Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Russian style nuclear powered drive for a space ship?

  1. Oct 10, 2018 #1
    Russia has developed a micronized nuclear powered drive for ballistic misiles and cruize misiles. This is obviously a very aggressive and environment polluting action.

    However, could such nuclear powered drive be used for space ships, that would start in space and do not touch the atmosphere of earth?

    There is a lot of background radiation in space allready, so that a little more wouldn't really be a pollution, right or wrong?

    How much power would such nuclear drive approximately have?

    Consuli
     
  2. jcsd
  3. Oct 10, 2018 #2

    russ_watters

    User Avatar

    Staff: Mentor

  4. Oct 10, 2018 #3
  5. Oct 10, 2018 #4

    russ_watters

    User Avatar

    Staff: Mentor

  6. Oct 11, 2018 #5
    Without details it's hard to say for sure. Just because it's nuclear?
    There are several different solutions known for nuclear powered jet and rocket engines.
     
  7. Oct 11, 2018 #6
  8. Oct 11, 2018 #7
    No, it is not. It was only a design choice for that Pluto project, which was intended to be a disposable engine used in a nuclear war.
    There is no rule stating that a nuclear powered engine must leave a trail of fission products behind.
     
    Last edited: Oct 11, 2018
  9. Oct 11, 2018 #8
    And the environmental friendly design of a nuclear (fission) ramjet engine - you are talking about - is what?

    Consuli
     
  10. Oct 11, 2018 #9

    russ_watters

    User Avatar

    Staff: Mentor

    All you need to do is not expose the core to the air like in literally every nuclear reactor in service. When I first googled this I thought it was an error because the idea of exposing the core to the air is just so stupid. But I guess during the cold war they would entertain ideas that were only viable if the world was already in the process of being destroyed.

    Anyway, there can be no "accepted" conventional wisdom for experimental projects, by definition.
     
  11. Oct 11, 2018 #10
    However it seems, that russian military has only managed to micronize a nuclear ramjet engine, that fits into a rocket or cruize missile, by operating a critical nuclear reactor unshielded and exposed to air.

    Consuli
     
  12. Oct 11, 2018 #11

    russ_watters

    User Avatar

    Staff: Mentor

    I'm aware. That doesn't make it "well accepted" that it has to be that way.
     
  13. Oct 11, 2018 #12

    anorlunda

    Staff: Mentor

    I don't think those engaged in global war, conventional or nuclear, are much concerned with niceties.
     
  14. Oct 12, 2018 #13
    Exactly. One who accepts, that a conventional warhead will automatically be also a (nuclear) dirty bomb, will - most probably - accept polluting the environment by radioactive material, either.

    However, this polluting the environment discussion by the russian nuclear ramjet engine is out of the scope of what I have been asking in my initial posting.

    I wanted to know, if the russian nuclear ramjet engine or Boeing's fusion drive engine could be used to propel a space ship.

    And Russ has answered my question so far, that
    • the russian nuclear ramjet engine is a jet stream engine, that requires air to produce thrust,
    • Boeing's fusion drive engine is also called a jet engine, but effectively would run without air.
    So my following questions are:
    1. Thus, Boeings fusion drive engine is much more appropriate to propel a space ship (if it works), because it does not need air or any other extra carried matter, that gets heated, so that it gets spit out with high velocity backwards (to produce thrust)?
    2. This is only the case, because the fusion products of Boeings fusion drive are gases (at the temperature of the reactor/ combustion chamber?
    3. Isn't it possible to select a very special fissible material as nuclear fuel, that has a fission chain, that produces a lot gases in the end (so that it wouldn't be necessary to carry extra matter for heating to produce thrust?)
    Consuli
     
    Last edited: Oct 12, 2018
  15. Oct 12, 2018 #14

    anorlunda

    Staff: Mentor

    Even if you have a lot of energy, you still need reaction mass to make a lot of thrust.

    But we do have ion engines that make small thrust for long periods of time to accelerate light weight space probes. Is that what you're thinking? or is it thrust large enough for manned spacecraft that you're asking about?
     
