Michael Smith wrote:

It would be interesting to work out how much of a
spacecraft you would have with a couple of submarine
style fission reactors and as many ion or hall thrusters
as you had power for.

Given the lack of enthusiasm for this approach I can
only assume that it doesn't deliver transit times short
enough to be safe for humans.

It would be interesting to know if there is currently
any propulsion approach available that would allow
significantly faster than Hohmann trips for humans
to other planets/moons/major asteroids. (Our moon
excepted, of course.) "Currently available" can be
interpreted to mean "available by 2025 at a development
+ procurement cost of no more than $10G in 2004 dollars
per year between now and then."

Equally intresting would be to know about the technology
for life support systems that would reasonably reliably
sustain a half-dozen people for two or more years in
space without help from Earth.