Cosmic radiation - Revision history

RichardWSmith: /* Mitigating Cosmic Rays: */ Improved accuracy, we want 2m of soil, not 1 meter.

2024-10-07T17:57:03Z

Mitigating Cosmic Rays:: Improved accuracy, we want 2m of soil, not 1 meter.

RichardWSmith: /* Chronic effects on life */ We want 2 meters of dirt not 1 for radiation protection.

2024-09-17T04:52:21Z

Chronic effects on life: We want 2 meters of dirt not 1 for radiation protection.

RichardWSmith: Removed redundant information which I removed because we don't need it twice.

2024-07-11T05:58:23Z

Removed redundant information which I removed because we don't need it twice.

RichardWSmith: fixed spelling error.

2024-07-11T01:58:52Z

fixed spelling error.

RichardWSmith: Increased amount of soil needed for shielding.

2024-07-04T03:56:25Z

Increased amount of soil needed for shielding.

RichardWSmith: Major danger of a mission at solar maximum is a solar storm.

2024-07-04T03:54:49Z

Major danger of a mission at solar maximum is a solar storm.

RichardWSmith: /* Mitigating Cosmic Rays: */

2024-07-04T03:51:43Z

Mitigating Cosmic Rays:

RichardWSmith: Changed sentence order. Used to sound like albedo neutrons were associated with Lava Tubes. :-(

2024-07-04T03:51:10Z

Changed sentence order. Used to sound like albedo neutrons were associated with Lava Tubes. :-(

RichardWSmith: Big correction. High energy cosmic rays (because of secondary radiation) need more shielding than gamma rays. Fixed.

2024-07-04T03:48:09Z

Big correction. High energy cosmic rays (because of secondary radiation) need more shielding than gamma rays. Fixed.

RichardWSmith: /* Composition */

2024-07-04T03:44:00Z

Composition

@@ Line 60: / Line 60: @@
 Note that small electromagnetic fields do not protect against cosmic rays (tho they do help with low and medium energy solar particles).  If people were somehow to give Mars a magnetosphere, (say with superconducting current around the equator), it would help against low energy cosmic rays but not against higher energy ones.  (Cosmic rays strike everywhere on Earth, not just near the magnetic poles.)
-The only protection from cosmic rays is lots of mass, either a thick atmosphere, or a meter or so of soil or water.  Even then, the protection is not perfect.  (Everyone on Earth is bathed by cosmic rays, despite our thick atmosphere and Earth's magnetic field.)  See also, albedo neutrons below.
+The only protection from cosmic rays is lots of mass, either a thick atmosphere, or a couple meters of soil.  Even then, the protection is not perfect.  (Everyone on Earth is bathed by cosmic rays, despite our thick atmosphere and Earth's magnetic field.)  See also, albedo neutrons below.
 Habitats in a [[Lava tube]] have been proposed as an inexpensive way to give many meters of protection from galactic cosmic rays.

@@ Line 113: / Line 113: @@
 The chronic effects on life are based on what the long term level of radiation is.  The average radiation level on Earth is 2.4 mSv (240 mrem) per year (note this includes ALL radiation, not just cosmic rays).  However, the Iranian city of Ramsar has natural levels of radiation 30 to 50 times higher than average on Earth, and show no statistical increase of cancers or early death than elsewhere. <ref>https://en.wikipedia.org/wiki/Background_radiation</ref>  This suggests that total radiation levels of up to 100 mSv per year, would be a reasonable target for Martian habitats.  This value is 5 times higher than the (very conservative) levels of radiation allowed for workers in nuclear plants. <ref>https://www.admnucleartechnologies.com.au/blog/what-safe-level-radiation-exposure</ref>
-Since [[Habitat|habitats]] have been designed, with a meter of dirt as radiation protection, which approach this value, a well constructed habitat would be unlikely to have a noticeable chronic effect on life.  Poorly constructed habitats with little or no thought given to radiation protection would be expected to have a statistically higher chance of cancer (the most common form of disease caused by radiation), and a noticeable decrease in average lifespans.
+Since [[Habitat|habitats]] have been designed, with 2 meters of dirt as radiation protection, which approach this value, a well constructed habitat would be unlikely to have a noticeable chronic effect on life.  Poorly constructed habitats with little or no thought given to radiation protection would be expected to have a statistically higher chance of cancer (the most common form of disease caused by radiation), and a noticeable decrease in average lifespans.
 ==References==

