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

Nuclear rocket propulsion

  1. Jul 6, 2007 #1
    I have been reading a bit lately about project orion and the NERVA project. Project orion seems like such a crazy project that you cant help to love it:approve: Im not suprised it got shut down however.

    But is there any research going on anymore in the states or any other country that is similar to NERVA?

    As I understand it NASA's recent Prometheus project was oriented towards using reactors for electricity production to power equipment and ion engines. But no nuclear thermal propulsion?

    Is nuclear thermal propulsion research more or less dead all over the world right now?
  2. jcsd
  3. Jul 6, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    The Russians have had an active program, at least up through about 2005, in direct nuclear thermal. Jim Tulenko and others at University Florida's Innovative Nuclear Space Power and Propulsion Institute (http://www.inspi.ufl.edu/ [Broken]) have had a program on high temperature materials for fuel, e.g. U-Zr-C and derviatives.

    There is no full scale NTR program in the US, but there are limited experiments on high temperature materials.

    Prometheus is more or less dead. There are very limited activities, and I believe some of the work has moved over to some of the GenVI activities.

    I have some contacts in DOE and NASA with whom I can check.
    Last edited by a moderator: May 3, 2017
  4. Jul 7, 2007 #3
    That would be great! :)

    A related question. If the states where to begin a big project again similar in scale to NERVA. Would it be completely impossible for a foreigner to work on the project?
    Next year Im going to have my masters diploma and then follow it up with a phd in reactor physics. I would love to work on nuclear propulsion at some time in the future, but sweden will never start such a program. I doubt ESA will either. So only the states, russia and china left.
  5. Jul 7, 2007 #4


    User Avatar
    Staff Emeritus
    Science Advisor

    It would not be impossible, and actually there may be collaborative projects between ESA and NASA. Now one complication might be if the research and development work were done by Bettis or Knowles Laboratories. These places do classified work on nuclear propulsion for the military, US DOD. It is effectively impossible for foreigners to work there.

    NASA's Marshall Center has the lead on boosters and heavy lift vehicles, so perhaps it would be possible to get a job there. However, it depends on whether or not there is an opening, and whether or not there is a program like Prometheus.

    Here is an abstract from a recent conference.
    Nuclear Thermal Propulsion
    Mars Mission Systems Analysis and Requirements Definition
    http://www.inspi.ufl.edu/space07/program/abstracts/2072.pdf [Broken]

    Another conference dedicated to space nuclear is STAIF
    http://www.unm.edu/~ISNPS/conferences/conferencec.html#ct203 [Broken]

    See also

    http://anst.ans.org/RelatedLinks.html [Broken] - lots of archival material on this page, like the link above

    If China has a program, they are not saying much if anything about it.
    Last edited by a moderator: May 3, 2017
  6. Jul 8, 2007 #5
    Who says you have to be a foreigner? Come be American!

    Always liked Orion myself. I thought we abandoned it because of some treaty we signed with the Soviets in the 60's.
  7. Jul 10, 2007 #6
    Thanks ALOT for the links! Just the kind of links I have been looking for. Perfect for the 22 hour trainride I will embark on tomorrow.

    It would seem like the best thing to do is to keep fingers crossed that nuclear thermal propulsion will get a new life now that nuclear power is becoming more and more accepted. :tongue2: Il be damned if I dont end up working on it at some point in my life.

    Well maby someday I will come and be a american if I see a need for it :approve: Lower taxes and higher salaries compared to Sweden sure is tempting :biggrin:

    It would have been nice to se if Orion could fly. If there was some way to limit the fallout.
    Last edited by a moderator: May 3, 2017
  8. Jul 11, 2007 #7
    Burning Plasma?

    It seems like most of the obstacles/liabilities with the nuclear rocket are
    a) fear of Chernobyl disaster due to launch failure
    b) fear of irradiating the crew

    Well, B could be addressed if the rocket is purely intended to lift heavy unmanned payloads, allowing the crew to get to orbit by separate alternate means.

    As for A, I'm wondering if the rocket could be designed to eject the core to have it parachute to the ground, in the event of a launch failure.

    Or else, what about the idea of a fusion process -- like a burning plasma?
    Fine, a burning plasma is just a temporary high-energy state which doesn't last, but likewise so too are the H2-burning space shuttle main engines only producing output for about 8 minutes.

    The longest duration burning plasma was made to last 28 seconds by Japan's JT-60 experiment.

