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Comment by ronsor | Hacker News Reader

Is "spontaneously explode" supposed to be a joke about how Russia will use them as bombs, or are they actually poorly designed?

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They actually explode.

https://spacenews.com/low-intensity-explosion-caused-russian...

To be fair the article also said it could have been a collision, even if it isn't super likely.

It's not the only one, just the most recent. A collision can't be ruled out, but there is a frequent tendency of old, retired Russian satellites just exploding for no reason:

https://en.wikipedia.org/wiki/List_of_space_debris_producing...

Before the Chinese A-Sat weapon tests, the #1 source of space junk was radioactive coolant leaking from old Soviet nuclear reactors in space (not RTGs, literally nuclear reactors)

This is true! Had no idea!

"The Soviet Union has been flying nuclear power sources in space since about 1965. For the most part these nuclear power sources have been low-power nuclear reactors using a thermoelectric conversion principle."

https://ntrs.nasa.gov/citations/19900051140

The thing 'rebelgecko is alluding to is specific, and fascinating! The coolant in these space reactors is a molten metal (low-melting point sodium-potassium eutectic). When they leaked in the space vacuum, the liquid dispersed into a large number of small, metal spherules, which formed rings around Earth. Because the spherules are metallic and smooth, they're (comparatively) easy to track by radar, from Earth.

https://ntrs.nasa.gov/api/citations/20190033494/downloads/20... (pdf) ("The NaK Population: a 2019 Status")

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