Author Topic: NASA & Georgetown University study on Cosmic Ray dangers to space travelers  (Read 5868 times)

Offline Eric Hedman

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I found this article on a study about the dangers from cosmic rays on long duration spaceflight beyond LEO.  It is here: https://www.independent.co.uk/news/science/nasa-mars-deep-space-journey-guts-gi-digestive-animal-study-gastrointestinal-health-a8563926.html

The title of the article sounds a bit over dramatic.  Does anyone know more details on this study?
« Last Edit: 10/02/2018 06:00 am by Eric Hedman »

Offline WBY1984

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The Independent is a trash website generally, they've just copy-pasted the entire article from the Georgetown website, but at least what they've said is not misreporting as a consequence:
https://gumc.georgetown.edu/news/Animal-Study-Suggests-Deep-Space-Travel-May-Significantly-Damage-GI-Function-in-Astronauts

From a brief google, it sounds like Proceedings of the National Academy of Sciences of the United States of America is a widely cited and respected journal. Other news articles are likewise parroting the Georgetown press release, not quoting from the actual study/authors. Sorry I can't find any more details on the actual study. It does, however, seem to fall in line with a growing body of work that says the space environment is going to be as much as, if not more serious an issue as the actual engineering of a spacecraft.
« Last Edit: 10/02/2018 06:36 am by WBY1984 »

Offline speedevil

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It does, however, seem to fall in line with a growing body of work that says the space environment is going to be as much as, if not more serious an issue as the actual engineering of a spacecraft.
It says '“With the current shielding technology, it is difficult to protect astronauts from the adverse effects of heavy ion radiation." - this does however get easier if you throw mass at it.
A half meter of polythene or methane, or a bit more than a meter of water, for example, cuts your GCR dose to a third.
This is quite a large a lot of mass, but in the further term, in the context of cyclers, and large transfer spacecraft >>8m in diameter, it gets less important.
An 8m*8m inside rounded cylinder, 50cm deep, filled with water, about halves GCR for a 100 ton cost, or several more launches of propellant on BFR.

Also, arguments about GCR being dangerous have to be looked at in the context of ISS astronauts.
They are minimally shielded against GCR, and do not, as a group, have huge health impacts that lead to the worst outcomes.
(May they be subtly affected, sure)

Offline RonM

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It does, however, seem to fall in line with a growing body of work that says the space environment is going to be as much as, if not more serious an issue as the actual engineering of a spacecraft.
It says '“With the current shielding technology, it is difficult to protect astronauts from the adverse effects of heavy ion radiation." - this does however get easier if you throw mass at it.
A half meter of polythene or methane, or a bit more than a meter of water, for example, cuts your GCR dose to a third.
This is quite a large a lot of mass, but in the further term, in the context of cyclers, and large transfer spacecraft >>8m in diameter, it gets less important.
An 8m*8m inside rounded cylinder, 50cm deep, filled with water, about halves GCR for a 100 ton cost, or several more launches of propellant on BFR.

Shielding sleeping quarters would help if shielding the entire crew compartment is not feasible. Have the crew do some of their work on computers in their sleeping quarters. Eight to twelve hours per day in the smaller shielded compartment would help.

Also, arguments about GCR being dangerous have to be looked at in the context of ISS astronauts.
They are minimally shielded against GCR, and do not, as a group, have huge health impacts that lead to the worst outcomes.
(May they be subtly affected, sure)

Since ISS is in LEO, the Earth blocks about half GCR exposure. With shielded sleeping quarters as mentioned above, an interplanetary ship would have about the same crew GCR exposure as ISS today.

Offline envy887

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The full paper is here: http://www.pnas.org/content/pnas/early/2018/09/26/1807522115.full.pdf

Some caveats: they hit mice with 10 Sv of heavy ions in a very short time (they don't specify the irradiation time but in previous papers they used 20 Sv/minute). This compares unfavorably with the estimated 1 Sv total dose (mostly from protons, not heavy ions) for a 860 day Mars mission, of which only 0.3 Sv results from a moderately shielded to unshielded 500-day surface stay. The 180-day transit each way makes up the other 0.6+ Sv, and this is linearly proportional to transit time.

Even without adding shielding to the transit ship, the total dose can be reduced dramatically below the 1 Sv level by ~100 day transits and heavy surface shielding (e.g. underground sleeping and work quarters). In principal, the radiation dose for a 860-day Mars trip can be reduced below that received in ~14 months on ISS.

Between the heavy dose, the extremely high dose rate, the extremely high fraction of heavy ions, and the disregard for surface shielding, this study probably overestimates the radiation effect by at least 10 times. And that's before any spacecraft shielding is accounted for.

