Poll

Are GCR's going to be a showstopper for long duration BEO missions?

Yes
11 (6.2%)
No
127 (71.3%)
It depends
40 (22.5%)

Total Members Voted: 178


Author Topic: Galactic Cosmic Rays (GCR) - Showstopper or What?  (Read 126215 times)

Offline gbaikie

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #220 on: 12/13/2014 07:34 am »
Radiation isn't THAT bad for you, anyway. Between launch from Earth, entry to Mars, launch from Mars and reentry at Earth, you're more likely to die at those points than from cancer (near the end of your natural life) from GCR radiation on the transit. I think this is way overstated. Smokers have a far greater cancer risk.

Exactly. And consider early exploration on Earth with exposure to new tropical diseases etc... this is significantly safer.

Radiation isn't THAT bad for you, anyway. Between launch from Earth, entry to Mars, launch from Mars and reentry at Earth, you're more likely to die at those points than from cancer (near the end of your natural life) from GCR radiation on the transit. I think this is way overstated. Smokers have a far greater cancer risk.

In engineering one builds in safety margins.
And I don't think NASA should require that the crew smoke cigarettes.
And it's matter of crew morale.
And of course, most importantly, it's a political and PR matter.

I strongly doubt that it's an issue of crew morale, or if it is, then there is something wrong with the crew selection process. The risk is just not that big -- and there are plenty of people who would be willing to accept much bigger risks to get to Mars.

The best of crews would be ones that have done it before.
And:
"Apollo astronauts traveling to the moon absorbed higher doses--about 3 times the ISS level--but only for a few days during the Earth-moon cruise. GCRs may have damaged their eyes, notes Cucinotta. On the way to the moon, Apollo crews reported seeing cosmic ray flashes in their retinas, and now, many years later, some of them have developed cataracts. Otherwise they don't seem to have suffered much. "A few days 'out there' is probably safe," concludes Cucinotta."
http://science.nasa.gov/science-news/science-at-nasa/2004/17feb_radiation/

I would say the problem it not with the ones who reported seeing such flashes, rather it's the ones that didn't report it. And also more than one Apollo crew thought they saw "UFOs".
There are no space aliens anywhere near earth.
But it's environment which is prone to have unusual things happen, in terms actual things and things imagined.
Also will refer to Chinese water torture:
"Victims were strapped down so that they could not move, and cold or warm water was then dripped slowly on to a small area of the body; usually the forehead. The forehead was found to be the most suitable point for this form of torture because of its sensitivity: prisoners could see each drop coming, and after long durations were gradually driven frantic as a perceived hollow would form in the center of the forehead."
http://en.wikipedia.org/wiki/Chinese_water_torture

I would say there is a lot unknown and would give high priority to shortening the trip time.
« Last Edit: 12/13/2014 07:36 am by gbaikie »

Online aameise9

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #221 on: 12/13/2014 11:27 am »
My 2 cents:

BENEFICIAL effects of radiation exposure are well established and are due to the stimulation of cellular repair mechanisms (anti-oxidants, apoptosis, necrosis, immune response, see below for source).  It is possible that these beneficial effects, which are known as `radiation hormesis', extend to exposures of 700 mSievert/year (perhaps even higher).

The number 700 mSievert/year comes from observations of populations in Ramsar, Iran, and has been proposed as a safe dose limit for continuous exposure.

http://www.ncbi.nlm.nih.gov/pubmed/11769138/

 
IMHO, empirical observations of large human populations exposed to moderate levels of radiation offer the most appropriate baseline this discussion.  The current regulatory limits (e.g., of 20 mSievert/year for radiation workers) seem to  have no rational basis, again IMHO.

....


The exposure on the ISS is approximately 160 mSievert /year (during solar minimum) and 320 mSievert/year (during solar maximum).

http://spaceflight.nasa.gov/spacenews/factsheets/pdfs/radiation.pdf


The highest level of natural background radiation is in the state of Kerala and city of Chennai in southern India, where people receive average doses above 30 millisieverts per year, according to the World Nuclear Association.  In Brazil and Sudan, exposure can reach 40 millisieverts a year or 4.57 microsieverts an hour. 

