Vasimr has promise
We will have to fight to get a nuke reactor in space to generate the needed thrust but the results would solve the radiation and log duration weightlessness problem for the trip. I am not sure how far in the future Vasimr is.
It would not solve the problem (if there is a problem) of long periods of 1/3 G on Mars or 1/6 G on the Moon. We really need some research on that.
