Even direct, person to person communication can be altered by the conditions of the space environment. The space atmosphere and weightlessness, as well as the presence of life sustaining equipment, can interfere with both verbal and nonverbal exchanges.
Verbal or linguistic communication refers to communication through grammar and syntax-that is, "what is said." High levels of ambient noise, along with atmospheric attenuation within the space vehicle, can interfere with spoken communication. In the future,  increases in the spatial volume of the vehicle's interior, along with larger and more diverse crews, are likely to increase the likelihood that the essentials of the message will be missed or misunderstood.
Poor signal to noise ratios- As noted in our discussion of habitability (chapter III), space habitats are acoustically noisy environments, with noise intense during launch and reentry. Although training may yield the high degree of interpersonal coordination required to function effectively during these phases, there is some risk that a need for deviations from prearranged procedures will arise and that queries and instructions will be difficult to communicate orally. During the cruise phase, the operation of life support systems makes the space environment at least as noisy as a busy office (Berry, 1973a). Thus, major propulsion system noise and aerodynamic noise may make oral communication virtually impossible during some periods, and the ambient noise level may make oral communication difficult under normal cruise conditions.
Additional complications are related to the channel of communication within a spacecraft. Artificial atmospheres, such as those used in space and in undersea environments, can hamper direct communication. First, if low air pressure is used, sound transmission is impaired. Under this condition, astronauts would have to speak louder than usual to be heard at a given distance. Also, some inert gases used to prevent excessive oxygen richness have voice altering qualities. In artificial atmospheres, then, there may be a tendency to speak too softly to be heard, and voice quality may be altered in such a way as to make it difficult to be understood. To avoid problems in direct verbal communication, ambient noise must be limited and the atmosphere configured to include considerations of speech transmission requirements.
Crew size and message complexity- As long as spacecrews remain small and select, each member can be expected to be well versed in the same technical language. Astronauts, like other specialists, have developed a special language in which acronyms and other speech habits are used to improve efficiency by condensing words. Myasnikov, Panchenkova, and Uskov (1977) term such specialized language "normalized." As crews become increasingly large and are selected on a broad range of criteria, the use of such language could lead to misunderstanding and conflict with other crewmembers who are using the commonly employed language or language "normalized" to another field of interest.
 Procedures must be identified to ensure that important messages are received and understood. These procedures should emphasize characteristics of clarity, redundancy, and feedback. To be clear, a message must be put in "the right words." That is, messages must be encoded or framed to take into account the receivers' abilities, training, and attitudes, remembering that successive generations of astronauts are likely to differ appreciably from each other. Redundancy or repetition should be employed to increase the opportunity for a message to be received and understood. Redundancy may involve repeating a message at two points in time, or transmitting a message to different people who have similar responsibilities or who perform similar functions. Beyond a certain level, redundancy is counterproductive because once a message has been received and acted upon, redundancy serves solely to block channels which are needed to transmit "new" or additional information. Feedback assures the source or sender that a message has been received. Certainly the simplest and probably most effective feedback procedure, when bidirectional verbal communication is possible, is to ask the receiver to restate the communication in his or her own words. However, even the practice of simple acknowledgment has been shown to result in reduced errors among aircrews (Foushee, 1982).
Once the message has been correctly framed, the task of mission planners and managers is to identify the optimal level of redundancy needed and the type of feedback required. Presumably, for a given message, the need for redundancy is inversely related to the availability of feedback.
Ethnic diversity and language barriers- Ethnically mixed crews, especially international crews, may experience serious language difficulties. The most extreme example to date of language diversity in space has been the use of "Ruston" (Russian Houston) on the Apollo Soyuz flight. After spending 1000 hr studying the language of the other, astronauts attempted to address the cosmonauts in Russian, and cosmonauts did their best to respond in English. However, these attempts were mainly symbolic, since the level of proficiency involved would be insufficient for communication on a typical flight. The flights which have brought together Soviet and other Eastern European crewmembers are more significant to the question of ethnic diversity. Here, Russian is the official flight language and non Russian crewmembers must demonstrate an  acceptable level of fluency. This requirement has not been overly restrictive, since most cosmonauts have shared a common Slavic background. It has, however, introduced new variables into the process of communication in space. Remek, a Czechoslovakian cosmonaut, recounts an interesting problem that he encountered in attempting to broadcast to his countrymen from space (Remek, 1977). As he was speaking, he realized that he had never before translated the specialized language of space from the Russian in which he had learned it. Struggling to find Czechoslovakian equivalents of Russian "space eze" resulted in a very uncomfortable broadcast, which was later analyzed to contain three times as many "ers" and "ahs" as his usual broadcast.
The ability of humans to process information is reduced when the environment is complex and demanding (Schroder, Driver, and Streufert, 1967) and linguistically heterogeneous crews add to the complexity of the environment. In the related area of flight control, solutions have been proposed for dealing with problems of linguistic differences. The Canadian government has experimented with the use of bilingual controllers (Stager, Proulx, Walsh, and Fudakowski, 1980), and the International Civil Aviation Organization has recommended that one language (English) be available on request at designated airports and on international service routes. A significant factor in this latter approach is that English may be the first language of neither the pilot nor the air traffic controller. Although both of these suggested approaches work reasonably well, neither provides a total solution. Billings and Cheaney (1981) have identified several incidents in which language difficulty played a significant role in aggravating problems of an aircraft in distress.