    IIRC, that was a hundred-fold improvement over previous trials.
    If that could be further improved by a factor of 15, then it could be enough to get a rocket into orbit.

    When the ITER experiment is conducted, it is expected/targeted to achieve a burning plasma duration of 500s, at 500megawatts of fusion power:

    So let's suppose that goal is achieved. Couldn't it then serve as the basis for a powerplant in an Earth-to-Orbit heavy launch vehicle?

    Comments? Analysis? Speculations?
  9. Jul 12, 2007 #8


    User Avatar
    Staff Emeritus
    Science Advisor

    Nuclear Thermal Rockets would likely be lifted into space for use in moving from LEO to Martian orbit. Radiation is certainly a critical issue, not only for the crew, but for anyone in the vicinity of the rocket motor.

    The greatest exposure from NTR's comes from the nozzle end, since there is effectively not shielding there - it's basics the exit (lower/bottom) plenum of the core.

    On the sides and top, shielding is provided by the structure and the propellant. Hydrogenous propellants (e.g. H2, NH3, CH4 or B2H6) provided shielding from neutrons, which 'leak' from the core. Metal hydrides like LiH or ZrH2 also can provide shielding for neutrons. However, the goal in rocket design is to minimize mass in order to minimize energy requirements.

    Fusion will not work for propulsion from the earth's surface. Then plasma densities are way too low, which means thrust is too low, AND the magnets of a confinement system are too heavy.

    In space, fusion propulsion MIGHT work - but I have strong reservations about that. We still need to perfect controlled fusion on ground. Propulsion systems are an entirely and much great challenge.
  10. Jul 12, 2007 #9

    Suppose the plasma is used to heat a propellant, even mixing into its exhaust stream for max heat transfer, with the plasma's energy supplementing the usual H2 + O2 heat of combustion. Suppose you also use the cold temperature of the liquid H2 & O2 to cool some magnets made out of some lightweight superconductor? Again, the purpose is to enable/provide heavy lift capacity from Earth-to-Orbit. Instead of lifting several tons or even 100 tons of payload to orbit, you want to lift hundreds of tons to make things more economical.

    Why wouldn't this then work? What further obstacles would there then be?
    Has anyone ever proposed anything like this approach, which I could try to read up on?
    Last edited: Jul 12, 2007
  11. Jul 12, 2007 #10


    User Avatar
    Science Advisor


    Astronuc is correct - the plasma densities are too low. If the plasma
    density is low - the amount of energy you are adding is TRIVIAL!!

    You have to work the numbers to see this is a shovel with a rope handle.

    Dr. Gregory Greenman
  12. Jul 12, 2007 #11


    User Avatar
    Gold Member

    I thought the idea for nuclear heavy lift was you carry your own thrust mass and heat it/accelerate it w/ nuclear sourced energies. And who said anything about magnets! Tokamaks are not the beginning and end of fusion.

  13. Jul 12, 2007 #12


    User Avatar
    Gold Member

    I find it frustrating that all of these press releases fail to release numbers in pure Lawson terms - density*time any maybe energy. A benchmark of time confinement alone is meaningless except for hinting at an increase in $ budgets. 'Normalized' plasma pressure? 'High' pressure? Come on.
  14. Jul 12, 2007 #13


    User Avatar
    Gold Member

    I believe that it was the original SALT, which banned the deployment of nuclear weapons in space. Since the Orion 'engine' was essentially a sizeable supply of H-bombs, they had to pull the plug. (I don't know, however, whether the story is true or a myth.)
  15. Jul 12, 2007 #14


    User Avatar
    Staff Emeritus
    Science Advisor

    IEC's are also too heavy.

    That's part of the it. The other part is the number of nuclear warheads? Do the math, and one finds metric tons of nukes. It's just not feasible.

    The plasma denisty and mass flow rate are too low! The mass of the plasma is too small compared to mass of H2 + O2. And one still needs to get the plasma heated, which takes a massive system.

    It is. The NTR was initiated to carry the prototype thermonuclear weapons which where too heavy for chemical rockets of the time. Then the thermonukes got lighter, and chemical rockets more powerfu. Then the nukes were supposed to used for missions to Mars - and then the program died in the 70's, resurrected under SDI in 80's and died again, resurrected in the 90's and died again, resurrected by Bush II only to die again.

