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I Nuclear batteries on space probes

  1. Oct 23, 2017 #1
    I've been reading about this a bit and stumbled across something that said its desirable that the heat source not be something that emits a lot of gamma radiation.
    Other than hazards to a technician, does this have any effect on the device its being used on? Why would it require extra shielding if its out in space?

    Thanks.
     
  2. jcsd
  3. Oct 23, 2017 #2

    jedishrfu

    Staff: Mentor

    The radiation could affect the electronics being powered.
     
  4. Oct 23, 2017 #3
    thats what i was thinking but i wasn't sure. maybe the gamma ray just passes on through the electronics.
    my initial thoughts were that they wanted a lot alpha particles hitting the inner walls of where the heat source is to create heat but i wasn't sure.
    thought id ask the pros.
     
  5. Oct 23, 2017 #4

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Gamma rays are harmful to electronics, and if they have high energies they can induce nuclear reactions harmful to basically all materials (although you need a very high dose before that becomes relevant).
     
  6. Oct 23, 2017 #5
    would a gamma emitter generate less heat because of gamma rays ability to easily pass through objects?
     
  7. Oct 23, 2017 #6

    mfb

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    2016 Award

    Staff: Mentor

    A part of that energy is lost, sure.
    The difference in overall activity is more important than that.
     
  8. Oct 24, 2017 #7
    awesome. thanks guys.
     
  9. Nov 5, 2017 #8
    In addition to damaging the control system's electronics, the gamma rays may increase baseline noise in the probe's sensors. That would be bad...
     
  10. Nov 6, 2017 #9

    davenn

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    Science Advisor
    Gold Member


    Calling them batteries as in your thread title isn't really a good description. These units are called Radioisotope thermoelectric generators, RTG's and get used on space craft and also for remote location terrestrial power.

    The radio isotopes used have been chosen specifically for their low gamma and neutron emission. Plutonium 238 is a common one used particularly because of high alpha emission and low gamma emission during decay. High alpha emission is desirable because of it's much higher heat production which equals better heat to electricity generation efficiency using the thermocouples.

    In the early space probes like the Pioneer an Voyager ones, the RTG was often located at the end of a long boom well away from the
    rest of the craft....

    on the Voyagers' they were like this .....

    upload_2017-11-7_12-55-8.png

    the RTG's on the boom facing downwards
    the magnetometers were on an even longer boom that can be seen heading towards the lower left of the image.
    with the passing years development of RTG's has improved and are now often much closer to the main body of the space craft

    on the New Horizons craft you can see the two RTG's sticking out on the left side.....

    upload_2017-11-7_13-4-28.png

    a couple of other resources .......

    https://solarsystem.nasa.gov/rps/rtg.cfm

    https://en.wikipedia.org/wiki/GPHS-RTG



    cheers
    Dave
     
    Last edited: Nov 7, 2017
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