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HISTORY
Early suggestions for future colonisers to reach the Moon and people subsequently living there were made by John Wilkins in "A Discourse Concerning a New Planet" in the first half of the 17th century.
The first known work on space colonisation was The Brick Moon, a work of fiction published in 1869 by Edward Everett Hale, about an inhabited artificial satellite. In 1897 Kurd Lasswitz also wrote about space colonies.
The Russian rocket science pioneer Konstantin Tsiolkovsky foresaw elements of the space community in his book Beyond Planet Earth written about 1900. Tsiolkovsky had his space travellers building greenhouses and raising crops in space. Tsiolkovsky believed that going into space would help improve human beings, leading to peace and immortality.
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In the 1920s John Desmond Bernal, Hermann Oberth, Guido von Pirquet and Herman Noordung further developed the idea. Werner von Braun contributed his ideas in a 1952 Colliers article. In the 1950s and 1960s, Dandridge M. Cole published his ideas.
Another seminal work on the subject was the book "The High Frontier: Human Colonies in Space" by Gerard K. O'Neill in 1977 which was followed the same year by "Colonies in Space" by T. A. Heppenheimer.
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HABITATS
Within the solar system suggestions have been made for a human presence on or in the following bodies:
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# Space Station # Asteroid # Earth’s Moon # Terrestrial Planet surface # Terrestrial Planet underground # Giant Planet Moon # Giant Planet atmosphere |  |
Many of these suggestions are not practical in the near term as they would involve modifying the environment to be suitable.
In the far future an interstellar environment may be possible.
In the near term, the list of possible habitats for human presence in space are more likely:
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# Space Station or Asteroid in Earth Orbit
# Space Station or Asteroid at the Earth-Moon L5 Lagrange point # The Moon # Mars
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SPACE STATIONS
Imagined
Space stations, constructed by humans in orbit have been a mainstay of science fiction novels for well over 80 years. These would usually be large enough to house a colony of people.
If the station is not rotating then the people inside will experience essentially zero gravity. However, many authors have chosen to have their stations rotating, so that there is a variable artificial gravity which ranges from zero at the centre of the rotation to a maximum – usually of one Earth gravity - at the rim of the station. A docking station at the centre requires the docking ship to match the station’s rotation.
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One thing to note is that none of these imagined space stations has any solar panels - maybe the authors considered nuclear power?
The Reality
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The Environment
All space stations built so far have not been given any axial rotation. Astronauts thus experience essentially zero gravity (zero-g) conditions and are thus weightless.
There are small residual gravitational forces due to the mass of the station and scientists prefer to call the environment a microgravity environment rather than a true zero-g environment. These small g forces do not affect astronauts but they can be significant for some sensitive experiments.
The atmosphere in a space station is of essentially the same composition as the Earth’s atmosphere (after a tragic learning experience with an oxygen only atmosphere), but is generally at a lower pressure (equivalent to being on a mountain).
Apart from zero-g, the other main environmental difference on board a space station in low Earth orbit (~400 km altitude), is the drastically increased radiation field that is experienced. This is mainly due to galactic cosmic rays with the occasional sporadic solar cosmic ray outburst. The Earth’s magnetic field provides some shielding at this altitude.
Working In Space
Inside a space station the air is close to what is experienced on Earth, and astronauts are essentially working in a ‘shirt sleeve’ environment. The absence of gravity means that there is no intrinsic sense of a vertical direction. This can be quite disorienting at first.
Also it must be remembered that a lack of weight is not the same as a lack of mass. Objects need a force to start them moving, but also a force to stop them moving, before they crash into something.
Small objects, dust and even bodily fluids float around in the atmosphere and can be quite unpleasant if not removed.
Outside the space station, an astronaut must wear a space suit as there is no atmosphere and thus no atmospheric pressure. This makes working much slower and more tiresome than on Earth. Fingers in the space suit tend to become rigid and require a deal of pressure to move.
The lack of gravity causes many physiological problems to be discussed later.
ASTEROIDS AS HABITATS
A rocky asteroid a few km in length could be mined for its resources leaving the interior hollow. This could be sealed and the interior could be engineered into an environment where humans could live. The mined resources could be sold to fund the project and used to provide water, atmosphere, regolith (soil) and building materials. It would be spun slowly to give Earth gravity and the shell would provide a radiation and meteoroid shield. Surface solar panels for power.
It has been argued that a hollowed out asteroid would make the best spaceship for interstellar exploration and colonisation. Radiation and debris impact shielding are major factors for a ship travelling at relativistic velocities. Also an asteroid may be the only habitat with sufficient volume to provide a livable environment for humans for many years.
ORBITS OTHER THAN LEO
| Gerard O’Neill’s 1977 book ‘The High Frontier: Colonies in Space’ advocated establishing a colony at the Earth-Moon L5 Lagrange point built of lunar material sent there by electromagnetic mass drivers on the Moon. NASA published two volumes exploring this concept. This led to the establishment of the L5 society which latter would become the National Space Society. | 
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THE MOON
The Moon is the closest planetary type body to the Earth. The trip only takes a few days, and there have already been 6 manned missions to the moon.
