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I was wondering, does anyone know precisely what the best shielding is for spacecraft to mars when it comes to storm shelters? I have seen estimates from 35g/cm2 to 500g/cm2 is required to shield against solar flares, could anyone elighten me on what value they think is most accurate and any other ideas on radiaiton shielding, for example, having water around radiation shelters, etc.
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I don't think anyone knows yet. The Martian atmosphere provides about 250 kg per square meter (the Earth's atmosphere provides 10,000 kg per square meter). The Martian value is equal to 25 gm/cm2. The Martian atmosphere screens out a lot of the solar radiation, though not in big flares. It provides little shielding against cosmis rays.
-- RobS
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Like many answers, it depends. For most of the radiation that space travelers will be encountering, I'm under the understanding that low Z materials are the best bet.
By low Z, I mean element like hydrogen and carbon and oxygen. High Z materials like lead stop certain kinds of radiation faster but with significant disadvantages. High Z materials tend to be heavy, making them unfavorable for spacecraft - no one wants to put foot thick lead bricks on spaceships. Low Z materials also don't produce Bremstrellung (sp?) radiation. This is the production of high energy X-rays from high energy radiation interacting with high Z materials.
A good candidate low Z material is ultra-high-molecular weight polyethylene which has the benefit of being relatively cheap and quite strong.
There's also the benefits of having a large magnetic sheild around the spacecraft. The M2P2 magsail drive is an experimental propulsion technology now being researched. Although the thrusts it produces are way too low for manned missions, the protective effects is has against solar wind make it a good candidate for providing additional shielding.
Also, as GCNRevenger pointed out, a VASIMR drive also has a similar effect due to the strong magnetic fields used.
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I think most of the radiation during interplanatary flight can be shielded by propellants, especialy when they are hydrogen-rich (LH2 or N2H4). They can easy turn t'he back of the spacecraft and the shielding for solar flares is sufficient, I think. Added shielding for deep-space cosmic radiation or exhibition to the sun during manouvres may be added, but it's even possible that these risks are acceptable. ???
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Shielding against the solar radiation is possible through judicious use of lots of low Z material. (eg: fuel, ultra high weight polyethylene, water, etc) Also any strong magnetic field also works, eg: M2P2.
However, IIRC, about 70% of the expected radiation exposure is from cosmic rays from which there is no good protection. They come from all angles and have a high enough energy that no practical shielding can stop them.
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SBird, Can a very strong magnetic field deflect cosmic rays sufficiently to provide partial shielding for a spacecraft? I was wondering whether a magnetic field could be used to concentrate radiation impact on a vehicle's north and south poles, where small but thick shields would be more effective than large but thin ones.
-- RobS
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SBird, do you know a site where I can find the locations, the energy and the kind of the cosmic radiation? I thought that more than 70% of dangerous radiation was from the sun, but this is really disappointing. The rather 'çheap' solution of using the fuel as shield doesn't really work, Im afraid.
I have searched internet for the cosmic radiation, but I can't find very clear information. Maybe you can help.
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RobS - a magnetic shield should be able to deflect much of the solar wind. It has to be fairly powerful, though. The average particle energy is 0.5 - 2 KeV, so a significant amount of energy has to come from the field to properly deflect the particles around the ship. Not being a physicist, I wouldn't even begin to know what magnitude of magnetic field would have to be.
bolbuyk - I'm using figures from Case for Mars. Although the inability to effectively shield agains cosmic rays kinda sucks, it's not too bad. The total radiation exposure isn't too bad. The nice thing about cosmic rays is that they tend to be more ofa steady flow. Solar wind can get truly stupendous with flares and CMEs. Having an effective shield against solar radiation takes alot of the sudden death threat out of the trip.
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since the moon is being used as a preliminary step, I was wondering if the materials there could used as a component of some sort of magnetic field solution? Since the field will need to be significant, could we make use of the lunar material. Could get a large amount of material to a orbiting mars craft from the moon a lot easier then earth.
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Actually, the M2P2 drive is tiny. The one they're using right now is the size of a coffee can. Of course, larger devices would be necessary for good shielding but it's nothing that can't be launched from Earth. Depending upon lunar resources for any spacecraft components, especially early on is big mistake.
