There's always micrometeorites in orbit, and they constantly hit the ISS. So my question is during EVA, how do astronauts protect themselves? Is their suit designed to take impact? Since there are micrometeorites that impact the ISS windows and can cause a crack, it seems unrealistic that the suit would provide any protection.
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1$\begingroup$ Well 'constantly' is a vague measure that covers some orders of magnitude of different levels. The ISS has a much larger surface area than one astronaut. I (believe) they don't schedule EVA's during expected peaks of micro-meteorite activity. Failing all those, they mitigate the risk by sending two astronauts out together. One who has not been hit can hopefully maneuver the other back into an air lock. $\endgroup$– Andrew ThompsonApr 4, 2017 at 7:03
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$\begingroup$ Read en.wikipedia.org/wiki/Space_suit "The Apollo/Skylab A7L suit included eleven layers in all: an inner liner, a LCVG, a pressure bladder, a restraint layer, another liner, and a Thermal Micrometeoroid Garment consisting of five aluminized insulation layers and an external layer of white Ortho-Fabric." Small micrometeorites may puncture one or some of the outer layers, but they don't puncture all layers. $\endgroup$– UweApr 4, 2017 at 7:43
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3$\begingroup$ Consider the possibility that all micrometeorites are not created equal. Windshields and face shields do not protect motorcycle drivers against large animals, but they still do provide "realistic protection" against the far more numerous insects. $\endgroup$– uhohApr 4, 2017 at 8:09
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2$\begingroup$ The suit can tolerate a small hole, it just pumps in more air from the backpack to keep the pressure up. Sorry I don't have any numbers on it, but there should be plenty of time to get back to the airlock. More serious would be a hole through the astronaut. $\endgroup$– InnovineApr 4, 2017 at 15:07
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1 Answer
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Essentially, they just accept the risk.
The suit is strong enough to withstand strikes from those micrometeoroids and pieces of orbital debris most likely to hit it, and it's small enough (and EVAs are short enough) that larger, more damaging strikes are quite unlikely.
The meteoroid and debris environments are only really understood in a broad average sense (weeks to years). Time scales as short as a single EVA are not particularly useful for determining an accurate level of risk.
Furthermore, the limiting condition for dealing with the unlikely-but-probably-inevitable strike is not going to be pressure loss, it's going to be crew injury, as any hole big enough to create a pressure problem is going to basically create a gunshot wound. As a result, the suit is designed to protect against strikes up to a certain size, beyond which an impact is quite unlikely.
