Interesting thoughts but, alas, not at all practical with our current technology. Lead is really heavy, and every gram of payload carries an immense cost in fuel. Then there's the problem of the effects of microgravity. It's bad enough for adults, who have to exercise like maniacs to maintain 85% of their bone and muscle mass, but all our data -- I asked the doc who gave the lecture to be sure of this -- is that bone growth will be severely affected in the lower limbs, not to mention balance and a bunch of other essential developmental processes. I hope we'll eventually solve the problems of creating a gravitational and radiation-shielded environment, but not anytime soon. Meanwhile, there is much for sf writers to consider.

In class, we played around with the idea of all-lesbian crews as a way to provide both sexual partners and protection against pregnancy, but that still leaves the problems of the psychological stresses of space flight leading to exacerbated interpersonal friction and compromised ability to work together. People are so complex!