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The obvious choice for creating a high magnetic field without getting too big & heavy would be a cryomagnet of some sort... a super conducting magnet, like the ones in MRI machines in hospitals or NMR machines in laboratories. They can generate a very powerful field from a magnetic ring about 15-20cm wide and a few thick and requires little/no electricity to maintain the field... the only drawback is that it must be kept cold for it to work.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Cryogenity in space?
There has been experience with that IR-telescope (don´t know it´s name yet).
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Anything that has an IR detector on it has cryogenic cooling systems on it these days. Even the Hubble, IIRC, has a cryogenic cooler on its main spectrometer. Getting stuff cool isn't too hard. In fact, the liquid H2 that a MArs Direct mission is carrying makes the perfect cryogenic storage container for a supermagnet. The best part is that once you get the magnet fired up, it runs indefinately as long as nothing bleeds the field energy away.
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Spatial Scale Of High-Speed Flows In The Magnetotail
Studing the earths own protective system is a must if we would want to design something that will work.
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an older thread worth bumping?
Gateway is said to have Instruments to Improve Radiation Detection in Astronauts
How Space Radiation Threatens Lunar Exploration
https://www.smithsonianmag.com/science- … 180981415/
Scientists are studying the possible impacts of the hazard on astronauts who will travel to the moon
What are the most effective shielding approaches to mitigate acute radiation risks, how do we know, and implement? (Closed. Transferred to Operations)
https://humanresearchroadmap.nasa.gov/G … aspx?i=360
and just because the Supernova topic comes up once in a while
Did Betelgeuse Consume a Smaller Star?
https://www.universetoday.com/163998/di … ller-star/
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Definitely worth reviving. We discussed this issue at some length previously in other threads. The answer of how much shielding is needed, is complicated and depends upon: (1) The type of radiation; (2) Exposure time; (3) The availability and effectiveness of other countermeasures; (4) The amount of residual risk a person is willing to live with. Exposure to radiation reduces a persons life expectancy. For small doses, the risks are small and loss of life expectancy is small and list in statistical noise. Risks increase in proportion to accumulated dose. There are all sorts of things that effect life expectancy. So background radiation will be one of many pollution hazards that has a negative impact.
The situation is especially interesting on Mars, which has a thin atmosphere. The debate effects decisions over allowable EVA duration and the design of cities, i.e under domes on the surface, or underground. Surface dose rate for an individual on the surface would be 80 - 200mSv per year, depending on location. This is much lower than the 600 -800mSv/year in open space. At low elevations, the Martian atmosphere is actually quite effective at shielding out cosmic rays. Although a background rate of 80-200mSv/year is a lot more than people would take in most locations on Earth, the atmosphere shields out heavy ion radiation. Most of the surface dose on Mars is due to protons and scattered neutrons, which have lower LET than heavy ions. This is important, because heavy ion radiation can lead to permanent nerve damage.
In a previous post, I calculated the loss of life expectancy that would occur if an individual were exposed to Martian ambient background radiation levels for a third of their total life. The loss of life expectancy was comparable to the effects of air pollution if living in a large city on Earth. This is not a risk to be taken lightly. But if we are willing to tolerate one of these risks, why would the other be intollerable? Maybe background radiation is something we need to take in our stride? I think the conclusion would be different on the moon or in open space. People exposed to high doses of heavy ion radiation are likely to suffer cardiovascular health problems as well as cancer. A lot more people would start dropping dead from heart attacks starting in middle age. We would notice a drop in life expectancy for individuals exposed to 800mSv/year of unfiltered cosmic rays because we are just dealing with a stocastic effect from distributed cell damage. The heavy ions physically degrade vulnerable tissues impairing their function over time. That includes motor neurons and the nerve tissue regulating heart beat. The Martian atmosphere is thick enough to give people a level of protection.
I think living underground on Mars is something we will probably need to do anyway because of the cold. We are talking about an environment that is as cold as Antarctica. We tend to underestimate how cold Mars is, because images show a largely ice free environment. This can fool us into imagining a place like Arizona or Nevada. But it is more like a dry version of Antarctica or North Siberia. The aesthetic value of living under an open air dome needs to be weighed against the heating bill. People generally don't like the feeling of confinement. But they hate the cold even more. There are also questions about the long term safety of pressure structures exposed to repeated thermal transients over day-night cycles.
Last edited by Calliban (2023-11-01 06:34:59)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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NASA prepares for intense sun storms on Mars during 'solar maximum'
https://www.space.com/nasa-mars-solar-m … sity-rover
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