Based on 736,586 person-years worth of observations, no excess cancer risk is evident

http://www.ncbi.nlm.nih.gov/pubmed/19066487


In Ramsar, Iran, two large populations living together in one city, either in a high background area of 300 to 700 milliSievert/year, or in a low background area of 2 to 3 mSievert/year have been compared.   The high background of 700 mSv/year in the city of Ramsar, Iran is a safe dose limit for continuous chronic exposure.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2664640/






Offline Waz_Met_Jou

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #222 on: 12/13/2014 11:38 am »
The number 700 mSievert/year comes from observations of populations in Ramsar, Iran, and has been proposed as a safe dose limit for continuous exposure.

http://www.ncbi.nlm.nih.gov/pubmed/11769138/

With 1.84 mSv per day as detected by MSL, the yearly exposure is actually within that limit, without any significant shielding. Considering the crew would spend maybe half a year in deep space before going onto the surface for 500 days, with only about 0.64 mSv per day, the risk seems pretty small to me.

Offline Torbjorn Larsson, OM

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #223 on: 12/13/2014 12:00 pm »
I am still not convinced that any special GCR mitigation is needed. The risks do not seem to me out of line with what is traditionally accepted for exploration. If we had regular business travel to Mars, sure, but for the early expeditions there will be much bigger things to worry about.

I think that is where we are led if we look at the evidence. The RAD instrument on Curiosity was used to measure the radiation dosage that astronauts would experience in the craft and on the surface of Mars. The released data said that a 2 year trip would mean a 5 % increase in lifetime lethality. [I won't dig up my references here and on the next part unless asked for, because of massive local DoS attacks all of this last week.]

To get a feel for what that corresponds to, I dug up the interesting fact that a human accepts a 10 % increase in lifetime lethality if he settles in a city. That is what 50 % of the population accepts today, and 80 % of it within a generation or two.  ::)

So it doesn't seem to be a practical problem. Instead I take it the 5 % lifetime lethality increase is a peculiar NASA ethical problem. As I remember it they want to see a maximum lethality increase of 2-3 % on their astronauts.

But even that procedural problem (can be signed off by individuals willing to take the increased risk) may be water under the bridge. There is an ISS experiment that have said recently that astronaut dosimetry seems to overestimate the real body effects, when exposed, with a factor 3:

Quote
A decade-long experiment using a human-like mannequin to assess radiation absorption inside and outside the international space station has concluded that the human body is much better at protecting astronaut internal organs than previously thought.

The experiments, which used U.S. technology monitored by U.S., Russian, Japanese and European teams, conclude that previous radiation-intake measures, mainly dosimeters worn by astronauts in their pockets or on their chests, overstate the radiation exposure to internal organs.

For an astronaut working inside the space station, the overestimate was about 15 percent — a fairly close correlation given that the station’s exterior shell provides much of the protection needed.

But for astronauts working outside the station, the radiation absorption measured was substantially less than what had been registered by the personal dosimeters worn by astronauts.

“Measurements of a personal dosimeter dramatically overstate the exposure of an astronaut, in the worst case by a factor of three,” according to a summary of the results by a Euro-Russian team. “(I)n an outside exposure the self-shielding of the human body is very effective. … (T)he effective dose equivalent is less than 30 percent higher than in an inside exposure.”


[ http://spacenews.com/42294dummy-astronaut-shows-iss-crew-better-protected-from-radiation-than/ ]

If the lifetime lethality increase is an order of magnitude less than modern humans accept for convenience, is this really a problem at all? The numbers start to come really close to "no change of risk" for urbanized astronauts.  8)

Offline muomega0

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #224 on: 12/13/2014 12:58 pm »
The dose rate and magnitude are two key parameters in determining the development of cancer.  As was mentioned previously, the same experiment, which took several years, needs to be conducted in the proper environment of deep space without the earth or moon blocking about half the GCR.  IOW:  The data has been obtained at the high and low end of the spectrum in gathering the evidence.  Some key questions:

For those willing to take the risk, is it still true that 1/3 (or less) of the crew's DNA would be hit by ions for each year in deep space?  Is it still true that broken DNA does not repair itself in most instances and will it break?  What are the best devices to monitor dose rate?   These then provide the design data:  In engineering terms, *If* the 10 g/cm2 is the answer, at ~ 1mT to 1 g/cm2, then the DRM still needs to add 6 to 8 mT of shielding mass.
 
In addition to cancer, the effects to the retina, the brain and the central nervous system, and whether the potentially accelerate the development of Alzheimer's is being examined.

Offline Avron

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #225 on: 12/13/2014 01:50 pm »
one would think that its would be best to send some mice to Mars and see if they make the trip. We can only measure what we know is out there beyond the earth moon system .

