Radiation Protection Today Winter 2021 - Page 10

that there were events in the years 774 / 5 and 993 / 4 that were about 10x larger than anything we have observed directly .

The radiation fields that astronauts are exposed to are complex , high-energy and very dependent on the nature of the space flight and the state of the Sun . Nowadays it seems that you only need to be super-rich to have your own space tourist programme , but
The highest route doses from the UK are about 120 μSv for a return flight to California , whilst long haul air crew can receive as much as 6 mSv per year . Generally , the dose rates are highest for flights that go close to the magnetic poles .
More problematic are the doses for longer , higher missions . Astronauts on the ISS receive about 100 mSv in a 200-day mission , about 40 mSv of which comes from neutrons generated by the craft itself . The doses are dominated by exposures inside the ISS , but on space walks a far higher dose is received from solar protons which would otherwise be attenuated by the hull of the craft . However , whilst the ISS is barely shielded by the Earth ' s atmosphere , it is shielded by the Earth ' s magnetic field and the shielding effect of the Earth itself .
Doses in “ free space ” are higher . Astronauts travelling to the Moon or Mars will be outside the protective influence of the Earth , and even whilst on Mars or the Moon , the absence of a protective magnetic field will lead to higher dose rates . Further , the thin Martian atmosphere and the absence of an these projects are really just getting to the “ edge of space ”: only the upper edge of the atmosphere . Long haul aircraft tend to fly at about 12 km and Concorde used to cruise at 17 km , whilst Virgin Galactic reaches 80 km and Bezos ' Blue Origin 100 km . These altitudes are high enough to see the curvature of the Earth and “ space ” above . But they are low compared to the 400 km at which the International Space Station ( ISS ) orbits , though that needs to be boosted regularly to maintain its altitude , because drag from the extremely thin atmosphere causes it to descend slowly .
Space tourists , I resist calling them astronauts , lose one of our main protections , the atmosphere , which attenuates the incident radiation from space . However , they retain the protective effect of the Earth ' s magnetic field , which deflects away all but the most energetic charged particles at low latitudes . But are their doses per flight high compared to those on long-haul flights ? Probably not , since they are flying well above the Pfotzer dose rate maximum at 20 km , which is caused by the build-up of secondary radiation in the atmosphere . Their flights are also short duration and at low latitude .
SpaceX Falcon 9 Rocket
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