Makes sense. A manufacturing defect in a Soyuz would be extremely surprising, they have a very well respected safety record.

Thanks! We've updated the link from https://www.independent.co.uk/life-style/gadgets-and-tech/ne....

How does it not happen more often?

Micrometeoroid impacts happen fairly regularly, but they're usually not energetic enough to make a hole. For example, there was a instance in 2012 where one hit a window: http://www.spacesafetymagazine.com/space-debris/kessler-synd...

But as that incident shows, such impacts are often relatively benign - in that case, they didn't even need to replace the outer layer window.

The hull is reinforced with four or five layers of shielding - the above article has a nice diagram: https://i2.wp.com/www.spacesafetymagazine.com/wp-content/upl...

This means the usual consequence of a micrometeroid impact is pitting of the outer layers that may not even be noticed.

For larger objects that present a serious danger, the US Space Surveillance Network attempts to track them and predict "conjunctions" with a zone around the ISS which extends 2km above and below it, and 25 km in each direction on the orbital path. Anything that's expected to intersect with this zone is analyzed and may result in the station being moved to get out of the way. These are mostly due to space junk of human origin. In 2013, there were at least ~70 of these "conjunction notifications", although this results in only about one move of the station per year, on average.

There's a description of how these cases are handled at https://arstechnica.com/science/2013/07/how-nasa-steers-the-... :

> "Any object with between a 1-in-10,000 and 1-in-100,000 chance of colliding with the station meets the "yellow" threshold. Flight rules say that the station must be moved out of the way in response to a yellow threshold object unless such a move results in a mission impact—"Like, if we do the burn, we're going to miss an opportunity to launch a Soyuz, for instance," explains Parris. "Do we delay the Soyuz, or do we do the maneuver?" A "red" threshold is assigned to any collision with a likelihood of between 1 (in other words, absolutely certain) and 1-in-10,000. Flight rules are more strict for maneuvers in response to red threshold objects: the station is always moved for a red threshold object, regardless of mission impact, unless a maneuver represents more risk than not maneuvering (for example, if there's a piece of equipment that's damaged on the ISS and a maneuver would exacerbate that damage)."

This doesn't help in the case of meteor showers, where the Earth is travelling through a zone full of small debris, typically caused by the trail of a comet. In those cases, the station has to rely on its shielding, but the debris sizes in those cases are almost all within the limits that the shielding can handle.

Very informative post, thanks!

ISS travels at a very low orbit which the earth’s atmosphere does a great job of keeping clean. They occasionally manover around anything large enough to be a significant issue. On to of that space is huge and largely empty even at the speed they are traveling.

The ISS is also designed to take a hit and can generally survive similar impacts without issue.

Does that mean there is a little meteor hanging out somewhere in the module?

At the typical velocities for this kind of impact, probably not. At these speeds, computer analyses ignore the solid properties of the colliding objects, modeling them as liquids, instead. (The shear resistances is just not relevant, and everything liquefies from the heat from the impact. Even that heat loss is negligible in terms of the total energy of the collision.)

Most likely, there would be fragments of the impactor and the hull, mixed together with each other and oxidized with the station air, floating about. I won't risk speculating about the fragment size, other than to say it would be pretty dang small. (I'm leaning toward "powder," but personally wouldn't rule out either "grit" or whatever "finer than powder" is.)

>or whatever "finer than powder"

silt.

if its even smaller its clay.

So the astronauts have breathed the meteor into their lungs? Funky ...

They're breathing far more dead skin. So are you, though.

I would expect much more stuff to be in the air under zero gravity. On earth dust will settle on the ground but I assume in the ISS it will keep floating around.

Yes, but that's organic and pretty normal. Aren't meteors and say moon dust dangerous because its very sharp and jagged?

Once it’s flashed to a plasma and turned into sub-micron dust? Probably not. The danger if there is any would be if the remaining particulates (assuming it wasn’t mostly reduced to heat, light and some basic elements) are friable.

This is mostly a myth:

https://www.livescience.com/32337-is-house-dust-mostly-dead-...

If it were a hole, as in something punching through. These are cracks. Probably nothing passed through, these opened up beside the impact point as material buckled.

What's the possibility a meteor could hit an astronaut? I imagine that wouldn't be good.

Depends on the size of the meteor. It's very likely survivable; micrometeroid protection is a design feature of the suits, which have plenty of layers, and a small hole won't cause rapid decompression. For a through-suit puncture it's going to be a lot like a gunshot wound.

If you're hit by a speck of dust or a grain of sand you're probably good for most impact sites. If you're hit by a marble you're going to be in real trouble (same is true of the ISS itself in this case).

In any case, it's pretty unlikely.

I'd imagine they have some pretty heavy duty air filters that could catch and remove that sort of particulate. Total speculation though...

MMOD impacts tend towards "vaporize" rather than "puncture". That's how (and why) a Whipple shield works.

The Wikipedia article on the topic https://en.wikipedia.org/wiki/Whipple_shield mentions that the ISS has 100 different kinds of shields on various parts of it -- presumably Soyuz doesn't have one thanks to its quite different launch and re-entry needs.

Soyuz wouldn't have much. Good thing it's in the orbital module; there are much more problematic places for a hole.

MMOD protection for visiting vehicles is actually a bit tough; they are on orbit for quite a while but have constraints around shielding. Both the new Boeing and SpaceX vehicles have had problems achieving high enough statistical survivability rates, mostly due to MMOD strikes. (Soyuz probably wouldn't pass those criteria either, but it's not asked to.)

According to Russian sources, the problem was found in the Habitation Module of the Soyuz MS-09 spacecraft, where the crew detected two small cracks, reaching 1.5 millimeters in size. Alexander Gerst apparently first discovered the leak.

Not only first discovered. The first temporary patch was Gerst's finger.