Since the earliest days of spaceflight, substantial concern has been expressed regarding the physical needs of astronauts, including any biological damage that might result from exposure to radiation or from reduction in gravitational forces. In contrast, relatively little concern has been directed towards people's psychological and social adjustment to space. At one time this difference in emphasis was justified. The Mercury, Gemini, and Apollo flights were measured in hours and days and it could be reasonably assumed that astronauts would be able to withstand certain deprivations for these brief periods. The longer flights of Skylab presented a different picture. Early in the development of Skylab, it was recognized that steps would have to be taken to accommodate a wider variety of human needs. However, the needs that were addressed remained narrowly defined and centered primarily on habitability considerations.
We are now at the point in the development of spaceflight where the range of psychological and social requirements of the human participant must be given full consideration. There is hope that NASA soon will move ahead with its long awaited space station. As this is written, information from the Russian space program suggests that the Soviet Union will soon launch a space vehicle capable of carrying a crew of twelve, possibly as a prelude to a manned Mars mission. Whatever the specific projects or time frames, it seems clear that tomorrow's manned spaceflights will involve large numbers of people living and working together under close confines and in  "unnatural" environments for long periods of time. Adjustment to such conditions has important implications for mental health, for social organization, and ultimately for mission success. Because tomorrow's astronauts are likely to expect, and even demand, greater autonomy in living and working arrangements, the planners' perspective must extend beyond concern for effective functioning within the space community and encompass the relationship between the space community and the home planet.
In this book we attempt to identify and assess, in a serious and systematic fashion, the psychological and social problems that may be associated with future space missions, and to explore some possible solutions. This task involves establishing both a structure in which relevant issues can be considered and a level of analysis that can contribute to a scientifically based understanding of human adaptation to space.
Several authors, expressly or tacitly, have affirmed the need for the integration of behavioral and social science methods and findings into space mission planning and management (e.g., Leonov and Lebedev, 1975, 1972; Berry, 1973a; Kubis, 1972; Sells, 1966). In 1972 the Space Science Board of the National Academy of Sciences issued a publication entitled Human Factors in Long Duration Space Flight, which attempted to approach the question of the human in space in a comprehensive fashion. Through a series of essays, the contributors to this volume looked at various aspects of human adjustment to space, placing particular emphasis on the neglected behavioral, psychological, and sociological factors of this "microsociety in a miniworld." The present volume attempts to build upon and broaden this past work, and, on occasion, to challenge the assumptions upon which it and other earlier discussions rest.
Much of the writing on man in space has focused at one extreme on narrowly defined experiments, usually involving basic biomedical processes, and at the other extreme on highly speculative and even Utopian views of potential social arrangements. The present work is an attempt to fill the gap between these two approaches by examining the behavioral science literature which has either direct or indirect application to the space environment. From this examination we hope to draw conclusions about adaptation to space and identify those areas where further psychological and social research is needed.
 Space missions have generally involved small crews, drawn from highly homogeneous pools (such as white, educated, young adult males) and functioned for limited periods of time. We anticipate that future missions will involve large crews drawn from diverse populations, and that these missions eventually could last years. As crew size, crew heterogeneity, and mission duration continue to increase we enter the realm of "extended spaceflight." The general question we attempt to answer in this book is "What are the psychological and social issues of future spaceflight?" Reformulated in terms of the variables of extended spaceflight, the question becomes "What will happen when space crews become larger, more heterogeneous, and as space missions become substantially longer?"