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Is it true that it is impossible to survive Van Allen Belt radiation? I mean do human die on the spot or latter in their life with cancer?

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    $\begingroup$ That is, without protection? No suit, no ship? So, equivalent radiation in an otherwise hospitable environment. $\endgroup$ – Don Branson Jul 20 '18 at 16:04
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    $\begingroup$ One problem with the big fear of radiation is the large spread of values encountered. (especially with the zoo of radiation-related units... yeah, convert becquerels to sievert, good luck!) Our daily life radiation doses are about a million times weaker than dangerous ones - so if you receive a dose ten thousand the standard, you're still right as rain and can take twenty times as much before you feel a thing. This chart really helps getting the orders of magnitude of radiation encountered. Apollo astronauts received about as much as you get from a chest CT scan. $\endgroup$ – SF. Jul 20 '18 at 18:09
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    $\begingroup$ Staying in the Van Allen belts is a bad thing. But passing through them relatively quickly like the Apollo astronauts did is not a big deal. $\endgroup$ – zeta-band Jul 20 '18 at 18:52
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    $\begingroup$ @JCRM: While the linked question is arguably related, nothing there directly answers this specific question. And I'm not convinced that "question could be related to typical conspiracy theory talking points" == "dupe-close of high-level Apollo conspiracy theory rebuttal". The dupe target is nice to have, but isn't the only way we can handle the penumbra of Apollo functionality questions. $\endgroup$ – Nathan Tuggy Jul 21 '18 at 1:38
  • $\begingroup$ @NathanTuggy I was going to write a meta question about the potential abuse of duping to that question in order to just "throw mud" on other people's questions. I'm glad to see the comment is gone now. $\endgroup$ – uhoh Jul 21 '18 at 12:15
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A satellite shielded by 3 mm of aluminium in an elliptic orbit (200 by 20,000 miles (320 by 32,190 km)) passing the radiation belts will receive about 2,500 rem (25 Sv) per year (for comparison, a full-body dose of 5 Sv is deadly). Almost all radiation will be received while passing the inner belt.[31]

25/365 = .07

5(Sv) / .07 = 71.2

So you have to spend a spit balled 71.2 days (with minimal protection) in the inner belt to receive a potentially lethal dose of radiation.

Bear in mind that's with only 3mm of aluminium shielding. Manned spacecraft have way more protection than that. The more matter radiation has to pass through, the less effective it becomes. So even the atmosphere inside the craft acts as shielding. And indeed proposed procedures for handling radiation spikes in space is to locate to a central most cabin (kinda like waiting out a tornado in a basement).

Going on:

Astronauts' overall exposure was actually dominated by solar particles once outside Earth's magnetic field. The total radiation received by the astronauts varied from mission to mission but was measured to be between 0.16 and 1.14 rads (1.6 and 11.4 mGy), much less than the standard of 5 rem (50 mSv) per year set by the United States Atomic Energy Commission for people who work with radioactivity.

The real reason everyone's concerned about radiation is because of the nasty long term effects it can have. Kind of hard sending your best and brightest out there with the knowledge they can have increased chances of developing cancer and/or having deformed offspring. However, this aspect is still very much under research as environmental/lifestyle aspects seem to have have equal or greater impacts.

A dose of under 100 rad will typically produce no immediate symptoms other than blood changes. 100 to 200 rad delivered to the entire body in less than a day may cause acute radiation syndrome, (ARS) but is usually not fatal. Doses of 200 to 1,000 rad delivered in a few hours will cause serious illness with poor outlook at the upper end of the range. Whole body doses of more than 1,000 rad are almost invariably fatal.

So in one day you need to subject an astronaut to 10 times the upper threshold of radiation exposure encountered by an astronaut over an entire trip. Just to make them sick.

Van Allen Belt

Rads

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  • $\begingroup$ I'd be very surprised if any spacecraft in use today had more than 3mm of hull plating. In some places you get more protection due to other equipment (e.g. the instrument panel), but you also have sections of bare wall. $\endgroup$ – Hobbes Nov 15 '18 at 9:31
  • $\begingroup$ I think "a full-body dose of 5 Sv is deadly" is about radiation sickness from a single dose, suddenly all at once or during a day. That is very different from slower exposure: The radiation kills cells. If these die before others have healed, that's bad. Really bad. A fraction of you dies. Many very small wounds are not a problem. Except when cells get hit but do not die, and end up as cancer. $\endgroup$ – Volker Siegel Nov 25 at 8:25
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No, it is not impossible. 9 Apollo missions sent humans through the Van Allen belts, and the astronauts survived just fine.

The radiation levels in the Van Allen belts are high, about 1000 times higher then normal space. Still, so long as one doesn't stay in that region for a long time, one is perfectly okay.

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    $\begingroup$ And most of the Apollo astronauts died at an old age or are still alive. $\endgroup$ – DarkDust Jul 20 '18 at 16:36
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    $\begingroup$ Worth noting that the Apollo trajectories were designed to avoid the densest parts of the Van Allen belts. In addition, since Apollo hoax conspiracy theorists often use the purported lethality of the Van Allen belts as evidence of hoax, claiming the success of the Apollo missions as evidence that the belts aren’t lethal is likely to be unconvincing to those people. $\endgroup$ – Russell Borogove Jul 21 '18 at 0:19
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    $\begingroup$ @RussellBorogove: nothing will be convincing to those people. $\endgroup$ – Martin Argerami Jul 21 '18 at 9:16
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    $\begingroup$ @Looper: "those days"? You mean the late 60s, ten years after the Explorer satellites measured the radiation? $\endgroup$ – Martin Argerami Jul 21 '18 at 9:20
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    $\begingroup$ The Van Allen belts were discovered by the first American satellite, Explorer 1, in 1958. I think it is pretty fair to say that they had a decent understanding of the belts. $\endgroup$ – PearsonArtPhoto Jul 21 '18 at 11:52

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