Space Radiation + counter measures

Calliban · 2024-02-22 19:08:26

Rather scary to think of a single subatomic particle with as much energy as a small bullet. If that hits a human being it is going to do substantial damage. I wonder if the unlikely person would actually feel the hit? If it hits a nerve fibre they probably would. In fact, if a particle like that hits tissue directly above a nerve, the damage to motor neurons from the secondary particle shower might be enough to impair the function of the nerve. Not nice.

Last edited by Calliban (2024-02-22 19:09:20)

SpaceNut · 2024-03-21 17:26:56

GW Johnson wrote:

The natural average Earthly background is about equal to the US average background of about 300-330 milli-REM. Sorry, I do not know how to convert that. It's 0.3 to 0.33 REM/year, which is not a very large number. (Supposedly, about a third of that background traces to coal burned in power plants. Coal is slightly radioactive, as is frack water backflow.) It is very important to note that natural background varies strongly with location. In the mountains where ore-bearing rocks are near the surface, and there is significant radon gas coming from underground, it is supposedly as much as 10 times higher (3-3.3 REM/year). REM is "Roentgen Equivalent Man", meaning radiation intensity multiplied by a human vulnerability factor.
For comparison, the space radiation environment outside the Earth's Van Allen belts is mostly a drizzle of cosmic rays plus some solar wind, peaking at 60 REM/year at solar minimum, and only about 24 REM/year at solar maximum. These were predicated on an expected 3% increase in the rates of cancer late in life. Apparently, the solar wind slows the cosmic rays down a lot, and the solar wind is stronger during solar max. That's a pretty good estimate for Venus/Earth/Mars space. Not so sure about Jupiter and beyond. Even with the heliopause way beyond Pluto.
Before they were recently changed (lowered slightly), the astronaut exposure criteria were no more than 50 REM accumulated in any one year, no more than 25 REM accumulated in any one month, and a career exposure limit that varied with age and gender, but which usually falls in the 300-400 accumulated REM ballpark. 50 REM accumulated over only an hour or two is fatal to 50% of those exposed, and 100 REM in an hour or two is fatal to 100% of those so exposed. Time makes an enormous difference.
Those larger doses are well known since not long after Nagasaki and Hiroshima. I saw them documented in AEC's report "Effects of Nuclear Weapons, 1957". It's the lower doses around 1-10 REM/year and less, that are not well known from any data, which is where the linear-with-dose-rate scaling is used. The assumptions underlying that dose rate scaling, are still only assumptions. There is no recognized data.
The fallout from a nuclear surface burst close by can be as high as 5000 REM/hour, based on the explosions in Japan, and after the war in the Nevada desert! It can be lower, even a lot lower. But you cannot count on it being lower, because sometimes it's just high! Air bursts at significant altitude are a lot lower in fallout radiation intensity. (500-5000 m is not significant altitude!) Lots lower if the fireball does not come close to touching the surface. Most of the fallout is surface dust brought up through the incredibly-radioactive fireball materials by the columnar suction that creates the mushroom cloud.
The lethal space radiation threat is NOT cosmic rays! Never was, never will be! There are many who tell you it is, but they are lying to you! It is instead radiation released in a burst by explosions on the sun. In a word, solar flare events, which occur erratically, and are very, very directional. These are quite comparable to nearby nuclear weapon explosions. Incredibly intense radiation intensity rates, and over in a few hours.
The only other thing to understand is that not all radiation is the same. Cosmic rays are mostly hydrogen nuclei moving at near lightspeed. These are very difficult to shield. Solar flare particles are mostly hydrogen and helium nuclei, moving very much slower at solar wind speeds. Those are much, much easier to shield against, which is what the 25 g/cm^2 figure of merit for shielding is all about. Van Allen belt radiation is mostly solar flare and wind particles caught in Earth's magnetic field, but still moving in circles about the field lines at something like solar wind speeds. Intensity resembles solar flare events and nearby nuclear explosions.
GW

SpaceNut · 2024-04-03 19:35:32

Scientists build breakthrough nuclear fusion device with household magnets] BB1kZVOX.img?w=768&h=366&m=6&x=298&y=46&s=852&d=181

Calliban · 2024-07-18 17:06:44

This is the most comprehensive study of Mars surface doserates I have seen to date.
https://agupubs.onlinelibrary.wiley.com … 21JE007157

The Martian atmosphere appears to increase surface wholebody equivelent doserates because of secondary neutron build up. So it matters relatively little where we build the base from a radiation protection viewpoint. The bottom of Hellas is not much better than the top of Olympus Mons.

