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A new spaceship launcher?

  1. Oct 22, 2015 #1
    Hello all!


    I have longed envisaged a new type of space launching device, one that would be reusable and cheap to operate.


    My idea is to have a large set of concentric circular tubes laid horizontally in some desert or something. The spaceship would use magnetic levitation to float in the tubes and propel it's self forward (we could also assist in acceleration using rockets).


    The idea is that you go round and round the innermost tube accelerating until you have reached your maximum gravity. Then a hatch/bridge opens to connect you to the next larger tube and you repeat the process, until you have reached the required escape velocity to achieve low earth orbit! Then you just point vertical and shoot out of the tube.


    So can you math boffin work out if this would be at all feasible without these tubes being the size of Russia...or Maybe it would just have to be that big?


    I'd love to see how you break this one down. I have tried before but couldn't get the acceleration part figured out.


    Hope you can help!


    Many thanks,

    Michael
     
  2. jcsd
  3. Oct 22, 2015 #2

    russ_watters

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    Welcome to PF!

    Why do you need multiple tubes? Just use one big one. But yeah, it would work.
     
  4. Oct 22, 2015 #3

    Vanadium 50

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    "Just"? To reach orbit, you need to be moving at at least 30,000 m/s. To switch to vertical requires an arc - if you make it with the radius of the world's tallest structure, 830 meters, the acceleration at the loop is 110,000 gravities.Your astronauts would be soup and your rocket would be confetti.
     
  5. Oct 23, 2015 #4
    @Russ. I was thinking you would need to swtich tubes for sake of the gravity to speed would max out before you would reach escape velocity. So you move to the bigger one to reduce the gravity and then accelerate again to max and so on.

    @vanadiam. Thanks for your reply. Yes i dee the problem! Hmm...how can we fix this? Maybe make it on the verticle rather than the horizontal? Or we make it unmanned? Or we make it with less of an angle...obviously requiring more speed though.

    Thanks again for the replies guys!
     
  6. Oct 23, 2015 #5
    Why would you need to switch to vertical the Earth is round.
    If the craft was launched horizontal the Earths gravity would pull it into orbit.
     
  7. Oct 23, 2015 #6

    Vanadium 50

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    Same reason they don't launch horizontally today.
     
  8. Oct 23, 2015 #7
    I think the main reason they don't launch horizontally today, is that the spaceship would hit the ground, the second reason is to clear the atmosphere quickly.

    If you accelerate the spaceship with orbital speed, the main reason would be to clear the atmosphere quickly, but you won't clear it quickly enough, and the spaceship would still be destroyed by air resistance.
     
  9. Oct 23, 2015 #8

    russ_watters

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    You didn't actually respond to what I said, you just repeated what you said. Again, why can't you start with the biggest tube? Gravitational (centrifugal) force would never "max out".

    Regarding angle:
    Horizontal is no good because you have more of the atmosphere to go through and you're still in an orbit that bottoms-out at the surface of the Earth. Vertical is no good because you're not in an orbit at all, and you really haven't done much to help achieve one. The optimum angle is fairly low (I've seen it before, but will guess about 30 degrees), striking a balance between how much re-shaping you need to do once at altitude and how fast you get out of the atmosphere.

    Regardless, the idea of a straight railgun launch has been proposed before, but the drawbacks are pretty rough. Your idea eliminates one (high g-force at launch), but adds another (an enormous track). At this point, you should give a shot at calculating just how big the track needs to be. Let's say you want a maximum of 4 g's from the centripetal acceleration and you want to launch at 20,000 mph: how big would the radius have to be? Do you know how to calculate that?

    The remaining drawback is still a big one, though. Have you ever seen pictures (simulations) of what a spacecraft looks like on re-entry? As if it is engulfed in a blowtorch flame? That would only be much, much worse with a full speed launch from a railgun.
     
  10. Oct 23, 2015 #9

    russ_watters

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  11. Oct 23, 2015 #10
  12. Oct 23, 2015 #11
    Damit russ! Haha can't believe they've beaten me to the punch! Oh well.

    Thanks for the explanation. I understand knw what you meant by only using the biggest ring. Makes sense.

    I'm really terrible at maths so any chance you could explain the formula for me? Am I correct in thinking pi r 2 should be in there? Lol

    Thanks all for the replies.
     
  13. Oct 23, 2015 #12
    P.s russ.

    I can just about make out your imaging setup in your profile pic. Very impressive! Is that a 12" or a 14"? I have a modest but more widefield setup with an orion ex80 and an old canon dslr. But does the job. Not so many clear nights though in Scotland to play though.
     
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