Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jack_ on 20/03/2019 12:10:48
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Gary has been watching space videos online and wants to know:
How are space capsules designed to be so thin?
With some space capsules being no more then a tin can or foil thickness in places, how do they hold their shape structurally given differences in pressure inside and outside the capsule?
And how is this able to shield the crew in the capsules from the cosmic rays (van Allan belts and charged partials from the sun) with no lead shielding of at least 7 inches in thickness?
What's going on, do you know how this works?
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For spacecraft with thin walls like that ( the Lunar landing module for example) the interior pressure is only a fraction of 1 Atm. You can get away with that as long as the percentage of oxygen is higher. (it is the partial pressure of oxygen that matters, not the total air pressure.)
The only craft that would have even had to worry about the Van Allen belt were the Apollo missions. And they were put on a trajectory that took avoided the worst radiation ( the belts are somewhat torus shaped, so you can "go around" them.
While the astronauts were exposed to some higher levels of radiation, It wasn't so intense as to be fatal or give them radiation sickness or anything. It likely did raise their chances of developing cancer later in their lives. The radiation risk is a bit overblown. Barring a major solar event, They didn't get that much radiation over the short period of the mission. Most of the danger from radiation in space comes from long term exposure.
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Astronaut radiation doses on the ISS are typically 5 - 10 times the annual dose limit for a radiation worker, or about 5 times the annual background dose in some of the more radioactive parts of the world. At 2 sievert received over a 6 - 12 month period, we would expect to find around 10% excess cancers in the irradiated population. There is no doubt that space flight is a hazardous occupation and extended work in space ought possibly to be restricted to the over-60's on radiological grounds, but the hazards of decompression, bone demineralisation, or pyrolysis before launch or on re-entry, are demonstrably more significant.