If astronauts must make repairs in a vacuum, why do they train in a swimming pool?

Because a swimming pool is as close as you can get to space: the gravity feels as if it's not there, you can't breathe without your suit, and the best part is that it's all on earth instead of in space, making training in a pool more efficient, reliable and safe.

So how do they train for micrometeroid impact? How do they train for Gamma and xRay radiation? Why not train in a zero G vacuum chamber? Wouldn't that be a simulated environment truer to what they supposedly work in?

Do you think a zero-G chamber is scientifically possible? Because so far it isn't. Also, they would train for the eventual impact of solar flares, one of the main harbingers of massive amounts of radiation, through drills within the pool. Same goes for micrometer impact. There wouldn't actually be any radiation or micro meteors, but it would train the astronauts on how to prepare for it. Also, if they worked in a vacuum chamber, they would be more at risk for death, since it takes longer to drain a vacuum chamber than it does to get or of your suit and float to the surface.

ummm...https://en.wikipedia.org/wiki/Zero_Gravity_Research_Facility
Whats more is water boils at room temperature in a vacuum. And micrometeroids are a CONSTANT THREAT in "space" supposedly. They are constantly falling from firmament down to earth. Draining a vacuum? Whatever youre smoking bro, puff puff pass! The change in pressure differential from vacuum to non-vacuum is instantaneous. What grade are you in anyway @Foxcheetahsp?

I'm currently in eighth grade, and one thing I have learned is that the lower the pressure, the lower temperature it takes for water to boil. But even that is beside the point. You can instantly put air into a vacuum, but if someone's suit is breached within a vacuum, and suddenly there's air again, that could easily kill the person inside the suit, as the sudden change in pressure could cause a condition commonly known as "the bends." For more reference, see https://en.wikipedia.org/wiki/Decompression_sickness. Also, about the source you mentioned, it uses a function known as a "drop test." What that does is take a container and drop it at a rate where the contents begin to "float." It isn't truly zero-gravity, but it simulates it. Also, notice how on the page, it says to " investigate the behavior of components, systems, liquids, gases, and combustion in such circumstances," and not to investigate people. Even further more, when in a vacuum without a pressurized suit, human blood can boil. And when blood boils, pockets of air develop that result in a bulge in an artery that flows to the brain. This bulge will cause a brain aneurysm. For more reference, see http://www.webmd.com/brain/tc/brain-aneurysm-topic-overview#1. So, having training for people with no experience at all in a vacuum held within a vacuum is quite risky in case of a suit breach. Finally, about the micrometeors. You demonstrate a valid point. Although, whether one is prepared or not is placed, normally, not in training, but in the protectiveness of the suits themselves. I believe http://www.smithsonianmag.com/smart-news/how-do-you-shield-astronauts-and-satellites-from-deadly-micrometeorites-3911799/ will answer your questions.

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