Galt's Gulch

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  • Posted by DrZarkov99 9 years, 6 months ago
    One flaw in the Orion concept was that because of the radiation released, it couldn't be safely used for ground launch. The other flaw was in the use of Earth testing data with conventional explosives to project performance in space. Firing explosives in Earth's atmosphere behind the vehicle was enhanced by the air compressed by the explosive acting as a pressure chamber, keeping most of the thrust behind the vehicle, but when fired in the vacuum of space, with no atmospheric resistance, the effective thrust would be a great deal less due to explosive force moving in all directions uncontained.
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    • Posted by plusaf 9 years, 6 months ago
      Thank you, Dr. Z, for bringing some good science to the discussion. Jules Verne's From The Earth To The Moon sank a large 'gun' into the Floridian soil to shoot a projectile to the moon carrying several passengers. Fortunately, it missed the moon, swung around the back side and returned to Earth.

      Correct: atomic bombs would still need to have something to 'push against' to move a spacecraft. Probably by vaporizing part of the aft-end of the ship itself. Otherwise, where does the 'push' come from...? Excellent point for science-naïve readers.

      Not to mention that if you want to get 'there' from 'here' by setting off multiple nuclear blasts, you'd damned-well position those blasts VERY carefully so the net motion is EXACTLY in the direction you want to go. With energy levels like those released by nukes, a tiny error might create a widely zig-zaggy course!

      Then, there's that issue of radiation....

      And also to note: when a nuke is set off, there's a lot of thermal and immediate radiation damage to nearby areas, but a LOT of the net destruction is from the thermally-induced atmospheric shock waves that rip down buildings, etc. The lack of air in 'space' is an excellent point to consider before rejecting the Orion Propulsion concept.

      Cheers!
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    • Posted by dbhalling 9 years, 6 months ago
      I see that near the surface of the Earth, but I don't see why that would be the case otherwise. The explosion should be roughly in a uniform sphere and the addition or subtraction of air does not seem to matter much.

