A Comment on the Space Colony

Much has been said in recent decades about the construction of an inhabited orbital station. Ever since man conquered the surface of the Moon, it has been the immediate goal toward which new aerospace plans will be oriented. The great powers of the space race are vying for the privilege of being the first to build and maintain a station where human beings can live as independently as possible, meeting all the needs of its inhabitants with its own resources. It is also intended that many and very varied experiments (impossible to carry out on Earth) be performed on such a station; and that it serve as a bridge, a starting point, and a link in later missions to Mars or other destinations.

Many precautions will have to be taken; many precise and rigorous studies will have to be carried out beforehand; thousands of details and aspects of various kinds will be taken into account; decades and billions of dollars will be invested to make the mission safe for the crew and successful in its objectives.

Here are several examples of the aspects that have been considered: some years ago, NASA scientists studied different materials for interiors, searching desperately for some that (apart from being light and very strong) would give off no odor of any kind and would be nonflammable, since in the confinement of a space capsule—where one cannot open a window to get some fresh air—a persistent and penetrating odor can drive anyone crazy, and an accidental fire can turn into a great catastrophe (as happened on January 27, 1967, in an Apollo spacecraft, where the astronauts Grissom, White, and Chaffee burned to death, on the ground). Besides considerations like these, it is necessary to prepare an artificial habitat or environment, with the precise pressure, temperature, and concentration of gases in the cabin air. It is necessary to create a world in miniature, and this world must reproduce as faithfully as possible the optimal conditions of life on Earth.

It is well known that the purpose of the orbital station is to carry out experiments in zero gravity. Very probably, the experience gained on the orbital station will serve to build in the future—a distant one, if you like—space colonies that will house hundreds of human beings for several years of their lives, in which plants will be grown to feed the occupants and to oxygenate the environment.

The purpose of this article is to draw attention to a detail that came to my mind some time ago, while I was thinking about I don’t know what. This detail, concerning a future space colony located in open space, is that the influence the Moon usually exerts on all the living beings that inhabit the Earth will have to be reproduced in it. Earth’s gravity fluctuates according to the movement of the Moon around it. Flowering and fruiting, as well as the intensity of the circulation of sap in plants; the mating, behavior, and spawning of some animals; and some traits and cycles of humans (some related to hormones) are governed by, or directly influenced by, the phase the Moon is in, that is, by its position with respect to the Sun at a given moment.

This phenomenon is due to the fact that the resultant force felt by living beings on Earth’s surface is the sum of the gravitational force of Earth and the other gravitational forces of the Moon and the Sun, and for that reason it is increased or decreased, depending on whether the Moon (and to a lesser degree the Sun) attracts bodies, in this case living beings, in the same direction as Earth’s gravity or in a different one. Tides and many atmospheric currents are produced in this way.

Its effect on humans is not fully known, and for now we should not rule out the possibility that irregularities may occur when this gravitational fluctuation is missing. Moreover, if the intention is to have food crops in the colony to make it self-sufficient, this gravitational fluctuation must be taken into account, for the healthy growth and yield of the plants on board. Let us remember that terrestrial life forms, plant as well as animal, have developed and evolved while subject to the conditions of the Earth, and are adapted to these conditions. A variation in them could result in a faulty metabolism in living beings.

How can this fluctuation be reproduced in a space colony? An orbital station will necessarily have to be located in a place where the sum of the gravitational forces of the Moon and the Earth is zero, since otherwise it would fall toward one of them. A space colony can be in Earth orbit, just like a station, as long as its dimensions are not very large. But, more probably, space colonies will be located in open space, some tens of millions of kilometers from Earth. Therefore, so that the humans who live in the colony can have an artificial gravity, which makes daily tasks such as walking, eating, dressing, and washing easier (remember that we are not talking about astronauts bagged in enormous suits, but about colonists who will have to live as normally as possible), what is planned is to build the colony so that it rotates or spins in place fast enough to obtain a centrifugal acceleration of 9.81 m/s². That is how, as has been known for decades, this artificial gravity will be produced.

Here is the solution I propose: to produce the gravitational fluctuation that I mentioned above as necessary, it would be enough to speed up or slow down the colony so that the centrifugal gravity produced also increases or decreases.

Before finishing, I want to clarify something. It is very likely that it will not be necessary to adapt these cycles in the colony, either because the disturbances do not occur or are not serious, or because they are corrected by other means. But it is necessary to evaluate, in the best way possible, what would happen to human beings and to plant crops under conditions of constant (unvarying) gravity. Lest, with the installation of the first space colony, we humans get an unpleasant surprise.