vised June 15, 1959. 60p. Presented at the National Summer Meeting of the Insti-tute of Aeronautical Sciences, Los Angeles, July 8-11, Various physical space attributes of the natural envronment in the solar system are estimated and discussed. A survey was made of the characteristics of solar radiations, the effects of solar and other thermal radiations on vehicle temperature, the characteristics of the earth's magnetic fields and other magnetic fields in space, the earth's exosphere and the solar corona, cosmic rays, and meteoroids. Estimates of the probability of vehicle skin penetration by meteoroids are aIso presented. (auth)