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Rail guns for launching projectiles to space

  1. Mar 18, 2009 #1
    What can you say about using the rail gun technology, which works under the principle of electromagnetic propulsion, in sending projectiles to outer space? Is it possible in the mere future? How can it help our soceity?
     
  2. jcsd
  3. Mar 18, 2009 #2
    Isn't a maglev train essentially using a rail gun propulsion system? In that case, the benefit to society is evident.

    I think that one of the limiting factors in sending projectiles into space (with people on board to control the projectile) with a rail gun is the length of the rail gun required to ensure that the acceleration generated is not too high at any moment to do phsyical damage. ie, you need to accelerate people at about the same rate as a rocket would up to escape velocity, which would require a pretty long rail gun. I think there have been concepts drawn up to use systems like this. It would probably be benenificial if used in combination with current techniques. Say, use a rail accelerator up to a certain point whereafter rockets take over. The benefit being that you need less fuel in your rockets less weight in your entire system.
     
  4. Mar 18, 2009 #3

    mgb_phys

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    The main problem is air resistance.
    Escape velocity is >11km/s or about Mach 30. A conventional rocket leaves the pad at low speed and accelerates as it gains altitude, so it travels at minimum speed in the thickest air and higher speed as the air becomes thinner.
    A projectile has it's highest speed as it leaves the barrel - in the thickest air.
     
  5. Mar 18, 2009 #4

    alxm

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    Main problem is, you can't find anyone to put up the huge capital investment required to build one of your giant satellite-launching guns.

    So then you shop around and finally end up building your giant gun for some Middle-Eastern dictator, and before you know what's happening, you've been assassinated by an intelligence agency.

    True story of http://en.wikipedia.org/wiki/Gerald_Bull" [Broken]. Read up about it.
     
    Last edited by a moderator: May 4, 2017
  6. Mar 18, 2009 #5
    First off, maglev and railguns are most certainly not the same thing. They both involve magnetic fields, but that is about the end of the similarity.

    I don't think anyone has reached the 11 km/s range with a rail gun yet, for any projectiles at all. For some very tiny projectiles, they have gotten up to about 7 km/s, but for anything bigger than a bb, the max is about 4 km/s. So,... as a launcher, it has a ways to go. And the power requirements are HUGE!

    They also tend to burn up rails really fast, so that they are only good for a few shots (<20). It is a fascinating technology, but it has a ways to go before it is useful for very much other than knocking holes in armor plate.
     
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