Radiation Protection Today Winter 2021 - Page 12

there are many variables that make the estimate imprecise . A permanent base on Mars would result in those who staff it getting about 200 mSv per year . Recent measurements on the surface of the Moon have shown dose rates of 0.5 Sv per year . Of course , if there were an extreme solar event during this period , significantly higher doses could be received .

NASA is acutely aware of how different the radiation fields are when compared to those for which we have developed our system of radiological protection . The epidemiological studies on which we base our calculations of radiation risk do not include fields of this type for chronic exposures . This is why the International Commission on Radiological Protection Publication 123 deals specifically with how astronaut exposures should be determined . There is also much study of noncancer effects such as brain function and cataracts , which could present high risks during long missions . It is possible that we will see effects in astronauts not seen in radiation workers who should never receive such large doses from fields of this type . Though for the foreseeable future , the cohort of astronauts will remain too small to provide statistically robust analysis .
Is there anything that can be done to reduce the doses ? Additional shielding tends to mean a thicker , heavier hull for the spacecraft . This may sound as though it would help , but whilst it attenuates the incident radiation a little , it also tends to increase the intensity of the secondary radiation . There are also consequential risks and costs associated with getting the extra material into space , as well as to the destination and back . Magnetic shields have been proposed : these would deflect the incident charged particle field away from impacting the spacecraft , but these seem to have fallen out of fashion . A water filled garment , using the crew ' s drinking water , to wear during periods of increased solar activity has been demonstrated on-board the ISS . More unlikely is the proposal to use a self-replicating radiation-shield for human deep-space exploration based on
MATROSHKA located on the outside of the ISS to measure doses to astronauts on space walks .
radiotrophic fungi : fungus that feeds off radiation and produces a shield you can grow and eat .
Reducing doses to astronauts relies on shortening mission times and employing shielding where it is possible . Studies are also looking at potential enhancements to diet and drugs that could mitigate against the effects of radiation . The next minimumenergy launch date for a mission to Mars is in 2033 , which does not give much time for preparation . Prior to that , NASA plans to establish Artemis Base Camp on the Moon from 2025 as part of its Mars mission preparations . Whenever the manned Mars mission is attempted , it is likely that understanding will have advanced , but also that high radiation doses will have to be tolerated as a part of the overall risk assessment .
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