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View Diary: On Mars: It is Not Yet Time for Humans to Go (98 comments)

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  •  You cannot be more incorrect (3+ / 0-)
    Recommended by:
    polecat, LeftOfYou, lehman scott

    about the technology to go to mars.

    yes, we can send a rocket, and yes, we can put people in the container for the trip, yes we can provide food and water and oxygen for the trip and we can remove/reprocess the materials.

    However,

    We do not yet know how to prevent terminal radiation poisoning from solar wind particles in the 1.5 year voyage that the trip would take.

    Shielding is too heavy and we cannot generate a magnetic field strong enough to contain the vessel.

    The Mars rover Curiosity has allowed us to finally calculate an average dose over the 180-day journey. It is approximately 300 mSv, the equivalent of 24 CAT scans. In just getting to Mars, an explorer would be exposed to more than 15 times an annual radiation limit for a worker in a nuclear power plant.

    Radiation Rules Manned Mars Exploration

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    by New Minas on Thu Jun 05, 2014 at 10:52:47 AM PDT

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    •  here is the video link (2+ / 0-)
      Recommended by:
      LeftOfYou, lehman scott

      Be the change that you want to see in the world

      by New Minas on Thu Jun 05, 2014 at 10:58:25 AM PDT

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    •  Not all cosmic radiation is magnetic -- even if we (2+ / 0-)
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      LeftOfYou, lehman scott

      could make strong enough magnetic fields, how do you stop a gamma photon or neutron?

      Happy little moron, Lucky little man.
      I wish I was a moron, MY GOD, Perhaps I am!
      —Spike Milligan

      by polecat on Thu Jun 05, 2014 at 12:39:35 PM PDT

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    •  Science correction (2+ / 0-)
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      lehman scott, kalmoth

      300mSv will not produce terminal radiation poisoning (and neither will 600mSv). At most it may increase your cancer risk 10 or more years in the future. 300mSv over 180 days may produce no effect at all - low dose rates like this have no evidence one way or the other.

      This is not a sig-line.

      by Joffan on Thu Jun 05, 2014 at 01:14:16 PM PDT

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      •  That was (1+ / 0-)
        Recommended by:
        lehman scott

        one way. . .

        so multiply it by 2 for the round trip.

        plus radiation exposure while on the surface (solar radiation can be potentially more damaging)

        So about 30-35 times the lifetime dose allowed for a nuclear worker.

        though you are right, not a 50% terminal exposure, We know that 100mSv per year shows an increased cancer risk.

        they will likely get 150% of that exposure for 3 full years.

        Be the change that you want to see in the world

        by New Minas on Thu Jun 05, 2014 at 02:44:06 PM PDT

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        •  100mSv as an acute dose (2+ / 0-)
          Recommended by:
          kalmoth, New Minas

          is around the lowest we know about as something that increases your cancer risk. The "per year" usage is just a regulatory convenience, not a fact.

          Incidentally, the worker lifetime dose limit recommended by the ICRP is 1000mSv (additional to  local background). And generally speaking these regulatory thresholds are set to be safe by a considerable margin, not to be at the health limit.

          100mSv as a chronic dose spread over two months (say 12mSv/week) actually has no data to indicate increased risk. Medical use of (higher-level) radiation suggests that the adult body recovers from low-dose-rate radiation without significant changes to cancer risk.

          For surface activities, I certainly expect that the Arean pioneers would have (or quickly make) shelter facilities that would avoid significant solar storm issues.