Whole body surface doserate is ~230mSv per year. About 3m of soil (rho = 1790kg.m-3) is needed to reduce doserate to 20mSv per year. Assuming we build habitats on the surface with minimal additional shielding, inhabitants would receive 6.9Sv of whole body effective dose over a 30 year period. Taking the radiation risk factor to be 0.05/Sv and assuming that a radiogenic cancer death costs 30 years of life expectancy, the total liss of life expectancy associated with living on the surface for 30 years would be 10.35 years. In other words, living unprotected on Mars surface will knock a decade off of life expectancy.

We could live under domes on the surface, within thick walled stone buildings. If we assume that the average Martian spends 2/3rds of his time inside buildings with 2m thick stone walls and 1/3rd outside, then effective year round dose would drop to 89.3mSv. Loss of life expectancy after 30 years would then be 4 years. This begins to look more manageable, and the health effects due to radiation could be counteracted by healthy lifestyle.

It takes 1.5m of soil to reduce annual doserate to 100mSv. This is 2600kg/m2. This is about one quarter of Earth's atmospheric column density. This suggests that any future terraforming effort must increase Martian atmospheric column by at least this much in order for dose control to no longer be an issue. On Mars, that is a 100mbar average surface pressure. It isn't clear that Mars has enough CO2 deposits to do that.

Last edited by Calliban (2024-07-18 17:38:21)

Void · 2024-07-18 20:34:56

If this is not reasonably understandable, then I can try to explain more:

It is sort of a pipe house with windows at each end, and appropriate loading of regolith and hydrocarbons to perhaps reduce radiation hazards.

I am rather pleased with the idea of making window wells with the 45 (Or so) degree angles covered with a tar, maybe asphalt. Then Aluminum foil on top of that.

For a solar flare if one window is East and the other West, then quite a bit of protection is provided. For GCR, the various tricks should help a lot, I feel.

The windows if of Alon could tolerate up to (Quote:

Melting point ~2150 °C[1]

degrees temp. But I don't think going that hot is desirable). But still it could be a boiler window, if its frame were tubing of some sort. Then while most heat got taken away light would pass through. I suppose it would be desirable to filter out quite a bit of UV.

You may note that the scheme may also tend to hold heat over the nighttime. But movable curtains might be included for the windows to make it better.

Angry Astronaut just put out a video about radiation on Mars that is less concerning, but I am not equipped to judge validity of it.
https://www.youtube.com/watch?v=j1JqYYiaCc0
Quote:

Wrong about Mars again!! Radiation not as deadly as Elon Musk's critics originally thought!
The Angry Astronaut

I am glad for your post. I think that Pipe Greenhouses similar to what I depicted, should help regardless of what the danger really is.

Done

I am thinking about building things with Asphalt on Mars. The temperatures in general may allow it to be stable, perhaps better if you embed a metal frame in it. But the combination of Regolith and a Hydrocarbon Tar Glue, might give structure that handles GCR and other hard radiation. The regolith may make the hard radiation fracture to make secondary radiation but then the Tar might handle that.

Temperature notions for Asphalt: https://greenfieldpavement.com/temperat … %20viscous.

I actually think that the pipes could be made of sintered regolith, and then covered with packed Martian brick. But Asphalt with reinforcement also seems like it might have a place.

As for the windows, you could hang plastic bags full of sterile water on the insides of the windows.

I think this collection of schemes might be close to something that could be workable and pleasant.

The pipes in any case could have a balloon of poly inside which may help to prevent air leaks.

Done

Last edited by Void (2024-07-18 21:07:04)

tahanson43206 · 2024-07-19 06:21:19

The idea advanced by Void, to use tar as a radiation protection material, is interesting and it inspired me to investigate a bit.

I asked Gemini to "think" about the idea, and it came back with a suggestion that polyethylene might be better than tar due to a higher proportion of hydrogen compared to that in tar, which includes oxygen and sulfur and possibly other atoms.

