The year 2019 began with news of the most distant object ever visited by a spaceship and the landing of a probe on the far side of the Moon. On New Year’s Day New Horizons, a robotic spaceship launched in 2006, was transmitting photographs of a bizarre, snowman-shaped object called “Ultima Thule” orbiting the outer edges of our solar system, the mysterious Kuiper belt. Sending a spacecraft to a destination 46 times the distance of Earth from the Sun, at a staggering speed of 57,936 km/h, have it fly by Pluto, and then redirect it to meet a relatively tiny object millions of miles away, is a truly astonishing feat of planning and engineering.
Two days later China’s Chang’e 4 was landing inside the Von Karman crater in the South Pole-Aitken basin, the largest, oldest, deepest crater on the Moon. The landing was celebrated by the space community: knowing more about the far side of the Moon will help work towards setting up a new generation of radio telescopes there, to explore the Universe without the radio interference produced by the human civilization on the other side. But the landing sent another message message too: that a new space race was on. The Chinese have never hidden their ambition to exploit space in order to meet geopolitical ends. They often use for the Moon the same language they use to describe their sovereign rights in the South Chine Sea. One may safely hazard a guess that, in the 21st century, the word “astropolitics” will become increasingly common in everyday conversations.
China plans to land humans on the Moon by 2030 and begin mining Helium-3, a valuable isotope used in nuclear fusion that the Moon has in abundance. For this to happen Chinese taikonauts will have to spend long periods of time in space, and must therefore have adequate resources to survive, including on-board food production capability. Tellingly, the Chang’e 4 carried a small, climate-controlled environment with potato and Arabidopsis seeds and silkworm cocoons. China also plans to militarize space.
Meanwhile, US and Europe are still heavily dependent on vintage Russian technology to send astronauts to the International Space Station (ISS). This dependency is soon coming to an end as three private companies are currently developing new spacecraft for human, interplanetary, travel: Boeing is developing the Starliner, SpaceX the Dragon, and Lockheed the Orion. Meanwhile, the “race for the Moon” has NASA and the European Space Agency (ESA) collaborating on plans to set up a permanent base there, possibly with an intermediate space station orbiting the Moon and acting as a launch pad for short-stay “Moon-camping” crews. A self-sustained moon station would thus become the fist step towards a permanent human base on Mars, and beyond. Water is the oil of space flight, for it can be broken down to hydrogen and oxygen and used as fuel; and there is quite a lot of iced water on the Moon. Using Helium-3 to power a Moon station and extract oxygen and hydrogen for fuel, as well as developing food producing technologies and methods that can sustain human habitation in space, could lead to a centuries-old dream becoming real: the human colonization of space.
Dreams of space colonization
Space travel has captured our imagination at least since the second century AD, when the Greco-Syrian writer Lucian of Samosata wrote of his fantastical voyage to the Moon. As Lucian, the first fantastical astronaut, sails into outer space he encounters strange alien life forms and takes part in an interplanetary war between the king of the Moon and the king of Sun, who battle over the right to colonise Venus! Many centuries later, at the peak of the first industrial revolution, the French writer Jules Verne pens a more scientific-based, but no less extraordinary, novel about a society of weapons enthusiasts who launch three people to the Moon using a gigantic canon. “From The Earth to the Moon” has been a much-loved book by millions of children, many of whom were inspired to become scientists and engineers. For the real power of Verne’s breakthrough novel lies in making the argument in favour of science and engineering as the means to realise our most outlandish dreams, including space travel.
Since the publication of Verne’s book science fiction has been pushing the boundaries of our collective imagination even further, by taking inspiration from scientific discoveries and asking what if. Millions of people have watched the Star Trek and Star Wars series, where the Galaxy brims with numerous civilizations and where space travel is as quotidian as taking a flight from London to New York. Or have read novels by sci-fi giants such as Arthur Clarke, Frank Herbert, Robert Heinlein and Ursula Le Guin, to name but a few. Or have enjoyed the television series Expanse, based on the novels by James S. A. Corey, describing a future of humanity as it colonizes the solar system and begins to evolve separate cultures and civilizations.
