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

Project Orion

  1. Jun 14, 2005 #1

    What do you guys think, is it time we start looking at options such as Orion again? Most of the necessary pieces of the project had/have been developed, and it is tempting to know that the first planned flight for an Orion-based spacecraft was to make a lap around the Solar System on a timescale of less than a year!

    http://www.bbc.co.uk/bbcfour/documentaries/features/mars-a-bomb.shtml [Broken]
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Jun 14, 2005 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    No! . . . .
  4. Jun 14, 2005 #3
    any particular reason?

    if it is over fallout/pollution, what about the potential solutions to the problem that the wikpedia article mentions?

    and even if they still cannot be overcome, why not assemble in orbit and blast off nukes to our hearts content outside of the earth's atmosphere?
  5. Jun 14, 2005 #4
    The whole project sounds very science fiction. In fact, I am reminded of the recent movie "The Core". The section talking about the problems mentions the fallout from using this technique, I do not think doing this in orbit would be any safer.
  6. Jun 14, 2005 #5
    ...and yet the project was very real. Experiments were done to test the concept.

    As far as doing it from outside the atmosphere (note: not necessarily from orbit), isn't there radiation out in space anyway? Wouldn't the radiation increase vs. background gamma radiation be a pittance? It would be like urinating in the ocean and calling it "pollution".
  7. Jun 14, 2005 #6


    User Avatar

    Staff: Mentor

    Depends on how you define "real" - from what I have seen it wasn't much more than some very theoretical back-of-the-envelope calculations. I would actually be curious to know what the total budget was and how many engineers they had working on it. edit: it says in the second link that it went from 1958 to 1965, but that doesn't really tell us how big it was... Considering that to really get such a craft off the ground would be a project perhaps an order of magnitude larger than the Apollo program (which was the most expensive and complicated engineering program ever), that doesn't say too much for what was really done.

    But maybe I'm getting ahead of myself - I think Orion was fatally flawed in three very basic ways: I don't think such a thing would be feasible from an engineering standpoint, an economic standpoint, or an environmental standpoint.

    re:building it in orbit -
    Building one in orbit eliminates virtually all of the economic benefit.
    Last edited: Jun 14, 2005
  8. Jun 14, 2005 #7
    True. Orion was never quite moved out of R&D phase to actual production, despite Werner von Braun's approval.

    As for the engineering challenges...when is this not the case when space travel is involved? It is imaginable that there would be considerable difficulties in making an orion spacecraft work, but the question is: is it worth it?

    Which brings up the point you mentioned, economics. In terms of economics, what could be worse than chemical rockets? Given the massive nuclear arsenal of 'overkill' that countries like USA and former-USSR possess, the main arguments for Orion were that you could move a great amount of mass more cheaply than with chemical rockets.

    It also makes current pipe-dreams like a manned mission to Mars and Jupiter a reality, if the technology were to work. The constraints imposed by the orbital periods of these planets with respect to the Earth would be alleviated. Astronauts could travel in large groups, in relative comfort, in a large ship capable of real travel around the Solar System...

    would these potential benefits be worth the effort nowadays? I myself am not entirely convinced, but at the same time I see alot of R&D going into alternative propulsion mechanisms again so it is relevant to bring up the topic once more, IMHO.
  9. Jun 14, 2005 #8


    User Avatar
    Staff Emeritus
    Science Advisor

    My terse answer is all that Orion deserves in my opinion.

    I share Russ's opinion on the matter.

    I advocate the economic, safe and responsible use of nuclear energy.

    Certainly Orion is unthinkable (and unconscionable) within the Earth's atmosphere.

    As for experiments, there was a scale model using chemical explosives. It's not the same thing full scale for a number of reasons.
  10. Jun 14, 2005 #9
    that depends...let's say we want to send a manned mission to Saturn. Let's say that for reasons related to human physiology, we need to restrict the total time for our astronauts in space to be a maximum of 1 year.

    Assuming that the orbital mechanics allow for a 6 month trip in each direction, how could we possibly do this with chemical rockets? We couldn't.

    So if we wanted to do it, constructing an orion craft from some place outside of our atmosphere (say, the L2 point of the moon-earth system) and launching from there could possibly work. Other alternative methods of propulsion for such a trip (ion drives, etc.) face all of the engineering concerns as orion plus more, since at this point we at least we have some idea of how nuclear explosions work, whereas alternate propulsion methods are at least equally unproven.

    you would agree, that putting things like satellites in orbit in an economically feasible way, is not the point of orion. the point would be that we could do things that are currently impossible given the state of propulsion.

    i am willing to conceed that launching an orion from the surface of the earth is not a good idea. but i have yet to hear an argument why we should not at least consider the idea for interplanetary travel.
  11. Jun 14, 2005 #10


    User Avatar

    Staff: Mentor

    ....and the USA had a GDP of $100 trillion.

