Is it true that it is impossible to survive Van Allen Belt radiation? I mean do humans die on the spot or later 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. $\endgroup$ Commented Jul 20, 2018 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.
    Commented Jul 20, 2018 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
    Commented Jul 20, 2018 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. $\endgroup$ Commented Jul 21, 2018 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
    Commented Jul 21, 2018 at 12:15

3 Answers 3


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 = 0.07

5(Sv) / 0.07 = 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 3 mm 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


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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
    Commented Nov 15, 2018 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. $\endgroup$ Commented Nov 25, 2019 at 8:25
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    $\begingroup$ As Robert Zubrin has pointed out, if you were to get someone to stop smoking so they could go to Mars, their mortality risk will actually go down. Radiation is a real harm, but it needs to be keep in perspective. $\endgroup$ Commented Nov 11, 2022 at 18:50

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 than 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
    Commented Jul 20, 2018 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. $\endgroup$ Commented Jul 21, 2018 at 0:19
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    $\begingroup$ @RussellBorogove: nothing will be convincing to those people. $\endgroup$ Commented Jul 21, 2018 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? $\endgroup$ Commented Jul 21, 2018 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
    Commented Jul 21, 2018 at 11:52

“Can we survive Van Allen belt radiation?”

Easily. Stop reading nutjob news.

Before Apollo 10, the Lunar Orbiters carried dosimeter experiments. One dosimeter had a layer of aluminum ober it (a few mm), another had barely anything at all between it and a sky view. These cover layers were no accident: the aluminum layer was the shielding equivalent of the Apollo capsule wall, and the lesser layer was the equivalent of the Apollo flight suit.

Results? The dosimeter readings were judged to be within the acceptable radiation dose, both in lunar orbit and the outbound phase of the missions (i. e., the Van Allen Belts). Had the radiation numbers been high, there was still time to add, e. g., shield layers to the suits, or perhaps a capsule liner, or more likely a “storm cellar” near the center of the Command Module.

It’s the job of management to think of things like this. In Space World, you generally don’t get a “do-over” because your first attempt was weak. It’s the job of space planners to succeed on the first try as often as possible, which includes outside, expert program reviews to uncover things one might have forgotten, or brushed off, or underestimated. If no expertise exists (because no one’s done it before), some sort of risk retirement is called for, such as the dosimeter experiment. In Ground World, one can get away with weak attempts because they’re attempts, and people trust their own diligence. If another attempt is needed, then it’s needed.

We laugh at Ground World.

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    $\begingroup$ Do you have a reference for the Lunar Orbiter dosimeter experiements? $\endgroup$ Commented Nov 10, 2022 at 14:25

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