Методы снижения радиационных нагрузок при длительных полетах

[sychbird]

Ученые выяснили, что молекула спирта поглощает свободные радикалы, которые при облучении приводят к генетическим нарушениям. При этом, эксперты подчеркнули, что безалкогольное пиво не обладает такими свойствами.

Интересно, пивоваренные компании засылали ученым наличными или натурой.
Эта байка про перехват радикалов этиловым спиртом  еще у нас на 5 курсе у радиационщиков и радио-химиков была очень популярна в общаге.    

[Туфи]

Нужно для начала чётко определиться, от чего конкретно защищаемся.
Если есть нейтроны, то нужен метровый слой парафина, керосина или воды. Зачем на орбите парафин, я не знаю, а остальное не пропадёт. Жидкий водород ещё лучше, но уж очень у него плотность маленькая. А уже потом, когда поглотим нейтроны в конструкции и защите, нужно бороться и с остальными видами излучения, и с наведённой гамма-активностью.
Если же нейтронов нет, то правильный ответ прост. Нужен кусковой свинец. Как ни странно, это будет самым лёгким вариантом защиты при заданном коэффициенте ослабления излучения. В принципе неплох и вольфрам, если нужна компактность, но его нет и он нетехнологичен. Всякая прочая нанотехнология приведёт не просто к удорожанию, а и к увеличению массы и габаритов защиты. Разве что действительно толстый хрусталь на окна. А в остальном - листы свинца хоть в обшивку кресла, хоть в трусы. Даже гибкую и лабиринтную защиту можно делать, используя обычную охотничью дробь.
И есть, конечно, нюансы по источникам излучения: свой (реактор), солнечный (есть выделенное направление) или всенаправленный. Конструкция защиты для этих трёх случаев будет отличаться.

P.S. На всякий случай - первый раз расчётом радиационной защиты довелось заниматься в 1981 году.

I expect to see all types of radiation in LEO. Here is a link to one paper http://www.physicamedica.com/VOLXVII_S1/78-BADHWAR.pdf . I have also read a paper about measurements done during Apollo missions. From those measurements they draw a conclusion that had the Apollo 16 or 17 been in space during the solar flare activity that occurred between those two missions crew would receive deadly dose of radiation. I think that hardest problem to solve is induced radiation and braking radiation. As for braking radiation you can add second layer of protection to dampen it to some extent but I think that induced radiation is much harder to solve. If I remember correctly aluminium is one of the first materials where induced radiation is shown and it is the basic spacecraft material. Lead and tungsten are mentioned as shielding materials here but I was suprised not so long ago when I found out that for some lightweight purpose radiation shields are made from depleted uranium. I don't think that anyone will use that material as the other side will rise with uproar shouting "they are building on orbit uranium enrichment facility" ;-) (I couldn't resist)

Chilik you are right about most likely way this problem will be attacked at this time as our space capabilities doesn't allow much more to be done. During the era of nuclear powered bombers they used partial reactor shields. Chilik idea of shielding some part of spacecraft resemble that. It can be assumed what are the regions of highest crew activity and from the used construction materials estimate stopping power for radiation in all spacecraft regions. Take Soyuz for example - we can assume that PAO give good amount of protection to back of the SA so except the crew chairs little shielding is needed from that side. Also for the BO we can assume that docking ring installation and support frame provides more protection from the front of the BO then the rest of the BO can do. So most likely step would be to shield those parts of SA and BO that provide less protection to even the penetration of radioactive flux on crew. That is not much but small step forward I think.

When I considered radiation issue I was thinking more about Sun radiation then background cosmic radiation as I assumed that closest source with almost permanent exposure is what makes most of the problem. In Solar flux we have protons, electrons, helium cores and even oxygen and iron particles(?). Protons have low half-life time if I remember well 12 minutes so during their travel from Sun good portion of them are converted to neutrons. Question is what is the amount of certain radiation types and what is the energy spectrum of those particles not are they present. After that it is up to medical experts and engineers to estimate the risk, tolerable level and possible achievable protection they can give to crews.

