Chapter 5-4

Conclusion: We Can Go On

There no longer is any doubt that humans can both survive in space and work hard and productively in this exotic environment for periods of many months. A sizable number of biological responses to weightlessness do take place fairly promptly but are reversible when the space traveler resumes his or her accustomed place on the surface of the Earth. Yet it is equally clear that some of the adjustments are slow and do not reach equilibrium even after many months of weightlessness. There also is concern that a few of these processes, if allowed to go on long enough, may produce irreversible changes. This could be particularly worrisome when older individuals or persons in different physical condition from the astronauts travel into space. Many scientists are seeking to detect, to understand, and ultimately to prevent these changes, so that long voyages into space will be both safe and feasible.

We still do not know whether weightlessness or reduced-gravity environments are suitable for indefinite lengths of time for any terrestrial species. All plants and animals not only are endowed with specialized gravity sensing devices, but also possess many cellular and subcellular structures whose orientation and perhaps even function will be influenced by the withdrawal of gravity. Actual spaceflight data are sparse, but so far gross anomalies in basic living processes have not been detected in the space environment. Much work, of course, remains to be done before the role of gravity in living processes is completely understood and before humanity can erect cities in the sky with the same impunity with which the spiders Arabella and Anita spun webs in Skylab.

conceptual illustration of space colony
Habitat of the future?
Part of a torus-shaped space colony proposed for the future by members of a study group. Farms would raise food for 100,000 inhabitants, while rotation at 1 rpm would provide artificial gravity.

conceptual illustration of a space colony in orbit
Station in space
An artist's depiction of a future space colony somewhere between the Earth and the Moon.

The physiological and psychological barriers to space flight are being methodically and successfully challenged. A major dividend of these space medicine studies is that much of what is learned is directly applicable to ordinary people who may never leave the Earth. The technology that permits the flight surgeon to monitor the heart rate of an astronaut walking on the Moon can be used to keep a careful and continuous watch on cardiac patients going about their daily work. The space suits that cooled and protected astronauts during extravehicular activity have been adapted to treat the cancer patient and to guard the immune-deficient child from the germs against which it has no natural defense. Even an astronaut's adverse reactions to weightlessness are in many ways similar to diseases on Earth. Such diseases are thus seen in a different light from the viewpoint of space. Their underlying mechanisms may become more apparent, and ef fective treatment may be developed.

photo of a spacesuited child looking in a mirror
Life-saving suit.
A child born with severe combined immune deficiency, a rare hereditary disease, is protected from potentially harmful microorganisms by a miniature space suit.

Much must be learned, much must be done before humans can spend indefinite periods of time beyond the confines of the Earth. It is still conceivable that prolonged or repetitive exposure to space may ultimately present an impassable barrier to our survival in that environment.

Today, however, from the vantage point of twenty years of space flight operations, many thousands of hours of flight experience, more than one hundred astronauts and cosmonauts, and many other living creatures, no such barrier is in view.


Belew, L. F. 1977,
Skylab, OurFirst Space Station
(Washington, D.C. NASA), SP-400.

Cooper, H.S.F., Jr. 1976,
A House in Space
(New York: Holt, Rinehart and Winston).

Gordon, S.A. and M. J. Cohen 1971,
Gravity and the Organism
(Chicago: University of Chicago Press).

Johnston, R.S. and L.F. Dietlein (eds.) 1977,
Biomedical Results From Skylab
(Washington, D.C.: NASA), SP-377.

O'Neill, G. K. 1977,
The High Frontier: Human Colonies in Space
(New York: Bantam).

Sharpe, M.R. 1969,
Living in Space
(New York: Doubleday).

Summerlin, L.B. (ed.) 1977,
Skylab, Classroom in Space
(Washington, D.C.: NASA), SP-401.

Previous Index Next