NASA Curiosity nuclear powered rover


  1. Strontium-90 has a shorter half-life, much lower power density then Plutonium-238 and produces gamma radiation. Plutonium-238 also has the lowest shielding requirements.

    Jim Adams, deputy director of planetary science at NASA, says that there’s enough of the fuel for NASA missions to around 2022. He says if NASA doesn’t get more after that, “then we won’t go beyond Mars anymore. We won’t be exploring the solar system beyond the asteroid belt.”

    1. DV82XL – you are correct that Pu-238 has characteristics that make it the best choice for space missions that are constrained by weight and heat rejection capability.

      However, certain land based applications for RTGs have no such concerns.

      1. Sr-90 and the Cs isotopes produce the most heat in the used fuel. They must be utilized to publicize the fact that even fission products are useful. These isotopes are also available in large quantities during reprocessing. There are tens of thousands of TV/Internet towers away from habitation and power grids where they can be usefully employed. They can be buried underground for shielding.
        Radiation is less of a problem in the unmanned space missions. Even the shorter half-life of 30 years would be useful.

  2. To this day it amazes me how little NASA hawks nuclear power in its spacecraft as opposed using solar cells! Nuclear is hardly EVER mentioned for Cassini, Galileo, Viking or the Pluto probe, but NASA’s falling all over themselves clucking that the twin rovers and Juno are solar powered! It’s like nukes were some kind of necessary evil! On NASA TV they had a MSL Twitter gathering with mission staff speakers and the RTG guy sounded almost APOLOGETIC that they had to use nukes! I gleaned from SpaceWorld that engineers with the Juno Jupiter probe balked at having solar cells used that far out because NASA at that conception period was in a massive PR binge to save its funding by appearing as “green” and PC friendly to a low science-amplitude public. We’re going to need nuclear reactors in space eventually for reliable deep space manned missions anyway so I wish NASA we’re so skittish about the atom tainting their squeaky-clean (at least to school kids) image.

    We’re coming up on the anniversary of the first nuclear reactor activation in Chicago back on Dec 2, 1942. The TRUE birthday of nuclear fission, NOT as a terrible explosion in a desert as the media and anti-nukers portray it. Any retrospectives possible?

    James Greenidge
    Queens NY

  3. Not only is 2 December the anniversary for CP-1 it is also the anniversary for Shippingport Criticality on 2 December 1957 at 04:30.

    It is my favorite day of the year. My kids look forward to Christmas. I look forward to Critmas.

    Merry Critmas!! And happy neutrons to all!

    The dawn of the nuclear era is as it should be in a time that was a historical celebration of the winter solstice. Where the beginning of the cold and hard winter brought a promise of hardship and privation, even in this modern age. I think it is appropriate to celebrate the birth of nuclear power as an end of suffering. This is why I look forward to December 2 more than any other day of the year.

  4. On one of the TV network news programs, they call the radioisotope thermal generator a nuclear reactor. Sigh…..

  5. NASA has purchases the entire amount Plutonium-238 for this spacecraft from Russia. So long as there is a demand for it, someone will be there to supply it.

    1. Pu-238 is no longer being produced in Russia (or anywhere else), and there is not a substantial amount of 238Pu left in Russia (or anywhere else) available to meet NASA’s needs, beyond that which Russia has already agreed to sell to the United States. Purchasing Pu-238 was intended as a stopgap measure until U.S. production was reestablished, and continued procurement from Russia cannot serve as a long-term solution to U.S. needs unless Russia itself reestablishes a 238Pu production capability. Such a move would require a major investment in Russian production facilities—an investment that Russia seems unlikely to make unless the United States pays for it.

      Restarting production of Pu-238 in Russia would take longer than restarting domestic production because of the long time it would take to negotiate an agreement with Russia and to complete the National Environmental Policy Act (NEPA, 1970) process, which would apply to Russian production of 238Pu if it were funded by the U.S. government. Based on prior experience, it would probably take 2 or 3 years just to negotiate and finalize an agreement with Russia before work could begin. In addition, Pu-238 obtained from Russia can be used only for civil applications and cannot be used to satisfy U.S. national security applications, should they arise. Russia has agreed to sell 238Pu to the United States with the limitation that it be used only for peaceful space missions, and that same stipulation would presumably apply to future purchases.


      1. DV82XL,

        There are however a whole bunch of Plutonium based war heads in Russia.

        The megaton to megawatt program only target Uranium based bombs.

        So there is plenty of supplies still.

        1. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, RTG’s use Plutonium-238. They are not interchangeable, nor are they made by the same process.

          Pu-239 is normally created in nuclear reactors by transmutation of individual atoms of one of the isotopes of uranium present in the fuel rods. Occasionally, when an atom of U-238 is exposed to neutron radiation, its nucleus will capture a neutron, changing it to U-239. This happens more easily with lower Kinetic Energy (as U-238 fission activation is 6.6MeV). The U-239 then rapidly undergoes two beta decays. After the 238U absorbs a neutron to become U-239 it then emits an electron and an anti-neutrino by β− decay to become Neptunium-239 and then emits another electron and anti-neutrino by a second β− decay to become Pu-239.

          Pure Pu-238 is prepared by irradiation of neptunium-237, one of the minor actinides that can be recovered from spent nuclear fuel during reprocessing, or by the irradiation of americium-238.

        2. Gallium, aluminium, americium, scandium and cerium are used to stabilize the δ phase of Pu-239. Pu-238 is considered to be a problematic isotope in nuclear weapon pits and is excluded along with Pu-240 from Supergrade plutonium

  6. According to the NASA plan if they had to go the alternative and use a solar array instead of the bigger RTG they would still have to put radioisotope heaters on the lander.

  7. It might be of some interest to readers here to note that Polaris Books have released a three book series this year by David Buden on radioisotope, nuclear thermal and fission electric space nuclear power systems. Available at Amazon. Might be worth checking out.

  8. @Joel – thanks for the comment, but I did mention the Pu-238 pacemakers in the original post. My initial interest in nuclear batteries was inspired by learning about the pacemaker batteries that were powered by 1/200th of an ounce of Pu-238.

  9. Hello Rod,

    I didn’t know Atomic Energy was such an issue in America, I guess that’s why I was so surprised to learn RTGs have been used for years (NASA documents said they were used in Apollo missions too).
    In France, we are all in nuclear energy (until recently), so I think the reactions would have been different.
    I wrote a page on curiosity’s nuclear battery:
    Please tell me if there are any mistakes. I tried to explain how it works in simple terms.

  10. Rod, since you saw the cardiac pacemakers at the MD science center, you might be interested to know that the RTG for the MSL mission, MMRTG, was made in Maryland but only fueled at INL. Teledyne Energy Systems actually made the generator and all the components that convert the heat directly to electricity. I’ve had the good fortune to work on this project and be involved with this technology for many years. As a result, I travelled to FL to watch the launch of MSL last November. The safety effort and analyses that are required make these generators extremely safe.

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