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.
Quote from: WBY1984 on 10/02/2018 06:34 am 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)
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.
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.
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?
Quote from: Russel on 10/10/2018 04:25 amPersonal 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.Quote from: Russel on 10/10/2018 04:25 amHere'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.
The full paper is here: http://www.pnas.org/content/pnas/early/2018/09/26/1807522115.full.pdfthey 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...
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.
Quote from: niwax on 10/10/2018 09:12 amQuote from: Russel on 10/10/2018 04:25 amPersonal 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.Quote from: Russel on 10/10/2018 04:25 amHere'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.
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.
Humans can be exposed to 0.1 Tesla without any harm... I'd be more concerned with tools and equipment.
Quote from: envy887 on 10/09/2018 05:40 pmThe full paper is here: http://www.pnas.org/content/pnas/early/2018/09/26/1807522115.full.pdfthey 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:QuoteWhile 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?
Quote from: WBY1984 on 10/02/2018 06:34 am 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)