space station,an artificial structure placed in orbit and having the pressurized enclosure, power, supplies, and environmental systems necessary to support human habitation for extended periods. Depending on its configuration, a space station can serve as a base for a variety of activities. These include observations of the Sun and other astronomical objects, study of Earths resources and environment, military reconnaissance, and long-term investigations of the behaviour of materials and biological systemsincluding human physiology and biochemistryin a state of weightlessness, or microgravity.

Small space stations are launched fully assembled, but larger stations are sent up in modules and assembled in orbit. To make the most efficient use of its carrier vehicles capacity, a space station is launched vacant, and its crew membersand sometimes additional equipmentfollow in separate vehicles. A space stations operation, therefore, requires a transportation system to ferry crews and hardware and to replenish the propellant, air, water, food, and such other items as are consumed during routine operations. Space stations use large panels of solar cells and banks of storage batteries as their source of electrical power. They also employ geostationary relay satellites for continuous communication with mission controllers on the ground and ... (200 of 4,801 words)

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space station -- Encyclopedia Britannica