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After seeing this question about a 135 camera being used during a space walk, I was wondering the following:

It is generally known that astronauts are exposed to increased radiation, also called space radiation.

Quote from NASA:

Astronauts are exposed to ionizing radiation with effective doses in the range from 50 to 2,000 mSv. 1 mSv of ionizing radiation is equivalent to about three chest x-rays. So that’s like if you were to have 150 to 6,000 chest x-rays.

Astronauts are protected from radiation by their spacesuits, but the camera does not seem to have any protective housing, as shown in these photos. As getting your film exposed with an x-ray machine is generally a bad idea, especially with higher ISO films, it would seem harmful for the film inside these 'space cameras' to be consistently exposed to high doses of radiation.
Still, photos from space missions evidently turned out fine. What is the reason for this? Does the radiation not harm the film, or is there a protective method not visible in the photos?

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There are two and a half parts to this answer.

First part: if you are in LEO (low Earth orbit) (The only EVAs outside LEO were part of the Apollo programme) then you're inside the Van Allen belt and the radiation environment is therefore significantly nicer. No humans have been higher than LEO since Apollo.

Secondly, if you're outside the Van Allen belt, such as on the Moon, then yes things are nastier. But you're not there for very long. In particular, the annual radiation dosage on the Moon is somewhere between 100 & 400 mSv: on the surface of the Earth (well, in the US: it varies a lot) it's around 6mSv (this comes from this page) (see below on the units for radiation dosage). So the Moon is about 66 times worse than the Earth: a film on the Moon for a week gets about the same dose as it would on Earth if stored in the same conditions for a year and three months. Well, you can store film on Earth for that long, and in fact much longer, without significant ill effects, so a week or so is fine.

Additionally, most the film used was fairly slow, with ISOs (really ASA then) of 160 or below, & slow film is less sensitive to radiation damage. However on at least some missions (Apollo 8 anyway) some very fast film was used: see this NASA page:

On Apollo 8, three magazines were loaded with 70 mm wide, perforated Kodak Panatomic-X fine-grained, 80 ASA, b/w film, two with Kodak Ektachrome SO-168, one with Kodak Ektachrome SO-121, and one with super light-sensitive Kodak 2485, 16,000 ASA film.


Radiation dose measurements are complicated, but the Sievert is a commonly-used measure; a rem is an older measure: 1Sv is 100rem, and a mSv is a milli-Sievert. None of these are necessarily very appropriate for film, since they all talk about the dose absorbed by humans. But they're the best I could find.

  • There's a third part: the film used for the Moon missions was relatively radiation-insensitive. The fastest film they used was ISO (well, ASA) 160; most of it was ISO 64 or ISO 80. – Mark Aug 5 at 21:18
  • @Mark: Good point. But I think it's not completely right: Apollo 8 at least carried some very fast film indeed (which I assume was B/W): see my edit from just now. It's not clear what images from that look like though or what it was for. – user82065 Aug 6 at 9:07
  • @tfb, according to ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700005062.pdf page 106 (Notes on Film Selection and Use), the high-speed film was intended for astrophotography experiments. Radiation fogging was a concern, but turned out to be within manageable limits. – Mark Aug 6 at 19:21
  • Becquerel originally discovered radioactivity because he had left uranium salts in a drawer with some photographic plates. The fact that this was such a non-issue for Apollo astronauts suggests that the radiation emitted from those samples must have been quite intense, at least at the small distances Becquerel had. – Ben Crowell Aug 6 at 22:12
  • During Apollo 15, 16 and 17 there were EVAs on the return trip from the Moon to fetch film and data recording canister from the Service Modules. I don't know whether they were inside the Van Allen Belt at those times. – DarkDust Aug 7 at 8:47
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While radiation above the atmosphere is indeed higher than on Earth, it is not so high as to ruin photographic film as quickly as your question would imply. The amounts you reference from NASA are exposures during a mission, not a short space walk.

In a NASA study on photographic film sensitivity during the shuttle years, NASA basically found that radiation mostly produced effects that are similar to that found in older film stock, where colors had shifted and contrast was impacted. Fogged film as one would expect was not found. NASA recommended that less sensitive film be used, as it was impacted less. 400 speed and above film seemed to be more sensitive to radiation, and NASA recommended lower ISO film be used.

Interestingly enough, it's gamma radiation, rather than X-rays or other ionizing radiation, that has the most impact on cameras (and humans) today. This is exacerbated by the fact that there is no practical shielding for either humans or cameras, as gamma radiation penetrates almost everything (it's one of the most dangerous aspects of a nuclear fuel meltdown i.e. Chernobyl). NASA has found that these gamma rays are even more impactful on digital cameras, where they can damage the sensor, essentially 'knocking out' a photosite on a sensor.

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    Although @tfb's answer practically covers this, "The amounts you reference from NASA are exposures during a mission, not a short space walk" makes one wonder if that matters: I would assume film would last a mission in space, until astronauts return to earth together with some equipment – timvrhn Aug 5 at 13:40
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    @timvrhn - When not on a spacewalk, the film is better protected inside the spacecraft. Just as the astronauts don't necessarily need to wear their spacesuits inside the craft for radiation protection. – IronEagle Aug 6 at 20:10
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Radiation encounterd during space missions, effect on film was well studied by NASA:

  • The Effects of Space Radiation on Flight Film (pdf)

A few days in space is generally the equal of about 150 days aging of the film. Some of NASA moon photography shows visible signs of degradation due to background radiation.

Do peruse the NASA study – it answers all your questions.

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