Space environments are characterized by isolation (a separation from the normal or daily physical and social environment), confinement (restriction within a highly limited and sharply demarcated physical and social environment), deprivation, and risk. Such environments may be expected to place heavy demands on astronauts' psychological and social resources.
The Physical Environment
Space itself is totally inhospitable to life as we know it. Penetration of the wall of a spacecraft or a major equipment malfunction  could lead to instant-or lingering-death. Although concern for astronauts' welfare will continue to be primary, there is a limit to the amount of safety redundancy that can be built into any system. Malfunctions or mistakes, should they occur, will have to be corrected by a relatively small group of people who have limited access to tools and supplies. Because space environments are so removed, the chances for outside rescue are slim. In addition to the high risk of the space environment, space travelers must contend with limited facilities, equipment, and supplies, and with a low level of perceptual stimulation.
Economic and engineering considerations limit both the size and the weight of a spacecraft. Like most sea and air vessels, a considerable portion of the spacecraft's total weight must be devoted to propulsion mechanisms, fuel, and navigational equipment. In addition, spacecraft require elaborate machinery to ensure an adequate supply of air and water and are likely to carry considerable scientific baggage. All such items use internal space that could otherwise be devoted to living quarters and recreational facilities.
Equipment transported to space needs to be carefully designed or selected, and thoroughly tested. In the future it will become increasingly important that equipment not only fulfill its intended function, but also operate in a way that does not yield dysfunctional social consequences. For instance, equipment that must be used by many people should have a reset requirement built into its operation. This would avoid the interpersonal frictions that have occurred in space simulation, when people fail to leave things as they find them (S. Smith, 1969). However, equipment that is completely satisfactory during pretesting on Earth may not meet expectations in situ, as has been shown in space flights from Mercury (Wolfe, 1979) through Skylab (Cooper, 1976) and Shuttle (Stockton and Wilford, 1981).
Within the space environment, life proceeds without abundant provisions or supplies. Even in the future, when space settlements may have certain renewable resources and when shuttling craft may supply orbiting laboratories, goods will be limited. Although it may be possible to guarantee adequate reserves of life-sustaining items, many of the common luxuries that can be found in the smallest U.S. communities will be either unavailable or extremely scarce.
Even the simple pleasures associated with mealtimes may be muted in space. Providing food that is tasty and otherwise appealing  has been a particular problem in space and in certain subaquatic environments that require artificial atmospheres. At the same time, foodstuffs and other oral supplies have been found to offer special gratification to isolated and confined people (Shurley, 1973; Berry, 1973a; Earls, 1969; S. Smith, 1969; Serxner,1968; Mullin, 1960). It is unlikely that alcohol as a social beverage will find its way into space, at least until relatively large and stable settlements are established. Alcohol, as a recreational drug, may be keenly missed by space travelers, since there is evidence that alcohol plays an important social role in exotic environments (Mostert, 1974; Shurley, 1973).
On many future missions, the perceptual field will be relatively unchanging. Inside the vehicle, the walls and furnishings must be functional. Machinery will hum monotonously, and the temperature and humidity will remain within narrow limits. Outside the spacecraft, the view may be spectacular; however, this view may be highly repetitive (as in the case of an extended orbital mission) or shift at a barely perceptible rate (as in the case of an interplanetary mission). Furthermore, since viewing ports are structurally costly, they are likely to be only sparingly available.
Early fears that space missions would produce hallucinations and other effects associated with prolonged and pronounced sensory deprivation (Zubek, 1969; Flinn, Monroe, Cramer, and Hagen, 1961; Heron, 1957) have been allayed (Kanas and Fedderson, 1971), but boredom remains a likely concomitant of extended-duration spaceflight. There are various techniques, involving judicious selection and arrangement of interior design and personal articles, that could raise the visual stimulation inside the space vehicle. However, the physical environment, when not terrifying, is likely to be bland.
