ABSTRACT
Historically, people have built progressively more elaborate habitats for protection and to facilitate their purposeful activities. Nowadays, people live in tents, submarines, houses, mansions, prison cells, hospitals, space vehicles, and sometimes on the street. The physical, operational, and social environments and activities vary greatly, and people have a remarkable capability to adapt, within certain limits. Features of these environments, activities, and their corresponding habitats are qualitatively very different. People weight the importance of different features according to their particular purposes and their state of adaptation. As humans begin to explore outer space, we face the greater challenges of different gravities and radiation and lack of oxygen, water, and food. Spacecraft have to carry all their life-support systems with them. Ironically, in outer space, interior space restriction of habitats is a major challenge because of the gravitational, temporal, and financial challenges of transporting materials into space. For the foreseeable future, spacefarers will be cooped up in a can or space suit for long periods of time. They will also face limited resupply opportunities and communication with earth.