Offline Russel

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I put forward an idea in a different context that is worth repeating here.

Personal wearable shielding, probably focused on the torso. The original context was that in a 0.2-0.4g environment, the extra mass is beneficial for exercise. So in a 0.2g environment you coild wear maybe 300Kg of shielding mass.

I'm well aware that there is a limit to heavy ion shielding by this method. But it would be part of a multi-layered defrnse.

Here's an interesting question. Strong magnetic fields will deflect heavy ions or cause them to spiral. Now instead of a uniform external magnetic field, Imagine a material with numerous zones of high intensity magnetic fields (passive or active).  A heavy ion forced to follow a longer path will see more of the material. In other words making the material effectively thicker. Can this be done for a spacecraft hull? Can this be scaled down to personal protection?

Online Robotbeat

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It'd be useful for solar flares.
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Offline KelvinZero

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Personal wearable shielding, probably focused on the torso. The original context was that in a 0.2-0.4g environment, the extra mass is beneficial for exercise. So in a 0.2g environment you coild wear maybe 300Kg of shielding mass.
The astronauts of tomorrow :) :



But seriously, it could be worth some extra coverage especially if certain organs turn out to be a particular risk.. and it could cost next to nothing to have some sort of water-bag suit so individuals can leave the solar shelter if they really needed to. The water would just be part of general stores.

Offline ChrisWilson68

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Between the heavy dose, the extremely high dose rate, the extremely high fraction of heavy ions, and the disregard for surface shielding, this study probably overestimates the radiation effect by at least 10 times. And that's before any spacecraft shielding is accounted for.

I really want to emphasize this point.  This study is really not very useful because what it studies is so much different from what a real space explorer would experience, and because we have much better data.

The much better data comes from flight crews of airliners.  They get much higher doses of this kind of radiation. than people who stay on the Earth's surface.  And the data shows that space travelers can expect some moderate increased risk from these particles, but not a huge amount.  Certainly for the current generation and the next couple of generations the other risks of space travel will outweigh the small risks from cosmic rays.  This new study does nothing to change that assessment.

Offline niwax

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Personal wearable shielding, probably focused on the torso. The original context was that in a 0.2-0.4g environment, the extra mass is beneficial for exercise. So in a 0.2g environment you coild wear maybe 300Kg of shielding mass.
Don't forget about inertia. Even in no gravity getting going and stopping in a 300kg suit will not be fun.

Here's an interesting question. Strong magnetic fields will deflect heavy ions or cause them to spiral. Now instead of a uniform external magnetic field, Imagine a material with numerous zones of high intensity magnetic fields (passive or active).  A heavy ion forced to follow a longer path will see more of the material. In other words making the material effectively thicker. Can this be done for a spacecraft hull? Can this be scaled down to personal protection?
There are threads on here about protecting Mars colonies with an artificial magnetic field (and some startups claiming to offer the same). It's slightly scifi for now but not impossible, especially when you have ample nuclear power to play with.
Which booster has the most soot? SpaceX booster launch history! (discussion)

Offline envy887

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Personal wearable shielding, probably focused on the torso. The original context was that in a 0.2-0.4g environment, the extra mass is beneficial for exercise. So in a 0.2g environment you coild wear maybe 300Kg of shielding mass.
Don't forget about inertia. Even in no gravity getting going and stopping in a 300kg suit will not be fun.

Here's an interesting question. Strong magnetic fields will deflect heavy ions or cause them to spiral. Now instead of a uniform external magnetic field, Imagine a material with numerous zones of high intensity magnetic fields (passive or active).  A heavy ion forced to follow a longer path will see more of the material. In other words making the material effectively thicker. Can this be done for a spacecraft hull? Can this be scaled down to personal protection?
There are threads on here about protecting Mars colonies with an artificial magnetic field (and some startups claiming to offer the same). It's slightly scifi for now but not impossible, especially when you have ample nuclear power to play with.

With superconductors the required power levels to maintain a high magnetic field strength are quite low, since the losses are fairly small.

Offline Russel

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Thanks Kelvin. Best laugh I've had all day :)

The bulkiness of personal radiation protection is the reason I think its limited to the torso. Just how thick is another interesting question.

In terms of a purely passive suit I wonder what the best materials are. There is probably a need for denser materials.

I get the point about inertia. Perhaps 300Kg is over the top.

