1,700 million km2 -- Total solid surface area of the Solar system potentially (if remotely) suitable for human habitation[1] (http://uts.cc.utexas.edu/~gwk/images/SolSys/SolSys)
... covered by US patents 3,726,146 (1973) and 5,353,655 (1994) by L.A. Mishler and US patent 5,800,311 (1998) by P.S.Chuang.
External links
www.gyrotwister.de ...