Cities in space - Singles or clusters?

Mike,

Now this is something I had not thought of, a circular orbit would be the
only type possible and if your ring was perfect and if the Earth was a
perfect sphere and completely homogenous and there was no other external
force, then I suppose it would be possible to have a ring-world type
arrangement. I remember reading how while the Gravity Probe B experiment was
being built, a couple of scientist used two satellites in the same orbit, by
measuring the small variations in the orbit they provided a rough
confirmation of the frame dragging effect. How they did this is important to
the idea if am orbital ring. They measured the very small variations in the
orbits of both sats as they responded to the changing field strength,
mountains, ocean trenches, undersea mountain ranges and deep mantle mass
concentrations makes the Earths gravity field anything but smooth. The orbit
of any rigid ring would soon be pulled out of true by these variations. This
would also be true of an arc, if it was large enough, I wonder just how much
stress this would put on a structure. At certain parts in its orbit one part
of the structure is going to be pulled and try to speed up, other parts are
going to try to slow down, the change in speed is going to mean some parts
will want to move into a higher orbit and others a lower orbit, in essence
it would be like some giant stretching it to make it longer and at the same
time bending one end up and the other end down. Alas my maths is not up to
calculating the forces without a pile of reference books that I do not have
with my right now.

Darren

From: "Combs, Mike"
Reply-To:
Date: Mon, 28 Aug 2006 10:20:50 -0500
To:
Conversation: [spacesettlers] Re: Cities in space - Singles or clusters?
Subject: RE: [spacesettlers] Re: Cities in space - Singles or clusters?

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com
] On Behalf Of Darren

> I dont know but I have huge reservations about a frame filled
> with habitats so large that in encircles the Earth. Im unsure
> of the stability of the ring, I seem to remember there being
> some problem with the stability of the ring in the ring-world
> book,

That's right. One could build an arc, and stop just short of joining the
ends, and there would be no stability problem. The stability problem of
Ringworld was a consequence of the fact that the ring was a continuous,
joined structure; one side of the ring could pull over the other. But every
part of an arc should orbit just as would a single object at that point on
the orbit, and there should be no stability problems.

But it does occur to me that circular orbits must be assumed. An arc in an
even slightly elliptical orbit would have a problem with stretching at
perigee, and compression at apogee. So one would need to stabilize against
any force tending to shift the orbit away from zero eccentricity.

Regards,

Mike Combs