@@ Line 65: / Line 65: @@
 ==Albedo neutrons==
 Cosmic rays when they hit Mars' soil will set off secondary radiation including free neutrons (called albedo neutrons).  Neutrons are not ionizing radiation, but can activate other atoms, which can then beta decay (which is a form of ionizing radiation).  This is a radiation source which is very low on Earth, but will add to the background radiation on Mars.
-Water, plastics, or substances such as Lithium Hydroxide would help absorb these neutrons for long term settlements. <ref>https://www.tandfonline.com/doi/abs/10.1179/1743284715Y.0000000105?journalCode=ymst20</ref>
+Note that the best way to slow albedo neutrons is mass made out of atoms with a low atomic number.  Water (with two hydrogen atoms) is very good.  Plastics (with about 2 hydrogen for each carbon atom on the carbon chain) are good for the same reason.  Lithium hydroxide (LiOH) has lithium (another low atomic number atom) and a hydrogen so it is effective as well.  LiOH is also considerably more dense than water, so it makes the best neutron absorber we currently know of.<ref>https://www.tandfonline.com/doi/abs/10.1179/1743284715Y.0000000105?journalCode=ymst20</ref>
 ==Variation because of the solar cycle==

@@ Line 5: / Line 5: @@
 Note that the lowest energy cosmic rays have similar energies to the highest energy particles from the sun, so the two blend into each other.  Strategies to mitigate the strongest solar events will help with the weakest cosmic rays.  Since cosmic rays come from every direction, being on a planet will automatically halve your cosmic ray dose compared to deep space, since half of the sky is blocked by the planet beneath your feet.
-The atmosphere reduces cosmic ray does.  It stops completely lower energy cosmic rays.  For the most powerful of cosmic rays, when they hit an air molecule, they shatter into a shower of [[secondary radiation]] traveling within 1 degree of the original direction.  Much of this secondary radiation can and does reach the Earth's surface.
+The atmosphere reduces cosmic ray dose.  It stops completely lower energy cosmic rays.  For the most powerful of cosmic rays, when they hit an air molecule, they shatter into a shower of [[secondary radiation]] traveling within 1 degree of the original direction.  Much of this secondary radiation can and does reach the Earth's surface.
 About 0.390 milliSieverts of radiation per year come from cosmic rays on Earth. (100 milliSieverts of radiation in a year is the smallest amount known to cause an increase of cancer; 400 milliSieverts of radiation in a short time, (under several days), might cause symptoms of radiation poisoning.)  In orbit astronauts take ~150 mSV of radiation / year, but this includes radiation from the sun.  (I'm trying to find solar and cosmic radiation broken out from each other but no success so far. Rick)

← Older revision		Revision as of 03:56, 4 July 2024
Line 89:		Line 89:


−	Now the Earth's thicker atmosphere is 62.5 times better at blocking out the high energy cosmic rays than Mars' atmosphere. (Because the mass column of Mars' atmosphere is 1.6% of what it is on Earth.) This means that Mars will have a higher radiation dose from GCR. Realistically, Martian colonists will accept a higher radiation dose, tho this can be mitigated by having a ~~meter~~ of water, or ~~a half meter of~~ soil between the people and the sky.	+	Now the Earth's thicker atmosphere is 62.5 times better at blocking out the high energy cosmic rays than Mars' atmosphere. (Because the mass column of Mars' atmosphere is 1.6% of what it is on Earth.) This means that Mars will have a higher radiation dose from GCR. Realistically, Martian colonists will accept a higher radiation dose, tho this can be mitigated by having a few meters of water or soil between the people and the sky.

