From: vince@offshore.ai (Vincent Cate)
Newsgroups: sci.space.tech
Subject: Re: Lunar Sample Return via Tether
References: <b0ce55f4.0312080607.61693634@posting.google.com> <20031209194336.06226.00001965@mb-m19.aol.com> <9186edb5.0312100949.3c86ca20@posting.google.com>
NNTP-Posting-Host: 207.42.133.230
Message-ID: <9186edb5.0312150938.15238200@posting.google.com>

vince@offshore.ai (Vincent Cate) wrote in message 
> If you want to rotate faster 
> you let it out on the down side and winch in on the up side so it spends
> more time going down (and pulled faster) than going up (and pulled slower). 
> So rotational momentum is an easily solved problem.

From page 18 (or 20 by PDF count) in:
    http://www.tetherapplications.com/papers/guidebook.pdf

(which is the space tether guidebook / bible) 
It says:

   "As discussed under Tether Control Strategies, changing
a tether's length in resonance with variations in tether
tension allows pumping or damping of libration or even spin.
Due to Coriolis forces, in-plane libration and spin cause
far larger tension variations than out-of-plane libration or 
spin, so in-plane behavior is far easier to adjust than 
out-of-plane behavior.  Neglecting any parasitic losses in 
tether hysteresis & the reel motor, the net energy needed
to induce a given libration or spin is simply the system's 
spin kinetic energy relative to the local vertical, when 
the system passes through the vertical."

So not only can we use a winch to pump the spin up, it is 
very efficient to do so.

   -- Vince