Space colonization is not only the subject of fiction but of serious science too. The late physicist Stephen Hawking argued that unless colonies were established in space the human race would become extinct. There are several natural phenomena beyond our control that could spell our obliteration. Over a long enough period of time our planet is vulnerable to catastrophic meteorite strikes, or getting exposed to the deadly radiation of a nearby supernova explosion. As our Sun burns its fuel it will start to expand and, in a few million years, will scorch Earth. We can also self-destruct by waging nuclear war, or by tilting our planet’s climate towards a runaway greenhouse effect. Space colonization is therefore the ultimate insurance policy of long-term human survival.
Physics and Biology: how to solve the challenges of interstellar travel
But colonizing space is hard. Three are the main problem categories for humans surviving away from Earth over an indefinite period of time. The first, and probably easiest to solve, is finding a place suitable for colonization. Our solar system provides several possible habitats, the most obvious ones being of course the Moon and Mars. The Jovian moons could also be colonization targets. The Artemis Project, a private venture to establish a permanent, self-sustainable human base on the Moon, has proposed the Jovian moon Europa as an alternative future habitat, given the possibility of a hot interior and a liquid ocean of water under the icy surface, both of which could provide for a sustainable human base. Colonizing the Solar System could be a stepping-stone for venturing to worlds beyond, of which there are aplenty. In 2009 NASA launched the Kepler space telescope to discover Earth-size planets orbiting other stars in habitable zones. More than 1,300 planets have been discovered so far, in about 440 star systems; the nearest planet may be “only” 12 light years away. Based on Kepler’s findings scientists estimate that there could be as many as 11 billion rocky, Earth-like planets orbiting habitable zones of Sun-like stars in our Galaxy. The possibilities for expanding humanity’s reach in the cosmos are truly astronomical.
The second problem category is how to get to these other worlds: space travel is a hugely challenging technological problem. After more than six decades of space engineering we are still dependent of heavy rockets that burn chemical fuel to get us out of the Earth’s gravity. Perhaps the greatest innovation so far is the reusable rockets pioneered by Elon Musk’s Falcon 9 and Jeff Bezos’s Charon. Having reusable rockets significantly lowers the cost of space flight. According to Elon Musk it costs $60 million to make the Falcon 9, and $200,000 to refuel it, so theoretically by reusing a rocket multiple times the cost of each flight lowers every time it flies. There are of course additional costs for refurbishment after each flight that must be factored in, but reusing rockets looks like the most practical way to advance space technology today. Alternatively, we could have a space elevator carrying people and equipment on low orbit, an idea envisioned by the pioneering Russian scientist Konstantin Tsiolkovsky back in 1895. Researchers in Japan’s Shizuoka University are presently advancing the concept by using two mini satellites to test elevator motion in space. Moreover, the Obayashi Corporation, which will build Japan’s largest tower, has put together a space elevator proposal that will take people from Earth to an orbiting space station. However, the solution requires 60,000 miles of cable made of carbon nanotubes or an as-yet undeveloped material.
Owing to developments in quantum computing in the next ten years, we may be able to exponentially advance the production of materials for constructing space elevators, as well as for developing new rocket fuels; and thus dramatically reduce the cost of space flight. By harnessing near-infinite computing power and accessing calculations at quantum level physicists may be able to unlock the mysteries of dark matter and dark energy, and probe deeper into the fundamental structure the universe.
