A circular railgun in space to propel objects to other solar systems?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by s0meguy, May 29, 2011.

  1. s0meguy Worship me or suffer eternally Valued Senior Member

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    Could a circular railgun in space accelerate objects (like probes) to near lightspeed (in an infinite loop until the desired speed is reached) and then release them by breaking the circle, launching them to different solar systems near us?

    Perhaps the circle could be around the planet or the sun, so that it's gravity accelerates the object faster.
     
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  3. billvon Valued Senior Member

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    Sure. Would be somewhat hard to build, though. If you put a loop around the sun that's at the same distance as the earth (i.e. a one billion kilometer long loop) and accelerated a probe to .1 of lightspeed (3x10^7 m/s) the object would experience 600,000 G's of centripedal acceleration. That's a lot to design for. People certainly wouldn't survive it. Electronics in artillery shells (the highest acceleration we can design for right now) see about 16,000 G's.

    Also, needless to say, designing a track a billion kilometers long that could support a million pounds (for a 1 kilogram probe) whipping around it would be a challenge as well.
     
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  5. chimpkin C'mon, get happy! Registered Senior Member

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    Seems like it would be easier to just keep looping it around the sun at acceleration.
    The cheapass way is to slingshot it round the sun, then deploy a solar sail for the outbound trip so that acceleration continues to increase.

    Although I wonder if you could make some sort of catapult roughly based on the same concept to get stuff out of ye olde gravity well...I always thought a railgun would be nice if we can't manage a space elevator.

    Meh.
    I wonder whatever came of the Romanians an their ballooning to the top of the atmosphere and launching from there.
     
    Last edited: May 30, 2011
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  7. kurros Registered Senior Member

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    http://en.wikipedia.org/wiki/Space_fountain
     
  8. leifanator Registered Senior Member

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    Not a bad idea. However, I heard somewhere that going near the speed of light will make the micro-mediorites very damaging, so I think that an energy shield would be necessary to protect that spacecraft.
     
  9. s0meguy Worship me or suffer eternally Valued Senior Member

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    I thought about that, but isn't the escape velocity a problem there? You can't go that fast without escaping from the suns orbit.
     
  10. Stoniphi obscurely fossiliferous Valued Senior Member

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    NASA was looking at a rail gun/SCRAM jet combo that would get to near escape velocity to toss a piggybacked spacecraft off into earth orbit. It was featured on a recent sci mag cover.
     
  11. phlogistician Banned Banned

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    Acceleration is the problem,.... a rocket spreads it's acceleration out using a relatively long thrust sequence, compared to a gun. To squeeze the acceleration up to escape velocity into rail gun would mean the payload would be under extreme G forces,.... far too much for humans, probably too much for satellite parts.

    Ah, I knew we'd had this conversation here before:

    http://www.sciforums.com/showthread.php?t=64600

    I screwed up the maths in my first post,.... a 27km long ring would pull 2000G's just as the payload reached escape velocity. A ring is the cheapest way to accelerate something, but as you can see, not without engineering problems.

    But to the OP, his idea is rather preposterous, ... what are you going to anchor the circular track to in space? Once you start accelerating your projectile, the circular track is also going to start moving,... simple force vs reaction,.... the faster the projectile moves, the more force there is on the ring, and of course, 'near light speed' is just plain stupid, one particle of dust, and BLAMMO! The whole thing is going to disintegrate.
     
    Last edited: May 30, 2011
  12. s0meguy Worship me or suffer eternally Valued Senior Member

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    I knew the idea was probably impractical, but on the off chance that it wasn't, I posted it. I guess the track could be held in its place by thrusters that are powered by the sun (or otherwise), or it could be physically attached to a planet or a moon, assuming we'll have materials strong enough to withstand those forces by then.

    So if an object that goes near light speed, like a probe or spaceship, comes into contact with a particle of dust, it'll disintegrate? So travel that fast in space is impossible? Or are there countermeasures.

    I saw a video from that physically handicapped physicist, who talked about how, in the future when they have the technology for the acceleration and fuel efficiency/storage, you could eventually get a spaceship to near lightspeed.
     