This little Python program shows one way of comparing the two substances.

The effectiveness of a given material may vary when it is subjected to radiation of various wavelengths and kinds.

# Define element symbols and atomic masses for easy calculation
elements = {
"H": 1.008,
"C": 12.011,
"O": 15.999
}
# Example composition of tar (can vary depending on source)
tar_composition = {
"C": 0.75, # 75% by weight
"H": 0.08, # 8% by weight
"O": 0.17 # 17% by weight (assumed oxygen content)
}
# Calculate weighted average atomic mass for tar
tar_mass = sum(elements[element] * weight for element, weight in tar_composition.items())
# Example polyethylene formula (C2H4)n
polyethylene_mass = (2 * elements["C"] + 4 * elements["H"])
# Calculate hydrogen weight percentage for tar and polyethylene
tar_hydrogen_pct = (tar_composition["H"] / tar_mass) * 100
polyethylene_hydrogen_pct = (4 * elements["H"] / polyethylene_mass) * 100
# Print the comparison
print("Hydrogen weight percentage in tar:", tar_hydrogen_pct, "%")
print("Hydrogen weight percentage in polyethylene:", polyethylene_hydrogen_pct, "%")
# Expected output (may vary slightly depending on assumed tar composition):
# Hydrogen weight percentage in tar: 7.940000000000001 %
# Hydrogen weight percentage in polyethylene: 14.285714285714286 %

(th)

Void · 2024-07-19 06:43:55

A useful question(s) (th).

Tar in Asphalt would contain protective materials such as Hydrogen and Carbon that regolith does not. Asphalt may also be of interest to make structure on Mars.

Graphite, has some history in reactors: https://en.wikipedia.org/wiki/Nuclear_graphite

But I want stone age tar, because it may be relatively easy to create by pyrolysis: https://www.researchgate.net/publicatio … mary%20tar.
Quote:

This creates a pyrolysis dominant zone where biomass is decomposed thermally without any reacting agent. The thermal decomposition of lignin, cellulose and hemicellulose at relatively lower temperatures below 600°C causes the formation of primary tar.

Neanderthal Tar: https://www.smithsonianmag.com/smart-ne … 180972994/

While Tar is not considered as "Space Age", this "Stone Age" material may be both beneficial and relatively easy to make. Possibly easy to grow organic materials will do to process to make Tar.

Asphalt as shielding: https://www.sciencedirect.com/science/a … 3918305646
Quote:

Abstract
The internal wall of the cavity of experimental assemblies, involved with high energy fusion neutrons, can be covered by an asphalt-sand layer for radiation protection purposes. The calculations have demonstrated that asphalt has a radiation protection capability superior to that of concrete, on equivalent weight basis.
For an experimental cavity using a 1012 neutrons/sec neutron generator, the best structure has been found to be a 10% asphalt - 90% red sand homogeneous mixture, against neutron + gamma energies, with a protection capability of more than 200% compared to the same thickness of a concrete structure.
This work has proved that the local and cheap asphalt and sand can replace the relatively expensive concrete in constructing biological radiation shielding of experimental assemblies on fusion neutronics.

I think a possible way to hold air pressure could be:
1) Hard Brick Arch (Possibly sintered brick materials).
2) Sandwich of Poly film/Asphalt or Tar/Poly film.
3) Packed Martian Earth.

The Sandwich #2, would be deformable so as to have hopes to tolerate some shape drifting over time of the arch structure.

This 1,2,3 setup may be fair to reduce Neutrons and other radiation concerns.

In the diagram of my previous post, we have both "Pass Through" and "Rebound", radiation concerns. "Rebound" would be when radiation/neutrons may strike and penetrate an apron and the resulting secondary radiation may be a concern as it rebounds out of the apron materials.

Layering of the apron may take care of much of the concern. But the windows may have sterile water bags placed behind them in the pressurized interior to help filter out secondary radiation.

An interesting thing about conducting light into a window well portal is that the Neutrons and most hard rediation are for the most part not conveyed by the mirror system.

Done

Last edited by Void (2024-07-19 07:10:46)

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#76 2024-02-22 19:08:26

Re: Space Radiation + counter measures

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