1. Tessitore

    Tessitore New Member

    Joined:
    Feb 12, 2018
    Messages:
    16
    Likes Received:
    4

    I Have A Question Involving Physics And A Spaceship

    Discussion in 'Research' started by Tessitore, May 6, 2018.

    Okay, this is a little complicated and my understanding of physics is rather shaky so please bear with me. Basically, one of my stories is set on a spaceship that has a rotating section to generate gravity. It has it because it's a really long trip, muscle atrophy is something that they really want to avoid, and the alternative means of generating an approximation of gravity in a reasonably hard sci-fi setting, acceleration, isn't feasible due to continual acceleration not being a viable option since as I said above it's a really long trip. Problem is that they still need to accelerate at the start of the journey to get up to cruising speed and decelerate at the end of it, which would result in two sets of g-forces going in different directions. How do I go about minimizing the problems that this may cause for those inside the ship? At the moment my leading idea is to have the ship accelerate/deceleration at a rate that generates fewer Gs than the rotating section so that there's always a dominant direction for "down" but I'm unsure if that would work and even more unsure how big the difference would need to be.
     
    honey hatter likes this.
  2. Iain Aschendale

    Iain Aschendale The Caliph of al-Abama Contributor

    Joined:
    Feb 12, 2015
    Messages:
    7,803
    Likes Received:
    12,628
    Location:
    Seat 29e, Air Gradia 452
    How long do they need to accelerate and decelerate? If it's a short time (less than a week or so) they could just forgo the gravity for a while, but if it's half the trip, you could build the "floor" in your rotating section at an angle to take advantage of both thrust and spin, kind of like a velodrome track.

    [​IMG]
     
    honey hatter and Cave Troll like this.
  3. Cave Troll

    Cave Troll Contributor Contributor

    Joined:
    Aug 8, 2015
    Messages:
    11,422
    Likes Received:
    11,419
    Location:
    Where cushions are comfy, and straps hold firm.
    I think it will be depend a bit on how effective your propulsion system is.
    An ion drive will not be your friend when the time comes to decelerate.
    The spinning part might be turned off during the first few days to not have
    a negative effect on the process of slowing down. Better safe than being
    thrown of course by the grav forces such a thing can produce, and will
    save a bit on wasting a ton of thruster fuel to keep on course.
     
    honey hatter likes this.
  4. honey hatter

    honey hatter Banned

    Joined:
    May 2, 2018
    Messages:
    804
    Likes Received:
    1,024
    Interesting i have read a few hard sci-fi books over the years. Joe Haldeman's Forever War. They talked about acceleration/deceleration during battle at... close to speed of light? I forget. My thought is this, the ship once in deceleration would cause the spinning section, as well as the rest of the ship to experience forward gravity in the direction of the deceleration. Anyone not secured would go flying forward as soon as deceleration began. I believe. I could be wrong. Most likely wrong.

    I had the idea if your spinning section of the ship was like a gyroscope it could, orientate itself and it's passengers so they would experience planetside like gravity while in deceleration. The ship would possibly take a while to decelerate, just as a train has to start stopping far in advance because they do not stop on a dime.

    For your amusement a japanese anime with a science lesson, though this one does not talk on acceleration/deceleration. It's still very well thought out science.
    skip to 30 seconds in they do talk about different types of propulsion drives.
     
    Cave Troll likes this.
  5. Cave Troll

    Cave Troll Contributor Contributor

    Joined:
    Aug 8, 2015
    Messages:
    11,422
    Likes Received:
    11,419
    Location:
    Where cushions are comfy, and straps hold firm.
    Maneuvering at those speeds would kill everybody onboard if they are accelerating
    to those speeds rapidly. The g-forces would literally smash their poor bodies into
    bulkheads, and at a certain point they become a fine paste of people goo. :p
    However if they are fighting alongside each other, then being at those speeds
    would not be too problematic. They would just need to lead their shots to hit
    their mark.
    The first rule in practical space warfare is not how fast you are, it is being bigger
    than the other guy. Keeping your distance, and making small course corrections
    so that the guy shooting at you is more likely to miss. :p
     
    John Calligan and honey hatter like this.
  6. Tessitore

    Tessitore New Member

    Joined:
    Feb 12, 2018
    Messages:
    16
    Likes Received:
    4
    Depending on how many Gs they pull while doing so, between almost three weeks and well over three months (I've got the exact figures written down but not to hand, credit to Greg's Space Calculations for making it easy for me to find out what they are).

    Also, as I said before, it'd be convenient if down is always in the same direction since there's a lot of things that would be complicated by it changing, especially for a prolonged period of time.

    It should probably also be noted that everyone on-board (well, everyone who's biological anyway) is supposed to spend the journey having a decades long nap, but pretty much the whole plot involves that not being the case.

    I was thinking that it'd be something more high-tech/currently theoretical than a ion drive since there probably isn't anything around today that's up the the task and the story's set some distance into the future so it's kind of expected.
     
