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References for a Lightspeed Ship

  1. Mar 27, 2012 #1
    I searched this site and could not find any referances for what a good lightspeed ship would look like. Does anyone know of any good books or references on how to design ships that travel near light speed? Here's a few things I do know people speculate on:

    It would be sleek.

    Stationary atoms become high energy bullets at such a ship.
    Microwave background radiation would cause drag forces.

    It would probably be matter/antimatter fuel.

    I'm going to pretend the large engine can be compressed into the reasonable size of a spaceship. Possibly, our ship would have vents with which to collect space particles, en route. These particles would serve as particle beams to create matter/antimatter beams, then react the matter/antimatter to produce the required energy.

    I don't think it will need wings.

    Wings are useful in flying craft for atmospheres, but out in space, I can't see any use for them.


    The ship could rip apart under its own acceleration

    There could be a time delay between when the forward part of the ship lifts off and the back end of the ship lifts off. So the rigidity of the ship may be compromised. Probably not a problem for slow acceleration though.

    Would electromagnetic shields be useful on such a ship for protection against space debri?

    Though such a ship is travelling near the speed of light, in its own frame, an electromagnetic shield would still propagate at light speed ahead of the ship.

    Steering and Turning

    I would envision a single, spherical rudder, that could rotate with a conical degree of freedom. There is nothing for the ship to push off against, except its own matter/antimatter engine.

    The color of the hull would be water-ice, an abundant material which we could put over most of our ship to help with the impacts of small atoms and dust grains. Such a layer would need to be replenished throughout the journey.

    The ship would need detectors for all frequencies

    As the ship goes through space, optical photons in front of the ship would appear as X-ray/Gamma-Ray Photons, while photons behind the ship would shift to radio/infrared frequencies. So you would need high-energy photon detectors in the ship's front, low-energy photon detectors in the ship's rear.

    How am I doing? Anything else interesting anyone can speculate on properties of a light speed ship?
     
  2. jcsd
  3. Mar 27, 2012 #2

    PAllen

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    A few basic observations:

    If you want to be close enough to the speed of light that aging compared to the galaxy is slow by a factor of 100, then you need gamma of 100. This means the energy imparted to the ship to reach this speed is 100 times its rest mass. Thus, you would need to annihilate an amount of matter and antimatter equal to 100 times the ships mass, successfully transferring 100% of that energy to the ships motion. Sound plausible? (Put in perspective, you need to give to each gram of the ship a KE of 2 megaton H bomb).

    As for shielding, forget it. At that speed every piece of dust will tear through the ship no matter what shielding you use. A one milligram speck would have the KE of a small nuclear bomb.
     
  4. Mar 28, 2012 #3
    Although near-absolute lightspeed was not taken into account during their design there are a number of possible interstellar spacecraft designs mentioned on an episode of Carl Sagan's Cosmos. They only really focus on methods of propulsion, but they are still interesting to consider, from a purely visual approach.

    Here is the link: .
     
    Last edited by a moderator: Sep 25, 2014
  5. Mar 28, 2012 #4
    If you could create a sail that was transparent to short wavelength radiation and reflective to long wavelength radiation you would be well on your way to solving the energy requirement problem. Once the ship got an initial boost light from in front would be blue shifted and pass through the sail while light from behind would red shift and be reflected off, providing thrust.
     
  6. Mar 28, 2012 #5

    PAllen

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    Have you thought about the energy content of ambient light (from stars and CMB) in insterstellar regions? Have you thought that red shifted light transfers less momentum the more red shifted it is? You would be well on your way to nowhere with this method.

    [Edit: red shift does not play much role in energy transfer for such a hypothetical sail. In rest frame of sail, energy transfer is reduced by doppler factor; but any energy gain in this frame is augmented by gamma in the galactic frame; the effects are of the same magnitude].
     
    Last edited: Mar 28, 2012
  7. Mar 28, 2012 #6

    PAllen

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    Answering my question above: To reach a gamma of 100 in 10 years with a magic sail with the following properties:

    1) Sail has zero mass
    2) Sail suffers zero drag from the interstellar medium; same for ship
    3) Sail passes all light through from the front, but reflects all light from the back

    and using a figure from here http://authors.library.caltech.edu/4487/1/ZWIpnas36b.pdf of 5*10-3 erg/cm^2 sec for average interstellar light intensity, then if your ship is half the mass of the international space station (about 10,000 kg), your sail would need to be 10 million kilometers on a side (10^14 square km).
     
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