Author Topic: NASA & Georgetown University study on Cosmic Ray dangers to space travelers  (Read 5884 times)

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 »

Offline 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.

Online 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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