Bootstrapping - Step Nine

Well, I'm back :) continuing on because the writing helps me clarify
the details for myself.

With Step 8-10, I think the bulk of the cislunar space
transportation system is laid out.

This post details the Mid Earth Orbit Tether.

But first some background.

The orbital plane of the moon's orbit around the Earth is such that
it's in a different inclination to that of most Earth orbits. Thus,
any travel to the moon must account for a change in inclination or a
launch must occur when the moon's orbital plane intersects that of
Earth. This happens twice per month and each intersection is
different thus making difficult travel to one point on the moon.

As I wrote in step 8, a LEO tether can launch payloads to the moon
during these two launch windows but the appeal of the tether system
is that it can launch frequently payloads of small masses because of
the tether:payload mass ratio and that returning mass back from the
moon will equalize the momentum loss of the tether. To scale the
tether for a few massive payloads per month really is a false
economy.

The problem is that without a propulsive device on the payload to
impart the inclination change the LEO tether must wait for one or
two launch windows per month.

But a solution is at hand.

At an altitude of 18,732 kilometers we place a large transfer
tether. The shape would be that of a bicycle wheel, with a rim
diameter 60+ kilometers and a central hub length of 2+ kilometers.
From the "top" and "bottom" of this cental hub or axle, there will
be a cable tether system attached with the tethers being on the
order of a few hundred kilometers long.

By exerting tension on either the "top" or "bottom" part of the
tether as the payload is spinning around the center of gravity of
the structure, the inclination of the payload can be changed to
match that of the moon.

Thus the operation would proceed by catching an incoming payload
from LEO, then over a few hours the tether tensioning would take
place until such time as the inclination matched that of the moon.
At this point the payload is released towards the moon and it has
the proper inclination and velocity. The MEO Tether has now
transferred momentum and is out of plane with the Earth. At this
time it can either use propulsive power to restore itself to its
previous orbit and incination or it can catch a payload of equal
mass incoming from the moon. If the plan is the latter, then the
process is reversed and the payload is caught, the inclination is
changed, and the payload is sent back down to LEO.

I foresee this MEO Station being built in LEO, near our first
foothold, our LEO base of operations. As other posters have pointed
out that LEO base may not be one of the first steps, and on
reflection, I don't disagree with them, but for the steps we take at
this point I have trouble imagining operations proceeding without
some human presence in LEO. What I'm not saying is that this entire
construction process is handled by a bunch of astronaut/welders. I
think there is a dominant role for robotics in the construction of
the LEO, MEO and Lunavator systems, but I don't think that robotics
are at the point where they can operate autonomously, so human
control and oversight is necessary, not to mention repair,
logistics, troubleshooting, etc.

The MEO station will be a very large structure that we will build
but it will be mostly a rim, with spokes and a central hub. I
envision the hub being constructed of a lattice of girders so as to
take the strain of the forces at work and possibly this hub will be
enclosed by sheetmetal or vapor deposition.

What uses could we find for an enclosed hub of a couple kilometers
length? What ancillary systems could be attached? Could it be a
platform used for other functions?

I envision that the mass returned from the moon, in the form of cast
basalt bricks, will be stored in the central hub, thus firstly,
returning the momentum lost from the system, and then adding to the
mass of the MEO tether, ultimately allowing payloads of increasing
mass to be launched.

Any comments?

TangoMan