Human Prospects for Colonizing Space
Discussion of the prospects for human colonization of space is constrained by the scarcity of data on the biological and psychological effects of extended space travel. Limited observations are available on a small number of men and a tiny handful of women who have spent more than a month in space (see Fig. 18.1). This is a far cry from the extent of knowledge that will be needed if humanity is ever to steer a permanent course outside the friendly confines of Earth. The biological aspects of space travel have been largely neglected by futurists and science fiction writers, who assume that engineers will create artificial gravity, regenerative life-support systems, self-contained agricultural capabilities, and spacious environments that will enable people to live normally in deep space in an Earthlike environment. From an engineering standpoint, given an adequate supply of power, there is no reason, theoretically, to object to this vision of space colonization. However, the resources that such systems will require are enormous, and certain biological and psychosocial considerations go beyond engineering solutions. This is not to say that the engineering problems of life-support systems are trivial, for, as indicated in the following section, they are formidable, particularly when raw materials are unavailable.