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"Why isn't it possible to build a space elevator at the north pole?" made me think...

Like the funny hat with a propeller on a kid's head - replace the head with Earth and propeller blades with space elevators.

Build a stubby tower / hill / mountain on one of Earth's poles. Add a huge motor, that spins in the same axis as Earth on top. Extend space elevator (or two, in opposite directions, for balance) from the motor's axis, going initially parallel to Earth surface, then out into space as Earth curves away.

enter image description here

enter image description here

Such an elevator could be much shorter than the traditional equatorial space elevator propelled by Earth spin alone - since the rotary speed would be much higher. The huge problem of construction vanishes: lifting the material up to GEO to unroll from there, as segments could be added at the axis instead. There would be the problem of the end moving at hypersonic speeds until there's enough of it extended to slow the spin enough that the part within the atmosphere doesn't exceed speed of sound. And of course the engineering problems of the mighty motor, and continuous energy expenditure to fight atmospheric drag. Never mind logistically awful location.

Would it be possible though, or am I missing something? Say, precession, or maybe Earth's gravity bending it to the ground, or Earth magnetic field, or something like this?

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    $\begingroup$ You may need a diagram to illustrate what you mean. $\endgroup$
    – gerrit
    Mar 15, 2017 at 11:07
  • $\begingroup$ Concur with @gerrit, I am trying to visualize this. The picture I get has less promise than a standard space elevator. $\endgroup$
    – James Jenkins
    Mar 15, 2017 at 11:24
  • $\begingroup$ @gerrit: done. The main promise is the whole thing shouldn't need to exceed Earth radius in length, as opposed to ~35000km of GEO. And should be possible to be fully built on Earth, zero space launches required for construction. $\endgroup$
    – SF.
    Mar 15, 2017 at 12:07
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    $\begingroup$ @OrganicMarble: That strongly depends on RPM. If this curves to equatorial latitudes, it can be just an equatorial LEO. If it's moving way in excess of that, kept mostly straight, the orbit will be inclined and elliptical - it may also be suborbital, if released "early". $\endgroup$
    – SF.
    Mar 15, 2017 at 12:42
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    $\begingroup$ @OrganicMarble: I don't know how much would be lost to atmospheric drag and magnetic field, which would be the continuous expenditures, but on top of that, after the initial spin-up, the only expense would be electric energy to propel the motor to recuperate momentum lost to released satellite. $\endgroup$
    – SF.
    Mar 15, 2017 at 12:57

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Because of bending

You assume that because your carousel is spinning that you do not need to lift it.

But you do.

The "orbit" that this carousel is spinning in is not a real orbit, because it is not centered around the Earth's center of gravity. So the "arms" are subjected to gravity, pulling them down towards the Earth's center of gravity.

This means that you have to deal with huge bending forces. And bending is a much harder problem to solve than just compression / tension forces.

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    $\begingroup$ Since it's not a rigid structure, it's stretching due to centrifugal force; sure it will bend towards equator due to gravity - but sufficient speed (and initial altitude) should keep it from hitting the surface. Plus if it's constructed as a lifting surface, it can fly until its ends exit the atmosphere. $\endgroup$
    – SF.
    Mar 15, 2017 at 12:32
  • $\begingroup$ @SF. Needs more detailed calculations before we decide to build it ;-) $\endgroup$
    – gerrit
    Mar 15, 2017 at 12:36
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    $\begingroup$ @MichaelKarnerfors: and yet as you spin a rock on a long string above your head, it doesn't hit the ground. The centrifugal force pulls it away horizontally, preventing the drop. Also, old helicopter-style lifting could be quite helpful in the initial segment, before enough centrifugal force kicks in. (add lifting surface, imagine the structure is a helicopter rotor). $\endgroup$
    – SF.
    Mar 15, 2017 at 12:48
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    $\begingroup$ Don't forget that you also have to rendezvous with this thing, which would be difficult if it isn't in a regular orbit. $\endgroup$
    – Steve
    Mar 15, 2017 at 13:09
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    $\begingroup$ @Steve: Or perform a very tightly timed docking maneuver; there are orbits tangent to the trajectory of the top, with matching speed at the contact point, but that would be very much like grabbing the skyhook except without aid of air to help maneuvering. Definitely not like current Soyuz-ISS docking, more like SpaceX hover-slam. $\endgroup$
    – SF.
    Mar 15, 2017 at 20:56

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