    A good book on NTR history is James Dewar's "https://www.amazon.com/End-Solar-System-Nuclear-Rocket/dp/0813122678"
    Last edited by a moderator: Apr 22, 2017
  16. Jul 12, 2007 #15
    Power Demand Profile, Zero-to-Escape

    Firstly, a thermonuclear reactor is not a weapon -- no more so than the RTGs which have gone up on various space probes. Actually it's even less so, since there's no potential for the radioactive fallout hazards you could get with fission reactors.

    Nextly, even if a tokamak/spheromak's plasma density is low, the power density is still high, and that's ultimately what you want to transfer to your propellant, to make thrust. 500megawatts continuously for 8 minutes (projection for ITER) is nothing to sneeze at. The low plasma density simply means that we have to find a different way to achieve the power coupling with the propellant. Perhaps some kind of magnetic induction heating process? Or else RF heating like VASIMR?

    Again, if we use a cryogenic propellant, we can get double benefit -- cryogenics keeps the propellant at a manageable volume, and also the low temp of that propellant can be used to supercool some superconductive magnets on our tokamak/spheromak.

    Perhaps carbon nanotubes could be used for lightweight wiring, in conjunction with other warm-temp superconductor materials, to make a sufficiently lightweight tokamak/spheromak.

    Check out China's EAST tokamak, which was built in just 7 months and used superconducting magnets, even though it didn't attempt any burning plasma experiments:

    If our burning plasma was made of the nifty Helium-3, then we could efficiently capture all its thermal proton output, while neglecting any trivial neutron emissions.
    With the density and mass of a burning plasma being so low, as you've pointed out to me, perhaps the available supply of 3He right here on earth (byproduct of nuclear weapons) might be sufficient for a large-scale tokamak/spheromak experiment, to achieve/demonstrate a burning 3He plasma with high energy harvest.

    The reason why I selected the burning plasma is because of the power demand profile of a space launch's flight envelope. Spacecraft expend the most energy up front, while going from zero to escape velocity. After they achieve orbit, the power demand requirements drop considerably. So even if you hypothetically had some ready-to-go nuclear reactor for your space launch, the fact is that you don't need the full mighty nuclear power output except for achieving escape velocity. After you achieve escape velocity, you've got more time to do whatever further acceleration you want for going elsewhere.

    If you can come up with a power source that will supply hundreds of megawatts (gigawatts?) continuously for several minutes before fizzling out, then that power source should be suitable for Earth-to-Orbit purposes, providing it's not too bulky/heavy. That's why I'm thinking that a burning plasma in suitably lightweight tokamak/spheromak would be the best fit for the power demand requirements.

    Why can't we pick which power source to develop based on the power demand profile of the application? If we don't need the full mighty nuclear power except for those first several minutes when we're trying to achieve escape velocity, then why can't a burning plasma do the trick?

    Again, the goal here is to lift payloads of at least a few hundred tons or more to orbit. What better way can you think of to lift that kind of mass without using nuclear power?
    Last edited: Jul 12, 2007
  17. Jul 12, 2007 #16
  18. Jul 12, 2007 #17

    http://www.engr.psu.edu/antimatter/Papers/AIMStar_99.pdf [Broken]
    Last edited by a moderator: May 3, 2017
  19. Jul 13, 2007 #18


    User Avatar
    Staff Emeritus
    Science Advisor

    One has to look at the kW/kg of the system.

    Also, the Space Shuttle system produces ~ 11.7 GW of power for several minutes according to Power of a Space Shuttle

    From NASA - At full throttle, the three SSMEs produce 37 million horsepower = 27.6 GW
  20. Jul 13, 2007 #19


    User Avatar
    Science Advisor


    He-3 is NOT a byproduct of nuclear weapons production!!

    The reaction by which Trititum is made for nuclear weapons gives you He-4; not He-3.

    Dr. Gregory Greenman
  21. Jul 13, 2007 #20


    User Avatar
    Gold Member

    Based on what? Its all 'E' - electrostatic, no superconducting magnets.* The lab units are typically < 1e2 Kg, and scaling up to 1M diameter units is probably still 1e3 Kg. Then I suppose you are assuming a massive blanket to manage neutron 1st wall damage? Perhaps, but at least for a rocket we'd carry all are own tritium at launch, no need for a Li breeder blanket.

    *Rostoker's Colliding Beam reactor uses FRC but I don't recall if its superconducting.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Nuclear rocket propulsion