National Aeronautics and Space Administration Logo
Follow this link to skip to the main content NASA Banner
Solar System Exploration
Return to Solar System Exploration
Facebook Twitter YouTube Facebook Twitter YouTube Flickr iTunes
Follow Us
Radioisotope Power Systems: Power to Explore
17 Feb 2012
(Source: )

For more than four decades, Radioisotope Power Systems (RPS) have played a critical role in the exploration of space, enabling missions of scientific discovery to destinations across the solar system. These pioneering voyages have helped reveal the composition and nature of Earth's Moon, allowed us to witness icy geysers and sulfur volcanoes on moons of the outer planets and sustained long journeys to the outer reaches of our sun's influence. NASA and the United States Department of Energy (DOE) are working together to ensure that space nuclear power technologies will be available to enable or enhance ambitious solar system exploration missions in this decade and beyond.

What is RPS technology and why does NASA use it?

One of the most important components for any space mission is a robust and reliable electrical power supply. For most space exploration missions where sunlight is abundant, solar power has been the preferred choice. But as the environments at chosen destinations grow harsher, and missions evolve to be more demanding, it becomes more likely that effective power and heating for a spacecraft would require the use of a radioisotope power system (RPS).

An RPS converts the heat generated by the natural decay of the radioactive isotope plutonium-238 into electricity; this material is not used in weapons and cannot explode like a bomb. A portion of this decay heat often has an important secondary use in helping to keep spacecraft subsystems warm in cold environments. RPS are designed and built with multiple layers of protective material designed to contain its plutonium dioxide fuel in a wide range of potential accidents, verified through impact testing. In addition, the plutonium used in an RPS is manufactured in a ceramic form, which limits its ability to become a health risk.

RPS offer the key advantage of operating continuously, independent of unavoidable variations in sunlight. Such systems can provide power for long periods of time (significantly longer than chemical batteries), and at vast distances from the sun. Additionally, an RPS has little sensitivity to temperature, radiation, dust or other space environmental effects. They are ideally suited for missions involving autonomous, long-duration operations in the most extreme environments in space and on planetary surfaces.

Targets of Exploration
RPS-enabled NASA Missions
Ulysses (1990-2009)
Apollo Lunar Surface Experiment Package (1969-1977)
Viking 1 and 2 (landers) (1976-1982)
+Mars Pathfinder (1997)
+Mars Exploration Rovers (MER) (2004-)
Mars Science Laboratory (Scheduled arrival 2012)
Jupiter and its moons
Pioneer 10 and 11 (1972-1973)
Voyager 1 and 2 (1979)
Galileo (1995-2003)
Saturn and its moons
Pioneer 11 (1973)
Voyager 1 and 2 (1980)
Cassini-Huygens (2004-)
Voyager 2 (1986)
Voyager 2 (1989)
Pluto and the Kuiper Belt
New Horizons (2015-)

+Solar powered missions enabled by radioisotope heater units (RHUs)

As part of an ongoing partnership with the DOE, NASA is conducting a mission-driven RPS Program whose purpose is to develop the next generation of reliable radioisotope power systems. These technologies could enable a broad range of science missions to operate more widely and efficiently than their predecessors. This program is developing and validating two basic RPS units: the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) and the Advanced Stirling Radioisotope Generator (ASRG).

In the future, radioisotope power systems could continue to support missions to some of the most extreme environments in the solar solar system, probing the secrets of Jupiter's ocean moon Europa, the liquid lakes of Saturn's moon Titan or the brutally hot atmosphere of Venus.

Additional information

For more information about NASA's use of radioisotope power systems, contact Radioisotope Power Systems Program.

News Release, August, 2011:"Power to Explore: 50 Years of Nuclear Space Power".

RPS information from the US Department of Energy:

Radioisotope Power Source Fact Sheets:

  • Radioisotope Power Systems Fact Sheet
  • Advanced Stirling Radioisotope Generator Fact Sheet
  • Multi-Mission Radioisotope Thermoelectric Generator
  • Space Radioisotope Power Systems Safety
  • Radioisotope Power and Heating for Mars Surface Exploration
  • Mars Science Laboratory Radiological Contingency Planning
  • Mars Science Laboratory Launch Nuclear Safety
Awards and Recognition   Solar System Exploration Roadmap   Contact Us   Site Map   Print This Page
NASA Official: Kristen Erickson
Advisory: Dr. James Green, Director of Planetary Science
Outreach Manager: Alice Wessen
Curator/Editor: Phil Davis
Science Writers: Courtney O'Connor and Bill Dunford
Producer: Greg Baerg
Webmaster: David Martin
> NASA Science Mission Directorate
> Budgets, Strategic Plans and Accountability Reports
> Equal Employment Opportunity Data
   Posted Pursuant to the No Fear Act
> Information-Dissemination Policies and Inventories
> Freedom of Information Act
> Privacy Policy & Important Notices
> Inspector General Hotline
> Office of the Inspector General
> NASA Communications Policy
> NASA Advisory Council
> Open Government at NASA
Last Updated: 17 Feb 2012