Offline Robotbeat

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #226 on: 12/13/2014 01:57 pm »
Of course the mice will survive the GCR. Heck, lab rats are so riddled with cancer, it might help them!
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Offline Burninate

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #227 on: 12/13/2014 03:27 pm »
Would you go to Mars if the figure was a 99% chance of being diagnosed with some type of cancer, between 5 years and 15 years after the conclusion of your mission?

Now - Do you think in 300 million people we could find a substantial fraction who would answer 'yes' ?

It's an often treatable illness that usually kills slowly, which we could easily direct inordinate amounts of money towards detecting and treating, for the money saved reducing mission cost.


The numbers on water shielding are *horrible* for small missions - last time I ran the figures extrapolated from a shielding paper, I ended up at IIRC 800kg/m^2 water shielding (80cm thickness) to cut radiation by ~99%.  Being this risk-averse prevents any progress from being made.  It's only for larger habitats, and in particular Aldrin cyclers, that tons of shielding makes sense.  If you're shipping hundreds of humans to Mars per habitat, you get to spend very reasonable amounts of mass per passenger making radiation go away: A hypothetical Bigelow BA-50,000 only costs 6000 tons of water at this standard, while a BA-330 need a little under 1 ton of water per cubic meter of volume.

Using propellant as shielding works out fairly well for the first half of the mission, if you configure it right and spend some resources on thermal subsystems.
« Last Edit: 12/13/2014 03:54 pm by Burninate »

Offline muomega0

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #228 on: 12/13/2014 04:13 pm »
one would think that its would be best to send some mice to Mars and see if they make the trip. We can only measure what we know is out there beyond the earth moon system .
To mars is not necessary, only to deep space, away from earth and moon-- the proper environment, and compare to mice and crew in LEO and earth environments.

Having 3 LVs provide flights to LEO, a fourth provide no flights BLEO ,and a fifth fly for 4 hours a bit outside of LEO,  however, is today's priority.  Perhaps more data is available (?), but not made public.

Of course the mice will survive the GCR. Heck, lab rats are so riddled with cancer, it might help them!
Rats rarely die of cancer and have many tumors, and Mice, by comparison, rarely live past the age of four and do often die of cancer.  The retina, brain and central nervous system, and Alzheimers also need to be considered.  Which leads to spinning, since all bone loss is basically permanent for older folks, what is the combined effect of GCR and bone loss,  is another question being examined.

Offline Vultur

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #229 on: 12/13/2014 09:33 pm »
Being this risk-averse prevents any progress from being made.

Exactly.

Offline sghill

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #230 on: 12/15/2014 07:10 pm »
Would you go to Mars if the figure was a 99% chance of being diagnosed with some type of cancer, between 5 years and 15 years after the conclusion of your mission?

Now - Do you think in 300 million people we could find a substantial fraction who would answer 'yes' ?

It's an often treatable illness that usually kills slowly, which we could easily direct inordinate amounts of money towards detecting and treating, for the money saved reducing mission cost.


The numbers on water shielding are *horrible* for small missions - last time I ran the figures extrapolated from a shielding paper, I ended up at IIRC 800kg/m^2 water shielding (80cm thickness) to cut radiation by ~99%.  Being this risk-averse prevents any progress from being made.  It's only for larger habitats, and in particular Aldrin cyclers, that tons of shielding makes sense.  If you're shipping hundreds of humans to Mars per habitat, you get to spend very reasonable amounts of mass per passenger making radiation go away: A hypothetical Bigelow BA-50,000 only costs 6000 tons of water at this standard, while a BA-330 need a little under 1 ton of water per cubic meter of volume.

Using propellant as shielding works out fairly well for the first half of the mission, if you configure it right and spend some resources on thermal subsystems.

That's a very good post, but I'll point out that it only matters in terms of cost.  If it's cheap enough to fling the extra water (and fuel, and structure, etc.) mass up there, the water is a nice GCR protection solution.

I'm only bringing this up because in the context of reusable rockets, a big dumb payload with a huge mass that you need lots and lots of is right in the sweet spot of reusable launch rationales.  E.G.  if you have the capability to fling water up there for cheap, you should do so.
Bring the thunder!

Offline Burninate

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #231 on: 12/15/2014 07:35 pm »
So my advice in the meantime is - Live with it.  Cancer is cancer - it's not Ebola.  It looks like only by subjecting the first few thousand explorers to a slightly increased (but statistically insignificant relative to lifestyle or career hazards) risk of cancer, can we achieve the kind of progress & scale necessary to reduce the risk to hypothetically minimal levels... and that's okay.

You know what it costs to enroll in a 5+ year career as an airline stewardess?

