Living in Space

Outer space is a harsh and unforgiving environment. To get there, astronauts must ride atop complicated rockets that rely on controlled explosions to attain the terrific speeds required to achieve orbit. Out there, spacecraft and spacesuits must protect their occupants from wild temperature swings, a near perfect vacuum , and in some cases poisonous atmospheres and corrosive dusts. People must adjust to "weightlessness" and they may be exposed to potentially harmful doses of radiation. In addition, spacefarers must adjust to the psychological and social conditions of flight.

Acceleration

The first step in leaving Earth—achieving orbital velocity —requires high acceleration. In the 1830s, some people feared that the human body could not withstand the greater than 40-kilometer-per-hour (25-mile-per-hour) speed that might be achieved by railroad trains. Today we know that people are capable of accelerating to very high speeds as long as they are protected from the wind and other dangers. If necessary, occupants can wear inflatable suits that apply pressure to the body and in this way help the heart circulate blood. During acceleration to orbit, riders face forward in form-fitting chairs that distribute the body's weight over as much of the surface of the chair as possible. This prevents the force of acceleration from being concentrated on one small part of the body. Acceleration was a much bigger problem in the 1960s when astronauts went into space atop modified military rockets. In those days, acceleration (and deceleration) sometimes approached eleven times the force of gravity. The maximum acceleration of the space shuttle is approximately three times the force of gravity.

Microgravity

In orbit, people live under conditions of microgravity, which is commonly referred to as "weightlessness." Floating in the interior of the spacecraft, effortless somersaults and pushing large objects with one hand are proof positive of arrival in space. Microgravity also has some less desirable aspects. No longer do people have a firm sense of up and down. Fluids shift within the head, and the otoliths (tiny mechanisms within the inner ear that provide humans with a sense of orientation and balance) no longer send a familiar pattern of signals to the brain. The information coming from the eyes and the balance mechanisms no longer match, and the result is space adaptation syndrome (SAS). Symptoms of this syndrome resemble those of car or boat sickness. Not everyone who enters space experiences SAS, and it can be treated with medicine. Even untreated, SAS tends to disappear after two or three days.

In microgravity, human muscles, including the heart, do not have to work as hard as they do on Earth. Consequently, spacefarers experience muscular deconditioning. This weakening is less of a problem in space than upon return to Earth when it becomes necessary, once again, to operate under conditions of normal gravity. On occasion, spacefarers returning from lengthy missions have had to be carried out of their spacecraft. Many astronauts report that after they return from space they feel as if they weigh a ton and that it requires tremendous exertion to do even simple things, such as breathe and walk from place to place.

Years of careful research have shown how the process of deconditioning can be slowed. The most important ingredient is regular and strenuous exercise, perhaps using a treadmill or stationary bicycle. Additionally, dietary supplements and careful regulation of fluid intake helps counteract de-conditioning and ease the transition back to Earth.

Radiation

High levels of radiation come from deep within the Galaxy and from flare-ups on the surface of the Sun. The invisible Van Allen belts that circle Earth in a region known as the magnetosphere trap much of this radiation and serve as an umbrella that protects people in low Earth orbit or below. Earth's atmosphere offers additional protection. Such shields are not available for people in transit or on the Moon, and the thin atmosphere of Mars affords but the slightest protection. Massive amounts of radiation produce debilitating sickness and even rapid death. Lower amounts may not produce immediate illness, but they do affect long-term health by increasing risks of infertility or birth defects, cataracts, and cancer.

Almost any kind of barrier provides some protection against radiation. The problem is that very substantial barriers—such as a concrete vault lined with sheets of lead—are too heavy and expensive to lift into space. It will be possible to bury habitats under the lunar and Martian regolith (soil), but protecting people in transit remains a central concern. The primary remedy is limiting individual exposure to radiation—for example, restricting the total amount of time in orbit—and finding efficient, lightweight shields to provide a "storm shelter" where spacefarers can retreat during peak periods of solar activity.

Personal and Social Adjustment

Early studies of adventurers in polar regions such as Antarctica suggested that isolation from family and friends coupled with close confinement with other members of the crew could affect safety, performance, and quality of life. The importance of psychological factors was brought home in Bryan Burrough's 1998 book Dragonfly: NASA and the Crisis Aboard Mir. This work gives vivid examples of loneliness, cultural misunderstandings, and interpersonal tensions, not only among crew members but also between the crew and flight controllers. Psychological factors will become even more important as larger and more diverse crews (including, perhaps, construction workers, accountants, chefs, and nurses) remain away from Earth for longer and longer periods of time. Selecting astronauts on the basis of their psychological and interpersonal as well as technical skills helps minimize such problems. Training in human relations is one part of astronaut training programs, and designers seek ways to make their spacecraft more comfortable and user-friendly. Psychological support groups that offer advice, encouragement, and entertainment by radio have been a big help.

Be Prepared

In the earliest days of space exploration scientists were not completely sure that people in orbit could breathe properly, swallow water, and digest food. Decades of careful biomedical research have enabled people to venture into space without suffering lasting debilitating effects. So far, there have been many challenges but no "show stoppers." With continued research we should be able to overcome the biomedical challenges associated with a permanent return of humans to the Moon and the establishment of the first human camp on Mars.

see also Habitats (volume 3); Human Factors (volume 3); Living on Other Worlds (volume 4); Long-Duration Spaceflight (volume 3); Microgravity (volume 2).

Albert A. Harrison

Bibliography

Burrough, Bryan. Dragonfly: NASA and the Crisis Aboard Mir. New York: Harper Collins, 1998.

Connors, Mary M., Albert A. Harrison, and Faren R. Akins. Living Aloft: Human Requirements for Extended Spaceflight. Washington, DC: National Aeronautics and Space Administration, 1985.

Harrison, Albert A. Spacefaring: The Human Dimension. Berkeley: University of California Press, 2001.

Nicogossian, Arnauld E., Carolyn Leach Huntoon, and Sam Poole, eds. Space Physiology and Medicine, 4th ed. Philadelphia: Lea and Febiger, 1994.

Stine, G. Harry. Living and Working in Space. New York: M. Evans and Company,1997.

Stuster, Jack. Bold Endeavors: Lessons from Polar and Space Exploration. Annapolis, MD: Naval Institute Press, 1996.