Steel is a poor material for radiation protection (because of high energy scattering effects causing secondary high energy particles - but I am no Physicist).

Steel is a poor material for radiation protection (because of high energy scattering effects causing secondary high energy particles - but I am no Physicist). Hyrdogen rich (eg water, polyethelene, etc) make better shielding. See also this paper on a potential location that requires little or no shielding: http://space.alglobus.net/papers/Easy.pdf http://space.alglobus.net/papers/Easy.pdf A related paper proposes a faster rotaion (upto 4 rpm) vs. the conservative 2rpm selected in the '70s which allows for smaller (easier, cheaper) colonies to be built sooner.