The gravity is 1/6 the Earth’s gravity, but there is no atmosphere. There appears to be water ice at the south pole.
Helium-3, a valuable gas, is abundant in lunar rocks. The far side of the moon, because it never faces the Earth, is a prime location for observatories and research laboratories.
Because there is no moderating atmosphere, lunar surface temperatures range from -200 to +200C. One metre below the surface the temperature is ~35C.
Most proposed moon colonies show the colony built on the surface of the moon. However, with no atmosphere the radiation levels on the surface make this an infeasible option. All long term moon colonisation will need to be subsurface. Hypervelocity meteoroid impacts also make flimsy surface structures questionable.
Extensive subsurface excavation may not be required as underground lava tubes are now known to exist. These could be sealed and turned into substantial habitats.
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MARS
Except for its smaller size, Mars is the terrestrial planet most similar to the Earth. It has a small atmosphere of mostly carbon dioxide. In its equatorial regions surface temperatures are similar to inland Antarctic temperatures. The polar caps contain reasonable water resources, and further water is speculated to exist below the surface.
Mars has no global magnetic fields (although it dies have small local fields), and this allows the solar wind to strip any atmosphere from the planet over time.
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Gravity = 1/3 Earth gravity Atmospheric Pressure = 4 to 9 hPa Surface temp = -225 to +20 C Average temp = (-60C) Day ~24 hours Year ~2 Earth years |
TERRAFORMING
Terraforming or Planetary Engineering is the hypothetical process of deliberately modifying the atmosphere, surface topography, temperature and any ecology of a planet to make it more like the Earth so as to be suitable for human habitation. This might be done by physical, chemical and/or biological means either directly and/or with catalysts.
An example of biological terraforming of an asteroid is shown below.
Many terraforming enthusiasts believe that microbiology is the key and cheapest route to terraforming a planet or asteroid. Either the establishment or many small biomes that are initially comprised of organisms that can thrive in the reduced atmospheric conditions of Mars, or even the release of extremophile organisms into the Venusian atmosphere to initially reduce the density of the Venusian atmosphere and lower the temperature there.
For a space colony to be viable it must be as close to a self sustaining ecosystem as possible. In the initial stages it will need supplies from a home base, just as the first Australian colony needed supplies from England.
There is currently no place in the solar system that has an ecosystem in which unprotected humans can live. Everything necessary for life will thus have to be brought and resupplied from elsewhere, at least until in-situ resources can be extracted , processed and utilised to provide some of life’s necessities (ISRU).
SIMULATIONS
Various Earth-based simulations have been conducted to study and examine the physical, physiological and psychological factors associated with living in space or on a planet or moon.
All of these simulations are constrained in that they cannot change the gravity environment of one g, although for some physiological experiments the horizontal position of bed rest may provide an acceptable analog.
Arctic/Antarctic bases provide the isolation and remoteness similar to a space colony and many psychological studies have been done of humans in this environment.
Caves have also been suggested as a planetary analog simulation facility as it appears very likely that on the Moon and even Mars, people will have to live underground to provide shielding against cosmic radiation and impacts.
BIOSPHERE TWO
Biosphere 2 was a 1990s experimental greenhouse-like habitat in Arizona that turned into a debacle. It housed different ecosystems and a crew of four men and four women in an effort to understand what would be needed for humans to live on other planets. The participants were supposed to grow their own food and recycle their air inside the sealed glass space.
But the experiment soon spiraled out of control, with the carbon dioxide level rising dangerously and plants and animals dying. The crew members grew hungry and squabbled so badly during the two years they spent cooped up that by the time they emerged, some of them were not speaking to each other.
MARS 500
The MARS-500 mission was a psychosocial isolation experiment conducted between 2007 and 2011 by Russia, the European Space Agency, and China, in preparation for an unspecified future crewed spaceflight to the planet Mars. The experiment's facility was located at the Russian Academy of Sciences' Institute of Biomedical Problems (IBMP) in Moscow, Russia.
The scientific goals of MARS-500 included the study of potential habitat designs, with a particular focus on medical and psychological support for the crew (who would necessarily be confined in a relatively small spacecraft, with relatively limited medical facilities, for the 7- to 9-month journey to Mars). Communication with the outside world was limited, and was conducted with a realistic time delay of up to 25 minutes, to simulate the real-life communications lag between Mars and Earth. Similarly, a realistically limited supply of on-board consumables was provided for the volunteers.
THE MARS SOCIETY BASE AT DEVON
"Crews at FMARS are required to conduct a sustained program of geological, microbiological and climatological field exploration in a cold and dangerous remote environment while operating under many of the same constraints that a human crew would face on Mars. It is only under these conditions, where the crew is trying hard to get real scientific work done, while dealing with bulky equipment, cold, danger, discomfort, as well as isolation, that the real stresses of a human Mars mission can be encountered, and the methods for dealing with them mastered. It is only under these conditions that all sorts of problems that Mars explorers will face can be driven into the open so they can be dealt with. Only by doing these missions can we make ourselves ready to go to Mars. Nothing like this has ever been done before."
