RE: skyhooks again

From: Damien Broderick (thespike@earthlink.net)
Date: Wed Feb 12 2003 - 00:18:46 MST

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    Spike mentioned a discussion he and I have been having about some
    (overlooked?) problems you get building a skyhook.

    > Imagine a planet with a high-carbon satellite
    > conveniently located in synchronous orbit. This
    > satellite is tidelocked to the planet

    > Imagine nanobes on the satellite decide to build a
    > diamondoid cable down to the surface. As they
    > do so, they manufacture and pay out cable into
    > space to maintain the CG at synchronous altitude.
    >
    > By the law of conservation of angular momentum,
    > the sidereal rotation rate of the satellite will
    > slow down as the moment of inertia of the satellite
    > goes up.

    My intuition told me that the ground-side of the cable would lift away from
    the surface the further it's paid out, perhaps in a parabola. The way I
    conceive it, the cable must conserve the same orbital speed as the
    geostationary center of gravity. But for Earth, the geostationary velocity
    is some 5500 km/hr, while the surface is only rotating at 1700 km/hr. So it
    should come to look something like an integral sign. The tip of the growing
    lower cable should be ripping overhead near the surface, no? Not dropping
    straight down? Once it's tethered to the surface, sure, tension and the
    counterweight will keep it stretched out--but isn't the bastard going to
    tear your head off before you've got it tied down?

    I assume Spike and I are forgetting to cancel some factors out.

    Damien Broderick



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