To the stars! Interstellar feasibility

So, there's a couple thoughts about realistic starships. One is that we can't do them and they're centuries of tech away. Another is what we could do them, or probably good with a decade or two of engineering research, but they'd be really expensive. Most people with a clue tend to think the first. But! The second might be more accurate, at least as far as the propulsion goes. The classic one is

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) and variant http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medusa

where you blow up nukes against a pusher plate. Advantage is that it utilizes the one kind of energy productive fusion we can actually do, fusion bombs. Disadvantage is people's nervousness about huge quantities of nuclear bombs, plus since a bomb has a minimum size, the vehicle has to be large. Which can be good if you're really out to send something big, but if you just want a probe, is problematic.

( Mercy cut )

I guess the takeaway lesson is that you need nuclear energies to have even kind of crappy interstellar ships, but we *do* have nuclear energies, and throwing large but reasonable amounts of fission, and maybe explosive fusion, at the problem will suffice for automated probes, such that propulsion may well be the easy bit.