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Questions on space travel for a sci-fi story

  1. May 27, 2006 #1
    Sci-fi writer looking for help

    Hello everyone. I am working on some ideas for a new science fiction comic... more of a space opera really. I'm not a cosmologist or even a physicist, but I actually can understand (or at least grasp) about half of what I've read on the subject.

    I am hoping that I can bounce some questions off these forums to get me on the right track for how to approach interstellar travel and ship mechanics, and maybe get some ideas... like when a Star Trek script just says [...TECH...] for dialogue.

    Obviously I don't want to get -too- mechanical. I'm just a storyteller at heart. Basically I want to know enough so that I don't sound like an idiot.

    Would this general "lounge" forum be the best place, or would such questions be more appropriate in the Cosmology or Astrophysics forums... assuming they are okay to post at all.
     
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  3. May 27, 2006 #2

    Mk

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    General Discussion and General Physics are good, although the mods might want you to stay in General Discussion. Ask as you like. :smile:
     
  4. May 27, 2006 #3

    Danger

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    Be prepared to sacrifice accuracy for art. I was a writer myself, specializing in hard SF (until I got on ADD meds and haven't been able to write since :grumpy: ), so I can help you to make something sound quite plausible to a non-scientist. It is a fact, though, that some things necessary for any inter-planetary, inter-stellar, or inter-species story are simply not possible in reality.
     
  5. May 27, 2006 #4

    Ivan Seeking

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    This is based on our current understanding of physics which may or may not be nearing completion - likely not. We can't say with certainty what might be possible. We can only speak to the limits within our current frame of reference - within the domain of applicability of today's level of knowledge.

    The most interesting thing to come along recently is the Heim Theory, which according to some could make possible an interstellar gravity drive system capable of traveling at many times the speed of light. We began here with links to other threads later.
    https://www.physicsforums.com/showthread.php?t=105915
    https://www.physicsforums.com/showthread.php?t=106059

    Without a unified theory, we can only guess at the absolute limits of physics. There is more information available at this site:
    http://www.nasa.gov/centers/glenn/research/warp/warp.html
     
    Last edited: May 27, 2006
  6. May 27, 2006 #5

    Danger

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    There's no point of me even looking at the Heim article; my math ability is zero. If you and Integral are on board with it, though, that's good enough for me. FTL travel, though, was only a component of the problem. There are also the issues of inertial effects upon a crew during battle maneouvres (Astro's beloved 'Raspberry Jam Delta-V'), the question of how much power can be not only generated, but also safely controlled, in a hand-held weapon, the dispersion of energy beams over distance, the impossibility of building a 'transporter' ala Star Trek, etc..
     
  7. May 27, 2006 #6

    Integral

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    All good SF breaks a few physical laws. The key to "good" is that the author must be aware of WHAT Physical laws are violated, then come up with some excuse (some made up tech etc) which allows the violation. The fewer laws broken the better, the better the understanding of the violation, the better.

    Heim theory, should be a rich source of future techs, trouble is very few really understand what Hiem is doing. In a few conversations with Ivan I am very intrigued, but do not know enough, nor am I ambitious enough, to attempt to actually learn about it in depth. It may be a decade before the jury is back on this one. Meanwhile the SciFi writers will be mining this like crazy. Should be a good time for the writers, while the physicist are puzzling it out.
     
  8. May 27, 2006 #7

    Ivan Seeking

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    I don't know if anyone is onboard with Heim yet, but many of us mere mortals anxiously await word from the ivory towers. It seems that the DOD, the USAF, and NASA were interested enough to take a look at the gravity drive concept - a spin-off from Heim's work.

    late post. This was in response to Danger. And yes, if Heim has something, it could a very long time before we know for sure.
     
  9. May 27, 2006 #8

    Ivan Seeking

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    Oh yes and Danger, don't worry about g's, after all, all that we need are some Heim gravity compensators.

    Transporters will take some time I think...still working on the Heisenberg compensators.

    http://en.wikipedia.org/wiki/Heisenberg_compensator
     
    Last edited: May 27, 2006
  10. May 27, 2006 #9

    Integral

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    So is it time to start work on the improbability drive?
     
  11. May 27, 2006 #10

    Ivan Seeking

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    Not likely...so I guess so.
     
  12. May 27, 2006 #11
    Glad to see I sparked some discussion already. I will have to look at those HEIM threads, since I was thinking along the lines of using gravity propulsion already.

    Oh yeah I know. I don't want to be hard SF. To much time on the numbers takes away from the story IMO. The episodes of Star Trek that seemed only about the numbers just made my eyes glaze over. On the other hand, the times when someone like Michael Stackpole got into the mechanics of X-Wings was really cool, because it wasn't the whole focus.

    Anyway... more questions later. Thanks guys.
     
  13. May 27, 2006 #12

    DaveC426913

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    Larry Niven has some good rules for writers interested in sci-fi.

    eg.

    1] For most advanced sci-fi tech, you will have to tell some lies ("warp drive was invented that can get us to the nearest star in one week"). Tell the lie as soon as possible in your story, so that the readser accepts it as a premise. The bigger the lie, the sooner you should tell it.

    2] You must be internally consistent about your lies (as well as any truths). If transporters can detect and beam every atom of an enemy crew member off their own bridge, then sensor technology can sure the heck tell what that crew member ate for lunch.