The Social Environment
Adapting to unusual and frustrating physical conditions in space is but half the battle confronting today's astronauts and tomorrow's space settlers. Challenges are also posed by the social environment. Participants on long-duration space missions will be temporarily, or perhaps permanently, extracted from the ongoing relationships that are important to them, and will be thrust into a microsociety which will impose its own social deprivations and hardships.
Withdrawal from the home community- People under normal circumstances are embedded in a complex social matrix that links  them with family members, friendship groups, one or more largescale organizations, and society. Space-mission participants are withdrawn from this social matrix. Space travelers are likely to be separated from loved ones and friends, with the concomitant loss of reassurance, affection, and respect that flow in such relationships.
A second effect of withdrawal from the larger society is a loss of variety in social relationships. A corollary of this reduced variety is a lessened opportunity to exercise one's typical social roles. In the course of daily life, people enact a variety of different roles (teacher, husband, father) with those who enact interlocking or reciprocal roles (student, wife, son). In addition to providing stimulation, such diversity allows the person to exercise different skills and talents, and may be important for a complete sense of identity (D. Miller, 1963). Variety in relationships also provides the opportunity to formulate a balanced response, as when a dispute at work is placed in perspective in a session with a spouse or a friend.
Withdrawal from preexisting relationships removes known comparison points and limits the self- evaluation process (Festinger, 1954). For this reason, withdrawal from one's usual relationships may make it difficult to maintain a sense of personal continuity or identity.
Challenges of the microsociety- At the same time that astronauts must cope with the effects of withdrawing from the macrosociety, they will be confronted with social challenges within the microsociety. Unlike the usual acquaintance process through which people get to know one another gradually and against a backdrop of other developing and continuing relationships (Altman and Taylor, 1973), space missions will involve intense contact with very few people. Acquaintance processes are thus likely to be forced, rapid, and relatively unbalanced by alternative relationships. Also, prolonged isolation and confinement appear to magnify the effects of attitudinal dissimilarities, need incompatibilities, annoying habits, irritating mannerisms, and other sources of interpersonal friction (Haythorn et al., 1972), while reducing the opportunity to express dissatisfaction. For example, under conditions of isolation and confinement antagonisms are frequently suppressed, apparently because of fear that their expression could spark a conflict with unacceptably costly consequences.
 Basic Reactions to Space-like Environments
We have considered some of the difficulties in extrapolating from data gathered on Earth to problems that could occur in space. We must also be aware that certain factors cloud the interpretation of the overall pattern of results among Earth-based studies. First and foremost is the noncomparability of studies themselves. Rarely have two studies involved similar degrees of isolation, confinement, and risk, and only occasionally do different studies involve similar dependent measures.
Second, there are many possible causes of most of the reported effects. The field settings in which these studies are conducted typically contain a number of elements, any one or a number of which might provoke psychological or social dysfunction.
Finally, most naturalistic studies of isolated and confined individuals do not include controlled observations of people who are living and working together in nonisolated, nonconfined locations. Although some informative data from natural settings may be available, these data rarely offer the degree of comparability desired.
Given these limitations in comparing data from Earth-based studies, certain behaviors occur with sufficient consistency in the various studies to command the attention of space-mission planners. (For a consideration of how data from isolated and confined groups compare with experiences on the Russian Salyut 6, see Bluth,1982).
Impaired intellectual functioning- There is some evidence that isolation and confinement lead to impaired intellectual functioning Several investigators have reported decreases in alertness, concentration, and memory among polar expeditioners (Natani, Shurley, and Joern, 1973; Strange and Klein, 1973; Mullin, 1960), with needinduced fantasies sometimes distorting perceptual judgments (S. Smith, 1969). In a carefully controlled laboratory experiment, Taylor, Altman, Wheeler, and Kushner (1969) found that isolation and confinement led to impoverishment of ideational and imaginative output, as evidenced by responses to the Rorschach Inkblot Test.