[Туфи]

Главная опастность - высокоэнергетичные ионы. Наиболее перспективный материал для защиты - полиэтилен. Как противометеоритная защита он тоже хорош. Есть довольно таки выдающиеся материалы на его основе. Вот например
Dyneema, the world's strongest fiber, is a superstrong polyethylene fiber that offers maximum strength combined with minimum weight and is up to 15 times stronger than quality steel and up to 40% stronger than aramid fibers such as Kevlar.

When I considered plastic materials as radiation protection insulation I was considering polypropylene or polystyrene as they have higher density and hydrogen content which is important for neutron/proton flux shielding. Do you have some numbers for high-energy ions? Also I knew that on Earth army built inside tanks similar shield for nuclear blast initial protection. Any info on what they used there?

[Chilik]

Нейтроны для космической техники, пожалуй, на последнем месте.

Возможно. Но если есть реактор на борту, то они будут и будет наведённая активность. А без реактора обсуждать тематику длительных пилотируемых полётов за магнитосферой как-то неинтересно.

[Chilik]

I have also read a paper about measurements done during Apollo missions. From those measurements they draw a conclusion that had the Apollo 16 or 17 been in space during the solar flare activity that occurred between those two missions crew would receive deadly dose of radiation.

IIRC they had some emergency procedure just for this case. Something like a special Apollo orientation with the fuel tanks acting as the radiation schield.

If I remember correctly aluminium is one of the first materials where induced radiation is shown and it is the basic spacecraft material. Lead and tungsten are mentioned as shielding materials here but I was suprised not so long ago when I found out that for some lightweight purpose radiation shields are made from depleted uranium.

If radiation will become an issue, the outer shell materials will be optimized for this. Now no such optimization is necessary. As for the depleted uranium, it's probably the best choice. Good for general mechanical workshop, best possible atomic number, extremely good density and almost no self-radiation (american military used depleted uranium in an anti-tank artillery shells during the Gulf war). And it's incredibly cheap, because millions tons of it were produced in the last half of a sentury and nobody needs it.

During the era of nuclear powered bombers they used partial reactor shields. Chilik idea of shielding some part of spacecraft resemble that.

Please don't credit me for this. It is a general knowledge fom the radiation safety. Such sheilding type was always supposed for a nuclear-powered spacecraft.

Protons have low half-life time if I remember well 12 minutes so during their travel from Sun good portion of them are converted to neutrons.

Just the opposite - protons are stable, neutrons are not. Hydrogen is stable, after all. And neutrons are more dangerous due to large absorbtion length and unpleasant induced radioactivity.

[Fakir]

Нейтроны для космической техники, пожалуй, на последнем месте.

Возможно. Но если есть реактор на борту, то они будут и будет наведённая активность. А без реактора обсуждать тематику длительных пилотируемых полётов за магнитосферой как-то неинтересно.

Вроде реакторщики говорили, что и в случае реактора основная масса защиты нужна именно от гаммы.

[Туфи]

I have also read a paper about measurements done during Apollo missions. From those measurements they draw a conclusion that had the Apollo 16 or 17 been in space during the solar flare activity that occurred between those two missions crew would receive deadly dose of radiation.

IIRC they had some emergency procedure just for this case. Something like a special Apollo orientation with the fuel tanks acting as the radiation schield.

The idea of orienting Apollo capsule in such way is corresponding nicely to this topic.

If I remember correctly aluminium is one of the first materials where induced radiation is shown and it is the basic spacecraft material. Lead and tungsten are mentioned as shielding materials here but I was suprised not so long ago when I found out that for some lightweight purpose radiation shields are made from depleted uranium.

If radiation will become an issue, the outer shell materials will be optimized for this. Now no such optimization is necessary. As for the depleted uranium, it's probably the best choice. Good for general mechanical workshop, best possible atomic number, extremely good density and almost no self-radiation (american military used depleted uranium in an anti-tank artillery shells during the Gulf war). And it's incredibly cheap, because millions tons of it were produced in the last half of a sentury and nobody needs it.

Toxicity of uranium will prevent its use in space until they make space operations less dependent from Earth such as that they have ability to treat the sick cosmonaut. Good friend of mine have been examining those depleted uranium rounds dug out of soft ground they hit and I must say that no radiation is a myth. If you ask me USA is dispersing its nuclear waste through other means by using those rounds. As for ability of depleted uranium to shield from radiation I have no doubts. There is a small weight advantage that lead have over uranium and that might win overall.

