I have just improved design of the bolo and the sling.
Here is complete, revised text:

This system of Earth-to-orbit transportation is called
"lunavator bolo exchange." It is trivial when compared
to rocket launchers, and it may reduce the cost of space
access to a few dollars per kilogram! The system is based
on GPS, a reusable sounding rocket, terrestrial bolo,
lunar rotovator, cargo sacks, and a small Zylon sling.

The lunar rotovator is called lunavator. It hurls sacks
filled with regolith (Moon dust) toward the Earth. The
lunavator is mounted on a rotating arm which is attached to
a large, rotating, toroidal greenhouse. The arm rotates
independently of the greenhouse, so it can easily change
the angular velocity of the lunavator. The maximum length
of the lunavator is about 200 km. When a winch reels its
cargo in, the cargo moves faster to conserve its angular
momentum. This fact makes it possible to increase the
orbital energy of the lunavator and the greenhouse without
the need for any external thrust. It is as simple as
picking the cargo from the Moon, reeling it in, and tossing
it backward. The orbital velocity of the lunavator is only
1.6 km/s, much less than the Moon's escape velocity (2.4
km/s). When the cargo is released from the lunavator, its
velocity relative to the Moon is 3.2 km/s. It is gradually
slowed down by the lunar gravity to 0.8 km/s (3.2 km/s -
2.4 km/s = 0.8 km/s). Gravitational pull of the Earth
accelerates the cargo by 11.2 km/s, which is the Earth's
escape velocity. An ion thruster guides the cargo toward
the terrestrial bolo. When the cargo is captured by the
terrestrial bolo, its velocity relative to the bolo is 4.3
km/s. (The cargo gains 3.5 km/s, which is the difference
between the Earth's escape velocity, and the orbital
velocity of the bolo, which is 7.7 km/s). The bolo is
larger than the lunavator, but it has the same design, and
is mounted on a rotating arm, which is attached to a large,
rotating, toroidal greenhouse. The bolo captures the cargo
and reels it in. Human crew divides the cargo, which is
called lunar cargo into 4 identical cargoes, which are
called terrestrial cargoes. The terrestrial cargoes and a
sling are secured to the bolo. The sling is placed at the
outer tip of the bolo, while the terrestrial cargoes are
evenly spaced along the bolo. When the bolo is accelerated
to its maximum angular velocity, the sling and the
terrestrial cargoes are released almost simultaneously. The
bolo reverses velocity of the cargoes and thus gains
orbital energy. The sling is released first. Its velocity
relative to the Earth is only 2 km/s. Before the sling is
released, small rocket engines permanently attached to both
ends of the the sling make it spin about the outer tip of
the bolo. At the same time a sounding rocket lifts a
payload to the altitude of 100 km. (My favorite propellant
for the sounding rocket is the hydrogen peroxide
monopropellant because it is safe and clean.) The payload
and the sling have the same mass; their total mass is the
same as the mass of the lunar cargo. The sling captures the
payload, which at this moment is stationary relative to the
Earth. The sling is made of Zylon and is strong enough to
reverse relative velocity of the terrestrial cargoes and
the payload. If we treat the momentum exchange as perfectly
elastic collision, the principle of conservation of linear
momentum implies that when the payload and the sling unite,
their velocity relative to the Earth is 1 km/s. The small
rocket engines permanently attached to the sling control
its angular momentum and guide it toward the terrestrial
cargoes. When the outermost terrestrial cargo is released
from the bolo, its velocity relative to the Earth is 3
km/s. After the exchange of momentum with the payload, its
velocity is reversed and reduced to only 0.2 km/s. At the
same time the payload velocity relative to the Earth is
increased from 1 km/s to 1.8 km/s. After momentum exchanges
with the four terrestrial cargoes the payload has the same
velocity (3.4 km/s relative to the Earth) as the bolo tip,
and it is captured by the bolo. If the payload is going to
be used in the greenhouse orbiting the Earth, the bolo's
winch reels it in. If it is going to be used in the
greenhouse orbiting the Moon, The bolo reverses payload's
velocity and hurls it toward the lunavator, which captures
it. Modern GPS technology guarantees high precision of all
maneuvers.

The lunavator and the bolo do not have to be made of
unobtanium, buckytubes, or even Zylon. Carbon fibers and
S-glass fibers are strong enough, and they are immune to
the radiation and temperature extremes of the outer space.
Perhaps the most practical material for the lunavator and
the bolo is a rope made of S-glass fibers fused together
under high tension and high temperature.

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PS. This is not just another newsgroup post, but history
in the making. I am going to post drawings and updates at:
http://www.islandone.org/LEOBiblio/S..._bolo_exchange