On the issue of magnetics. The distinction I'm making is between fields generated in free space and fields generated within an ion absorbing material. The field isn't there to totally deflect the particles but instead to lengthen their path. That means you increase the effective thickness of the material.
« Last Edit: 10/11/2018 04:34 am by Russel »

Offline LMT

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The full paper is here: http://www.pnas.org/content/pnas/early/2018/09/26/1807522115.full.pdf

they hit mice with 10 Sv of heavy ions... This compares unfavorably with the estimated 1 Sv total dose (mostly from protons, not heavy ions) for a 860 day Mars mission...

Looking at their reasoning and method:

Quote
While protons are the major component of space radiation, energetic heavy ions such as 56Fe, 28Si, and 12C contribute significantly toward the dose equivalent, and ∼30% of astronauts’ cells are predicted to be hit by heavy ions during a round trip to Mars...

Since the estimated radiation dose for a 1,000-d Mars mission is about 0.42 Gy (21), with an estimate of an 860-d Mars mission dose equivalent of ∼1.01 Sv (22) so doses of 0.5 Gy or less are more relevant, we have used 0.5 Gy to study IEC migration, which is important for intestinal homeostasis.

Wild-type mice... were irradiated (dose: 0.5 Gy) using a simulated space radiation source at the NASA Space Radiation Laboratory (NSRL), Brookhaven National Laboratory for iron (56Fe; energy: 1,000 MeV per nucleon; LET: 148 keV/μm) irradiation, and a 137Cs source was used for γ-ray (LET: 0.8 keV/μm) whole-body irradiation of mice.

How did you calculate 10x overdose?

Offline LMT

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Personal wearable shielding, probably focused on the torso. The original context was that in a 0.2-0.4g environment, the extra mass is beneficial for exercise. So in a 0.2g environment you coild wear maybe 300Kg of shielding mass.
Don't forget about inertia. Even in no gravity getting going and stopping in a 300kg suit will not be fun.

Here's an interesting question. Strong magnetic fields will deflect heavy ions or cause them to spiral. Now instead of a uniform external magnetic field, Imagine a material with numerous zones of high intensity magnetic fields (passive or active).  A heavy ion forced to follow a longer path will see more of the material. In other words making the material effectively thicker. Can this be done for a spacecraft hull? Can this be scaled down to personal protection?
There are threads on here about protecting Mars colonies with an artificial magnetic field (and some startups claiming to offer the same). It's slightly scifi for now but not impossible, especially when you have ample nuclear power to play with.

With superconductors the required power levels to maintain a high magnetic field strength are quite low, since the losses are fairly small.

Yes, negligible losses in, say, our suggested superconducting cables for the Omaha Field design.  Most power goes to refrigeration of coolant, as in Motojima & Yanagi 2008.  In our case, < 80 kW to shield the floor of a 9 km crater.

Refs.

Motojima, O., & Yanagi, N. (2008). Feasibility of Artificial Geomagnetic Field Generation by a Superconducting Ring Network. Research Report NIFS-Series.

Offline LMT

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On the issue of magnetics. The distinction I'm making is between fields generated in free space and fields generated within an ion absorbing material. The field isn't there to totally deflect the particles but instead to lengthen their path. That means you increase the effective thickness of the material.

Unfortunately, a GCR proton deflects at kilometer scale in a superconductor's strong magnetostatic field.  It's a leisurely turn, even with field exceeding 0.1 T at the cable surface, as below.



[Omaha Field.  9 km crater (red ellipse), field measured 6.5 km above crater rim, 500 MeV proton deflection tracks in black.]

And you don't want that superconducting field generator on your person.  0.1 T is far above the common human safety limit of 5E-4 T.
« Last Edit: 10/12/2018 04:53 am by LMT »

Online Robotbeat

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Humans can be exposed to 0.1 Tesla without any harm. A good neodymium magnet (pretty common nowadays) is like 0.5 Tesla on the surface, and there's no problem. I'd be more concerned with tools and equipment.

But anyway, there are field configurations that null out the field in the center.
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Offline LMT

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Humans can be exposed to 0.1 Tesla without any harm...  I'd be more concerned with tools and equipment.

Hence the safety limit, yes.
« Last Edit: 10/14/2018 12:23 pm by LMT »

Offline LMT

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The full paper is here: http://www.pnas.org/content/pnas/early/2018/09/26/1807522115.full.pdf

they hit mice with 10 Sv of heavy ions... This compares unfavorably with the estimated 1 Sv total dose (mostly from protons, not heavy ions) for a 860 day Mars mission...

Looking at their reasoning and method:

Quote
While protons are the major component of space radiation, energetic heavy ions such as 56Fe, 28Si, and 12C contribute significantly toward the dose equivalent, and ∼30% of astronauts’ cells are predicted to be hit by heavy ions during a round trip to Mars...

