Paul B:
Richard A:

I like the plan to have a perpetually cycling ferry running between
Earth and Mars. It could be a simple craft.

I like the idea of a cycler, too.

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Like the idea, but would go unmanned at first and bootstrap using scrap.
No space rock required with over 180 tons of aluminum in orbit. Russia
has a small number of reactors up and station-keeping ion engines will
be more plentiful. Add large antennas and new programmable control systems
to be combined with the excellent but less than state of the art sensors
in orbit and a few new sensors as required.

The building site would be a telerobotic platform in geostationary
orbit, itself partially built from available materials using a solar
furnace to extrude tubing and die cast joints.

The thinking is along the lines of a long spaceframe with an array of
attachment points for container freight. At first this would go out
with exploration craft and generic supplies including survival gear.
Early returns would be mostly samples. Later trips could include
landing craft, fuel, and bulk supplies for early flag-planting events.
Space station modules....

I always wanted to do this, but I'll cheer on anyone who creates the
hardware or any related system.
--
Anvil*