          This is not a sig-line.

          by Joffan on Thu Jun 05, 2014 at 03:23:17 PM PDT

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          •  in the article they said that (0+ / 0-)

            the 1-way exposure to cosmic radiation was 15 times the annual worker limit.  THis would be 15 times 5 rem or 75 rem.  The 50% mortality exposure for single dose radiation is 1000 rem.  the idea that someone would travel for 3 straight years in spase, receiving a total of 150 rem of radiation exposure in transit, plus the potential for massive solar flare radiation from heavy ion particles in space and on the surface of mars, makes the risk of exposure far too great.

            these threshold limits are for single exposure but for a long-term chronic exposure at these levels, it is clear that the effects are significant

            THRESHOLD EFFECTS

            High doses of radiation received in a short period of time result in effects that are noticeable soon after exposure. These are known as threshold effects. A certain dose range must be exceeded before they can occur. These effects include radiation sickness and death, cataracts, sterility, loss of hair, reduced thyroid function and skin radiation burns. The severity of these effects increases with the size of the dose.

            Radiation Sickness - At doses of about 60 rem, 5% of exposed individuals may vomit. This increases to about 50% at 200 rem. At doses between 300 and 400 rem and without medical treatment, there is a 50% chance that a person will die within 60 days. With proper medical care, however, some people exposed to 1,000 rem could survive.

            Cataracts - A single exposure between 200 and 500 rem could cause cataracts (clouding of the lens of the eye). If an exposure took place over a period of months, however, it would take about a total of 1,000 rem to produce a cataract.

            Sterility - In men, a single dose of 15 rem can cause temporary sterility, and a single dose between 400 and 500 rem can cause permanent sterility. In women, a total dose of 400 rem received over two or three exposures has been known to cause permanent sterility.

            http://www.health.ny.gov/...

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            by New Minas on Fri Jun 06, 2014 at 10:36:25 AM PDT

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            •  It's stupid to guess dose when they give you it (0+ / 0-)

              ... - it's 300mSv for the one-way trip. So forget the bogus multiples of regulatory limits - they are not interesting and not useful, and much more likely to be journalistic error or hyperventilation.

              It's also pointless to talk about travelling in space for 3 years when the combined transit times - there and back - is about 1 year.

              These are known things from the article you were citing, about 3 steps up the chain: http://www.space.com/...

              We also know that the doses we are talking about do NOT get into the scare-value symptoms you quote from the NY health site.  So just drop the idiocy and debate the reality.

              There's no radiation poisoning involved. The legitimate question worth talking about is - is there any long term effect on cancer susceptibility?

              My evaluation: no, there's no effect. The dose-rate is too low to get ahead of the body's usual repair mechanisms that cope with oxidative damage every day of your life.

              This is not a sig-line.

              by Joffan on Fri Jun 06, 2014 at 01:08:52 PM PDT

              [ Parent ]

              •  These are very high energy gammas (0+ / 0-)

                and our ability to shield from high speed iron ions from the solar wind is not perfect, those particles are intensely destructive to human tissue.

                The current NASA maximum mission dose is 100 rem per mission.

                I know you really like to believe what you think and it is hard not to assert what you want to believe but if you do that in the face of proof of your being incorrect, you are only a disservice to yourself and those around you.

                title of the video, radiation will kill mars astronauts

                Be the change that you want to see in the world

                by New Minas on Fri Jun 06, 2014 at 06:01:16 PM PDT

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                •  Boring (0+ / 0-)
                  I know you really like to believe what you think and it is hard not to assert what you want to believe but if you do that in the face of proof of your being incorrect, you are only a disservice to yourself and those around you.
                  ... so why do you do it?

                  100 rem is 1000mSv. So the stated dose of 300mSv is well below that. That's the part we can't shield against, so why bother talking about being able to shield against it?

                  The energy of the radiation is factored into the sievert ( or rem) calculation. So it is dishonest to try to count that energy twice, as you appear to be attempting here.

                  And no. The title of the video is the question "Will Radiation kill Mars Astronauts?" And it's intentionally dramatic and provocative, omitting any of the useful numbers that we have already been over.

