No shaft, no; the tensioned nano-fiber ribbon would be the tramline to which the cars would cling, like a cablecar; erecting a shaft around it would be too expensive.

Once the thing was in place (a voyage of many many steps) the inertial mass of the space platform would be sufficient to keep it stationary, and presumably the perturbations of loading and traveling the ribbon would be miniscule compared to the tendency to stay stable.

All this would work fine unless and until, as you say, something happened at the platform to suddenly decrease its velocity, such as an accidental retrorocket firing, or a meteorite impact at the wrong angle. Such an event could disrubt all the equations.

Under ordinary conditions, however, the ribbon would be quite stable just as a high earth-orbit satellite is, but with a lot more mass. It would also have the means, I assume, to nudge its velocity up a bit every few years to compensate for the very slight decay factor.


A


A