	==Acute effects on equipment==		==Acute effects on equipment==

@@ Line 84: / Line 84: @@
 Solar cosmic rays are relatively easy to shield against, with the exception of the rare, very high particles from the most powerful of CME.  These are 10 thousand to a million times more powerful than normal.  For simplicity sake, these once in a decade events can be lumped in with galactic cosmic rays, with the understanding that if they occur during local night, there is complete protection against them by the mass of Mars itself.
-Galactic cosmic rays blend in (at low energies) with solar cosmic rays.  The low energy ones we will basically ignore.  (If we are shielding against solar CR, we will shield against these.)  However, these lower energy galactic cosmic rays have an interesting property: the sun's magnetosphere gives us partial protection, so when the sun is most active during a [[Solar Maximum]], we end up getting fewer of these low energy cosmic rays then when the sun is less active.  Thus for people in space, the total cosmic ray count is LOWER when he sun is active!  (Tho this is mitigated by the higher solar radiation.)  The high energy galactic cosmic rays move so fast that they punch thru magnetic fields.  Thus on Earth, we get GCR at all times of the year, near the magnetic poles and at the equator, regardless of the sun's activity.  The only protection is to go deep underground.  On Earth, we accept the dose of these rays, year in and year out.  There is no protecting against them for normal people, so we ignore them.
+Galactic cosmic rays blend in (at low energies) with solar cosmic rays.  The low energy ones we will basically ignore.  (If we are shielding against solar CR, we will shield against these.)  However, these lower energy galactic cosmic rays have an interesting property: the sun's magnetosphere gives us partial protection, so when the sun is most active during a [[Solar Maximum]], we end up getting fewer of these low energy cosmic rays then when the sun is less active.  Thus for people in space, the total cosmic ray count is LOWER when he sun is active!  (Tho this is mitigated by the higher chance of a very dangerous massive solar storm.)  The high energy galactic cosmic rays move so fast that they punch thru magnetic fields.  Thus on Earth, we get GCR at all times of the year, near the magnetic poles and at the equator, regardless of the sun's activity.  The only protection is to go deep underground.  On Earth, we accept the dose of these rays, year in and year out.  There is no protecting against them for normal people, so we ignore them.
 The Extra-galactic cosmic rays and the OMG particles (both rare) likewise defeat any shielding, and we just have to live with them.

@@ Line 56: / Line 56: @@
 Cosmic rays are blocked by planets, so people on a planet (or in close orbit around one), receive half the cosmic rays that you would in deep space.  (The horizon blocks out half the sky, a bit more if you are in a valley.)  Cosmic rays (and their [[Secondary radiation]]) will penetrate fairly deep thru earth and rock, so only by being deep underground can they be totally eliminated.  Experiments on Earth which wish to avoid cosmic rays are done in mines more than 2,000 meters below ground.
-That said, people receive cosmic rays everywhere on Earth.  People living at high altitudes (which get a higher dose than those living at sea level) show no higher signs of health problems. So trying to eliminate all cosmic rays is impossible and futile.  But habitats with a meter of water (or a half meter of soil) between people and the sky would reduce this radiation to levels approaching high altitude regions on Earth.  See [[Radiation shielding]] for more details.
+That said, people receive cosmic rays everywhere on Earth.  People living at high altitudes (which get a higher dose than those living at sea level) show no higher signs of health problems. So trying to eliminate all cosmic rays is impossible and futile.  But habitats with 4 meters of water (or a couple meters of soil) between people and the sky would reduce this radiation to levels approaching the higher natural back ground radiation regions on Earth.  See [[Radiation shielding]] for more details.
 Note that small electromagnetic fields do not protect against cosmic rays (tho they do help with low and medium energy solar particles).  If people were somehow to give Mars a magnetosphere, (say with superconducting current around the equator), it would help against low energy cosmic rays but not against higher energy ones.  (Cosmic rays strike everywhere on Earth, not just near the magnetic poles.)
 The only protection from cosmic rays is lots of mass, either a thick atmosphere, or a meter or so of soil or water.  Even then, the protection is not perfect.  (Everyone on Earth is bathed by cosmic rays, despite our thick atmosphere and Earth's magnetic field.)  Habitats in a [[Lava tube]] have been proposed as an inexpensive way to give many meters of protection from this radiation.  See also, albedo neutrons below.
 ==Albedo neutrons==

@@ Line 11: / Line 11: @@
 ==Composition==
-Cosmic radiation comprises 85% protons, 14% alpha particles, and 1% heavy ions.<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>. (Except for the heavy elements, this is very much like the composition of the [[solar wind]].<ref name="SME">W.K. Tobiska - ''The space environment'' in J.R. Wertz, D.F. Everett & J.J. Puschell eds. ''Space mission engineering: The new SMAD''. 2011. pp. 127-137. ISBN 978-1-881883-15-9</ref>.
+Cosmic radiation comprises 85% protons, 14% alpha particles, and 1% heavy ions.<ref>Schimmerling W. (2011, Feb 5). The Space Radiation Environment: An Introduction. <nowiki>https://three.jsc.nasa.gov/concepts/SpaceRadiationEnviron.pdf</nowiki></ref>. Except for the rare heavy elements, this is very much like the composition of the [[solar wind]].<ref name="SME">W.K. Tobiska - ''The space environment'' in J.R. Wertz, D.F. Everett & J.J. Puschell eds. ''Space mission engineering: The new SMAD''. 2011. pp. 127-137. ISBN 978-1-881883-15-9</ref>.
 ==Energies of Cosmic Rays:==