Tuesday, August 07, 2007

"Separate the waters..."

Hopefully, the habitats will be large enough to acommodate clouds ("waters above"). Even more important, there should be enough water to form substantial reservoirs, "waters below". Of course, water has many functions and is necessary for life.

To acommodate above water separation, AI devices will have to build a shell around the raw materials. This shell will accomplish following functions:
--Contain materials essential to following phases:
-----As water and and other potential liquids start to liquify and even sublimate, it will tend to esape NEO's weak gravity field. A shell will retard and perhaps even prevent this loss of essential materials.
-----Asteroids are believed to contain many tons of regolith dust which will greatly facilitate agriculture and even ready extraction of minerals. Many millenia were involved in creating this huge collection of dust, if AI devices have to grind hard asteroid rocks and core material into more dust, that's a lot of wasted power.
-----Enable an artificial atmosphere of breathable air. This will enable humans to more easily join our AI devices in constucting the habitat.

--Eventually, completed shell will become outer hull of habitat and will start spinning to simulate gravity via centrifugal force.

(Following material extracted and edited from associated web page. Credit for original content go to original authors; misrakes are mine.)
Terraformation increases both temperature and atmospheric air pressure to an Earth-like level. Temperature increases will allow water to flow and plants to live. Plants will turn the carbon dioxide into oxygen so people can breathe.

Terraformation's first step: add water vapor to the atmosphere. Water is a prime way to increase the atmospheric mass. In addition to thickening habitat's vaporous layer, this water vapor would also form clouds. Clouds are especially effective in trapping solar heat.

While water could be added to the atmosphere a variety of ways, we would consider extracting water from a convenient comet. Once we locate a comet that will cross the habitat's orbit within a few years, guide it to a more useful position. Extracting water from a nearby comet will take much less effort then exporting similar amounts from Earth's surface. We will also need to consider storing massive reservoirs of water in the habitat's "underground" which would be in the habitat's cylindrical outside hull. These artificial lakes will aid habitat's agriculture and other plant life.

Thus, water separation is a good place to build a habitat to contain both the liquid water reservoirs and the gaseous water vapor (clouds) in the habitat's "sky".
Following are some pertinent extracts from the web. Every effort is made to retain links so that orginal authors can rightfully claim credit. Misrakes are all mine.
Much of following material has been extracted from Wikipedia’s article (http://en.wikipedia.org/wiki/Space_colonization). As always credit for content must go to the original authors, misrakes are all mine.

Space colonies could orbit around the Earth, Sun, or Lagrangian point. Several design groups at NASA and elsewhere have examined orbital colony feasibility. They determined:
---ample supplies of necessary materials on Near Earth Asteroids
---solar energy is readily available in very large quantities
---don't need new scientific breakthroughs (tho a lot of engineering would be required)

Building colonies in space will require access to space, people, food, construction materials, energy, transportation, communications, life support, simulated gravity (via steady rotation), entertainment, and radiation protection. All those requirements will need careful consideration when determining habitat’s location.

The Moon is deficient in volatiles (principally hydrogen, carbon and nitrogen) but possesses a great deal of oxygen, silicon, and metals such as iron, aluminum and titanium. Launching materials from Earth is very expensive, so bulk materials could come from the Moon or Near-Earth Objects (NEOs - asteroids and comets with orbits near Earth), Phobos, or Deimos where gravitational forces are much less, there is no atmosphere, and there is no biosphere to damage. Many NEOs contain substantial amounts of metals, oxygen, hydrogen and carbon. Certain NEOs may also contain some nitrogen.
Further out, Jupiter's Trojan asteroids are high in water ice and probably other volatiles.

Transporting large quantities of materials from the Moon, Phobos, Deimos, and Near Earth asteroids to orbital settlement construction sites might be required.
Using off-Earth resources for propellant in relatively conventional rockets would greatly reduce in-space transportation costs compared to now; propellant from the Earth is likely to be prohibitively expensive for space colonization, even with improved space access costs.
Other technologies such as tether propulsion, VASIMR, ion drives, solar thermal rockets, solar sails, and nuclear thermal propulsion can all potentially help solve the problems of high transport cost once in space.
For lunar materials, one well-studied possibility is to build electronic catapults to launch bulk materials to waiting settlements. Alternatively, Lunar space elevators might be employed.

Communication is now relatively easy for Earth orbits (including Luna). Much of current terrestrial communications already passes through satellites. Yet, as colonies progress further from the Earth, communication will become more difficult. Transmissions with Mars suffer from significant delays due to the speed of light and the greatly varying distance between conjunction and opposition - the lag will range between 7 and 44 minutes - making real-time communication impractical. Other means of communication that do not require live interaction such as e-mail and voice mail systems should pose no problem.

People need air, water, food, gravity and reasonable temperatures to live comfortably for long periods. In space settlements, a relatively small, closed ecological system must recycle or import all the nutrients without "crashing."