Since the estimated radiation dose for a 1,000-d Mars mission is about 0.42 Gy (21), with an estimate of an 860-d Mars mission dose equivalent of ∼1.01 Sv (22) so doses of 0.5 Gy or less are more relevant, we have used 0.5 Gy to study IEC migration, which is important for intestinal homeostasis.

Wild-type mice... were irradiated (dose: 0.5 Gy) using a simulated space radiation source at the NASA Space Radiation Laboratory (NSRL), Brookhaven National Laboratory for iron (56Fe; energy: 1,000 MeV per nucleon; LET: 148 keV/μm) irradiation, and a 137Cs source was used for γ-ray (LET: 0.8 keV/μm) whole-body irradiation of mice.

How did you calculate 10x overdose?

If useful for calcs, NSRL publishes its Beam Ion Species and Energies, including data on each species' energy, LET, range and intensity.  The NSRL simulated SPE beam spectrum is also characterized.

The simulated GCR beam is detailed in Slaba et al. 2015.

Refs.

Slaba, T. C., Blattnig, S. R., Norbury, J. W., Rusek, A., La Tessa, C., & Walker, S. A. (2015). GCR simulator reference field and a spectral approach for laboratory simulation.

Offline ThinkerX

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It does, however, seem to fall in line with a growing body of work that says the space environment is going to be as much as, if not more serious an issue as the actual engineering of a spacecraft.
It says '“With the current shielding technology, it is difficult to protect astronauts from the adverse effects of heavy ion radiation." - this does however get easier if you throw mass at it.
A half meter of polythene or methane, or a bit more than a meter of water, for example, cuts your GCR dose to a third.
This is quite a large a lot of mass, but in the further term, in the context of cyclers, and large transfer spacecraft >>8m in diameter, it gets less important.
An 8m*8m inside rounded cylinder, 50cm deep, filled with water, about halves GCR for a 100 ton cost, or several more launches of propellant on BFR.

Also, arguments about GCR being dangerous have to be looked at in the context of ISS astronauts.
They are minimally shielded against GCR, and do not, as a group, have huge health impacts that lead to the worst outcomes.
(May they be subtly affected, sure)

Put the living quarters inside the fuel tank?  most propulsion schemes seem to involve substantial amounts of fuel.

Offline Russel

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Does anyone know roughly what the radius of curvature is for heavy ions (and protons) in a much stronger field - say 5 Tesla?

Offline Dalhousie

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There is a whole cottage industry involving this form of study.  They feature giving massive doses (many times what astronauts would experience) in a very short period of time (minutes as opposed to years).  They typically use the wrong units (Grays rather than Sieverts).  They generally unrealistic Mars mission radiation doses.  The results are always of the "we exposed mice to massive radiation doses over short periods of time surprise!  They don't do very well.   

I struggle to see how this work can get funded, pass ethical or peer review.  It's relevance and usefulness appears zero.
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Offline envy887

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The full paper is here: http://www.pnas.org/content/pnas/early/2018/09/26/1807522115.full.pdf

they hit mice with 10 Sv of heavy ions... This compares unfavorably with the estimated 1 Sv total dose (mostly from protons, not heavy ions) for a 860 day Mars mission...

Looking at their reasoning and method:

Quote
While protons are the major component of space radiation, energetic heavy ions such as 56Fe, 28Si, and 12C contribute significantly toward the dose equivalent, and ∼30% of astronauts’ cells are predicted to be hit by heavy ions during a round trip to Mars...

Since the estimated radiation dose for a 1,000-d Mars mission is about 0.42 Gy (21), with an estimate of an 860-d Mars mission dose equivalent of ∼1.01 Sv (22) so doses of 0.5 Gy or less are more relevant, we have used 0.5 Gy to study IEC migration, which is important for intestinal homeostasis.

Wild-type mice... were irradiated (dose: 0.5 Gy) using a simulated space radiation source at the NASA Space Radiation Laboratory (NSRL), Brookhaven National Laboratory for iron (56Fe; energy: 1,000 MeV per nucleon; LET: 148 keV/μm) irradiation, and a 137Cs source was used for γ-ray (LET: 0.8 keV/μm) whole-body irradiation of mice.

How did you calculate 10x overdose?

0.5 Gy of 56Fe is 10 Sv, already more than 10x the estimated biological effective dose of ~1 Sv for a 860-day Mars mission.

Factor in shielding, dose rate, dose mix, etc. and this has no basis in reality for an actual Mars mission.

Offline Dalhousie

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The full paper is here: http://www.pnas.org/content/pnas/early/2018/09/26/1807522115.full.pdf

they hit mice with 10 Sv of heavy ions... This compares unfavorably with the estimated 1 Sv total dose (mostly from protons, not heavy ions) for a 860 day Mars mission...

