Ringworld options

Anton Sherwood wrote:
> absalomdraconis wrote:
>> If I was put in charge of such a [Ringworld] project, then I'd try
>> to design the ring so that individual segments were traveling at
>> just the right speed to maintain their orbit. The actual population
>> areas would be quite far from the center of mass. This pushes your
>> populous away from the sun if the center of mass is between sun and
>> habitat, or it allows the sun to pull them towards it if the
>> habitat is between center of mass and sun. This design would even
>> allow you to effectively have two rings in the same orbit. Note
>> that this would also probably require reflectors for the inner
>> ring, and maybe using lakes with clear bottoms to light the outer
>> ring.
>
> I am not seeing what you mean.
Sorry, I was probably too vague.

Take a long rope, and stick a weight to each end, then send one weight
towards the sun, and the other away from it, making sure that their
collective center of gravity is orbiting fast enough to keep from
falling into the sun, and slow enough to stay in the same orbit.
Because the weight closer to the sun isn't moving at orbital velocity
for it's position, gravity tries to pull it towards the star, and
because the other weight is moving too fast for it's position, it'll
try to fly away from the star. Anything on trhe two weights will
experience the same forces.

Therefor, by building two ring structures, fastening them together,
and rotating them so that their collective center of mass is at
orbital velocity, you can have two ringworlds without needing the
stuff Niven's ringworld is built of.