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  1.  (10953.1)
    I'm writing a story that involves interplanetary and intergalactic travel and am trying to keep it grounded in reality. While the story in not heavily reliant on the tech side of things, I am wondering what type of thoughts there are about power sources for shuttles that would travel between galaxies. I can imagine solar would be something, but in deep space that it would be difficult to come across. Nuclear fusion is another idea.

    I'm looking for ideas more than anything...theoretical or practical ideas. Once again, it is not a huge plot point, but it is something that I would like to have an idea about.

    • CommentAuthor256
    • CommentTimeJan 3rd 2013 edited
    For the record:
    "travel". Longest journey on earth (length of the equator) = 40,000 km.
    "interplanetary travel" = "between planets (in a solar system)". Example: Earth to Mars - about 55,000,000 km at closest. (x 1,000)
    "interstellar travel" = "between stars". Example: Sun-Alpha Centauri 40,000,000,000,000 km. (Factor: ~1,000,000)
    "intergalactic travel" = "between galaxies". Example: Milky Way-Andromeda Galaxy: 24,000,000,000,000,000,000 km. (Factor ~1,000,000.)

    Notice that the distance scale goes up by a factor of 1,000 after the first step, and then by 1,000,000 for each of the next two steps.

    Interplanetary travel is the only stage of which we have any experience, and it's still a wide open frontier. Current technologies include chemical rockets, ion engines, and electric propulsion. Solar sails have, I believe, been tested in Earth orbit with mild success, but not for interplanetary missions. (Wiki also has a section on Hypothetical propulsion methods.) Power sources are solar out to about Jupiter, and radio-thermal generators thereafter (basically, generating a tiny bit electricity from radioactive decay, far less than from fission or fusion)

    Interstellar travel could use any of those methods assuming you have several hundred thousand years to get there. Radical propulsion techniques include the ever-popular Lots And Lots Of Atomic Bombs Method which has been speculated to be able to deliver a probe to Barnard's star (6ly) within a human lifetime, which I suppose would be nuclear fusion. And also things like lightsails driven by lasers or masers, which require planetary-scale power sources, I think.

    Intergalactic travel (which, let's remember, is on a scale 1,000,000,000,000,000 (one quadrillion) times larger than terrestrial journeys) is so beyond what's possible that there is effectively no "reality" to it at all: Getting to the closest galaxy in anything under 2.5 million light years requires breaking known physics (because that's how long it takes at the speed of light). I suppose you could do some stellar engineering to slingshot a small sun out of the galaxy, but the fastest moving star (relative to the sun) is only going at about 1000km/s, and so would take about 750 trillion years to reach Andromeda.

    Other than that, if you're going to invent physics anyway (a noble tradition), you could just create a method of warping space or creating wormholes, and define it to have as large or small a power demand as you want. It could run on the heat from a cup of tea.
  2.  (10953.3)
    Hmm, here are ten different versions of space travel, from the practical to the downright outrageous. I am thinking that interplanetary travel might be the way to go with this story, something in our solar system, to maintain the idea that this is somewhat realistic.

    Thanks @256 for your info. Lots and lots of atomic bombs method.:)
    • CommentAuthorOddcult
    • CommentTimeJan 4th 2013
    You need an engine constructed from unobtanium that runs on imaginarium.
  3.  (10953.5)
    years ago I read a book called "time travel in Einstein's Universe" which introduced me to a couple of different concepts.
    One of the coolest was a theory that Faster Then Light travel could be achieved if spaced had been "pre-warped"

    Effectively, a slower then light speed ship would warp space akin to laying train tracks, then FTL speeds could be achieved by different ships using those tracks of warped space.
    • CommentTimeJan 4th 2013
  4.  (10953.7)
    A while ago I came across a massive site for people writing sci-fi stories and wanted some scientific accuracy / reference to other authors' handwaves. They have a fairly extensive page on FTL.
    • CommentTimeJan 5th 2013
    Aside from Slick's link, there's the story of the young, Egyptian quantum physic who's theorised a way of travelling: Inhabitat link
    • CommentTimeJan 6th 2013
    @Magnulus saw that a while back but it's just a casimir effect power source providing free energy rather than a space travel method.
  5.  (10953.10)
    The quickest way to get me to lose interest in a sci-fi story is to start talking about galaxies as if they were land masses, with people casually travelling from one to another. A society in which that's possible would not have "people" as we know them, or much of anything else that we would recognize.

    Even if you limit the setting to interplanetary travel, it's important to keep the scale intact. If it takes hours to get to the Moon from Earth, it'd take weeks to get to Mars. If they can get from Earth to Saturn in a matter of hours, then they've probably also started interstellar (many-year) travel, because they're already up to a large fraction of the speed of light.
    • CommentAuthorStefanJ
    • CommentTimeJan 6th 2013
    The greatest one-stop resource for information on space ships and space travel is Winchell Chung's "Atomic Rockets" site:
    • CommentAuthor256
    • CommentTimeJan 6th 2013
    @Jason - yeah, that's something that always bothers me. Particularly since it's generally unnecessary for anything to be from another galaxy.

    I guess it's because most people - including quite a lot of people interested writing in science fiction - don't have a good handle on the relative sizes and distances of the cosmos. It is understandable, though, because even when you know the numbers (cf. my first post) it's hard to get an intuitive feel for things that involve such large numbers.