Difference between revisions of "Lunar Settlement Artificial Atmosphere"

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The lunar colony will have a pressurized selection of acceptable gaseous environments. We have experimental knowledge with some artificial atmospheres,say, space stations like [[ISS into the Pacific|ISS]] or the [[MIR]]. Yet, we need to experiment more on the effects of long term exposition. On the Moon, the atmosphere will be made in accordance with the architecture followed. Some variables like the use of [[Air Lock]]s, the thickness and materials of the walls may change the gas composition, pressure and other variables.
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== Introduction ==
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A lunar colony that is economically viable, with agricultural production to feed the colonists, air recycling, industrial production to support housing construction, transportation and exports, will need both industrial process atmospheres and a human life support atmosphere.  Since there will need to be artificial environments for agriculture and air recycling, these processes will be less differentiated from other industries than they are on Earth.  Air recycling on Earth is nearly free. Only within the last century have industrial concerns about preserving a healthy atmosphere on Earth been widely recognized as important.  On Luna the atmospheres for the various industrial processes will be a bigger concern than the atmosphere that supports the life of the colonists, even if life support is more urgently important.  Vast amounts of industry per person will support the colonists.  Some processes run best in reducing atmospheres.  Others require oxidizing atmospheres, inert atmospheres, or vacuum. 
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A lunar habitat will require a pressurized mixture of gasses to sustain the life of the inhabitants. There is some experimental data with artificial atmospheres from space stations, the [[ISS into the Pacific|ISS]] and [[MIR]]. These stations have been manned by human crew for extended periods of time. However, projected lunar habitats will manned for longer time frames, and more experimentation will be required on the effects of long term dependence on the artificial life support.  ESA is doing controlled ecological life support system research in Barcelona, Spain.<ref>[http://www.astrobio.net/pressrelease/3151/melissa-to-the-moon-and-mars ASTROBIOLOGY MAGAZINE]</ref>.  On the Moon, the atmosphere will be made in accordance with the architecture followed. [[Air Lock]]s, will prevent loss of atmosphere to the outside and prevent the mixing of different atmospheres in different compartments.  Ambient vacuum as part of sintered brick walls or regolith fines packed in walls will provide adequate insulation.  Air conditioning will include cooling with [[Lunar Radiator|radiators]].
  
== Gas Combination ==
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== Pressure/Gas Combination ==
<sub>See also: [[Atmosphere]]</sub>
 
  
Full oxygen Atmosphere or gas combination?. Pure [[Oxygen]] was used in the first Gemini Missions and it is a fact that oxygen will be a major by-product of the manufacturing activities on the Moon. It would be very easy to fill reasonable big spaces with Oxygen. However, in a long term exposure, pure oxygen becomes poisonous.<ref>Malina, Frank J., ed. Life Science Research and Lunar Medicine. London: A. Wheathon and Co. Ltd. 1967 pg. 3-4 </ref> A combination of one or more [[inert gases]] with Oxygen would allow normal life and proper oxygenation. An example: a mix of 80% [[Helium ]]and 20% oxygen.
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Exact choice of a habitats internal pressure and gas combination will have various effects on the inhabitants and the structure itself. Pressure is expected to be used to support the lunar structure under normal operation, though the level required for this is low enough that virtually any livable level will be more than enough (see [[Roof Support]]). As such, the higher the habitat pressure, the stronger a habitat must be constructed to withstand it. In addition, a high pressure interior will loose atmosphere faster than a low pressure one if a leak is developed. The choice of gas combination will greatly effect the achievable pressures.
  
Nitrogen would be used on the moon as nitrates, part of the [[Plant Nutrients]]. The Moon does not have any trace of [[Nitrogen]]; therefore, this gas would be imported from Earth. It is very easy that nitrogen leaks from the solutions getting dissolved in the artificial atmosphere. An strict control has to be used to ensure the proper utilization of nitrogen. Other gas that will be present in the artificial atmosphere are CO<sub>2</sub> and H<sub>2</sub>O.
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Since [[Oxygen]] is expected to be a major by-product of [[manufacturing activities]] on the moon, a pure oxygen atmosphere is attractive as it is likely to be the easiest (and hence, cheapest) gas to procure on the moon. To avoid fires, the partial pressure of oxygen in the habitat must be kept to earth like levels (no more than 21 kPa / 3 psi). This low pressure is advantageous, and the lack of any filler gasses would greatly simplify atmospheric processing equipment. For these reasons, a pure oxygen atmosphere was utilized in the Gemini project, early designs of the Apollo spacecraft, and is currently used in spacesuits. However, some studies suggest that a pure oxygen atmosphere becomes poisonous to the inhabitants on long term exposure, making it unsuitable for a lunar habitat.<ref>Malina, Frank J., ed. Life Science Research and Lunar Medicine. London: A. Wheathon and Co. Ltd. 1967 pg. 3-4 </ref> However, as mentioned previously, a pure oxygen environment is useful for space suits, as pressure must be kept low in order for the suit to stay pliable. Using a pure oxygen environment for space suits and a high pressure mixed environment for the habitat would require a period of breathing pure oxygen before donning the suit in order to remove all nitrogen from the blood and avoid decompression sickness (also known the bends). This is currently practiced on the ISS.
  