It *doubles* breast cancer risk, currently at 12.4% for the general population, to ~25%.
http://www.webmd.com/breast-cancer/news/20031021/flight-crews-have-higher-cancer-risk
http://www.cancer.gov/cancertopics/factsheet/detection/probability-breast-cancer

For full-adult-career-length cohorts, it was 5x the risk.

The supplemental healthcare checkups associated with being an astronaut will improve these peoples' health relative to the general population - it more than makes up for the slight change in lifetime cancer risk.
« Last Edit: 12/15/2014 08:22 pm by Burninate »

Offline redliox

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #232 on: 12/15/2014 07:51 pm »
The supplemental healthcare checkups associated with being an astronaut will improve these peoples' health relative to the general population - it more than makes up for the slight change in lifetime cancer risk.

I don't think NASA wants to risk getting sued or ruining its P.R.  Secondly, the researchers behind life sciences want their money as does every other department and company, which is the real reason why we haven't had a Mars mission...

Regarding any radiation, I believe Mars (or even the Moon) is worth the risk, and might be easier to mitigate than expected.
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Offline Burninate

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #233 on: 12/15/2014 08:17 pm »
The supplemental healthcare checkups associated with being an astronaut will improve these peoples' health relative to the general population - it more than makes up for the slight change in lifetime cancer risk.

I don't think NASA wants to risk getting sued or ruining its P.R.  Secondly, the researchers behind life sciences want their money as does every other department and company, which is the real reason why we haven't had a Mars mission...

Regarding any radiation, I believe Mars (or even the Moon) is worth the risk, and might be easier to mitigate than expected.
Why does NASA, which is a public agency (with sovereign immunity) charged with doing things that are canonically difficult, dangerous, pioneering things, using volunteers extremely well-informed about those risks, fear a lawsuit and PR more than a private airline, for several orders of magnitude less risk?

Things like 3rd-order and 4th-order backup systems for every last device earn more risk_diminished : mass ratio points to design into a small spacecraft than craft-wide radiation shielding.
« Last Edit: 12/15/2014 08:19 pm by Burninate »

Offline IslandPlaya

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #234 on: 12/15/2014 08:27 pm »
The supplemental healthcare checkups associated with being an astronaut will improve these peoples' health relative to the general population - it more than makes up for the slight change in lifetime cancer risk.

I don't think NASA wants to risk getting sued or ruining its P.R.  Secondly, the researchers behind life sciences want their money as does every other department and company, which is the real reason why we haven't had a Mars mission...

Regarding any radiation, I believe Mars (or even the Moon) is worth the risk, and might be easier to mitigate than expected.
Why does NASA, which is a public agency (with sovereign immunity) charged with doing things that are canonically difficult, dangerous, pioneering things, using volunteers extremely well-informed about those risks, fear a lawsuit and PR more than a private airline, for several orders of magnitude less risk?

Things like 3rd-order and 4th-order backup systems for every last device earn more risk_diminished : mass ratio points to design into a small spacecraft than craft-wide radiation shielding.
I would say it is because there is no precedent.
They are doing everything they can to prevent a lawsuit that may never come...

Offline Robotbeat

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #235 on: 12/15/2014 11:36 pm »
The supplemental healthcare checkups associated with being an astronaut will improve these peoples' health relative to the general population - it more than makes up for the slight change in lifetime cancer risk.

I don't think NASA wants to risk getting sued or ruining its P.R.  Secondly, the researchers behind life sciences want their money as does every other department and company, which is the real reason why we haven't had a Mars mission...

Regarding any radiation, I believe Mars (or even the Moon) is worth the risk, and might be easier to mitigate than expected.
Why does NASA, which is a public agency (with sovereign immunity) charged with doing things that are canonically difficult, dangerous, pioneering things, using volunteers extremely well-informed about those risks, fear a lawsuit and PR more than a private airline, for several orders of magnitude less risk?
...
You know my feel, bro. ;)

But seriously, lots of reasons. Losing astronauts is emotionally tramatic because many of us get to know them and put a LOT of energy into keeping them safe, so the idea that we aren't doing our jobs in keeping them safe is very troubling on a personal level. But I agree that the risk-tolerance has gone overboard at NASA nowadays (more on the technical side than the astronaut safety side, though, I'd argue... except for the radiation issue which I think is a bit over-blown).
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline gbaikie

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #236 on: 12/16/2014 12:21 am »
The supplemental healthcare checkups associated with being an astronaut will improve these peoples' health relative to the general population - it more than makes up for the slight change in lifetime cancer risk.

