I got blasted some years ago on the Mars Society web site because I stated that it would be smarter to design and create robots for the voyage to Mars for this very reason. People kept telling me that Robert Zubrin's book, "The Case for Mars", had it all figured out how you could do it for $10-$20 billion dollars.
Needless to say I did not stay on that site very long.
Zubrin doesn't strike me as having much credibility; suffers too much from a combo of hand-waving and wishful thinking.