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Fission space propulsion

  1. Jul 22, 2016 #1
    Hello I'm working on a project to create spacecraft engines that use fission to produce thrust. I will be coming up with many equations and I wanted to have them checked. If you could review them and give me some feedback that would be great. Here is the first equation that describes how the fission produces force:


    where: em - mass of energy released
    ea - acceleration of energy released
    sc - mass of spacecraft
    sca - acceleration of spacecraft
  2. jcsd
  3. Jul 22, 2016 #2


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    Staff: Mentor

    The units of this equation do not work.

    F(propellant) = F(spacecraft) or ma(propellant) = ma (spacecraft).

    (em*ea)/sc=sca would be more appropriate, but that's too simplistic. This is only an equivalence and does not describe how fission produces thrust, rather it only describes the acceleration of a spacecraft assuming some thrust from a fission system. In order to describe thrust, one must show the change in momentum of the propellant and the mass flow rate of the propellant.
  4. Oct 15, 2017 at 11:48 AM #3
    Fission produces energy in the form of heat. That heat is then used to heat water to create pressure which propels it through a pipe to turn a turbine and create electricity. But even then the electricity cannot create propulsion because it's a space craft in a vacuum. There's no medium to manipulate to move yourself in a vacuum.

    The only way I can see this would work on a space craft is if you heated water into steam and shot it out the back of the ship. But that would be a significant waste of a very finite resource and would not produce much thrust.
  5. Oct 15, 2017 at 12:08 PM #4
    its idea in general is very interesting but the equation does not demonstrate the rate of variation of the acceleration, that is in a celestial body approach its acceleration will have to assume the minimum possible, having this in mind you have to have control of the fission depending of the chemical compound you will use, but the idea is very good, continue to refine the calculations that you will go away, but the calculations can not take simplistic calculations.
  6. Oct 16, 2017 at 9:09 PM #5
    Rockets powered by nuclear fission were under development in the USA from 1955 to 1972.
    See Project Rover at Los Alamos.
    And the NERVA and KIWI nuclear-powered rocket engines.
  7. Oct 16, 2017 at 9:35 PM #6
    Oh that's cool. I didn't know that was a thing. Just saw a video that they're starting to look into it again as an engine for going to mars.
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