During the era of nuclear powered bombers they used partial reactor shields. Chilik idea of shielding some part of spacecraft resemble that.

Please don't credit me for this. It is a general knowledge fom the radiation safety. Such sheilding type was always supposed for a nuclear-powered spacecraft.

I just wanted to comment your post Chilik the way I have seen it. I see no harm in mentioning that you first mention that in this topic.

Protons have low half-life time if I remember well 12 minutes so during their travel from Sun good portion of them are converted to neutrons.

Just the opposite - protons are stable, neutrons are not. Hydrogen is stable, after all. And neutrons are more dangerous due to large absorbtion length and unpleasant induced radioactivity.

Ouch man it was a long time since I looked at those figures and I started to forget some things and worse as seen here to switch their places. And I posted after two days of having no sleep (too much work can damage your health and I must find right time for this hobby) or I should remembered that if my post is correct then hydrogen maser based atomic clock would be impossible. At least I still remember half-life time rough range although I see that they now estimate that half-life time for neutrons is 10,3 minutes. I know that neutrons penetrate more then any other sort of radiation as they have no charge so that they can be slowed down by electrostatic forces within material, if they are absorbed then they often produce isotopes that are radioactive and decay leading to other types of radiation. Hydrogen-rich materials seems to slow down neutrons through elastic collision.

[ronatu]

I think that lead/barium glass based screen might be simpler (mature technology from CRT monitors) to make although that is heavier than nanotubes but you could pour molten glass between two metal plates and they should remain bonded after cooling. I like aerogel idea as it has also micrometeorite protection properties and much more important thermal insulation properties too but it has small radiation shielding compared to other solutions. Liquid metal based shield (something similar to Wood alloy maybe cerosafe) might be used and that one should have also fantastic heat transfer properties. My idea is to use layer of bentonite clay between capsule outer and inner wall and let the water inside that clay shield the crew from radiation. Bentonite also can be used as gel when it contains more water but then I guess spacecraft interior must be padded with rubber sacks filled with that gel.

I once considered would it be possible to add 2-3 cm high density plastics inside spacecraft to reduce radiation (good for blocking neutron and beta radiation). When the numbers for BO of Soyuz turn out to be more then 1 t of material I gave up. This lead based idea will suffer from same problem.

Is there some work on the amount of induced radiation on spacecraft materials after prolonged exposure to space radiation?

I can see it - life inside solar batteries... :wink:

[Туфи]

I think that lead/barium glass based screen might be simpler (mature technology from CRT monitors) to make although that is heavier than nanotubes but you could pour molten glass between two metal plates and they should remain bonded after cooling.
...
 My idea is to use layer of bentonite clay between capsule outer and inner wall and let the water inside that clay shield the crew from radiation. Bentonite also can be used as gel when it contains more water but then I guess spacecraft interior must be padded with rubber sacks filled with that gel.

I once considered would it be possible to add 2-3 cm high density plastics inside spacecraft to reduce radiation (good for blocking neutron and beta radiation). When the numbers for BO of Soyuz turn out to be more then 1 t of material I gave up. This lead based idea will suffer from same problem.

Is there some work on the amount of induced radiation on spacecraft materials after prolonged exposure to space radiation?

I can see it - life inside solar batteries... :wink:

Ronatu I see the wink but I don't know are you just joking or are you saying that I like amateur reinvented the wheel. I don't know what solar panel in space use for protection :oops:. I have no idea of putting the cosmonauts inside the glass jar if that was the joke about :-) I said glass between two metal plates (outer and inner hull plates for example). I have (barely) seen the papers dealing with influence of space radiation on electronic components but up until you said this I have never think what covers silicon based (or any other) solar panel in space to protect it from radiation. There is a serious problem with that glass - it is at least 3,5 times heavier then plastic I considered and wrote about it in that post :roll:. Since everyone think that lead based shield is what is needed I assumed they have more information then I have about cosmic radiation types and intensity. I would like to have your opinion on other means of protection I mentioned as your comments are often very useful for an amateur like me.