    And other goodies.
     
  14. May 27, 2006 #13

    Mk

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  15. May 27, 2006 #14
    Both are good advice. I've had a chats with authors at cons that said similar things. Consistency is definitely the key. In essence you are creating your own universe with it's own laws of physics. :)

    Another approach is the Farscape model. How does it work? It just does.

    Starburst is never actually explained, but establishing it up front is basically the same thing as what Niven says here.

    But regular ship propulsion through normal space is never explained either. When confronted about this by NASA engineers in the episode where Crichton returned to Earth, he just said... "Then your calculations are wrong."

    Can't work for everything, but yeah if you are going to explain it at all, do it up front. My goal is to inject just enough science to keep the story grounded without getting too caught up in it. :smile:
     
  16. May 27, 2006 #15
    1. Does mass or distance factor into red shift equations?

    Specifically, if a spaceship exhausted a large enough energy burst to be seen from a great distance... would the energy stream and the ship appear red as they accelerated toward lightspeed? How fast would it need to go to appear red? Or does this principal apply only to large celestial bodies lightyears away?

    2. How fast would a VASIMR drive make a ship go? (asked like a Pakled) :bugeye:

    I saw that this kind of magnetic/plasma drive has a theoretical exhaust velocity of 300,000 m/s. But what does that actually mean in terms of speed of the ship? In km/h and % of lightspeed? Assume a freighter sized ship, which I'm thinking would be the size of a destroyer, eg 5500 tons.

    3. How much velocity could a ship gain with aid of a magnetic sail helping the engine with the thrust/mass ratio? Same size ship.

    4. How much velocity does a slingshot actually add?

    Those last three questions can be rephrased... how does a decrease in mass/thrust ratio convert into actual speed?

    I understand the concepts, but the math is making my head explode. Be gentle. I got through Calc 1 and 2, but flunked Calc 3 in college :yuck: ... which was over 10 years ago. :uhh:
     
  17. May 27, 2006 #16
    One more while I am thinking about it...

    5. How much space is between galactic arms?

    The ideal spot for habitable planets is in the empty space free of the dust that concentrates in the spiral arms. How wide and long is the sliced area between Sagittarius and Orion, for example?
     
  18. May 27, 2006 #17

    Danger

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    You're rapidly weirding me out here, pal. You passed Calc 1 & 2, and took 3, in college, and yet you're here asking questions that seem remedial. I don't mean any offense by that, but it confuses the hell out of me. I have a grade 9 math level, and never finished high-school, but some of your questions seem like grade 8 stuff. Most of your questions in the last post, for instance, depend upon factors that you haven't introduced. Exhaust velocity, as a case in point, can't be directly related to the speed of the vehicle unless you also specify the mass of the reaction thrust v/s the mass of the ship. The 'slingshot' effect, similarly, depends upon the mass and velocity of the incoming vessel combined with the mass of the planetary body. We need a lot more information before we can even start to assist you.
     
  19. May 27, 2006 #18
    Sorry for making the separate thread. Mods keep a tight ship here.

    Anyway, I'm not surprised that my questions sound odd. It seems that no matter what subject I try to tackle... I reach a point where the mechanics of it get so overwhelming that it's like my brain shuts down.

    Case in point: math. I got A's in my accelerated courses through high school. The downward curve started when I took Calc... then I hit college level math and you could literally hear my brain break down. Any time I get from high end concept down into the nuts and bolts or pretty much anything, I get lost.

    What all that means is that I probably shouldn't think so hard about speed because I have NO idea what thrust would be in these kinds of drives. I'm lost on the concept and how to use mass/thrust ratio to determine speed.

    And yet I can read Stephen Hawking and follow it! :eek:

    All I can figure is that I overestimated the size the ship I'd use. It'd be more like 100 tons.

    I was hoping that there was a figure for how many times a magnetic sail or a slingshot could multiply any given speed for a ship like that. I am now guessing there is not.

    Picking arbitrary numbers out of the air, I was wondering if you had a hypotheical drive that got a ship up to .1c in real space... would a sail get it up to .3c?

    From what I understand, a sail or a slingshot are just ways of conserving energy, because they won't require as much thrust to get the same speed... so with the boost, you'd effectively go faster by channeling the engine's output more effeciently.

    Or am I completely misunderstanding? Explain it to me like I'm an 8th grader at Star Fleet Junior Academy.

    I'm actually most concerned with the redshift question. It's a "minor" detail that affects what I was hoping would be a signature of the series.
     
  20. May 29, 2006 #19
    I got wrapped up in the "Blog" thread, and forgot why I originally came here. I'd like to bump this by reposting the main question that I hope can still be answered about redshift...

    On space travel times, I think I just need to come up with arbitary numbers. The math, factoring mass/thrust ratio is just completely beyond me.

    Unless someone can give me a general idea of how much velocity a magsail or slingshot relative to the size of the planet/moon would add to a starship's travel, I'll just wing it and hope I don't sound retarded.
     
  21. May 29, 2006 #20

    Astronuc

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    That's hard to beat!

    But I'd still like to know how Max Quordlepleen got from the Big Bang Burger Bar (beginning) to Milliways. Whatever method he used, it must be very froody! :cool:
     
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