This will allow the settlers to regulate the climate as they wish, and cities can be built not only on the surface, but also on both sides of the shell. One day, people will learn to turn inhospitable planets into a replica of the dear Earth. It's called terraforming and has long featured in the sci-fi genre, especially when it comes to long interstellar travel.
But today we are not talking about the dreams of writers and screenwriters, but about what the engineer Ken Roy told in Dallas (USA) at a congress dedicated to the development of an interstellar spacecraft (Project Icarus).
Keeping an absolutely serious mine, the speaker described the shell worlds to those present: upon arrival on a suitable planet for this, people literally cover it entirely with a protective sphere of Kevlar, mud and steel. The space between the shell and the central body is filled with atmosphere. The chemical composition of the air, temperature, pressure - to taste.
The force of gravity on the surface of the planet remains unchanged, everything else is made (if desired) very similar to the Earth - after all the necessary materials have been delivered. Moreover, it is even better than Earth for the following reasons.
First, if a business or some other institution needs access to a vacuum, it can be built from the outside of the shell.
Secondly, the star's ultraviolet radiation is not a problem at all, because the planet is completely protected. The same is with any cosmic radiation.
Third, the length of daylight hours, seasons, etc., does not depend on the planet's orbit around the star.
Fourthly, we have before us a space of practically unlimited creativity. For example, cities can be built not only on the surface of the planet, but also on platforms hanging from the shell: you look at the sky, and from there they wave to you.
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You don't need to fly far: Mars and even Pluto are perfect. The force of gravity on Mars is equal to about a third of the earth's, and the surface area is equivalent to the land area of the earth. Mars has no magnetic field, nor does plate tectonics seem to be; the core is frozen. On the one hand, only heroes can live in such conditions. On the other hand, it is these characteristics that make the Red Planet an ideal candidate for the first shell world. Is it bad that there are no volcanic eruptions and earthquakes there?
Of course, the most difficult technical problems have to be solved. A colossal amount of nitrogen and water will be required, and the construction of the envelope is an undertaking of inconceivable scale. But if we do decide to use terraforming, the protective sphere is the preferred option, says Roy.
After all, what is usually offered? Place mirrors on Mars that will reflect sunlight in order to cause a greenhouse effect on the small planet. But what is the use of this if the atmosphere is constantly flowing into space? According to Mr. Roy's calculations, to create there an analogue of the Earth's atmosphere will require about half of the mass of this latter, and in the case of the construction of the shell - only 6.6%.
The essence of this speech is that it makes no sense to develop a ship for interstellar travel if we do not think over the purpose of the trip in advance. And the goal is obvious - colonization. At the same time, the probability that, having arrived somewhere, we will find a habitable world there, is extremely small.