Looking at their reasoning and method:

Quote
While protons are the major component of space radiation, energetic heavy ions such as 56Fe, 28Si, and 12C contribute significantly toward the dose equivalent, and ∼30% of astronauts’ cells are predicted to be hit by heavy ions during a round trip to Mars...

Since the estimated radiation dose for a 1,000-d Mars mission is about 0.42 Gy (21), with an estimate of an 860-d Mars mission dose equivalent of ∼1.01 Sv (22) so doses of 0.5 Gy or less are more relevant, we have used 0.5 Gy to study IEC migration, which is important for intestinal homeostasis.

Wild-type mice... were irradiated (dose: 0.5 Gy) using a simulated space radiation source at the NASA Space Radiation Laboratory (NSRL), Brookhaven National Laboratory for iron (56Fe; energy: 1,000 MeV per nucleon; LET: 148 keV/μm) irradiation, and a 137Cs source was used for γ-ray (LET: 0.8 keV/μm) whole-body irradiation of mice.

How did you calculate 10x overdose?

0.5 Gy of 56Fe is 10 Sv, already more than 10x the estimated biological effective dose of ~1 Sv for a 860-day Mars mission.

Factor in shielding, dose rate, dose mix, etc. and this has no basis in reality for an actual Mars mission.

Even that 1 Sv dose is based on  wrong assumptions.
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Online Slarty1080

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Has anyone ever actualy tried to simulate the likely radiation environment of an actual Mars mission?
The first words spoken on Mars: "Humans have been wondering if there was any life on the planet Mars for many decades … well ... there is now!"

Online guckyfan

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Has anyone ever actualy tried to simulate the likely radiation environment of an actual Mars mission?

Why would they? Not scary enough.

Offline DaveJes1979

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Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #25 on: 11/28/2018 10:41 pm »
The results from experimenting on mice with heavy ion galactic cosmic rays (GCR) aren't promising, their GI tracts took a heavy toll.  Note, this is not electromagnetic radiation, but atomic nuclei traveling very fast:

https://www.space.com/42018-deep-space-travel-damage-astronauts-gut.html

See also: 

https://www.extremetech.com/extreme/278004-deep-space-exploration-could-permanently-damage-human-gi-tracts
https://phys.org/news/2018-10-animal-deep-space-significantly-gi.html
http://blogs.discovermagazine.com/d-brief/2018/10/01/deep-space-could-seriously-damage-astronaut-gi-tracts-a-new-study-finds/#.W_8k3zCIZaQ
https://www.sciencedaily.com/releases/2018/10/181002102727.htm

The fact is that before we send people to Mars on a ship that can't direct-abort, someone should do a near-earth mission to establish with certainty the actual health impacts of human travel outside of the earth's magnetosphere for 6+ months.
« Last Edit: 11/28/2018 10:42 pm by DaveJes1979 »

Offline ncb1397

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Offline DaveJes1979

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #27 on: 11/28/2018 10:58 pm »
It is hard to read in to such a small sample size as the Apollo astronauts, and their deep space exposure was only on the order of a few days.  That simply isn't enough time.  It could simply be that some of them ate more carbs than others!

I've also heard that the Apollo missions were timed for both low solar activity and for periods where earth's magnetosphere provided some protection, although I can't find a source to confirm this.
« Last Edit: 11/28/2018 11:12 pm by DaveJes1979 »

Offline ncb1397

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #28 on: 11/28/2018 11:17 pm »
Hard to read in to such a small sample size, and their deep space exposure was only on the order of a few days.  That simply isn't enough time.  It could simply be that some of them ate more carbs than others!

If you have a bigger sample of people exposed to a deep space environment, let me know.

Put together this list of those who traveled to "deep space" and have since died with cause noted if under 80.

John Young - 87
Gene Cernan - 82
Neil Armstrong - 82
Pete Conrad - 69 (motorcycle accident...presumably not Apollo related unless related to brain degeneration)
Richard Gordon - 88
Alan Bean - 86
Jack Swigert - 51 (cancer)
Alan Shepard - 74 (leukemia)
Stuart Roosa - 61 (pancreatitis
Edgar Mitchell - 85
James Irwin - 61 (heart attack)
Ronald Evans -56(heart attack)

average life expectancy -  73.5 years
average male life expectancy in U.S. - 76.5 years

Apparently, a trip measured in days/weeks isn't a huge problem in terms of living a roughly normal length life afterwards.

edit:and just for fun, those that have made a trip into deep space twice:
John Young - 87
Gene Cernan - 82
average: 84.5
« Last Edit: 11/28/2018 11:28 pm by ncb1397 »

Offline ChrisWilson68

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #29 on: 11/28/2018 11:28 pm »
This is an old story, and it was already discussed in these forums when the story first came out.