The closest terrestrial analogue to space life support is possibly that of Nuclear submarines. Nuclear submarines use mechanical life support systems to support humans for months without surfacing, and this same basic technology could presumably be employed for space use. However, nuclear submarines run "open loop" and typically dump carbon dioxide overboard, although they recycle oxygen. Recycling of the carbon dioxide has been approached in the literature using the Sabatier process or the Bosch reaction.

Changing the environment to become a life-friendly habitat, a process called terraforming.
Note that plant based life support systems are very inefficient in their use of energy; about 1-3% energetic efficiency is common[citation needed]. This means that 97-99% of the light energy provided to the plant ends up as heat and needs to be dissipated somehow to avoid overheating the habitat.

Cosmic rays and solar flares create lethal radiation. In Earth orbit, the Van Allen belts make living above the Earth's atmosphere difficult. To protect life, settlements must be surrounded by sufficient mass to absorb most incoming radiation. Somewhere around 5-10 tons of material per square meter of surface area is required. This can be achieved cheaply with leftover material (slag) from processing lunar soil and asteroids into oxygen, metals, and other useful materials, however it represents a significant obstacle to maneuvering vessels with such massive bulk. Inertia would necessitate powerful thrusters to start or stop rotation.

Self-replication (habitats building more habitats) allows a much more rapid increase in colonies and greatly decreases dependence on Mother Earth. Intermediate goals include colonies that expect only information from Earth (science, engineering, entertainment, etc.) and colonies that just require periodic supply of light weight objects, such as integrated circuits, medicines, genetic material and perhaps some tools.
See also: von Neumann probe, clanking replicator, Molecular nanotechnology

In 2002, the anthropologist John H. Moore estimated that a population of 150–180 would allow normal reproduction for 60 to 80 generations—equivalent to 2000 years.
A much smaller initial population of as little as two female humans should be viable as long as human embryos are available from Earth. Use of a sperm bank from Earth also allows a smaller starting base with negligible inbreeding.

Researchers in conservation biology have tended to adopt the "50/500" rule of thumb initially advanced by Franklin and Soule. This rule says a short-term effective population size (Ne) of 50 is needed to prevent an unacceptable rate of inbreeding, while a long‐term Ne of 500 is required to maintain overall genetic variability. The Ne = 50 prescription corresponds to an inbreeding rate of 1% per generation, approximately half the maximum rate tolerated by domestic animal breeders. The Ne = 500 value attempts to balance the rate of gain in genetic variation due to mutation with the rate of loss due to genetic drift.
Effective population size Ne depends on the number of males Nm and females Nf in the population. (Formula to be added.JimO)

Free space locations in space would necessitate a space habitat, also called space colony and orbital colony, or a space station. These permanent settlements would be literal "cities" in space, where people would live and work and raise families. Many design proposals with varying degrees of realism are in science fiction and articles written by engineers.
A space habitat would also serve as a proving ground for how well a generation ship could function as a long-term home for hundreds or thousands of people. Such a space habitat could be distant enough for autonomy but near enough to Earth for help.

Earth orbit has substantial advantages and one major, but solvable, problem. Orbits close to Earth can be reached in hours, whereas the Moon is days away and trips to Mars take months. There is ample continuous solar power in high Earth orbits, whereas all planets lose sunlight at least half the time. Weightlessness makes construction of large colonies considerably easier than in a gravity environment. Astronauts have demonstrated moving multi-ton satellites by hand. 0g recreation is available on orbital colonies, but not on the Moon or Mars. Finally, the level of (pseudo-) gravity is controlled at any desired level by rotating an orbital colony. Thus, the main living areas can be kept at 1g, whereas the Moon has 1/6g and Mars 1/3g. It's not known what the minimum g-force is for ongoing health but 1g is known to ensure that children grow up with strong bones and muscles.
The main disadvantage of orbital colonies is lack of materials. These may be expensively imported from the Earth, or more cheaply from extraterrestrial sources, such as the Moon (which has ample metals, silicon, and oxygen), Near Earth Asteroids, which have all the materials needed (with the possible exception of nitrogen), comets, or elsewhere.

A contour plot of the effective potential (the Hill's Surfaces) of a two-body system (the Sun and Earth here), showing the five Lagrange points.
Another near-Earth possibility are the five Earth-Moon Lagrange points. Although they would generally also take a few days to reach with current technology, many of these points would have near-continuous solar power capability since their distance from Earth would result in only brief and infrequent eclipses of light from the Sun.
The five Earth-Sun Lagrange points would totally eliminate eclipses, but only L1 and L2 would be reachable in a few days' time. The other three Earth-Sun points would require months to reach.
However, the fact that Lagrange points L4 and L5 tend to collect dust and debris, while L1-L3 require active station-keeping measures to maintain a stable position, make them somewhat less suitable places for habitation than was originally believed.

