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Periboob: Yes, the principal problem is how to set the cable. When I do my litlle research I found something about this but, being honest, it was such a messy explanation I decided not to include it.. Very interesting the Launch Loop...
Thanks

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I have not been keeping up with the nano-fiber stuff too much, but I think the major problem is creating (never mind lifting) the millions (billions?) of tons of "cable" in orbit. Since (AFAIK) there are no materials which are strong/stiff enough to build a tower up from the ground, we have to build down. And like someone else mentioned, we have to build out also. Start at synch altitude, and start building down, it would fall due to tidal forces on the dangling cable, so you have to simultaneously build out for a counterbalance. And with the required taper...

Suppose we have a fiber to build a cable that can hold 3000 lbs, that weighs 0.1 oz per foot (33 lbs per mile), so 100 miles up, the fiber will have to hold the payload, plus the weight of the 100 miles of cable below, and therefore has a doubled strength requirement. (and the weight/ft) so at 200 miles, we will need 4 times the strength and weight... Of course as the height increases, the strength requirements will grow more slowly, because gravity is decreasing. But still a lot of fiber is going to be required.

On the anchor problem, I remember one fictional treatment, where the whole stalk was constructed in orbit, and then "flown" carefully down to a pre-prepared pit where big bull dozers were ready to push rock down onto the mushroom shaped "anchor" of the stalk, as soon as it was in the pit. What could go wrong? I think if it missed the pit, the loose stalk would wrap around the earth nearly twice. Possibly with some collateral damage.

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