The bottom line conclusion was that the study isn't very convincing.  It's just too different from reality to be able to draw any conclusions about effects from space travel and/or Mars life from this study.

Meanwhile, numerous other studies have provided evidence that there is some small amount of increased risk of death from the dosage Mars travelers would get, but not a huge amount.  The other risks of space travel -- the space ship blowing up, the airlock leaking, etc -- are likely far higher than the risks from radiation.

The exception is is there's a coronal mass ejection from the sun that happens to be directed right at the space travelers.  That can be fatal.  For that, a storm shelter is needed to avoid serious radiation injury.

Offline eric z

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #30 on: 11/28/2018 11:28 pm »
 There is an obvious answer to this problem: Get there a helluva lot faster!

Offline ChrisWilson68

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #31 on: 11/28/2018 11:31 pm »
It's important to note that on Earth we are not immune to Galactic Cosmic Rays.  Some portion of them hit the surface of the Earth.  Air crews on airliners have significantly higher dosage of such GCR strikes than the general population.  So we have a lot of good data to go on about how much GCRs affect human health.

Offline DaveJes1979

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #32 on: 11/28/2018 11:42 pm »
This is an old story, and it was already discussed in these forums when the story first came out.

It is not old, it is from October.

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Meanwhile, numerous other studies have provided evidence that there is some small amount of increased risk of death from the dosage Mars travelers would get, but not a huge amount.  The other risks of space travel -- the space ship blowing up, the airlock leaking, etc -- are likely far higher than the risks from radiation.

Most of these focus on electromagnetic radiation or protons, but not the heavy ions that exist in our solar system independent of solar activity.

Airliners and astronauts in LEO are well within earth's magnetosphere, so their GCR doses are quite small.

It would be unethical to send people to Mars until a near-earth research mission is conducted on humans- or at least some primates.  It might be difficult to find volunteers to be the guinea pigs.

Offline DaveJes1979

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #33 on: 11/29/2018 12:15 am »
There is an obvious answer to this problem: Get there a helluva lot faster!

Sadly, not practical with chemical rockets.  As Robert Zubrin points out, you really don't want to go any faster than a 6 month transit to Mars anyway, or you lose your free return trajectory.

Also, your worries have not ended when you get to Mars, because Mars has no magnetosphere along with a very thin atmosphere.
« Last Edit: 11/29/2018 12:16 am by DaveJes1979 »

Offline ChrisWilson68

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #34 on: 11/29/2018 12:32 am »
This is an old story, and it was already discussed in these forums when the story first came out.

It is not old, it is from October.

Yeah, the press release was October 1.  Seven weeks ago.  Which is old, in the context I used the term -- old enough that it was discussed here and the discussion ended weeks ago.

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Meanwhile, numerous other studies have provided evidence that there is some small amount of increased risk of death from the dosage Mars travelers would get, but not a huge amount.  The other risks of space travel -- the space ship blowing up, the airlock leaking, etc -- are likely far higher than the risks from radiation.

Most of these focus on electromagnetic radiation or protons, but not the heavy ions that exist in our solar system independent of solar activity.

No, I'm talking specifically about GCRs.  There have been studies of their effects, and those are the studies I'm talking about.

Airliners and astronauts in LEO are well within earth's magnetosphere, so their GCR doses are quite small.

It doesn't matter if they're small.  They're an order of magnitude greater at the altitude airliners use than at the surface of the Earth, which is enough to be able to detect the health effects, if there are any.

It would be unethical to send people to Mars until a near-earth research mission is conducted on humans- or at least some primates.  It might be difficult to find volunteers to be the guinea pigs.

No, not unethical if they volunteer.  And plenty of people are willing to volunteer.

Offline ChrisWilson68

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #35 on: 11/29/2018 12:35 am »
Here's the original thread on this study:

https://forum.nasaspaceflight.com/index.php?topic=46477.0

Note that the discussion started October 1, the day the press release came out.

Mods: can we merge this thread with the original one?

Offline DaveJes1979

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #36 on: 11/29/2018 12:43 am »
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No, I'm talking specifically about GCRs.  There have been studies of their effects, and those are the studies I'm talking about.

Unless those studies also irradiated mammals with iron nuclei and examined effects on the GI tract it is hard to imagine how they would overturn these results.  This research was done because it, in fact, has not been done before.

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It doesn't matter if they're small.  They're an order of magnitude greater at the altitude airliners use than at the surface of the Earth, which is enough to be able to detect the health effects, if there are any.