The declines observed thus far have not appeared among all, or even the majority of participants. Also, the declines that have been reported are not necessarily severe, and many studies report no intellectual decline at all (see, e.g., Cleveland, Boyd, Sheer, and  Reitman, 1963). A continuing concern, however, is that prolonged isolation and confinement can lead to cognitive impairment of sufficient magnitude to prevent satisfactorily coping with emergency situations.
Motivational decline- Many studies suggest that prolonged isolation and confinement results in a loss of motivation. A common report is that study participants begin confinement with every intention of engaging in creative activities such as writing, completing a project, or accomplishing some serious reading. These worthwhile goals rarely are achieved, or even attempted. Instead, most hours of confinement are spent in time-marking activities such as solitaire.
Gunderson and Nelson (1963) observed a general decline in work satisfaction and group accomplishment among polar expeditioners, and Natani and Shurley (1974) have reported fatigue, inertia, and general apathy among a similar group. In the course of an Arctic trek, scientists interviewed by Pope and Rogers (1968) reported increased feelings of helplessness and worthlessness, feelings which are hardly conducive to goal-directed activity. Cleveland et al. (1963) report a "diminution of vitality" among fallout-shelter confinees, and Earls (1969) has found that the high motivation shown by submariners during the first few days of a cruise dissipates as the cruise progresses.
Somatic complaints- Relatively common correlates of isolation and confinement are insomnia, headaches, digestive problems, and other somatic complaints. For the most part, it is felt that these findings do not simply reflect unappetizing rations, cramped sleeping quarters, or extreme conditions; there is presumed to be a fairly strong psychological component as well.
Insomnia and other sleep disturbances are the most prevalent complaint. Sleep disturbances have been noted among members of polar parties (Natani and Shurley, 1974; Strange and Klein, 1973; Gunderson and Nelson, 1963; Law, 1960), among submariners (Earls, 1969; Weybrew, 1963; Mullin, 1960), and among experimental subjects (Hammes and Osborne, 1965).
Headaches are a common problem in various confinement settings (Natani and Shurley, 1974; Earls, 1969; Kubis and McLaughlin, 1967), and upset stomachs, constipation, and other digestive complaints also appear with considerable frequency (Natani and Shurley, 1974; Hammes and Osborne, 1965). In general, sick calls increase  over time in confinement, with the highest incidence occurring during the third quarter of the expedition's term.
Psychological changes- Studies to date do not support the notion that isolation and confinement result in severe psychiatric disturbances (Lug", 1973; Gunderson, 1963). However, mild psychiatric symptoms have been reported with considerable consistency. A large number of incidences involve depression (Natani and Shurley, 1974; Natani et al., 1973; Strange and Klein, 1973; Serxner, 1968; Gunderson and Nelson, 1963; Palmai, 1963; Law, 1960) and anxiety (Pope and Rogers, 1968; Serxner, 1968; Ruff, Levy, and Thaler, 1959). Other psychological changes that have been noted in confinement are regressive, highly polarized and immature attitudes (Lug", 1973; W. Smith, 1966), increased defensiveness or belligerence (Palmai, 1963; Ruff et al., 1959), and a high emphasis on oral satisfaction (Serxner, 1968; Mullin, 1960). Ruff et al. (1959) offer a general explanation for these observations by suggesting that isolation and confinement are conducive to the "eruption of the unconscious. "
Social tensions- It has been suggested repeatedly that prolonged isolation and confinement impairs people's ability to get along with one another (Kubis, 1972; Haythorn et al., 1972; Kanas and Federson, 1971). Touchiness or social irritability has been observed among polar expeditioners (Natani and Shurley, 1974; Gunderson and Nelson, 1963; Palmai, 1963; Law, 1960), submariners (Rohrer, 1961), fallout-shelter confinees (Cleveland et al., 1963), and space-simulator subjects (George Washington U., 1974). It appears that the confinement environment magnifies incompatibilities which might otherwise be overlooked (Haythorn, 1970, 1968; Haythorn et al., 1972).
