RTG -- History, the Curiosity, Voyager, and New Horizons

Curiosity · New Horizons · Voyager · Resources with Additional Information

Radioisotope Thermoelectric Generators (RTG)

Courtesy of DOE Office of Nuclear Energy,
Science and Technology

Radioisotope Thermoelectric Generators (RTGs), called "space batteries" or "nuclear batteries", have provided spacecraft power for many years.

"RTGs provided by DOE have enabled American scientists to explore the solar system for many years. Prior to New Horizons, the Apollo missions to the Moon, the Viking missions to Mars, and the Pioneer, Voyager, Ulysses, Galileo and Cassini missions to the outer solar system all used this safe, efficient and long-lasting power source."


Curiosity is the rover that "will investigate Mars' Gale Crater for clues about whether environmental conditions there have favored the development of microbial life, and to preserve any evidence it finds.

NASA chose to use a nuclear power source because solar power alternatives did not meet the full range of the mission's requirements. Only the radioisotope power system [the RTG] allows full-time communication with the rover during its atmospheric entry, descent and landing regardless of the landing site. And the nuclear powered rover can go farther, travel to more places, last longer, and power and heat a larger and more capable scientific payload compared to the solar power alternative NASA studied."

- Edited excerpts from INL's Mars Contributions

This artist concept features NASA's Mars Science Laboratory Curiosity rover, a mobile robot for investigating Mars' past or present ability to sustain microbial life.

Image Credit: NASA/JPL-Caltech

NASA Rover Now Exploring Mars Using INL Power System

Powering Curiosity: Lab Tech Goes to Mars

NASA Lands Car-Size Rover Beside Martian Mountain (Mars Science Laboratory)

Mars Science Laboratory, Idaho National Laboratory (INL)

Mars ‘Curiosity’ has ORNL Tech

Energy Department Nuclear Systems Are Powering Mars Rover

Nuclear Systems Powering a Mission to Mars

A Mars Rover Named "Curiosity"

Curiosity Zaps First Martian Rock

Twelve Months in Two Minutes:  Curiosity's First Year on Mars (video)

Department of Energy R&D for the Mars Science Laboratory


New Horizons

The RTG provides power for the New Horizons spacecraft which was launched January 19, 2006, 'from Florida's Kennedy Space Center on a 9-1/2 year journey to explore Pluto and its moons. The spacecraft will receive heat and electricity from a long-lasting plutonium-238 powered generator developed and assembled by scientists and engineers at the [Department of Energy's] Idaho, Oak Ridge and Los Alamos National Laboratories.

New Horizons
New Horizon space craft

Courtesy of NASA/Johns Hopkins University
Applied Physics Laboratory/Southwest Research Institute

For the mission, the Department of Energy developed and delivered a radioisotope thermoelectric generator, or "RTG." This "space battery" provides an uninterrupted and reliable source of heat and electricity in remote and harsh environments such as deep space. The RTG will provide power and heat for many years to the New Horizons spacecraft and its on-board scientific equipment through the radioactive decay of nuclear material. Heat generated by the radioactive decay of plutonium-238 is converted into electricity by solid-state thermoelectrics.'1

"Oak Ridge National Laboratory developed and fabricated the material used to encapsulate the plutonium; Los Alamos National Laboratory purified, pelletized into a ceramic form and encapsulated the plutonium; and Idaho National Laboratory assembled and tested the RTG and safely delivered the flight-ready RTG to the Kennedy Space Center (KSC)."2

New Horizons Mission Powered by Space Radioisotope Power Systems

New Horizons - NASA's Pluto-Kuiper Belt Mission

NASA's New Horizons Mission Also a New Horizon for INL, Idaho National Laboratory

To Pluto and Beyond: Powering New Horizons’ 3-Billion-Mile Journey

NASA’s New Horizons Team Selects Potential Kuiper Belt Flyby Target



After 36 years and over 12 billion miles, a pair of RTGs continue to power the Voyager 1 spacecraft -- now officially the first man-made object to enter interstellar space. These RTGs are expected to keep on working until 2025.

'New and unexpected data indicate Voyager 1 has been traveling for about one year through plasma, or ionized gas, present in the space between stars. Voyager is in a transitional region immediately outside the solar bubble, where some effects from our sun are still evident. … "Voyager has boldly gone where no probe has gone before, marking one of the most significant technological achievements in the annals of the history of science, …" Scientists do not know when Voyager 1 will reach the undisturbed part of interstellar space where there is no influence from our sun.'


Resources with Additional Information

Additional information about Radioisotope Thermoelectric Generators (RTGs) is available in full-text and on the Web.



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