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Popular misconception is that a space elevator should step on the planet exactly on point of its equator and that the cable should stretch laying onto the equatorial plane. Even the idea of the "forked" elevator suffers the same mistake - cause it envisages the cable to run along the vertical equatorial oriented path and in some point to bifurcate toward two strictly meridional ( i.e. orthogonal to the equator) points on the planetary surface.
See: http://www.mit.edu/people/gassend/space … ...ex.html
where off-equatorial orbital elevators designs are described and shown.
1. It is easy to conveive that indeed an off-equatorial sinchronous skyhook can be build which touches the planet only at the pole or the poles.
Thus with only one contiguous cable we can build the picture 2 from the link`s scheme ( imagine the blue line forming the same loop from the left side of the Earth). The cable in order to be releafed significantly from the tension due to the curving, could be lied in the polar regions several hundred or thousands of km on the ground, so to have enough surface area to transfer the downward component of the push vector to the earth-base. Another advantage is that the trains ( maglev!) can go directly from their ground network courses to the cable, and so the vable to be made significantly more massive, able to cary statites, pipes, electric cables...
The gaps between the legs of the cable are especially good for putting solar energy tapping "sails". Imagine the Earth as a hub of not only 4 cables forming poles passing contiguous loop, but with 6, 10 or more spikes, locked in one, two or more orbital wheels - like the Artur Clarke`s orbital pipe sity or a.k.a. Geopolis. Our Geopolis could be by-piped counter-rotating in order to not impart excessive rotational momentum in the structure, similar in overall shape to ship`s rule.
Such elevator runing comperatively low across the sky could be very usefull in other manner too - it provides very low and off-equatorial tether site where any kind of communicational equipment could be hooked/hanged only hundreds of km over the serviced territory. Also using materials with lesser strenght than the necessary to build the skyhook itself or the same ( carbon nanotubes ), we could easily hang "towers" from the main tether to the serviced territories bellow. Such towers BTW may occur to be necessary to compensate the awfull pollar tension caused by bopth the centrifugal force of the rotating structurte and the full scale planetary gravity pull. Imagine a polar elevator crossing all the sky over North America ( very conveniently situated in north-south direction), covering all the needs of communication with hyper-wide band pocket devices with time-lag 100 times smaller than the geosyhcronous satelites ( super-real time in human subjective dimensions), and from this cable hanging 1000km high and 5x5 km wide tower - just a byproduct of the necessity of additional support. Such building will have constructued inner living area ( if we take 25 meters per level hight) of 100 000 km2 !!!
Such structures will be very usefull for terraforming. Deployed on Mars or Uranus, the enormous capability to provide air-conditioned human life supporting areas, even could give an alternative to the classical terraforming... Some kind of hybrid between the clasical space colonies with their closeness, the burch supramundane scenarios , but rellying on static tension, not dynamic compression, etc.
2. Polar skyhooks` systems could be deployed above slowly rotating or non-rotating axially worlds , too. Of course they`ll be non synchronous. The only point which will co-rotate with such tether system which rotates with different pace according the planetary axial rotation are the POLES.
That means - such types of skyhooks is plausible for such bodies, not only the type which rotates on the plain of its orbit ( rotavators).
The polar touch down of the cable would be replaced by artificial physical axis - a space fountain for example, which to serve to keep up above the atmosphere the non-corotating cable and also along which to be run the up- and down-directed traffic. In the ideal case the traffic itself will serve as pusher mass-stream, the ascending vehicles should go up with speed as much bigger than that of the descending, so the tension/pull to be canceled. Orbital ring or just Lofstrom loop arc can do the same. On smaller worlds - just tall tower with rotating hub with maglev coupling on the top.
Imagine Venus provided with such system of contiguous double polar spikes - hundreds in number.
The gap between the cables used for solar power capture, the space fountain dynamic compression "axes" at the poles could be used the excess atmosphere to be exported in comperativelly short time - the towers could support numerous pipes used as plasma guides and the atmosphere ionized prioir to launch in portions to be coilgunned upwards...
Over the Moon poles the modern lack of atmosphere further faciliates the construction of non-synch polar elevators. The cage that formes several spiked elevator system ( looking like a spider web from "above"), could be used later to be put atmosphere retention instalations. The weak gravity allows also on the Moon the Axis to be formed by erecting two very high static towers.
3. The polar orb-elevators are compatible with the equatorial ones. Say single meridian on Earth or Mars could be touched down by several cables - on the equator in the classical way, off-equator and polar way + over the whole structure could rotate non synchronously a polar or other type of non-synch over-polar off-equator tethers.
4. The off-equator or the off-planet at all designs actually exploit the MOravec`s idea of free rotators, but this way put considerably closer to pulling gravitationaly body, so three forces complicate the picture and distort the pure centrifugal scenario...
Only such networks based on static tension and/or dynamic compression structures directly transfering momentum to the cargo and to each other would allow the SolSys to be changed, taken the necessity to move such enormous masses...
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