If supporting ISS is the only reason to have manned space capability, I find it hard to suppress a yawn. We need some exciting options.
The Russians are talking about building a nuclear powered manned craft for interplanetary voyages. They won't do it of course, just like the Chinese are also all talk and no action. But we could do it. For the cost of ISS, we could build something like the TMK (
http://en.wikipedia.org/wiki/TMK) and actually do something more interesting than keeping a crew twiddling their thumbs in low earth orbit.
Such a ship could do a manned landing on asteroids and small moons. It could do real time interactive control of science rovers and remote laboratories on planetary surfaces, while the crew orbits nearby. I think manned landings on large planets is hard, but if we did that a TMK could be a major part of the mission.
