[mitchty]

But if we do just robotic exploration, we miss out on the unintended side effects of putting people in space.

Kidney dialysis machines for example. And basic research on bone loss which has been a huge help for Osteoperosis patients.

I think the issue here isn't that we know that putting humans in space is expensive, it is, in time as well as resources. I think the issue is that if we don't put humans in space we'll never know what advances we could have made by doing it.

[nate_meurer]

Granted, but I'm not sure that the progress that can be attributed specifically to the presence of humans in space has been worth the expense.

Your two examples are instructive. I guarantee you that these medical advances would have been made in the absence of a space program. It's not a matter of if, but when. The best that be said about the scientific contribution of human bodies in orbit is that it has provided some acceleration of progress -- I know of no evidence to the contrary.

The crucial question is, what are we willing to pay for that acceleration?