This is simply false.  You can't simply extrapolate across environments that are orders of magnitude difference in dosage.

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No, not unethical if they volunteer.  And plenty of people are willing to volunteer.

I'm not willing to go as far as to say that the voluntarism of the customer is ethically exculpatory for the carrier.  The carrier is responsible to do some due diligence research.

Offline envy887

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #37 on: 11/29/2018 12:50 am »
As Robert Zubrin points out, you really don't want to go any faster than a 6 month transit to Mars anyway, or you lose your free return trajectory.

There aren't many situations where a free return from Mars is useful. If you aren't able to either land or perform a propulsive Earth injection at Mars, you also won't be able to land or propulsively capture when you get back to Earth.

In most cases, if you have an emergency post-TMI, the fastest way to get help will be to go to Mars, not take an extra 8-month trip to swing back to Earth.

Offline DaveJes1979

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It wouldn't be all that hard to send a Starliner or Dragon with a small habitat/mission module to a Lagrange point outside of earth's magnetosphere for 6 months or so with a handful of astronauts. If anyone's health declines too rapidly, they can come home anytime.

Forget the ethics, it makes business sense to retire this risk before spending billions developing and building a Mars spacecraft.

Offline freddo411

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Are moderate levels of radiation problematic?  Maybe not so much.

Here's one example from Wikipedia:
https://en.wikipedia.org/wiki/Radiation_hormesis#Effects_of_no_radiation

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Very high natural background gamma radiation cancer rates at Kerala, India
Kerala's monazite sand (containing a third of the world's economically recoverable reserves of radioactive thorium) emits about 8 micro Sieverts per hour of gamma radiation, 80 times the dose rate equivalent in London, but a decade long study of 69,985 residents published in Health Physics in 2009: "showed no excess cancer risk from exposure to terrestrial gamma radiation. The excess relative risk of cancer excluding leukemia was estimated to be -0.13 Gy_1 (95% CI: -0.58, 0.46)", indicating no statistically significant positive or negative relationship between background radiation levels and cancer risk in this sample.[45]


Offline DaveJes1979

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Again, electromagnetic radiation probably isn't much of a risk. Even proton radiation, up to a point. We are talking about heavy ions...the nuclei of iron and other heavy elements.

Offline ChrisWilson68

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #41 on: 11/29/2018 10:54 am »
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No, I'm talking specifically about GCRs.  There have been studies of their effects, and those are the studies I'm talking about.

Unless those studies also irradiated mammals with iron nuclei and examined effects on the GI tract it is hard to imagine how they would overturn these results.  This research was done because it, in fact, has not been done before.

No, this particular study hadn't been done before.  Much more useful studies were done.  Studies of what actually happens to human beings who are exposed to more GCRs than other human beings.

The answer is: not much.

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It doesn't matter if they're small.  They're an order of magnitude greater at the altitude airliners use than at the surface of the Earth, which is enough to be able to detect the health effects, if there are any.

This is simply false.  You can't simply extrapolate across environments that are orders of magnitude difference in dosage.

It's not orders of magnitude different.

If you'll look at the older thread on this very paper that I linked to upthread, you'll see some numbers.  The total expected dosage from GCRs on an 860 day Mars mission is about 1 Sv.  Airline workers get 3 mSv exposure per year.  So in a 40 year career, an airline worker would get 0.12 Sv of exposure.

The difference between 0.12 Sv and 1 Sv isn't too great that we wouldn't expect to see the trends in airline worker health if there were to be a major health risk for the Mars mission.  It's less than one order of magnitude.

Compare that to the study this thread is about:

1. Mice, not humans
2. 10 Sv versus 1 Sv, so ten times the dosage.
3. The study did all the exposure over a very short period instead of evenly spreading it over several years, as the Mars mission would be.
4. The study used all heavy nuclei, while in real life the 1 Sv GCR dosage expected of a Mars missions would be mostly single protons.

All in all, the study of air crews is much more compelling than the October mouse study.

http://hpschapters.org/njhps/ShonkaAircrewRadExposure.pdf

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No, not unethical if they volunteer.  And plenty of people are willing to volunteer.

I'm not willing to go as far as to say that the voluntarism of the customer is ethically exculpatory for the carrier.  The carrier is responsible to do some due diligence research.

