Spacelab--the coming of age of space physiology research.

Spacelab is a cylindrical pressurized laboratory (approximately 7 m long and 4 m in diameter) that is part of the payload of the Space Shuttle. It provides an orbiting "shirtsleeves" environment for laboratory experiments on the physiological effects of weightlessness. The first Spacelab flew in November 1983 with great success. Of special interest to physiologists is Spacelab 4, which is scheduled for early 1986 and will be the first dedicated to life sciences. It will contain 24 experiments covering the area of vestibular, cardiovascular, pulmonary, renal, endocrine, blood, bone, and muscle physiology, with additional experiments in gravitational biology. Opportunities for research on subsequent life science Spacelabs have recently been announced, and this is therefore an opportune time to review progress to date in the field of space physiology and to point to some of the challenges of this emerging discipline.