One method by which confined individuals control interpersonal tensions is by shunning those activities, such as competitive games, which might lead to conflict. More broadly, interactions among confined individuals tend to lack affect. For instance, Flinn et al. (1961) found that most of the social acts performed by subjects in a space simulator fell into the interpersonally neutral categories of Bales' (1950) Interaction Process Analysis.
A second method by which confined individuals avoid conflict is by withdrawing from one another. Haythorn and Altman (1967) have termed this withdrawal behavior "cocooning." However, unlike a physical cocoon, the barriers which confined individuals establish are primarily psychological. Although confinees become disinclined  to interact with one another, they do not necessarily wish to be physically separated. The result is an aggregation of people engaged in individual activities in what might be thought of as an adult version of parallel play. Rogers (1978) has found that this preference for shared space over private space extends to mixed-gender crews. Being in line-of-sight contact with others seems to comfort the confined individual, probably by keeping him current on what is happening in the group.
Another commonly reported method for dealing with interpersonal tension in confinement is to direct it to outsiders. Numerous studies show that confinees direct their hostility towards those who maintain communication with the confined group, or to others associated with the confinement project. Space travelers are not immune to this phenomenon; members of certain Apollo and Skylab crews have expressed peevishness and defiance towards ground-control personnel.
Almost any condition, note Kanas and Fedderson (1971), can be tolerated for a brief period of time. It is with the passage of time that the deleterious effects of isolation and confinement gain prominence. In the Antarctic, work satisfaction, social relations, and group accomplishment have been found to deteriorate with time (Gunderson and Mahan, 1966; Gunderson and Nelson, 1965). In a Boeing 30-day simulation, increased time was associated with (1) increased annoyances, interpersonal conflicts, and hostility; (2) decreased feelings of being happy, comfortable, and satisfied; and (3) increased dislike for the experimenter (George Washington U., 1974).
Although some studies show a general relationship between time in confinement and negative feelings, other studies indicate that mood and morale do not deteriorate monotonically. Rohrer (1961) has identified three broad stages of reaction to prolonged isolation, confinement, and stress. The first stage is a period of heightened anxiety brought about by the perceived dangers in the situation. Moderately heightened anxiety may improve alertness and performance, and is hence not necessarily detrimental. The second stage, which emerges as the crew settles down to a routine day-to-day existence, is marked by depression. Moods during this stage are likely to result in regrets about having joined the mission. The third stage is a period of anticipation which occurs as the end of the mission draws  nigh. During this period emotional outbursts, aggressiveness, and rowdy behavior are likely. This expressiveness can be dangerous because at the end of a mission many complicated operations may have to be performed (Kanas and Fedderson, 1971).
Departing one stage and entering another appear to be more dependent upon the relative than the absolute passage of time. Substantial evidence suggests that whether the mission lasts days, weeks, or months, morale reaches a low ebb somewhere around the one-half to two-thirds mark. For example, Palmai (1963) reports that morale reached its lowest ebb somewhere around the second third of a 1-yr Antarctic stay. In 30-day submarine missions, morale reached nadir at about day 15, and in 8-wk missions, morale reached nadir during the fourth and fifth week (George Washington U., 1974). In the McDonnell-Douglas 90-day simulation study, crew morale was rated as good except for a period of 10 days which occurred about two thirds of the way through the mission. One- and two-week confinements in fallout-shelter simulations undertaken by the American Institute for Research also show a pattern of depression toward the midpoint of the stay (George Washington U.,1974).
These evidences of temporal mood shifts are not perfectly in accord for, as already noted, some reports make no mention of an upswing in morale toward the end of a mission, whereas in the Sealab II study, morale did not decline over time (Helmreich, 1973). However, many studies do suggest that mood is related to those psychological anchor points which help the individual mark his confinement.
Although morale may recover as the end of a mission comes in sight, there is no evidence that the withdrawal behavior just described similarly abates. Confinees have been reported to remain withdrawn throughout confinement and to show increasing signs of proprietary attitudes towards possessions as the confinement progresses (Grumman Aerospace Corp.,1970; S. Smith, 1969; Haythorn and Altman, 1967).