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Writing Sci-fiction Graphic Novel need advisement in space travel

  1. Jul 18, 2011 #1
    Writing Sci-fiction Graphic Novel need advisement in "space travel"

    I've used VASIMR rockets as a reference and cited them as precursors to what now allows "rapid stellar travel" at say Earth to Mars in forty eight hours. Any advice on how this could be at least theoretically possible?
     
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  3. Jul 18, 2011 #2
    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    I'll directly post a dialogue bubble that I've used to explain this within the story.
     
  4. Jul 18, 2011 #3
    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    "October, 2014. Terra-Cotter revolutionizes magneto plasma rockets by hybridizing thermal syncs and cyclical cyclotron resonance to decrease Earth Mars transit to forty-eight hours."
    Am I on the right track here?
     
  5. Jul 18, 2011 #4

    ghwellsjr

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    Don't you at least want to make the trip take longer depending on the relative positions of Earth and Mars so that if they are on opposite sides of the solar system it will take a lot longer (and cost a lot more)? In fact, you probably don't want to travel too close to the Sun so instead of making a bee line for Mars, you would travel more or less along a curve that would always take you farther away from the Sun. Every two years, Earth and Mars are relatively close together and 1 year later they are the furthest apart. Sounds like some interesting drama could unfold: round-trips to Mars for a six-month period but after that you have to stay on Mars for a year and a half or pay a huge premium to get back home.

    But as far as you technology goes--it sounds far out so who's going to object?
     
  6. Jul 18, 2011 #5

    Ryan_m_b

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    Using a link like this we see that for less than 48 hours Earth-Mars at median distance requires a constant 4g acceleration (with a flip round to decelerate halfway) which would require, taking the Isp of VASIMR to be 12,000, roughly 1000 parts fuel for every 1 part ship.. It seems highly unlikely that this breakthrough would happen by 2014 seeing as a small test engine is planned IRL for the ISS. The biggest problems with a VASIMR engine is the supply of power and the waste heat. This severely limits the thrust and acceleration that a VASIMR can give. If you rewrite it to something like 2030 and suggest a travel time of a few weeks that may seem more realistic.

    Also in the other thread (in the GD forum) you were talking about interstellar flight. VASIMR is nowhere near the technology required for this!
     
  7. Jul 18, 2011 #6

    Janus

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    To get to Mars (at closest Earth-Mars distance) in 48 hrs would require a thrust of 1g (accelerating for half the trip and decelerating for the other half).
    Since VASIMRs are typically of much lower thrust, I have to assume that it is this where the major improvement occurs.

    However, even using a high end estimate for the ISP( an indication of rocket efficiency) of a VASIMR,(50,000) Your ship would require ~35 kg of fuel for every kg of ship to make such a trip in the given time frame.
     
  8. Jul 18, 2011 #7

    ghwellsjr

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    In science-fiction, you're allowed to invent impossible technology, aren't you? But you're not allowed to rearrange the solar system, are you?
     
  9. Jul 18, 2011 #8

    Ryan_m_b

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    It depends on how http://en.wikipedia.org/wiki/Soft_science_fiction" [Broken] you want your sci-fi to be. If you want it to be realistic inventing magic propulsion drive X that runs on handwavium isn't going to cut it.
     
    Last edited by a moderator: May 5, 2017
  10. Jul 21, 2011 #9
    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    What's a realistic time frame for the output I've seen mentioned here? I'm working with a 300 year span. Also a Terra-formation process which I assume would take centuries. As to my story, I want it to be as rooted in reality as I can possibly make it. It creates a better formed "suspended disbelieve". I don't want to use fanciful words just to make it seem sci-fi. I want it to BE science.
     
  11. Jul 21, 2011 #10
    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    What would you suggest then? What feasible impetus system? Anything currently existent, or theoretically possible that doesn't defy physics?
     
  12. Jul 21, 2011 #11

    ghwellsjr

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    Nope.
     
  13. Jul 21, 2011 #12

    Ryan_m_b

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    This is going to be hard. We are nowhere near the technology and science needed to even hypothesise about terraforming, even if we did it would require fantastic industrial power (orders of magnitude above the Earth today) and would probably still take millennia.

    It depends on what you are wanting, interplanetary or interstellar and how long in the future you want these technologies to exist? For interplanetary you could propose a VASIMR drive that can do the Earth-Mars in a matter of weeks/months and propose that such systems exist ~2050-2100. I'm not saying this is likely, but you may get away with it for SF. For interstellar I agree with ghwellsjr, there is no feasible way.
     
