New paper suggests a much easier path to space settlement

"Space Settlement Population Rotation Tolerance," Al Globus and Theodore Hall, preprint, May 2015. This paper reviews the literature to find that space settlement residents and visitors can tolerate at least four, and proabaly six, rotations per minute to achieve 1g of artificial gravity. This means settlements can be radically smaller, and thus easier to build, than previously believed. Combined with a second paper on radiation shielding which is being revised, the first space settlements can be two orders of magnitude less massive and much closer than previous designs making launch from Earth practical.

For full text see http://space.alglobus.net/papers/RotationPaper.pdf

Full abstract

To avoid a number of very negative health effects due to micro-g, free-space settlements may be rotated to provide 1g of artificial gravity. Since the NASA/Stanford space settlement studies of the 1970s the settlement design community has assumed that rotation rates must be no more than 1-2 rpm to avoid motion sickness. To achieve 1g, this rotation rate implies a settlement radius of approximately 225-895 m, which is much larger than any existing satellite. In this paper we examine the literature and find good reason to believe that much higher rotation rates may be acceptable to residents and visitors alike, significantly reducing the minimum size of settlements and thus the difficulty of building them. We find that rotation rates of up to 4 rpm, corresponding to a 56 m radius, should be acceptable, although visitors may require some training and perhaps a day or so of adaptation for those particularly susceptible to motion sickness. A rotation rate of up to 6 rpm (25 m radius) should be acceptable for residents but visitors will almost certainly need training and/or a few days to adapt. While higher rotation rates (up to 10 rpm) may be acceptable with training, such small structures are not suitable for permanent residence (9 m radius at 10 rpm). With some caveats due to the quality of the available data, it appears that the lower limit of space settlement size is not determined by human response to rotation rate but rather by other factors. This means that the effort necessary to build the first space settlements may be significantly less than previously believed, simply because they can be much smaller than heretofore expected.

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For full text see
http://space.alglobus.net/papers/RotationPaper.pdf
Full abstract
To avoid a number of very negative health effects due to micro-g, free-space settlements may be rotated to provide 1g of artificial gravity. Since the NASA/Stanford space settlement studies of the 1970s the settlement design community has assumed that rotation rates must be no more than 1-2 rpm to avoid motion sickness. To achieve 1g, this rotation rate implies a settlement radius of approximately 225-895 m, which is much larger than any existing satellite. In this paper we examine the literature and find good reason to believe that much higher rotation rates may be acceptable to residents and visitors alike, significantly reducing the minimum size of settlements and thus the difficulty of building them. We find that rotation rates of up to 4 rpm, corresponding to a 56 m radius, should be acceptable, although visitors may require some training and perhaps a day or so of adaptation for those particularly susceptible to motion sickness. A rotation rate of up to 6 rpm (25 m radius) should be acceptable for residents but visitors will almost certainly need training and/or a few days to adapt. While higher rotation rates (up to 10 rpm) may be acceptable with training, such small structures are not suitable for permanent residence (9 m radius at 10 rpm). With some caveats due to the quality of the available data, it appears that the lower limit of space settlement size is not determined by human response to rotation rate but rather by other factors. This means that the effort necessary to build the first space settlements may be significantly less than previously believed, simply because they can be much smaller than heretofore expected.
If you want off this list, just reply to this email and ask out.