[Arkie2]

Actually, the ideal engine would be a nuclear power plant driving an ion engine. The advantage of the nuclear powerplant is in the excess power available for instruments. Instead of relying on solar power the scientists would have huge amounts of power to use on more powerful radar and communication arrays. The real benefit of nuclear power is more apparent in outer solar system missions where solar power is very limited.

[demecleze]

Need helium-3 from the moon first so that fusion can be used.

Then there is less worry over particle radiation as you aren't working with really big molecules that give off particles easily.

I would say that moon base for harvesting helium-3 is very important. After that flying around the solar system should be quite an easy thing to do. Then we can also start sending probes to proxima.