On Tue, Feb 27, 2018 at 06:34:35PM -0500, Richard Aiken wrote:
> Multiple stacked take-up reels:
> First reel ~5 kilometers up the cable, for kilometer-scale adjustments,
> made while the tip is still ~10 kilometers out from the pickup point.
[...]
> Given laser range finders, I'm fairly sure today's level of automation
> could easily handle something like the above.

The main problem was the fact that if you want to keep the tip at
constant altitude for more than a couple of seconds, the reels need to
wind cable fast enough to break the sound barrier while hitting
time-at-position requirements of a few tens of milliseconds under
hundreds of tonnes of load force.

I haven't seen anything near that in reality, and none of the tether
proposals include anything like it either, for pretty good engineering
reasons.

I'm sure that it's not impossible, but it would take a heck of a lot
more research and development, complexity, weight, and maintenance for
essentially no benefit.

- Tim