                  This is not a sig-line.

                  by Joffan on Fri Jun 06, 2014 at 10:01:56 PM PDT

                  [ Parent ]

                  •  "don't stop believing!!!" (0+ / 0-)
                    Long-term population studies have shown exposure to radiation increases a person's lifetime cancer risk. Exposure to a dose of 1,000 millisieverts is associated with a 5 percent increase in risk for developing fatal cancer. NASA's current career limit for increased risk for its astronauts currently operating in low-Earth orbit is 3 percent.

                    http://www.jpl.nasa.gov/...

                    so lets assume that for the honor of being on mars they want to risk a 5% terminal cancer in their lifetimes.
                    “The RAD data show an average GCR dose equivalent rate of 1.8 millisieverts per day in cruise.

                    The total during just the transit phases of a Mars mission would be approximately 0.66 Sv for a round trip with current propulsion systems

                    http://www.astrobio.net/...

                    So, the trip to mars and back is 660 mSv and that is with very low solar activity (the article says 5% of total dose from solar radiation), the potential for a massive solar flare and a greatly exceeded whole body dose from solar energy during flight must be included in the analysis.

                    during a 150 day surface mission the cosmic ray exposure is .67mSv per day.  so add another 100 mSv for exposure during this period from cosmic radiation

                    so total cosmic radiation source during trip is 760 mSv.

                    in addition:

                    But Mars' radiation environment is dynamic, so Curiosity's measurements thus far should not be viewed as the final word, Hassler stressed. For example, RAD's data have been gathered near the peak of the sun's 11-year activity cycle, a time when the GCR flux is relatively low (because solar plasma tends to scatter galactic cosmic rays).

                    http://www.space.com/...

                    So 760 mSv is a minimum for cosmic radiation (and that is with only 150 days on the surface.  current mission specs hold 350-500 days on the surface.

                    Now, after that we must include GCM induced thermal neutrons on the surface of mars:  http://onlinelibrary.wiley.com/...

                    We still don't know what the potential energy deposition will be from these sources:  but it is more than without them.

                    finally, the solar energetic particles while on the surface of mars is very high,

                    The diagram indicates a main radiation exposure of 20mrad/d = 1.7 Gy/a. JPL reported that MARIE-measured radiation levels were two to three times greater than at the International Space Station (which is 100-200mSv/a).[2] Levels at the Martian surface might be closer to the level at the ISS due to atmospheric shielding -- ignoring the effect of thermal neutrons induced by GCR. Average in-orbit doses were about 400-500mSv/a. However occasional solar proton events (SPEs) produce a hundred and more times higher doses, see diagram above. SPEs were observed by MARIE that were not observed by sensors near Earth, confirming that SPEs are directional.
                    so 760 mSv, plus the potential of high energy neutron spikes from the sun at 100-150 mSv during the trip with the potential for much greater incident radiation during solar flare activity, and then include the thermal neutron flux on the surface of mars from GCM and you are well exceeding the 1,000 mSv limit that is already 25% more than the current low earth mission limit established by NASA and would lead to a 5% risk for terminal cancer.

                    Be the change that you want to see in the world

                    by New Minas on Sat Jun 07, 2014 at 09:31:04 AM PDT

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    •  I am sorry, my friend... (1+ / 0-)
      Recommended by:
      Joffan

      but in all likelihood, I have forgotten more about the subject than what most people know. Mars travel (nuclear-powered) was already perfectly viable in the 1970s. What was (and is) lacking is not the technology, but the will. And you are not helping.

      •  apparently you have (0+ / 0-)

        forgotten more than you know.
        Nasa says the radiation is preventative, the linked video from space.com says that we are needing new technological developments to make the trip feasible.  

        I know you really like to believe what you think and it is hard not to assert what you want to believe but if you do that in the face of proof of your being incorrect, you are only a disservice to yourself and those around you.

        title of the video, radiation will kill mars astronauts

        Be the change that you want to see in the world

        by New Minas on Fri Jun 06, 2014 at 05:59:55 PM PDT

        [ Parent ]

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