  16. Oct 12, 2018 #15
    I am asking for thrust of a large manned spacecraft.
     
  17. Oct 12, 2018 #16

    anorlunda

    Staff: Mentor

    In that case, no. Outgasses from a nuclear reactor will provide nowhere near enough thrust.
     
  18. Oct 12, 2018 #17

    Astronuc

    User Avatar
    Staff Emeritus
    Science Advisor

    Well accepted by whom. In the article cited in the OP, details are insufficient to render definitive perspective on activity release. Nuclear ramjets are not inherently polluting with fallout, but they could if poorly designed. I suspect in the case of a nuclear powered cruise missile, it would not be conventional. Roughly one third of fissions produce volatile or gaseous (Xe, Kr) fission products, and these can be limiting if burnup goes much beyond 6-7% fission of initial metal atoms. A cruise missile is designed for minutes to hours of operation, and the burnup will depend on the fraction of fissile material consumed during the flight.

    Forget fusion systems, since we do not have a controlled nuclear fusion system generating power over hours as steady-state.

    As for propulsion, there has to be a propellant, e.g., hydrogen or some other fluid. There are various types of electromagnetic thrusters, which could use a nuclear power plant to supply electricity with which to accelerate a propellant. Then there are the more conventional low Isp nuclear thermal systems that simply force the propellant through the core.
     
  19. Oct 12, 2018 #18

    Astronuc

    User Avatar
    Staff Emeritus
    Science Advisor

    1. Still need propellant. One would have to feed the fusion reactor to make up for whatever plasma is used in the propulsion system.
    2. Fusion systems use plasmas, but the plasma has very low density, so low mass flow rate. And fusion systems are massive.
    3. No.
     
  20. Oct 13, 2018 #19
    Correct me if I'm wrong but I feel the need to add something here,
    Russ commented that we don't expose reactor cores in modern reactors (we did in some early test reactors for bomb production) and that is true, we have secondary loops etc, the thing is in a nuclear reactor in order to get water superheated into steam you only need about 300-400 celsius to do that which is well within the material and steel alloy temperature limits so there is no problem of making secondary loops.


    Now if i'm not mistaken in a rocket in order to have some serious thrust the exhaust temperature needs to be high (I read in conventional rockets it is about 3000 celsius) now 350 celsius which is the average design temp of primary loop in a water cooled reactor is nothing compared to that temp. I can make 350 degrees in my home using a gas burner and it won't take or lift off the ground anytime soon.

    In a chemical type rocket the two fuels are mixed but they burn in a special chamber which directly ventilates into the atmosphere so metal parts are not directly subject to this temperature so they don't melt, in a nuclear reactor rocket that is also environmentally friendly you would have to make a heat transfer loop in order to shield the core but since you need to heat the bypassing air to such high temperatures you would need the metal parts that would transfer the heat to the air to be also at this temperature and as far as I'm aware this is the problem also the limitation.
    either you get low temps and the air has very low thrust or you expose the core and the rocket becomes a "one use only" item that simply needs to reach the target and spews "Chernobyl" along the way.



    This is why they were interested in fusion rockets because with fusion you could let the byproducts directly into the air since they are not harmful (Helium for example) but we are yet to reach a point where we can achieve self sustaining fusion so this is off the table for now.
     
  21. Oct 13, 2018 #20
    Ok, I give up. You guys find the environment pollution of the russian nuclear power drive for balistic and cruise missiles more interesting. So, we have to finish this one first, I guess, before we can deal with the thread-openers question. :wink:

    Sounds very plausible to me.

    I also referenced to this miniaturization problem of a nuclear reactor. A cruise missile is not big enough, to install a high temperature heat exchanger in it, if such thing has been engineered yet, at all ! However, no one understood me, as I used - the maybe wrong - term micronisation for it.

    Consuli

    [moderator: p.s. removed]
     
    Last edited by a moderator: Oct 13, 2018
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook