View source for Talk:Coronal Mass Ejections

== Radiation shielding on Mars == 
The article states that "the Earth's atmosphere has the protective thickness equivalent to 32 meters of water".  The Lunarpedia article referred to for the thickness of water that has a protective equivalent of Earth's atmosphere actually stated that Earth's atmosphere is equivalent to 32 feet of water.  That equals about 9.75 meters.  That is closer to the correct answer, but we can do better than that.  According to the Wikipedia article on the pascal, the Earth's atmospheric pressure is equal to 101,325 pascal (or newtons per square meter).  Divide that by 9.8 newtons per kilogram (Earth's gravity) and you get 10,340 kilograms per square meter.  For water that is 10.34 cubic meters.  A column of water 1 meter square and 10.34 meters high would have that volume and exert the pressure of one atmosphere on it's one square meter base on Earth.  So 10.34 meters or 34 feet is the water equivalent of one atmosphere of pressure.  That thickness of water also provides about the same radiation protection as Earth's atmosphere.  If you divide that by the density of Mars, 3.9, you get 2.65 meters of Mars to give radiation protection like Earth's atmosphere.  However the regolith at the surface is porous so we should only count on a density of 3, giving us a thickness of 3.4 meters of regolith to provide an Earth's atmosphere of radiation protection to a dwelling on Mars.  --[[User:Farred|Farred]] 02:00, 26 October 2010 (UTC)
:I wasn't aware that our terrestrial atmosphere has such a marvelous protection effect. So, it's pretty hard to provide the same protection for our Martian settlers. Multilayered windows filled with 10 meters of water seem not viable. These figures suggest an underground settlement, don't they? Hopefully, the food crops proof more radiation tolerant. -- [[User:Rfc|Rfc]] 06:54, 29 October 2010 (UTC)
::As far as I remember what I read, plants are in general more tolerant of radiation than people.  While the atmospheric pressure of Mars as is only about one percent of that of Earth, in Mars' low gravity the atmosphere must have a mass of two and three fifths percent of that of Earth in order to exert that pressure at the surface.  That combined with quadruple paned greenhouse windows for insulation is expected to provide sufficient radiation protection for plants.  They only live a year anyway.  Greenhouse workers would not spend all day in the greenhouse.  Most of the tasks could be handled by automated devices.  That is the way it should be set up.  
::Peter Kokh in the Moon Miners' Manifesto wrote an article about an underground house on Earth that had good views through periscope windows, broad windows that allowed looking outside in one direction for each window.  Also periscope type sky-lights made the whole place seem open and airy.  So living underground should not be too bad.  Only 3.4 meters or 11 feet of regolith are required for protection.  People would just avoid working in the greenhouse during a Coronal Mass Ejection event.  --[[User:Farred|Farred]] 01:28, 30 October 2010 (UTC)
::Even if there is some specially sensitive food crop that we want to provide better protection for, such as perhaps growing the seed, 3.7 meters or twelve feet of water should be enough.  That could be done on Mars once sufficient industry is established.  What I do not approve of is sending people to Mars before this industry is established.  --[[User:Farred|Farred]] 01:46, 30 October 2010 (UTC) 
::People fly routinely at 30,000 feet and think little of the danger from extra radiation.  At that altitude less than a third of Earth's atmosphere is between them and the sun or between them and space.  That is why I think 12 feet of water or 3.7 meters should be sufficient for the most demanding greenhouse applications.  I am sorry I do not have better references at the moment.  There just seem to be too many things to do.  --[[User:Farred|Farred]] 03:01, 30 October 2010 (UTC)

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