    Cave Troll likes this.
  7. TwistedHelix

    TwistedHelix New Member

    Joined:
    May 6, 2018
    Messages:
    19
    Likes Received:
    5
    Maybe I am misunderstanding, and it depends how technologically advanced you want your people to be, but you could fudge a bit of Mach's principle



    They know it is a mechanism as the data shows, but they don't understand why the reference frames work. I would paraphrase the video, but prof merrifield explains it perfectly.
     
  8. John Calligan

    John Calligan Contributor Contributor

    Joined:
    Aug 8, 2015
    Messages:
    974
    Likes Received:
    884
    The floor of the rotating portion could be inside a tube, and the floor of the tube could rotate in sections where important rooms/buildings are. During acceleration, the floor is perpendicular to the force (did I say that right?) and during periods of no acceleration, the floor is on the floor farthest from the center of the rotation.
     
    Iain Aschendale and Cave Troll like this.
  9. Iain Aschendale

    Iain Aschendale The Caliph of al-Abama Contributor

    Joined:
    Feb 12, 2015
    Messages:
    7,803
    Likes Received:
    12,628
    Location:
    Seat 29e, Air Gradia 452
    Excellent idea!
     
    John Calligan likes this.
  10. newjerseyrunner

    newjerseyrunner Contributor Contributor

    Joined:
    Apr 20, 2016
    Messages:
    1,079
    Likes Received:
    934
    It is u likely that spinning will ever be used to simulate gravity. I’ll post more later about my thoughts on how this could work. The reason that the force generated by spinning is not the same as the force of gravity. It introduced torque so if you are standing still it will feel like gravity hit if you accelerate or turn you will twist relative to the “ground”. So like in order to move forwards, you’d need to walk diagonally and if you turn along your axis, you’ll have to lean into it. Angular momentum must be preserved.
     
  11. John Calligan

    John Calligan Contributor Contributor

    Joined:
    Aug 8, 2015
    Messages:
    974
    Likes Received:
    884
    According to legend, the issues you're talking about would diminish if the radius of the circle is sufficiently large.
     
  12. Iain Aschendale

    Iain Aschendale The Caliph of al-Abama Contributor

    Joined:
    Feb 12, 2015
    Messages:
    7,803
    Likes Received:
    12,628
    Location:
    Seat 29e, Air Gradia 452

    o_O
     
  13. Cave Troll

    Cave Troll Contributor Contributor

    Joined:
    Aug 8, 2015
    Messages:
    11,422
    Likes Received:
    11,419
    Location:
    Where cushions are comfy, and straps hold firm.
    You seem to not have heard of the mysticism behind science. :D
    Don't feel bad I am worried by the 'According to Legend' thing too. :confused:
     
    John Calligan likes this.
  14. newjerseyrunner

    newjerseyrunner Contributor Contributor

    Joined:
    Apr 20, 2016
    Messages:
    1,079
    Likes Received:
    934
    It would, but how large are we talking? It wouldn't be noticeable on something the size of Halo, but on a ship a hundred yards across, the effect would be very noticeable. The distortion effect will disappear at a rate of the square root of the radius. I calculate that you'll need an object about a half a mile across for the effect to disappear. Besides torque, you'll also contend with a gravity gradient (the floor will feel greater gravity than the ceiling.

    As for getting there, why would a large acceleration at the beginning be preferable to a long slow burn? In space, it doesn't matter how fast you are going, if you can continue to accelerate, you'll eventually reach very very high speed. It is also significantly more efficient to burn fuel slowly. It produces less heat waste. This would be true for any type of population: rockets, ion thrusters, nuclear pulses, and antimatter. If I were a designer, I would give it an engine that used a single atom hydrogen and anti hydrogen and send them into the chamber at a regular rate. It'd result in a very slow acceleration over a long period of time. Of course, then you can throttle the antimatter rocket up for a deceleration burn.
     
    John Calligan and Cave Troll like this.
  15. newjerseyrunner

    newjerseyrunner Contributor Contributor

    Joined:
    Apr 20, 2016
    Messages:
    1,079
    Likes Received:
    934
    Oh and don’t be scared of antimatter. It’s not as sci-fi as people think. Our ability to make antimatter now greatly exceeds our ability to create refined uranium in 1935. If we had a sudden reason to create a lot of it like we did with uranium, the industrial power of the USA could easily create large amounts of antimatter in a decade.
     
    Iain Aschendale likes this.
  16. Iain Aschendale

    Iain Aschendale The Caliph of al-Abama Contributor

    Joined:
    Feb 12, 2015
    Messages:
    7,803
    Likes Received:
    12,628
    Location:
    Seat 29e, Air Gradia 452
    Wow. Honestly had no idea, thanks for sharing that bit of info.
     
    newjerseyrunner and Cave Troll like this.

Share This Page