Several times a decade, many small asteroids pass closer to Earth then Luna. In between these events, the asteroid may travel out to a furthest distance of some 350,000,000 kilometers from the Sun (its aphelion) and 500,000,000 kilometers from Earth. These asteroids could be the human populated space habitats.

The asteroid belt has significant available material, though thinly distributed over a vast region. With little technological advance, unmanned supply craft can cross 1/2 billion kilometers of interplanetary cold vacuum.

ADJUSTED ORBIT. The habitat's occupants would have a strong interest in assuring that their asteroid did not hit Earth or any other body of significant mass; however, they might have extreme difficulty in moving an asteroid of any size. The orbits of the Earth and most asteroids are very distant from each other in terms of delta-v and the asteroidal bodies have enormous momentum. Perhaps we can use mass drivers to put an asteroid into a more useful orbit.

Beyond our solar system, neighboring suns might be possible colonization target. An interstellar colony ship would be similar to a space habitat, except with major propulsion capabilities and independent energy generation.
Concepts proposed both by scientists and in hard science fiction include:
Generation ship, hypothetical starship that would travel much slower than light between stars, with the crew going through multiple generations before the journey is complete
Sleeper ship, hypothetical starship in which most or all of the crew spend the journey in some form of hibernation or suspended animation
Embryo carrying Interstellar Starship (EIS), hypothetical starship much smaller than a generation ship or sleeper ship transporting human embryos in a frozen state to an exoplanet
Starship using nuclear fusion or antimatter propulsion.
Project Orion, a concept proposed by Freeman Dyson which could use nuclear bombs to propel a starship.
A continually accelerating starship, using a propulsion device such as a solar sail to approach the speed of light, allowing short subjective time to the crew, because of time dilation.
[edit] Example
The star Tau Ceti, about eleven light years away, has an abundance of cometary and asteroidal material in orbit around it. These materials could be used for the construction of space habitats for human settlement.
[edit] Terrestrial analogues to space colonies
The most famous attempt to build an analogue to a self-sufficient colony is Biosphere 2, which attempted to duplicate Earth's biosphere.
Many space agencies build testbeds for advanced life support systems, but these are designed for long duration human spaceflight, not permanent colonization.
Remote research stations in inhospitable climates, such as the Amundsen-Scott South Pole Station or Devon Island Mars Arctic Research Station, can also provide some practice for off-world outpost construction and operation. The Mars Desert Research Station has a habitat for similar reasons, but the surrounding climate is not strictly inhospitable.
[edit] Literature
The literature for space colonization began in 1869 when Edward Everett Hale[7] wrote about an inhabited artificial satellite.
The Russian schoolmaster and physicist Konstantin Tsiolkowsky foresaw elements of the space community in his book Beyond Planet Earth written about 1900. Tsiolkowsky had his space travelers building greenhouses and raising crops in space.[8].
Others have also written about space colonies as Lasswitz in 1897 and Bernal, Oberth, Von Pirquet and Noordung in the 1920s. Wernher von Braun contributed his ideas in a 1952 Colliers article. In the 1950s and 1960s, Dandridge Cole and Krafft Ehricke published their ideas.[citation needed]
Another seminal book on the subject was the book The High Frontier: Human Colonies in Space by Gerard K. O'Neill[9] in 1977 which was followed the same year by Colonies in Space by T. A. Heppenheimer.[10]
M. Dyson wrote Home on the Moon; Living on a Space Frontier in 2003;[11] Paul Eckart wrote Lunar Base Handbook in 2006[12] and then Harrison Schmitt's Return to the Moon written in 2007.[13]
[edit] Justification
Main article: Space and survival
In 2001, the space news website Space.com asked Freeman Dyson, J. Richard Gott and Sid Goldstein for reasons why some humans should live in space. Their respective answers were:[14]
Spread Life and Beauty throughout the Universe
Ensure the Survival of Our Species
Make money from solar power satellites, Asteroid mining, and space manufacturing
Save the Environment by moving people and industry into space
Provide entertainment value in order to distract from immediate surroundings
Ensure sufficient supply of rare materials, including from the Outer Solar System - natural gas (in connection with expected world-wide hydrocarbons peak) and drinking water (in connection with expected world-wide water shortage)
Louis J. Halle, formerly of the United States Department of State, wrote in Foreign Affairs (Summer 1980) that the colonization of space will protect humanity in the event of global nuclear warfare.[15]
The scientist Paul Davies also supports the view that if a planetary catastrophe threatens the survival of the human species on Earth, a self-sufficient colony could "reverse-colonize" the Earth and restore human civilization.
The author and journalist William E. Burrows and the biochemist Robert Shapiro proposed a private project, the Alliance to Rescue Civilization, with the goal of establishing an off-Earth backup of human civilization.


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