    Not a realistic scenario.

    edit: put another way, when the time comes when we need to send a man to Saturn, then maybe it would be time to have another look at Orion.
    Last edited: Jun 14, 2005
  12. Jun 14, 2005 #11
    Well, at the current GDP of $11 trillion and 4.4% growth (assuming growth to hold constant) it will be ~53 years from now, hopefully in my lifetime.

    I guess interplanetary travel is completely out of the question then for the next 50 years.

    I appreciate all of your input (everyone). Thank you.
  13. Jun 14, 2005 #12
    GDP growth of 4.4%? It has only been over four a few quarters in the past several years, I have had to study it for the past week in economics: http://www.bea.gov/briefrm/gdp.htm. That is very optimistic, and I think that is russ' point; he does not rule it out, it is just beyond realistic.
  14. Jun 15, 2005 #13


    User Avatar

    Staff: Mentor

    Sorry to be such a downer - I'd love to see massive spaceships carrying explorers to the outer planets in my lifetime too (I'm 29). We'll just have to see of course, but it very well may be 50 years before this becomes feasible - and then we still need to have the motivation to do it....
  15. Jun 16, 2005 #14


    User Avatar

    I can see where he obtained the 4.4% figure he quoted
    Anyone know what NASA's annual budget is? I'm wondering how it compares with America's military budget of $370+ billion (which accounts for 47% of the world's military expenditure)
    Last edited by a moderator: Apr 21, 2017
  16. Jun 16, 2005 #15


    User Avatar
    Staff Emeritus
    Science Advisor


    Last year -
    for FY2005, according to RedNova.com and other sources.
    Last edited by a moderator: Apr 21, 2017
  17. Jun 16, 2005 #16


    User Avatar
    Staff Emeritus
    Science Advisor

    Back in the mid 80's, some colleagues and I did some scoping studies for manned missions to Mars. We should have been there by now, but . . . .

    So now we have Project Prometheus, the latest space nuclear redux to consider the application of nuclear energy for space exploration, both as surface power source and spacecraft propulsion. Well the program has already changed priorities. :rolleyes:

    JIMO was to be the first application with Nuclear Electric Propulsion, however due to uncertainties about the technology, that mission has been postponed, and the program re-prioritized. The priorities are:

    1. Surface nuclear power system (to be demonstrated on the Moon)
    2. Nuclear Thermal Propulsion system
    3. Nuclear Electric Propulsion system (this was first priority until recently)

    JIMO and exploration of Saturn's moons are important because they will provide materials in support of a human presence out near Jupiter or Saturn, if ever that happens.

    An ORION is not under serious consideration.

    That's one of the problems - massive spaceships - which need lots of energy.

    Designers have to look at the mass to power ratio (inverse of specific power), kg/kW. A figure of merit is about 1 kg/kW. JIMO at 200 kWe with a mass of 15,000 kg's (of which payload is about 1500 kgs) would have a ratio of 75 kg/kWe. It's more complicated than that.

    The problem with ORION is the mass (pusher plate) as compared to the propulsive energy recovered from the nuclear detonation. Then one has to consider how many nuclear propulsive units (each perhaps several 100 kgs). There is a lot of physics to consider and ultimately the actual Isp.
  18. Jun 16, 2005 #17
    Awesome, this sounds very interesting, I would be grateful to hear any cool stories you may have.

    It was my understanding that as you increase the mass of the Orion craft, your Isp actually goes up..Is this not true? The highest estimate I have seen was around 10,000 Isp for a very massive ship.
  19. Jun 21, 2005 #18
    Orion's Isp calculations

    It might seem strange for a problem with ORION to be the mass of the pusher plate, given that favorable-seeming Isp's have been calculated.

    Calcuation of Isp is generally simple arithmetic. Where does complicated physics enter in the case of the Orion?
  20. Jun 21, 2005 #19


    User Avatar
    Staff Emeritus
    Science Advisor

    It's not complicated hitssquad. Rather as you say it is quite simple. However, thrust divided by mass (also a simple principle) yields very low acceleration (a problem with high Isp systems which also have high masses). Very low acceleration means long times to get to particularly high velocities.

    The other point - "Favorable Isp's have been calculated" - but not demonstrated.
  21. Jun 25, 2005 #20
    It wouldn't work. The only reason nukes have shockwaves here on Earth is because explosions cause sudden and violent air compressions. And in case you haven't noticed yet, there is no air in space. The only use I see for it is a literal interstellar ark to save the human race. If earth was on the verge of becoming uninhabitable, we could build maybe twenty of the "super" Orions and launch them all at the same time. The whole reason would be to relocate to another planet with an Earth-like atmosphere.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook