Ralph McNutt takes a detailed but flawed look at human missions to the outer solar system. He looks at using Extremely heavy lift launch vehicles (EHLLV chemical rockets) to lift about 1000 tons to low earth orbit and then scaled up versions of the Vasimr magnetoplasma rocket to move about the solar system.
There is some useful information about radiation levels in space and active electric and magnetic shields.
(H/T Ars Technica)
I believe that combination of existing technology would technically work but clearly there is too much misinformation and misunderstanding about risks for this to proceed.