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Going to Alpha Centauri

  1. Aug 3, 2003 #1
    Using a VASIMR rocket, 1320 years of voyage are needed
    Using an Orion drive, the duration of the voyage is 132 years
  2. jcsd
  3. Aug 3, 2003 #2
    I fail to see the relevance in this thread, but bon voyage anyways...
  4. Aug 4, 2003 #3
    Good news!!

    I've just read what Robert Forward has proposed for a travel to Alpha Centauri.He proppose to construct a laser with a power of 10 million Gigawatts.the laser will be stationary on earth. Outside the earth, you let floating a Fresnel lens of a thousand km diameter. Then construct a starship with a sail of one thousand km long. Making the laser light pass through the lens and impacting on the sail it can provide a big impulse to the starship. With this system the voyage to Alpha Centauri is only ten years long!

  5. Aug 4, 2003 #4
    Interesting theory, but what if they miss?;)

    Whoah Momma!
  6. Aug 5, 2003 #5
    Not to mention the lens. How are they going to put it in orbit?
    And the military implications of the laser? (knocking down satellites...)
  7. Aug 5, 2003 #6
    and the simple wondering of how they would get back :) maybe if the laser was rigged to the starship itself it may work.

    and does the laser have to stay on ?
  8. Aug 5, 2003 #7
    Yeah, the return trip came to my mind as well.

    I agree with Bunting's statement about the laser being attached to the rocket when it comes to the return trip.

    Then again, wouldn't you have to take into consideration Einstein's Theory of Relativity (time dilation, etc.)?
  9. Aug 5, 2003 #8


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    The laser couldn't be mounted to the back of the rocket. It's called the conservation of linear momentum.

    - Warren
  10. Aug 5, 2003 #9


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    Have you but any thought into the amount of energy required to make this happen? If I recall correctly going by energy/mass equivelence there may not be sufficient mass in the solar system to make a trip at that speed. Minor detail, why would you worry about it.
  11. Aug 5, 2003 #10
    <slaps himself really hard on the head>
  12. Aug 5, 2003 #11
    There are a few problems with a spacecraft traveling about 1/3 C as it leaves our solar system. If it’s a one-way mission, it will likely need a course correction early on using on-board engines with limited fuel supply. Communications to the craft will have to be at a higher frequency to compensate for the Doppler shift. Communications from the craft will be received at a lower frequency. As the craft approaches Alpha Centauri, we’d probably want to shoot some photos. Again due to the Doppler shift, normal optics would not focus. It would probably be better to use X-ray imaging. Perhaps the laser sail could be used as an x-ray receiver.

    If it’s meant to be a round-trip mission, there’s no way to turn around with conventional rocketry but the gravitational field of the Alpha Centauri system could be used to do a 180. Since that system has at least 2 stars, its might be possible to get a gravitational velocity boost and return to Earth at a higher velocity. Of course the forces on the star craft would be enormous as it does the 180, but perhaps a converted nuclear sub might make it.

    Now were approaching the solar system at 1/3 C+ we need to fire up the laser again to put the brakes on or find out what happens when a nuclear sub traveling at 1/3C hits the sun.

    Just having fun.
  13. Aug 6, 2003 #12


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    Sure it could. You point it BACKWARDS and take away the sail.

    Its like the old cliche' of setting up a fan in your sail boat to blow against the sail. It doesn't work, but if you turn the fan around and point it backwards, it works just fine (they use them in swamps).

    Of course there are negatives to doing it that way - half the thrust and the added weight.
  14. Aug 6, 2003 #13
    OK, who's in to build this thing?
  15. Aug 6, 2003 #14
    ME ME! Let me just check my bank account

    damn never mind :(
  16. Aug 7, 2003 #15
    I've found new information about the project. The laser would be orbiting Mercury, using then the Sun's photons to excite the laser.
    The lens would be located between Saturn and Uranus and would have a mass of 569 million kg (560000 tons)
    A complete info of the project by the same Robert Forward can be found here:
    http://planetary.org/interstellar/forward.html [Broken]

    There's a system that could permit to travel faster than light: the Alcubierre drive. Consists of create a bubble of space around you and make that bubble travel through space faster than light. It doesn't violate relativity, because in the space inside the bubble you are not travelling faster than light.
    Last edited by a moderator: May 1, 2017
  17. Aug 7, 2003 #16
    You don't launch the lens and such. You build them in space, preferably using some function nanotech thingies to form an absolutely perfect lens. I would guess we are only a couple of decades away from such capability.

    You don't shoot a big laser at the spaceship because there's no big laser on the other end to shoot it to slow it down. Or I suppose using nukes at the far end to slow it down (ie. Orion Project) could be done.
  18. Aug 9, 2003 #17
    The gravity of the system could not be used to turn around at 1/3 c. The radius would have to be miniscule, and this is not possible as the star is not miniscule.
  19. Feb 14, 2004 #18
    1/3C slingshot anybody?
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