A Near Sea Level Radiation One Gravity (NSLR1G) environment is the prerequisite for Human Space Flight Beyond Earth Orbit (HSF-BEO). A massive cosmic ray water shield (CRWS) and Tether Generated Artificial Gravity (TGAG) system are the only practical ways to provide this.
The keys to providing NSLR1G crew compartments are double-hulled “Fat Workshops” lofted as the upper stages of Super Heavy Lift Vehicles (SHLV’s) and the ice at the lunar poles, which can be lifted into space as cosmic ray water shielding using 20 times less energy than from Earth.
The salient feature of HSF-BEO is “The Parker Minimum” of 500 tons of water shielding for a small capsule as specified by Eugene Parker. This is generally rejected as impractical but, in reality, is the single determining factor.
Nothing stops the heavy nuclei component of galactic cosmic radiation except mass and distance. The 2006 Scientific American article “Shielding Space Travelers” by Eugene Parker remains the classic popular guide on this subject and no technological miracle is likely to change the conclusions made by Parker. “Reflecting cosmic radiation” with “a strong ion field” is pure fantasy.
The particular terminology and acronyms I have used over the years have changed a little, but they are a fairly consistent lexicon of my particular view on the future of space exploration.
Ice on the Moon 