== Lower Pressure ==
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A combination of one or more [[inert gases]] with [[Oxygen]] would allow proper oxygenation over longer time-frames. Examples include [[nitrogen]], [[helium]], and [[argon]], all of which are present in the lunar regolith and can be extracted by heating (see [[volatiles]]). [[Nitrogen]] is attractive as it would allow for an earthlike mix, though the low availability of nitrogen in lunar soil (compared to other [[volatiles]]) could raise difficulties in this regard. [[Argon]], even less abundant than [[nitrogen]], would also have this problem. [[Helium]] could also be added to the oxygen mix, as it is more abundant in lunar soil, and its low density means significantly less mass is required for a given volume. However, the addition of any appreciable quantities of helium to the atmosphere would result in a higher vocal pitch for those persons breathing it, similar to (though less intense than) the effects of inhaling pure helium. This effect is currently seen on earth in very deep diving operations, where helium-oxygen mixes are utilized, sometimes a digital voice alteration device is used to ameliorate this problem.
  
Plants <ref>Henninger, D. L., ed. Lunar Base Agriculture. Texas: NASA & Soil Science Society of America. ISBN 0- 89118-100-8 Introduction</ref> and Humans can live in lower pressure atmospheres properly oxygenated. The limit is clear: when the vapor  of a liquid inside equals the pressure outside, the liquid boils. Blood and other body fluids will boil if an abrupt drop of the pressure occurs.
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Another factor to consider with any combination is the direct effects of pressure. A notable effect is in the boiling point of water, which decreases with decreasing pressure.
  
We would need to lower the pressure inside the buildings to lower the force applied to the walls. (somewhere around 40kPa would be ideal for many structures). Also, precise atmospheric pressure controls would be needed to prevent gas leaking.
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{| border=1
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! colspan="2" | Total Pressure !! colspan = "2" | Boiling Point Of Water !! Comments
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|-
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| kPa || psi || °C || °F ||
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|-
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| 101.3 || 14.2 || 100 || 212 || Sea Level, ISS
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|-
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| 84 || 12.17 || 95 || 203 || Denver, a high altitude city
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|-
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| 81.4 || 11.74 || 94 || 201 || Mexico City, a high altitude city
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|-
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| 74.0 || 10.2 || 92 || 197 || Open airplane, ISS ports
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|-
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| 59.1 || 8.3 || 86 || 187 || ISS spacesuit
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|-
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| 33.5 || 4.7 || 72 || 162 || Apollo spacesuit
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|-
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| 30.6 || 4.3 || 70 || 158 || Shuttle spacesuit
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|-
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| 26.0 || 3.65 || 66 || 152 || Top of Mount Everest
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|}
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The main problem this would pose would be cooking of food, as lower boiling points would make many foods impractical to cook. However, these foods could still be prepared using a pressure cooker. Many hikers utilize lightweight pressure cookers for this purpose when climbing to high altitudes, and adapting such devices to lunar use should not be difficult.
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== Agriculture ==
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Plants <ref>Henninger, D. L., ed. Lunar Base Agriculture. Texas: NASA & Soil Science Society of America. ISBN 0- 89118-100-8 Introduction</ref>, like humans, are capable of tolerating lower atmospheric pressure so long as all required gasses are available. Some studies indicate that plants can survive at pressures lower than any human can. Whatever the pressure, an environment optimized for plant growth would benefit from having an atmosphere enriched with carbon dioxide, as they would grow faster. This enrichment is used in some terrestrial greenhouses for both growth boosting and pest control, as plants will tolerate CO<sub>2</sub> levels that will kill insects.
  
 
== See Also ==
 
== See Also ==
Line 22: Line 51:
 
== References ==
 
== References ==
 
<references/>
 
<references/>
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[[Category:Atmosphere Maintenance]]

Latest revision as of 07:28, 20 July 2012

Introduction

A lunar colony that is economically viable, with agricultural production to feed the colonists, air recycling, industrial production to support housing construction, transportation and exports, will need both industrial process atmospheres and a human life support atmosphere. Since there will need to be artificial environments for agriculture and air recycling, these processes will be less differentiated from other industries than they are on Earth. Air recycling on Earth is nearly free. Only within the last century have industrial concerns about preserving a healthy atmosphere on Earth been widely recognized as important. On Luna the atmospheres for the various industrial processes will be a bigger concern than the atmosphere that supports the life of the colonists, even if life support is more urgently important. Vast amounts of industry per person will support the colonists. Some processes run best in reducing atmospheres. Others require oxidizing atmospheres, inert atmospheres, or vacuum.