      It seemed to me that it would have made more sense to make the pusher plate concave rather than flat for stability.
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      • Posted by DrZarkov99 9 years, 6 months ago
        The devil is always in the details. Lots of stability and dynamic issues with Orion, starting with the enormous shock absorber system required. Later variations on the theme included use of deuterium/tritium pellets set off in a large chamber by laser (kind of like the current effort to create fusion power). Smaller, more numerous explosions to create a kind of pulse motor. These latter designs obviated the need for large shock systems.
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  • Posted by dbhalling 9 years, 6 months ago
    Very interesting. Personally, I have always favored electromagnetic rail guns at least for getting stuff into orbit, however the space elevator is also interesting.
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    • Posted by ObjectiveAnalyst 9 years, 6 months ago
      Yes. A modulated rail-gun to control acceleration so man can survive the g-forces. Then something like Ion drive to constantly push the vehicle to greater velocities once in space. Still there is the problem of how to avoid or deflect projectiles... I am fascinated by these subjects, but lack expertise... Any ideas or promising technologies for deflectors? Of course we could ask a Liberal for methods of deflection... :)
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  • Posted by Temlakos 9 years, 6 months ago
    I remember it was called NERVA, for Nuclear Engine for Rocket Vehicle Application. And it would have worked--but you would never have dared take off on a Nerva engine.
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    • Posted by DrZarkov99 9 years, 6 months ago
      NERVA was actually a nuclear reactor, through which hydrogen fuel was flowed, gaining heat from the reactor before being ejected through a conventional rocket nozzle. While it was tested, and showed the promise of relatively high specific impulse (around 900 sec - twice that of the best chemical engine possible), the expected operating life was uncertain, as the very high temperatures and radiation destroyed seals fairly rapidly. As you state, the exhaust had a high radiation level, and would not be suited for ground launch.
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  • Posted by Owlsrayne 9 years, 6 months ago
    So, it looks like no one has read "Project Orion" by George Dyson, Pub: Henry Holt & Co.2002.
    It is very well done account about Project Orion and the young gun scientists at the time who worked for General Atomics. These guys thought outside the box and were on the crux of having their atomic explosive powered ablative pusher plate hydraulic cylinders driven spaceship considered for sending men to the moon and beyond. If it weren't for the Nuclear Test Band Treaty at that time and Werner Von Braun's schmoozing of Gov't officials we would be colonizing Mars and beyond.
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    • Posted by dbhalling 9 years, 6 months ago
      There was also a strong faction that felt vertical takeoff rockets were a mistake. They wanted to see more of a airplane/space plane design. One of their arguments is that it would have been cheaper in the long run. The Shuttle seemed to be a very bad compromise to that idea.
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      • Posted by Owlsrayne 9 years, 6 months ago
        NASA also tried the AeroSpike Engine which was an expensive engineering design. But, couldn't get the fuel mileage for a Space Plane either.
        Maybe Richard Branson will have better luck.
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  • Posted by strugatsky 9 years, 6 months ago
    What about small nuclear explosions creating superheated gases that can provide thrust just as in a chemical reaction motor? The gases would be irradiated due to contact will with the fission material, but it would be a fraction of the radiation as compared to ejecting the core of the bomb itself. Less efficient, but much safer for the ones left behind.
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  • Posted by Hiraghm 9 years, 6 months ago
    Footfall describes the Archangel Michael, an Orion-class spaceship we threw together to get the Traveling Fithp's foot off our chest.
    (you gotta love a story that has Kansas Jayhawkers fighting baby elephants with two trunks on hang gliders and wearing elevator shoes while carrying assault rifles...)
    http://www.baenebooks.com/chapters/03453...
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    • Posted by freedomforall 9 years, 6 months ago
      One of my favorite books, perhaps the best 'alien invasion' book. What an inspiring movie it would make with digital effects!
      Also can recommend Poul Anderson's novel Orion Shall Rise.
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      • Posted by Hiraghm 9 years, 6 months ago
        Two fake movie "trailers" I want to make (cause Pournelle will never let them make the movies after what they did to Starshit Troupers...)

        (spoiler alert)

        A trailer for "Fallen Angels"; starting with the scoopship entering atmosphere, the crash landing.
        Starts with a black screen, then a typical view of Earth, with textover saying, "*They* told us global warming would cause the world to end in fire." (fade out text; fade in text) "*They* were wrong." Then the globe is slowly engulfed in white, starting at the poles. And then you see Piranha screaming through high atmosphere. (with cuts to the cockpit interior and back outside)
        Then the missile attack, then the re-entry.

        Voiceover saying, "Orphans of creation... hunted by the world as enemies of the Earth". Then showing a whiteout after the crash, the sound of feet trudging through snow, then the picture fades in from white 'til you see men & women trudging through the snow.
        And white text on black screen, "ANGELS DOWN... (blank screen) FANS TO THE RESCUE!"
        Then fast clips of the bed race and the "vectors" pointing down from the St Louis Arch, and the funeral and the alderman and Ron Cole, and Larry and Curly racing down I-40, and the Phoenix asleep in her nest... then as the screen goes black, you hear a voice;

        "We'll get them high with illegal droogs".

        Then the screen remains blank as you hear the roar of the Phoenix awakening.
        Then flash the credits and "Coming soon to a future near you".

        The second is Footfall. Not exactly sure how I'd want the trailer to go, but I want to build and animate a model of the Archangel Michael, and a scene of the Kansas invasion, and a scene of the battle between Michael and the Chtaptisk Fithp.

        (you *know* we could freaking build him today if we really wanted to... and if we didn't mind scrapping Bellingham :)

        The two stories have a "character" in common... Harry Reddington, whose honor could be trusted with the future of the human species, but whose judgement couldn't be trusted to get the beer. :)


        (edited to improve description)

        Archangel Michael (found a link...)
        http://www.up-ship.com/apr/michael.htm
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