Although to date no serious incidents have resulted from linguistically heterogeneous spacecrews, cross cultural activity in space is in its infancy. In fact, Spacelab offered the first opportunity for a non American to fly a NASA mission. Therefore, it is conceivable that in times of emergency or overload there would be a tendency for international crews to miscommunicate, for instance, by reverting to their native tongues. With linguistically heterogeneous crews, it might be necessary to rely more heavily on the slower, but more precise, written mode. It may also prove helpful to code much of the instrumentation and equipment with international symbols, or at least with symbols whose meaning has been previously agreed upon (Remek, 1977).
 Even in a monolingual crew, there could be problems related to accents and regional dialects. Within the English language there also are subtleties of intonation, inflection, context, meaning, and interpretation which can influence the degree of communication and understanding among users. In addition, it can be anticipated that dissimilarity in background will make message interpretation difficult. Rogers and Agarwala Rogers (1976) report that heterophilous communication (i.e., communication between senders and receivers differing in education, status, beliefs, etc.) often leads to message distortion, long reaction times, restricted channels, etc. In terms of cultural differences, much remains to be understood about how miscommunication could develop in the space environment, and how such miscommunication could be prevented or corrected.
Communication through the linguistic mode (grammar and syntax) is supplemented by communication through three other nonverbal modes. These are (1) the paralinguistic mode (communication through the amplitude, rate, and tenor of speech); (2) the kinesic mode (communication through facial expressions and gestures); and (3) the proxemic mode (communication through distancing or placement). Research suggests that a large proportion of affective information transmitted under face to face conditions is conveyed through nonverbal channels (see Mehrabian, 1971). Nonverbal messages can substitute for verbal messages, modify verbal messages, and contradict verbal messages. For this reason, nonverbal factors must be considered an integral part of communication in space.
The space environment- High ambient noise and low air pressure will interfere with paralinguistic and with linguistic communication. Background noise of certain frequencies and timbres may mask informative intonations. Artificial atmospheres which transform or alter voice quality could prove particularly troublesome. The extent to which such limitations on paralinguistic channels could impair or distort task and socioemotional communication flow needs to be examined.
Weightlessness has the potential of interfering with both kinesic and proxemic aspects of communication. Weightlessness is associated with a certain puffiness or immobility of the face. Communicators may lack emotional expressiveness or else convey misleading or inappropriate emotions. Myasnikov et al. (1977, p. 2) note:
 According to the experience of Soviet cosmonauts and American astronauts, strongly expressed puffiness distorts usual facial expressions, [and] impoverishes the set of mimics required by a given situation. Under such conditions the relationship "speaker listener" is changed to one unusual for partners in intercourse...
Under normal circumstances, people express attraction to one another by decreasing interpersonal distance (Altman and Taylor, 1973). In space, floating and the use of safety lines, clamps, and other anchoring devices, and operating in cramped quarters tend to reduce the expressive value of interpersonal distancing. Additional limitations are imposed when communicators are encased in protective garments.
Weightlessness can change the physical and anatomical cues on which people depend for information about others, leading to false or prejudicial interpretations. Space travelers must be sensitized to these changes related to weightlessness, and compensatory mechanisms must be devised.
Crew heterogeneity- We can expect that increasing crew heterogeneity in space will be associated with an increase in the likelihood of nonverbal and verbal miscommunication. Pace of speaking, intonation, and the like vary from one group to another, with or without a common language. Problems in proxemic and kinesic expression are also likely to arise with increasing crew heterogeneity. For example, interpersonal distancing is a culturally conditioned response (Hall, 1959). Since appropriate interpersonal distance zones are specific to a society or subgroup, one participant in an intercultural exchange may view the other as too close, whereas the other is likely to view the one as too distant. Such discrepancies could be exacerbated by the cramped and isolated conditions associated with spaceflight.
Ekman and his associates (Ekman and Friesen, 1972, 1975; Ekman, Friesen, and Ellsworth, 1972) have found that a given emotion will yield similar facial expressions across cultures. Although this reduces the possibility of kinesic miscommunication, there remains intercultural variability in the stimuli which give rise to specific emotions among representatives of different cultures, and in the display rules or strategies used for managing or controlling expressions within different cultures. Such variability could cause significant problems under conditions of isolation, confinement, and risk For instance, a verbal report of a potentially dangerous situation  might not be given sufficient weight if the facial expression of the communicator suggests nonchalance to a recipient from a more expressive culture. On the other hand, a rebuke that was intended to be mild might be perceived as severe if the communicator's face seemed "overemotional" to a recipient from a less expressive culture. Our limited experience to date provides only hints concerning intercultural, nonverbal aspects of communications in space. We need to determine which cues lead to misinterpretation and what problems are likely to follow.