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Centrifugal Spaceship Accelerator

  1. Dec 1, 2014 #1
    Suppose we launch two ships and move them close to the Sun. They have solar collectors and can absorb a massive amount of energy thanks to their proximity to the Sun. The ships are connected by a 1000 meter long rod of titanium, and each ship's rocket is position opposite the other's, so that when they are both active, the entire contraption begins to spin around the connecting rod. The spin accelerates with every exertion of power from the ships and the spin is along a single axis only.

    At a given time, when the system is spinning very rapidly, the rockets stop exerting force. Instead, they use their energy to "climb" inward along the rod, toward each other, toward the center. This causes the spin to increase dramatically. When they are 10 meters apart, the spin is so rapid that each ship is moving at almost the speed of light.

    The ships detach, and each takes off on opposing vectors, ultra fast, into the depths of the universe.

    Question: What are the flaws in this approach? Can ships accelerate in space with only a solar panel, or do they need a material mass to use as propellant? What would be the maximum rotational speed of this system using titanium parts, or whatever real-world materials are available? I assume at some point well before the speed of light, the whole thing would tear apart, even if the "ships" are only 1 kg each.

    Your thoughts? Thanks!
  2. jcsd
  3. Dec 1, 2014 #2


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    Staff: Mentor

    They need fuel, but that is not the main point.

    The rod will break long before the spacecrafts become fast (even for solar-system speeds). A few kilometers per second are possible. For a solid wheel, see here (footnote 8), other geometries allow to exceed that speed a bit, but not much.
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