Spacecraft Accelerator

Discussion in 'Science' started by NetGX, Sep 22, 2008.

  1. NetGX

    NetGX Member

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    I was just watching some of the theory behind the LHC and it got me thinking.

    Financial costs aside what is stopping the development of something like this in space.

    A large ring in which a space craft enters and where its velocity is increased using magnetic fields. The spacecraft continues its journey around the ring continually until a specified velocity is reached when it is then propelled on the desired trajectory.

    Energy requirements would be lower as space provides lower temperatures which makes superconducting easier.

    Obviously it would not reach the speed of light (e= mc^2) but theoretically it could be accelerated to speeds significantly higher than standard rocket fuel propelled craft.

    Obviously this is an over simplistic view but I don't understand why the underlying principal couldn't be used.

    Hmmm better get back to some uni assignments.
     
  2. Ionos

    Ionos Member

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    You'd need massive amounts of power when you're talking about something the size of a spaceship. Could possibly be powered by a hydrogen fusion reactor, that would last just about forever with a decent supply of hydrogen.

    Sounds like a good idea. :thumbup:
     
  3. Ashpool

    Ashpool Member

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    Use solar power, With little energy lost(low or zero friction, gravity etc) you just have to add a little energy on each pass of the loop and it would get faster and faster. Massive solar array?

    The benefit to this system is that the ship itself doesn't have to carry the fuel so the fuel mass doesn't need to be accelerated.

    Problem is slowing down at the other end. You cross 1000 light years only to pass through a target system in a couple of hours. You could fling off hundreds of thousands of small probes to other systems. Have them pipe up when the reach the 'habitable zone' in the target systems. If anything is good then you could fling off the parts for another ring. Problem is at sub light speeds it still takes a long long time to get anywhere. Given that some of the closest systems would still take 20 years the speed of light, 40 at half of that. What would be the travel time on the ship for someone traveling to another system that is 20 light years away at half the speed of light?

    So we would observe someone getting there in 40 years but they would observe themselves getting there in about 35 I guess. If you can get to 0.86 C then I think the dilation is about 1/2 so we would observe 24 years and they would observer 12.
     
    Last edited: Sep 22, 2008
  4. OP
    OP
    NetGX

    NetGX Member

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    mmm time dilation, isn't it great.

    Physics is so interesting, could easily spend a lifetime in a field and still only scratch the surface of what's possible
     
  5. Whisper

    Whisper Member

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    The G-forces would kill you if you wanted to accelerate to any sort of reasonable percentage of c within your lifetime.

    The calculations are lying around the net somewhere, maybe even in this forum.

    Inertial dampening or something that has the same effect is going to be a must have, even if we crack the other problems associated with travelling anywhere near the speed of light or faster.
     
  6. Ionos

    Ionos Member

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    Well the G-forces for linear acceleration to C equals about 2G for 6 months. Certainly sustainable by a human being.

    However, the centrifugal forces in a circular accelerator would definately kill you at even a fraction of the speed of light, even if accelerator was the size of the Earth.

    Consider that if the accelerator was the size of earth, and you were travelling just 1/1000th the speed of light, that is 300 km's per second, going around an accelerator the size of earth (radius 6378km's). Hope these calculations are correct. :)

    F = (300000^2/6378000)/9.8
    (all converted to metres)

    F = 1439G's

    In otherwords, you would be experiencing a centrifugal force equivilent to 1439G's. Enough to crush you to a sticky goo.
     
    Last edited: Sep 22, 2008
  7. oculi

    oculi Member

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    depends entirely on the radius of the ring. oh, which would have to me massive when you get up to 100 km/second or so. also you have the problem of friction to keep the spaceship off the outside wall of the ring.

    i don't see the point of this at all, you might as well cover some distance while you are accelerating.
     
  8. daztay

    daztay Member

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    Nasa already use "sling shotting" a planet to increase speed. I think the first voyager probe was sling shotted around venus than back to earth and sling shotted again and then off to deep blue. Similar but uses gravity rather than magnetics.
     
  9. SLATYE

    SLATYE SLATYE, not SLAYTE

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    A few things:
    • LHC is not exactly light-weight. An equivalent for a spacecraft would be substantially heavier. Getting such a thing in to space would probably take about as much fuel as a million or so normal launches, so it'd take a long time for it to become worthwhile (much longer than any politician will be around, so they won't want to fund it).
    • Conservation of momentum means that if you accelerate a spacecraft around the ring really fast and then launch it, the ring will accelerate backwards. The energy needed to accelerate the ring back to its initial velocity is the same as the energy needed to accelerate the spacecraft to its final velocity (plus assorted losses, because nothing is 100% efficient). As mentioned above, there is still an advantage because the spacecraft itself is far lighter (no additional fuel).
    • You still have to get the spacecraft off the Earth in the first place. Given the relatively small number of spacecraft that we actually send out of Earth's orbit, a huge space-based accelerator wouldn't really be needed.
    • Super-powerful magnetic fields would probably cause chaos for most sensitive electronics.

    Quite apart from that, the moon and planets already provide for a gravity assist (as mentioned above). They have the advantages that they're free and they're extremely massive (so just accelerating a spacecraft isn't going to cause any measurable change in their velocity).
     
  10. Ionos

    Ionos Member

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    Not so, the acceleration is done in a circular path, so the net force on the ring will be zero. Once the spacecraft is "released" it is already travelling at high speed, the ring is simply letting it go so to speak.

    Consider a heavy weight on the end of a rope. You spin it around to high speed then release it. You are not pushed backwards when you release the rope.
     
  11. Shamrock

    Shamrock Member

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    yes but wouldn't the whole ring be spinning now? in the opposite direction at a velocity equal the weight proportion of the spacecraft/ring and the final speed of the space craft
     
  12. SLATYE

    SLATYE SLATYE, not SLAYTE

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    Even so, conservation of momentum holds. Spacecraft goes one way, ring goes the other way.

    When you spin a heavy weight on a rope, you don't notice it because you're providing a counterbalancing force naturally (to avoid falling over). The force is still there, but you don't notice it (just like you don't normally notice the slight movements of your feet when standing that your body makes to keep you stable).
     
  13. Ionos

    Ionos Member

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    Oh I see what you're both saying ... the ring would spin in a circle, not be pushed in a specific direction.

    You're right. :D
     
  14. SLATYE

    SLATYE SLATYE, not SLAYTE

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    It should be pushed in a specific direction too; see conservation of linear momentum. The centre of mass of the system will remain stationary; so if the spacecraft launches in one direction, the ring will accelerate the other way.

    The exact details don't really matter. The fact is that keeping the ring stationary is going to take as much fuel as would have been spent accelerating the ship up to the launch speed.
     
  15. underskore

    underskore Member

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    an imaginary force?
    kill me?
    i don't think so :lol:
     
  16. Ionos

    Ionos Member

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    Don't be a smarty pants. ;)
     
  17. pduthie_au

    pduthie_au Member

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    That was my thought as well.

    Centripedal force is the one you are thinking of.
     
  18. Ionos

    Ionos Member

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    Righto. Here's hoping my maths was still correct.
     
  19. Smoke87

    Smoke87 Member

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    I was just about to shoot it down with the centripetal force comment ;)
     
  20. Assasinator_2

    Assasinator_2 (Banned or Deleted)

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    Centripetal acceleration.

    Basically, what's stopping us are insurmountable engineering feats that would be required to do this with our current technology.
     

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