I don't think NASA wants to risk getting sued or ruining its P.R.  Secondly, the researchers behind life sciences want their money as does every other department and company, which is the real reason why we haven't had a Mars mission...

Regarding any radiation, I believe Mars (or even the Moon) is worth the risk, and might be easier to mitigate than expected.
Why does NASA, which is a public agency (with sovereign immunity) charged with doing things that are canonically difficult, dangerous, pioneering things, using volunteers extremely well-informed about those risks, fear a lawsuit and PR more than a private airline, for several orders of magnitude less risk?

Things like 3rd-order and 4th-order backup systems for every last device earn more risk_diminished : mass ratio points to design into a small spacecraft than craft-wide radiation shielding.
I would say it is because there is no precedent.
They are doing everything they can to prevent a lawsuit that may never come...

I don't think governments fear lawsuits- I think as general rule governments tend to be reckless in terms of lawful behavior. As example, the EPA recently performed human experiments which could be regarded as war crimes. White police officer strangles black suspect in New York city - only reason you know about it because the color of the skins which are involved. Or drug enforcement raids the wrong house and innocent children are shot.
The list is endless.
And I think one problem could be because there is precedent, "As of November 6, 2013, a total of 536 people from 38 countries have gone into space"
http://en.wikipedia.org/wiki/List_of_space_travelers_by_name
And 40% of people who have not gone in space get cancer.
So, 536 times .4 is 214.4
Now if 200 of 536 people get cancer you will still get thousands if not millions of people who will think a good portion or all got cancer because they went into space.
And if 215 people get cancer it will become a pseudo scientific fact that going into space causes cancer.
We have hundreds of millions of people who think nuclear power is dangerous- yet it has been the safest and cleanest way to generate electrical power.

And I assume that everyone knows all politicians are completely crazy and a majority of voters re-elected Obama [the lame duck with dreams of Emperor].

The question will boil down to could NASA have done more to stop it's crew from being exposed to harmful
radiation. And one gets a bigger problem if NASA should have known better, and they ignore the problem. The public did it's part, they paid over 200 billion dollar for Space station that was suppose to find out about such matters.
Or the problem is, this type of thing will be spun.
You don't give your opposition [[there is lots of opposition to doing anything rational and lots of support
to do stupid stuff]] ammunition- and space exploration hinges on politics.
« Last Edit: 12/16/2014 12:27 am by gbaikie »

Offline bkellysky

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #237 on: 10/17/2015 01:52 pm »
Article today on http://spaceweather.com about cosmic rays and the movie The Martian.  It references calculations by Ron Turner http://www.anser.org/docs/The_Radiation_Threat_to_the_Martian.pdf  about potential radiation exposures to the characters in the movie.

Offline Robotbeat

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #238 on: 10/17/2015 02:36 pm »
Article today on http://spaceweather.com about cosmic rays and the movie The Martian.  It references calculations by Ron Turner http://www.anser.org/docs/The_Radiation_Threat_to_the_Martian.pdf  about potential radiation exposures to the characters in the movie.
Pssh, just 72 cSv for the crew of the Hermes? Spread out over almost 3 years? No big deal. They're at an increased risk of cancer, but at less risk of cancer than a smoker is. That's also still under the Russian and European radiation career limit (which is 100 cSv, if I recall correctly).
« Last Edit: 10/17/2015 02:36 pm by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Russel

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Re: Galactic Cosmic Rays (GCR) - Showstopper or What?
« Reply #239 on: 10/17/2015 06:23 pm »
To those who are more immersed in the radiation numbers I just wanted to ask this.

Lets assume that the space habitat is a modest affair. The best you could expect from the structure is a few mm of aluminium and maybe 5-10 mm of carbon fibre reinforced polyethylene. Lets also assume that your ship carries upwards of 20 tonnes of consumables. That includes life support gases, but there would also be several tonnes of liquid water, or its equivalent in food. So what I'm suggesting here is a pragmatic approach with some attention to radiation protection in the hull, but otherwise deliberate concentration of water around the sleeping area. Bear in mind also that equipment, external solar panels, thermal radiator panels, and other plumbing will also absorb some radiation.

What's your best guess as to the radiation dose due to GCR on a 6 month flight? And separately what would be the bare minimum in terms of equivalent thickness of water for a solar storm shelter? 20cm? 50cm?

Its also occurred to me to store water as part of the bunk structure itself, or even add deliberate metallic shielding  in places physically close to where the crew would usually be in for long periods (like chairs).

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