Understanding how an 11-dimentional universe folds into the perceived four dimensions of space and time could allow us to build engines that fold space – similar to the concept of an Alcubierre warp drive – and achieve superluminal travel. But even if we never reach that advanced level of scientific understanding and spacecraft technology, just by travelling at 0.1% of the speed of light would permit human settlement of the entire Galaxy in around 250 million years, which is less than half of a galactic rotation period. Knowing where to go in order to build sustainable colonies, and building spacecraft that will get us there, are a only matter of time. The real problem for space colonization is therefore not physics, computing, or space engineering, but our fragile biology.
Outer space is an extremely hostile environment for human life. Long-term weightlessness causes loss of calcium in the bones, decreased production of blood cells and muscle atrophy, while high frequency cosmic radiation can penetrate our body cells and cause cancer. That much we know already. However, our knowledge of the effects of space on the human body is still quite limited. The sum of human experience in understanding how our bodies adapt to space is less than 58 solar years, with most data coming from missions of relatively short duration. And although the ISS is used as a test bed to study the effects of space and mitigation of risk, the space environment is still largely unknown. But what if we developed space habitats that simulated Earth?
Bernal Spheres and Interstellar travel
In 1929 the Irish scientist John Desmond Bernal (1901-1971) described a type of long term habitat of humans in space that reproduced artificial gravity as well the other conditions of Earth’s familiar habitat. In his book The World, the Flesh and the Devil Bernal was first to describe a self-sustained space colony as a closed ecological system travelling through space. These so-called “Bernal spheres” were then elaborated by American physicist Gerard O’Neill (1927-1992) in the 1970s. O’Neill speculated that, given the vast distances between the stars, human colonists would have to travel over hundreds of years to get there. This would require many generations of colonists surviving inside gigantic spacecraft he called “cylinders”. The 2014 sci-fi movie Interstellar depicted such an O’Neill cylinder of a diameter of 500m rotating round its axis to simulate Earth’s gravity. The inside surface of the cylinder resembled a large valley, a habitat suitable for a population of 10,000 colonists. Such a spacecraft would be shielded by cosmic radiation, safely floating through space over aeons, like an interstellar Noah’s Ark, until the colony reached their final destination. To construct such complex, ecologically self-sustainable, life-support systems would require materials and technologies not yet at our disposal, but not impossible to imagine.
Long-term space travel may also get forms different from O’Neill’s concept; for example, sending frozen human embryos instead, or genetically modifying human colonists so they can survive exposure to cosmic radiation, hibernate for hundreds of years, and awake equipped with biological adaptations to planetary environments dramatically different from Earth’s. Technology, science and engineering have the potential of solving most of the problems surrounding space colonization, given enough time, funding and focus. Which leaves us with a question of politics, or astropolitics to use the newest term: who gets to go into space, and who stays behind? (This question is addressed in this post on space republics).
 The first picture of Ultima Thule was taken at 0501GMT on New Year’s Day 2019, from a distance of about 18,000 miles, 30 minutes before New Horizons made its closest pass of the space rock.
 Arabidopsis Thaliana is a small flowering plant, and a popular model in plant biology. It was the first plant that had its genome sequenced.
 Lucian’s novel was entitled, tongue-in-cheek, “True Story”. In Greek: Ἀληθῆ διηγήματα
 NASA’s Griffin: “Humans Will Colonize the Solar System”, Washington Post, September 25, 2005, pp B07.
 The Acubierre drive is a speculative idea proposed by Mexican physicist Miguel Alcubierre, who used Einstein’s field equations in general relativity to demonstrate how a spacecraft could travel faster than light. There are serious doubts about the survival of astronauts during a hypothetical voyage.
 NASA’s Efforts to Manage Health and Human Performance Risks for Space Exploration , (2015), IG-16-003. Retrieved from: https://oig.nasa.gov/audits/reports/FY16/IG-16-003.pdf
 Bernal J D, (1929), The World, the Flesh and the Devil: An enquiry into the Future of Three Enemies of the Rational Soul, Foyle Publishing.
 O’Neill G K, (1977), The High Frontier: Human Colonies in Space, William Morrow & Co, NY.