Dr. Robert Zubrin President, The Mars Society
HI_SEAS
Near the top of the Mauna Loa volcano is the University of Hawaii facility called the Hawaii Space Exploration Analog and Simulation, or HI-SEAS. The project will study the psychological difficulties with living in isolated, confined conditions for an extended period.
CAVES
CAVES stands for Cooperative Adventure for Valuing and Exercising human behaviour and performance Skills. The three-week course prepares astronauts to work safely and effectively in multicultural teams in an environment where safety is critical – in caves.
The cave environment provides many space-relevant conditions, including isolation from the outside world, lack of diurnal cycles, confinement, minimal privacy, technical challenges, limited equipment and supplies for hygiene and comfort, and the constant presence of risk.
During six editions of CAVES, from 2011 to 2019, 34 astronauts from six different space agencies (ESA, NASA, Japan's JAXA, Russia's Roscosmos, the Canadian Space Agency and China's CNSA) have taken part in the training. The CAVES training program has been recognised by all participant astronauts and, in particular, by those who have travelled to space, as one of the best space analogue experiences on Earth.
PLANS AND PROPOSALS
The two longest standing personalities with interests in colonising mars are Dr Chris McKay and Robert Zubrin. The former was a founding member of the 'Mars Underground', a group of students in Colorado in the late 1970s / early 1980s with similar interests. Robert Zubrin was the founder of the Mars Society which has a branch in Australia.
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MARS ONE was a mission led by Dutch entrepreneur that planned to establish a permanent human colony on Mars by 2023. He even held competitions to select 100 individuals to form the first settlement via a one way trip to Mars. Due to number of reasons the venture never came to anything.
Elon Musk, the inventor of Paypal and the vary successful director of the SpaceX corporation also has plans to send a million people to Mars by 2050.
The Artemis accords, led by the USA and now involving 42 countries (2024), including Australia hopes to go back to the moon and establish a base/ gateway there by mid-decade, and then use the information gained from a permanent lunar habitation to expand to a permanent base on Mars by the middle of the century.
PHYSIOLOGICAL FACTORS
Weightlessness looks fun but it places demands on your body. Initially you might feel nauseated (although not all people suffer this initial space sickness), dizzy and disoriented.
You head and sinuses swell up and your legs shrink. The former congestion gives rise to the feeling that you have a head cold.
There are both general and specific changes in body physiology:
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GENERAL * balance disorders * cardiovascular deconditioning * decreased immune function * muscle atrophy * bone loss * visual disturbance |
SPECIFIC * decrease in blood volume * decrease in red blood cell mass * decrease in muscle strength and work capacity * decrease in maximum cardiac output * loss of bone mass * loss of calcium and phosphate from bones |
Recovery of some of these problems on return to Earth have proven very problematic. For a 3 to 6 month space flight or stay in zero - g it may require 2 to 3 years to regain lost bone.
Another problem is that you really have to exercise a lot, both in space and after returning to Earth. Several hours a day in the zero-g environment, and this takes away from time that could be spent performing other tasks. Getting a good sleep in zero-g has often proven problematic for many astronauts.
Many of the problems are directly due to the state of zero gravity, but some are due to the increased ionising radiation environment, particularly as the length of stay in space increases. Some physiological effects are also due to psychological effects associated with the isolation and confinement.
Stressors encountered during flight in space from zero-g weaken the immune system and have a positive impact on some pathogens.
Reproduction is essential for long duration self sustaining space colonies. However, we do not yet know if reproduction is possible in these conditions.
High energy continuous galactic cosmic radiation and sporadic outbursts of solar cosmic radiation may well be the most limiting factor for space colonies and space travel. The lethal dose to kill 50% of a human population in 30 days is 4000 mSv. A round trip to Mars and a two year stay on the Martian surface could bring you close to 2000 mSv.
PSYCHOLOGICAL FACTORS
Psychological factors are important in crew selection and in crew behaviour and interactions, and are often more difficult to predict and deal with than physiological ones.
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* Isolation * Lack of privacy * Health * Sensory deprivation * Confinement * Human Interactions |
* Performance * Risk * Emotions * Quality of life * Competition * Circadian rhythm disturbances |
ARGUMENTS FOR THE COLONISATION OF SPACE
Many arguments have been made both for and against the colonisation of space:
ARGUMENTS AGAINST THE COLONISATION OF SPACE
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There are of course counter arguments to these and counter arguments to the counter arguments.
In particular the cost factor is a big problem, until we remember that the NASA annual budget (~$20B) is consumed by the US military every 10 days. |  |
LEGAL ISSUES
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Books have already been written proposing legal frameworks for human expansion into the celestial sphere and space colonisation.
There is room and need for all professions and interests in this undertaking. |  |
REFERENCES
Australian Space Academy