Just to add one point to Robert Frost's answer. Ordinary meteorites, e.g. destroying the lunar module, not really a concern. Because, although even a tiny meteorite would destroy it, one that would burn up in our atmosphere as a shooting star - those are also rare. How often do you see shooting stars in the night sky? And those are tiny things - and you are looking into a fairly large region of space there.
Perhaps you might avoid scheduling an EVA at the very height of the worst of the Leonids meteor storms?
At its height the 1833 meteorite storm had perhaps over a thousand meteorites a minute. Leonids
But even then it's not nearly as much of a danger as you might think because that's thousands of meteorites spread over the entire sky, i.e. corresponding to probably of the order of tens of square miles, perhaps more like hundreds of square miles of upper atmosphere (I'll need to do a calculation to make sure what the area is that you see from the ground in a meteor storm - could do that from typical height of a meteorite when it burns up as a shooting star, and the radius of the Earth).
So you are talking still about perhaps at most ten to a hundred meteorites per square mile (very rough order of magnitude back of envelope guess at present).
Still during a meteor storm like the Leonids in 1833 I think there would be a non trivial probability of one meteorite hitting the Apollo landing area. I think if a major storm like that was forecast, they'd probably not schedule EVAs during the storm itself. (If anyone knows the answer here do say in comments).
But there was some concern about micrometeorites. Really tiny, even smaller than shooting stars. On Earth then we get those also but they just fall down to the ground as a very fine dust in the atmosphere and are no harm to anyone.
How to Collect Micrometeorites in Your Backyard
But in space, these tiny things, micrometer scale, are traveling at kilometers per second. Reasonably easy to stop, because though far faster than a high velocity bullet they are also tiny and low mass so not that much momentum - but they are dangerous and do have to be stopped.
The most dangerous time for those is during the EVA. The spacesuits have multiple layers to protect against micrometeorites.
To protect against this - spacecraft have Whipple shields. Multiple layers of thin material. But a little bulky. Because you need an air gap like this:
The high velocity impact here comes from the right, goes straight through the first layer - but this then breaks it up and spreads it out so that by the time it gets to the second shield it consists of small particles that are easier to stop.
Variations on this have multiple layers and often filled with material - the "stuffed whipple shield". Or you can just have a very thick, heavy dense layer. One way or another a spacecraft has to be shielded from micrometeorites. Basic Concepts
But this is impractical for spacesuits, they'd be huge and bulky, because the whipple shield idea needs a large air gap, and dense material also has to be thick.
Still they use a similar kind of approach but in miniature.
Spacesuits have the Thermal Micrometeoroid Garment. Multiple thin layers to protect against micrometeorites as well as to help with thermoregulation.
There's another indirect threat from micrometeorites in the case of the ISS
These show micrometeorite impacts on a handrail that create sharp edges that can damage the gloves of an astronaut who handles it. A 34.8 cm long handrail returned from space after 8.7 years had six craters like that. That's roughly two micrometeorite craters per meter of railing per year. (6/(0.348*8.7) )
This shows a potential tear in a glove probably caused by handling a micrometeorite damaged hand rail. Astronaut Rick Mastracchio terminated his third EVA on STS 118 when he spotted this. Two EVAs were ended prematurely due to tears like this. They have to do that, as a tear like this could kill an astronaut through depressurization if not immediately dealt with and it takes a while to get back inside the ISS in an emergency. The inside of the spacesuit is under a lot of pressure which has to be contained.
If you spent a long time on the Moon, e.g. a moon base, then that would be an issue also, probably do similar things to what they do for the ISS
See
Perhaps you might avoid scheduling an EVA at the very height of the worst of the Leonids meteor storms?
At its height the 1833 meteorite storm had perhaps over a thousand meteorites a minute. Leonids
But even then it's not nearly as much of a danger as you might think because that's thousands of meteorites spread over the entire sky, i.e. corresponding to probably of the order of tens of square miles, perhaps more like hundreds of square miles of upper atmosphere (I'll need to do a calculation to make sure what the area is that you see from the ground in a meteor storm - could do that from typical height of a meteorite when it burns up as a shooting star, and the radius of the Earth).
So you are talking still about perhaps at most ten to a hundred meteorites per square mile (very rough order of magnitude back of envelope guess at present).
Still during a meteor storm like the Leonids in 1833 I think there would be a non trivial probability of one meteorite hitting the Apollo landing area. I think if a major storm like that was forecast, they'd probably not schedule EVAs during the storm itself. (If anyone knows the answer here do say in comments).
But there was some concern about micrometeorites. Really tiny, even smaller than shooting stars. On Earth then we get those also but they just fall down to the ground as a very fine dust in the atmosphere and are no harm to anyone.
But in space, these tiny things, micrometer scale, are traveling at kilometers per second. Reasonably easy to stop, because though far faster than a high velocity bullet they are also tiny and low mass so not that much momentum - but they are dangerous and do have to be stopped.
The most dangerous time for those is during the EVA. The spacesuits have multiple layers to protect against micrometeorites.
To protect against this - spacecraft have Whipple shields. Multiple layers of thin material. But a little bulky. Because you need an air gap like this:
The high velocity impact here comes from the right, goes straight through the first layer - but this then breaks it up and spreads it out so that by the time it gets to the second shield it consists of small particles that are easier to stop.
Variations on this have multiple layers and often filled with material - the "stuffed whipple shield". Or you can just have a very thick, heavy dense layer. One way or another a spacecraft has to be shielded from micrometeorites. Basic Concepts
But this is impractical for spacesuits, they'd be huge and bulky, because the whipple shield idea needs a large air gap, and dense material also has to be thick.
Still they use a similar kind of approach but in miniature.
Spacesuits have the Thermal Micrometeoroid Garment. Multiple thin layers to protect against micrometeorites as well as to help with thermoregulation.
There's another indirect threat from micrometeorites in the case of the ISS
This shows a potential tear in a glove probably caused by handling a micrometeorite damaged hand rail. Astronaut Rick Mastracchio terminated his third EVA on STS 118 when he spotted this. Two EVAs were ended prematurely due to tears like this. They have to do that, as a tear like this could kill an astronaut through depressurization if not immediately dealt with and it takes a while to get back inside the ISS in an emergency. The inside of the spacesuit is under a lot of pressure which has to be contained.
If you spent a long time on the Moon, e.g. a moon base, then that would be an issue also, probably do similar things to what they do for the ISS
See
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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