We could turn the asteroid Bennu into the first space colony

Astrophysicist Adam Frank is a theorist, specialist in hydrodynamics and plasma physics applied to computer modeling of stars at the University of Rochester. The scientist is used to exploring ideas on the border between science and science fiction, since he was scientific advisor for the first film. Doctor Strange as Futura explained.

Together with colleagues and students, he has just published an interesting article in Frontiers in Astronomy and Space Science, article in which he revisits the ideas already put forward about the famous concept of space colonies in the early 1970s by Gerard Kitchen O’Neill (February 6, 1927 – April 27, 1992), one of the pioneers in particle accelerator physics, a professor at Princeton University when the Apollo program took place. Gerard O’Neill was the originator of particle physics storage rings, a key technology for modern accelerators, such as at CERN for example with the LHC.

As Futura had also previously explained in an article from which we reproduce part of the content, O’Neill marked the general public with a book published in 1976 about space colonies, whose title in English is The high limit. You can learn about O’Neill’s vision of the future in the early 1980s with another work freely available online: 2081: a hopeful view of the human future.

Energy and raw materials in abundance

It all started with exercises offered to O’Neill students to do physics and engineering.” back of the envelope calculations “, that is, estimates “on the back of the envelope” also called Fermi estimates. To this end, to teach how to make correct approximations, without precise data, but on the basis of carefully chosen hypotheses – an art in which the physicist Fermi excelled, which enabled him to have plausible orders of magnitude and simple explanations for certain physical phenomena or to quickly test whether certain ideas had a chance of being valid – O’Neill asked his students to determine whether the development of a technologically advanced civilization was easier on the surface of a planet or in a space colony .

The unexpected and surprising results leaned in favor of the second hypothesis. Here some of the arguments are outlined (not for technical explanations, but with calculations, can be found in an article published in 1974 by Gerard O’Neill in Physics today).


The trailer for a documentary about Gerard O’Neill and his ideas. For a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Select “French”. © The High Frontier Movie LLC

Calculations showed that it is much easier to put materials from the Moon or asteroids into orbit, be it metals, water that can be electrolyzed to obtain oxygen and hydrogen, or even lunar regolith to make concrete, only from Earth. The gravitational field on our planet requires large amounts of fuel. For the same reason, transporting materials and people from one region to another in interplanetary space is also less energy-intensive than on the Earth’s surface.

In the case of the Moon, as in the case of space near the Earth, the Sun shines 24 hours a day, no atmosphere absorbs this energy, and large solar panels, since gravity is weak or non-existent, are possible and would make it possible to have a large amount of energy at low cost once space colonization is advanced. For example, O’Neill showed with his students that the moon’s electricity would easily magnetically accelerate payloads to the point of putting them into orbit toward Lagrange points where space colonies could be built. Electricity can also be used to mine aluminum, titanium, iron, silicon, necessary for the construction of space colonies containing metals and glass.

Giant solar stations in geostationary Earth orbit could send large amounts of energy back in the form of microwaves to deserts on Earth, where they would be collected before being redistributed across the planet. The concept was first explored by engineer Peter Glaser (not to be confused with Nobel laureate Donald Glaser, inventor of the bubble chamber) in 1968. O’Neill followed suit.

In short, if we transpose after 2050, advances in artificial intelligence, robotics, according to exponential laws and because the basics of physics tell us that huge amounts of energy and minerals (lunar soil, icy metal and carbon asteroids) are available in space , and that it costs less energy to transport and use these resources than on Earth, machines could quickly create those needed to build space colonies in a few decades.

O’Neill’s calculations also showed that not only could part of humanity leave Earth so that billions of people could live comfortably in space by 2100, but that industrial production, lighter in space and based on solar energy, could in turn irrigate Earth.


The opening of the previous documentary. For a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Select “French”. © Erik Wernquist

The key to humanity’s future after the 21st century?

In the end, still on the horizon of the end of the XXIe century, assuming that humanity cannot easily regulate its population growth and consumption in the beginning, especially since a certain standard of living is a non-negotiable minimum, and even without this the Earth could still become a kind of sanctuary. A sanctuary where there would no longer be nuclear power plants or the consumption of fossil fuels, and where the reduction in the occupation of the continents and the exploitation of nature could initiate a recovery phase for the biosphere, after the tumult caused by the industrial revolution without rational control and overpopulation . In the transition to an ideal balance, sustainable development and with the aim of ensuring for all a standard of living at least equivalent to the inhabitants of the present rich countries, part of the human population would therefore be in the intended colonies of O’Neill and his supporters.

There are of course several objections. Harnessing asteroids would no doubt be a good thing, but it is not clear how to bring the produced materials back to Earth, although some have thought about the concept of a space elevator. Sending hundreds of millions of people into space, for example after 2050-2075, is problematic precisely because of the Earth’s gravity. What about radiation during solar storms for space colonies?

Finally, if we have the technology to make these colonies, why wouldn’t it be enough to solve the problems on Earth without embarking on the massive colonization of space? Can’t we also control the population enough to reach an ecological balance in 2100 without these colonies? These are all questions that should be answered, and one can be legitimately pessimistic when one sees that, according to some of O’Neill’s estimates, we should already be building these colonies. We are still very, very far away…

During the confinement imposed by Covid-19 in the United States, Adam Frank and his collaborators therefore took the principle of ” back of the envelope calculations by Fermi to see what it would look like with modern knowledge of asteroids and with the idea of ​​finding a more credible and easier to realize alternative to a space colony than extracting the main material from the lunar soil.

The asteroid in question is simply Bennu, which we know well from the mission of NASA’s Osiris-Rex probe. Bennu belongs to the Apollo family of near-Earth asteroids – a family of asteroids with a heliocentric orbit larger than Earth’s, but with such an eccentricity that it crosses Earth’s orbit. It is therefore particularly within the reach of humanity when it is close to Earth. About 500 meters in diameter, his study showed it to be a pile of loosely bound rock fragments and particles and therefore highly porous to the point of being referred to as a “hernia mound asteroid”.

If we were to put it into rotation fast enough to create on the surface an artificial gravity adapted homo sapiens, Bennu would surely fragment in response. But this problem becomes an advantage if the asteroid is first enveloped in a kind of belt consisting of a kind of woven fabric of carbon nanotubes, where carbon is precisely an abundant material in Bennu, and therefore we could manufacture on site.

We would then obtain as a cylindrical bag strong enough to retain all the granular material and the rocks of Bennu, which would then constitute a soil that blocks the passage of cosmic rays towards the interior of the bag and which we can cover with a solar panel on the exterior exterior as shown in the artist image above.

The end result may not be as impressive and magical as O’Neill’s cylinders, but the interior surface that humans could live on would be about the size of Manhattan for any NEO used around 300 meters in diameter. .

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