    Last edited: May 30, 2011
  13. CptBork Valued Senior Member

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    I dunno which would take longer- building the accelerator, or waiting millions/billions of years for the space probes to reach anything of interest. Reality sucks like that, but it looks like, barring some radical revolution in our understanding of physics, we're pretty much stuck on this rock until the sun burns out.

    The one nice thing is if you can get a spaceship up to near lightspeed, time will move very slowly for the passengers inside, so at least those passengers would have a chance of reaching something in their lifetimes, assuming they have a means of decelerating (whatever they reach will probably be long dead, though). The closest thing I could imagine based on our present understanding of physics, is to construct a ship where essentially 99% of its mass is intended for eventual conversion to kinetic energy for accelerating/braking, and even that's pretty freakin' far-fetched.
     
  14. Eagle9 Registered Senior Member

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    Very interesting idea

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    can anybody tell me is the railgun able to accelerate the payload to subluminal speeds in principle? I have heard that due to some technical reasons the maximal speed is restricted to 30 km/sec, is it right?
    Also: why do we need the circular railgun? Will not be easier to build linear one, like very high skyscraper? For example on the Moon, its height would be equal to several hundred thousand kilometers and we would be able to launch the payloads to stars in a continuous mode….

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  15. s0meguy Worship me or suffer eternally Valued Senior Member

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    I got the idea for a circular one cause i read that a linear one would have to be longer than the solar system and even then it would barely accelerate to a fraction of lightspeed. In a circular one it could accelerate for however long it needs, if the materials were strong enough i guess.
     
  16. billvon Valued Senior Member

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    There's no technical reason you can't accelerate payloads to any speed you like, although to get them to fractional lightspeed the accelerator has to be very long, the object has to be very light and/or capable of dealing with insane accelerations (millions of G's.)

    However, if you can do all that, why not just mount the gun on the ship and have it be the engine?
     
  17. Giambattista sssssssssssssssssssssssss sssss Valued Senior Member

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    Crazy. I remember thinking this same idea a while ago. Sounds feasible. Somewhat. Building it is the catch.

    Get yourself a warp capable Federation starship. That's the ticket.
     
  18. phlogistician Banned Banned

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    Exactly, then a high G gives you a nice big impulse, softened by the fact the acceleration of the craft is smaller, given it's much heavier than the ejected mass.
     
  19. phlogistician Banned Banned

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    Er dude, it's only 250,000 miles to the Moon from Earth, ... you only need to get 200km up and you're in space, from Earth,... so a railgun of several hundred thousand kilometres? I mean really, look at the numbers! In the thread I linked to, I put some numbers on accelerators, ... CERN is 27Km long, and cost a couple of billion dollars. How much would your accelerator cost, that's 1 hundred thousand Km? Not that it's possible to build such a large structure, or even necessary.
     
  20. Eagle9 Registered Senior Member

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    I will try to calculate the necessary length of the railgun if the initial speed is zero and final-200 000 km/sec (two thirds of the speed of light), the acceleration 100 000 m/sec^2 (about 10 000 g, the electronic and avionics probably will withstand it). The formula for calculating the distance is following:
    S=(V(final)^2-V(initial)^2)/2a
    So, if we put our data we receive:

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    It means that the railgun should be 200 million km long….

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  21. billvon Valued Senior Member

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    If you can really do that, scrap the accelerator and just build a 200,000km high tower on Earth. By the time you get to the top of it you're doing over 300 km/s. Escape velocity for the solar system is only 42 km/s, so you'd be able to launch payloads to the stars without any need for that accelerator.

    The entire structure wouldn't even have to be rigid. It could be a rope.
     
  22. Fraggle Rocker Staff Member

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    Ya think? Imagine what one grain of sand would do to your ship if it was traveling at a relative velocity of only one-tenth the speed of light: sixty-seven million miles per hour!

    Sure, it wouldn't be very healthy for the sand either, but it would bore a hole right through your hull and out the other side. And anybody inside who happened to be in the way.
     
  23. philosopheer Registered Member

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    what object would you send?
     

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