Ethics is fundamentally subjective.  In my ethical system, if people give informed consent, it's ethical.  It would, in fact, be unethical to me to have a company second-guess the customer and refuse to provide a service on its own judgement about whether it's good for the customer.  The customer should get to decide that.  Companies shouldn't be second-guessing what the customer wants.  If the company doesn't want to provide the service for some other reason, that's fine, but second-guessing the customer and thinking they are refusing service for the customer's benefit when that's not what the customer would choose is unethical.
« Last Edit: 11/29/2018 10:57 am by ChrisWilson68 »

Offline DaveJes1979

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #42 on: 11/29/2018 05:04 pm »
  Much more useful studies were done.  Studies of what actually happens to human beings who are exposed to more GCRs than other human beings.

Not useful.  We don't know what the curve looks like at higher doses unless we test at higher doses.  Toxicology curves are not linear or even continuous.

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It's not orders of magnitude different.

If you'll look at the older thread on this very paper that I linked to upthread, you'll see some numbers.  The total expected dosage from GCRs on an 860 day Mars mission is about 1 Sv.  Airline workers get 3 mSv exposure per year.  So in a 40 year career, an airline worker would get 0.12 Sv of exposure.

So it is just shy of an order of magnitude of difference.  And wildly differing exposure periods, to boot.

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1. Mice, not humans

Mice GI tracts are a decent analogue for humans.  It is not conclusive, but suggestive.  It should throw a red flag up.

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2. 10 Sv versus 1 Sv, so ten times the dosage.
Not sure where this comes from.  The study says "Since the estimated radiation dose for a 1,000-d Mars mission is about 0.42 Gy (21), with an estimate of an 860-d Mars mission dose equivalent of ∼1.01 Sv (22) so doses of 0.5 Gy or less are more relevant, we have used 0.5 Gy to study IEC migration"

Also worth keeping in mind that the Curiosity rover's measured radiation is going to be about the minimum of GCR bombardment given the solar cycle at the time.

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3. The study did all the exposure over a very short period instead of evenly spreading it over several years, as the Mars mission would be.
Yes, this is a problem, the result of the practical constraints of the experiment.

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4. The study used all heavy nuclei, while in real life the 1 Sv GCR dosage expected of a Mars missions would be mostly single protons.

Correct, that is a problem.  We don't know what the full GCR radiation cocktail will do until we subject humans to the actual deep space environment.

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In my ethical system, if people give informed consent, it's ethical.  It would, in fact, be unethical to me to have a company second-guess the customer and refuse to provide a service on its own judgement about whether it's good for the customer.

That can be true up to a point.  It isn't like carriers are obliged to fly into a volcano if the passengers demand it.
« Last Edit: 11/29/2018 05:40 pm by DaveJes1979 »

Online Slarty1080

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My 2cent summary: there have been some studies that raise some concerns, but the data is far from ideal and more research is required to draw any firm conclusions. This research could most profitably be achieved with a volunteer crew and multi-month stay in near Earth space where a rapid return to Earth would be possible. Arguments about the ethics of sending crews on dangerous missions are at best paternalistic when we are talking about well informed and high educated volunteers. However companies might still wish not to offer such missions on the basis of risk to the company image if something goes wrong.
The first words spoken on Mars: "Humans have been wondering if there was any life on the planet Mars for many decades … well ... there is now!"

Offline RonM

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #44 on: 11/29/2018 05:40 pm »
3. The study did all the exposure over a very short period instead of evenly spreading it over several years, as the Mars mission would be.
Yes, this is a problem, the result of the practical constraints of the experiment.

Since mice don't live long, spreading out the exposure over many years is impossible. However, a massive dose over a very short time period neglects cells ability to repair radiation damage. That's why I don't trust studies like this. It would be better to give a realistic dose over six months to simulate a fast trip to Mars.

Offline envy887

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Re: Galactic Cosmic Rays - A Deep Space Travel Show-Stopper?
« Reply #45 on: 11/29/2018 07:46 pm »
3. The study did all the exposure over a very short period instead of evenly spreading it over several years, as the Mars mission would be.
Yes, this is a problem, the result of the practical constraints of the experiment.

Since mice don't live long, spreading out the exposure over many years is impossible. However, a massive dose over a very short time period neglects cells ability to repair radiation damage. That's why I don't trust studies like this. It would be better to give a realistic dose over six months to simulate a fast trip to Mars.

Also, the entire dose was 56Fe, while more than 98% of GCR is protons and alpha particles (H and He nuclei). 56Fe (Z=26) makes up less than 0.1% of the spectrum, as shown in the attached graph. And it is the heaviest significant component of GCR, and thus has the highest biological effect PER PARTICLE, which is why exaggerating the number of particles of 56Fe has a greatly disproportionate effect on the study results.

Here is an article that points out many of the shortcomings current studies, and includes the GCR spectrum plot:

https://www.nature.com/articles/s41526-018-0043-2
« Last Edit: 11/29/2018 07:48 pm by envy887 »

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