A lunar habitat will require a pressurized mixture of gasses to sustain the life of the inhabitants. There is some experimental data with artificial atmospheres from space stations, the ISS and MIR. These stations have been manned by human crew for extended periods of time. However, projected lunar habitats will manned for longer time frames, and more experimentation will be required on the effects of long term dependence on the artificial life support. ESA is doing controlled ecological life support system research in Barcelona, Spain.[1]. On the Moon, the atmosphere will be made in accordance with the architecture followed. Air Locks, will prevent loss of atmosphere to the outside and prevent the mixing of different atmospheres in different compartments. Ambient vacuum as part of sintered brick walls or regolith fines packed in walls will provide adequate insulation. Air conditioning will include cooling with radiators.

Pressure/Gas Combination

Exact choice of a habitats internal pressure and gas combination will have various effects on the inhabitants and the structure itself. Pressure is expected to be used to support the lunar structure under normal operation, though the level required for this is low enough that virtually any livable level will be more than enough (see Roof Support). As such, the higher the habitat pressure, the stronger a habitat must be constructed to withstand it. In addition, a high pressure interior will loose atmosphere faster than a low pressure one if a leak is developed. The choice of gas combination will greatly effect the achievable pressures.

Since Oxygen is expected to be a major by-product of manufacturing activities on the moon, a pure oxygen atmosphere is attractive as it is likely to be the easiest (and hence, cheapest) gas to procure on the moon. To avoid fires, the partial pressure of oxygen in the habitat must be kept to earth like levels (no more than 21 kPa / 3 psi). This low pressure is advantageous, and the lack of any filler gasses would greatly simplify atmospheric processing equipment. For these reasons, a pure oxygen atmosphere was utilized in the Gemini project, early designs of the Apollo spacecraft, and is currently used in spacesuits. However, some studies suggest that a pure oxygen atmosphere becomes poisonous to the inhabitants on long term exposure, making it unsuitable for a lunar habitat.[2] However, as mentioned previously, a pure oxygen environment is useful for space suits, as pressure must be kept low in order for the suit to stay pliable. Using a pure oxygen environment for space suits and a high pressure mixed environment for the habitat would require a period of breathing pure oxygen before donning the suit in order to remove all nitrogen from the blood and avoid decompression sickness (also known the bends). This is currently practiced on the ISS.

A combination of one or more inert gases with Oxygen would allow proper oxygenation over longer time-frames. Examples include nitrogen, helium, and argon, all of which are present in the lunar regolith and can be extracted by heating (see volatiles). Nitrogen is attractive as it would allow for an earthlike mix, though the low availability of nitrogen in lunar soil (compared to other volatiles) could raise difficulties in this regard. Argon, even less abundant than nitrogen, would also have this problem. Helium could also be added to the oxygen mix, as it is more abundant in lunar soil, and its low density means significantly less mass is required for a given volume. However, the addition of any appreciable quantities of helium to the atmosphere would result in a higher vocal pitch for those persons breathing it, similar to (though less intense than) the effects of inhaling pure helium. This effect is currently seen on earth in very deep diving operations, where helium-oxygen mixes are utilized, sometimes a digital voice alteration device is used to ameliorate this problem.

Another factor to consider with any combination is the direct effects of pressure. A notable effect is in the boiling point of water, which decreases with decreasing pressure.

Total Pressure Boiling Point Of Water Comments
kPa psi °C °F
101.3 14.2 100 212 Sea Level, ISS
84 12.17 95 203 Denver, a high altitude city
81.4 11.74 94 201 Mexico City, a high altitude city
74.0 10.2 92 197 Open airplane, ISS ports
59.1 8.3 86 187 ISS spacesuit
33.5 4.7 72 162 Apollo spacesuit
30.6 4.3 70 158 Shuttle spacesuit
26.0 3.65 66 152 Top of Mount Everest

The main problem this would pose would be cooking of food, as lower boiling points would make many foods impractical to cook. However, these foods could still be prepared using a pressure cooker. Many hikers utilize lightweight pressure cookers for this purpose when climbing to high altitudes, and adapting such devices to lunar use should not be difficult.

Agriculture

Plants [3], like humans, are capable of tolerating lower atmospheric pressure so long as all required gasses are available. Some studies indicate that plants can survive at pressures lower than any human can. Whatever the pressure, an environment optimized for plant growth would benefit from having an atmosphere enriched with carbon dioxide, as they would grow faster. This enrichment is used in some terrestrial greenhouses for both growth boosting and pest control, as plants will tolerate CO2 levels that will kill insects.

See Also

References

  1. ASTROBIOLOGY MAGAZINE
  2. Malina, Frank J., ed. Life Science Research and Lunar Medicine. London: A. Wheathon and Co. Ltd. 1967 pg. 3-4
  3. Henninger, D. L., ed. Lunar Base Agriculture. Texas: NASA & Soil Science Society of America. ISBN 0- 89118-100-8 Introduction