One features I dislike about O’Neill style cylindrical habitats is the outside windows. Most transparent materials are brittle or fragile in other ways. The outer surface of the cylinder will need to withstand the stress of psuedo gravity as well as endure micrometeor impacts. Much better if the outer hull is opaque steel or other strong material.

To the left is a scheme for illuminating the habitat with a series of mirrors.

Large parabolic mirror A concentrates the suns rays. Small parabolic mirror B shares A’s focus and redirects the concentrated light back into parrallel rays. These parrallel rays are sent to a flat mirror C which sends them to axial mirror D. D illuminates the walls of the cylindrical habitat from within.

I’ve placed the Cheng Ho on the Near Earth Asteroid Saunders 7336. Saunders has a 3.5 year period and comes close the Earth every 7 years in September.

The habitat shares an axis with Saunders. It sits atop Saunders’ North pole.   		Cheng1.gif

 
cheng2.gif  The central axis also holds the mirrors in place.
The parabolic mirrors are counterbalanced by
an array of communication and radar dishes.

Cheng Ho has a radius of 400 meters
and revolves once every minute.
It’s gravity is about half a Gee.

The mirrors are always pointed at the sun.
So the mirrors and communication array revolve once every 3.5 years. 


 
The Cheng Ho is built from materials mined from Saunders.
It starts as a much shorter cylinder resembling a Stanford Torus. This torus only requires a fraction of the light so only a fraction of the mirrors need to be built at the outset.

Ultimately, the cylindrical habitat will be comprised of 8 Stanford Tori stacked on top of each other. At the time Elizabeth meets Luke, the habitat is 3/8 completed.  		cheng3.gif

   
Cheng.jpeg
Sketch of Cheng Ho when it
is 3/8 finished.


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