  14. Jul 21, 2011 #13

    ghwellsjr

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    I was talking about his original question of going to Mars in 48 hours. That will never happen.
     
  15. Jul 21, 2011 #14

    Ryan_m_b

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    I see, why do you say that?
     
  16. Jul 21, 2011 #15

    ghwellsjr

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    I thought you and Janus both indicated that it would take many times the mass of your ship in fuel to carry out such a mission. And did you calculate the energy required to escape Earth's gravity and the energy to land safely on Mars?
     
  17. Jul 21, 2011 #16

    Ryan_m_b

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    No to the latter question but on the subject of the impracticalities I was trying to indicate it would be highly expensive to do so, not necessarily that it would never happen. It is conceivable (but probably not with a VASIMR) that in the future we will have rockets capable of accelerating at the required level for the required time, whether or not we do it though is another question.
     
    Last edited: Jul 21, 2011
  18. Jul 21, 2011 #17
    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    The amount of mass required depends on the length of the journey, the acceleration desired, and impulse of your engine. So, you should work in reverse. Figure out how long you want your journey to be and the acceleration needed to achieve it (as mentioned above, Earth to Mars in 48hr at minimum separation requires around 1g constant accel.) and decide how big a fuel to mass ratio you are willing to tolerate for the sake of your story. That will give you the impulse you need.

    From there, it's up to you to figure out a physical process capable of providing sufficient power to your engine. A VASIMR is probably not the technology you want, but I could imagine a mid-term future variant that generated a fusing plasma might get you closer to the types of impulses you need. And, if that doesn't work out, there's always Project Orion to fall back on.
     
  19. Jul 21, 2011 #18

    pervect

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    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    If you have a variable specific impulse rocket, the good news that in general you can minimize the amount of energy it takes to accelerate at 1g for 48 hours straight, by setting some mass ratio that you want to use (say 90% fuel), and then adjusting the exhaust velocity / specific impulse you need so that you achieve this with the lowest amount of energy.

    The bad news is that this minimization is still a fantastic amount of energy.

    To see this, just calculate the final exhaust velocity you get if you accelerate at 10 m/s^2 for 48 hours. This is 1 728 000 meters/ second.

    Now, calculate the amount of energy it takes per kilogram to accelerate something up to this velocity.

    That's .5 m v^2 / m = .5 v^2 = 1 492 992 000 000 joules / kilogram

    This assumes 100% rocket effeciency, which is unrelasitic. But will serve to give you some idea of what you're talking about.

    You should do what your plot demands, but as far as the real physics goes, the problem is (and always has been) getting the needed energy / energy density. Saying that you have a "vasimir rocket now", isn't going to really answer how you suddenly got a power supply that could put out a trillion joules per killogram - you can think of that as 1kg supplying about 41,000 megawatt-hours.

    It also doesn't explore the ramifications on society that access to this sort of energy would logically have - and it would be interesting,but probably not fit in with the plot you're trying to write,to speculate about what society would be like if such extreme concentrations of energy were available (especially at a reasonable price).

    Cheapness is implied (from the plot plus a bit of logic) by the fact that people do this, rather than use less energy and take a week for their trip.
     
  20. Jul 21, 2011 #19
    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    Keep in mind that the story is revolved around the Sol system, so we're looking interplanetary. Also that there are numerous posts for fueling which I call way-stations, they're kind of like your universes "road side diners", and that everything's done from a branched out perspective. E.g. set things around Mars, move to Jupiter, then to Saturn, so on and so on. So it's like a systematic expanse that's build upon establishing the necessary things needed to fuel and equip then go further. Also, the "Company" responsible for these technological advances are indeed a "fantastic industrial power". It's written in the lore that they at one time accounted for over a third of the worlds job market and nearly half of the economic market via subsidization and uncountable satellite corporations. "Talk about too big to fail". They make GMC look like the entirety of the worlds banking firms. Imagine if they all went bankrupt.
     
  21. Jul 21, 2011 #20
    Re: Writing Sci-fiction Graphic Novel need advisement in "space travel"

    Additionally this "Company" does in fact leave the Sol system. I haven't quite figured whether or not I'm going to have them in another system or just on some massive planetary sized space station. This is because they were pushed out due a war.
     
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