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Comment by Dragonborn | Hacker News Reader

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Starlink satellites are in low enough orbit to decay on very short timescales. More worrisome are Russian satellites in high / very long lived orbits that tend to spontaneously explode.

Not just Russian. There have also been a few cases recently where spent Centaur upper stages -- which were thought to have been completely passivated -- broke apart for unknown reasons. These were in a geosynchronous transfer orbit (with apogee near geosynchronous orbit, perigee down near LEO) so the debris won't decay any time soon.

Upper stages breaking apart is kinda expected. It's a rocket, and it has rocket fuel (explosives) on board. Derelict spy satellites, on the other hand, shouldn't be just going kaboom for no reason. But the Russian ones do.

As noted by another poster, prior to the recent ASAT tests, one of the largest sources of junk was old Soviet nuclear-powered satellites leaking coolant and/or having their pressure vessels explode. Mind you these are actual nuclear reactors, not RTGs.

No, all residual fuel (and anything pressurized) should have been vented after the last burn and there shouldn't be anything left on board with enough energy to cause it to break apart.

It's a real mystery.

(May I ask what definition of ‘passivate’ you are applying here? Even allowing for flexibility in the definition or autocorrect, and applying context, I can’t fathom what is intended to be conveyed by ‘upper stages - which were thought to have been completely passivated’)

https://en.wikipedia.org/wiki/Passivation_(spacecraft) ("Passivation (spacecraft)")

And used in context (this context),

> "The incident is the fourth time a Centaur upper stage has broken up since 2018. In the earlier three cases, the breakups created hundreds of pieces of debris, but no known collisions. That has raised questions about a potential design flaw with the stage or a failure to “passivate” the stage by venting propellant tanks and draining batteries, removing energy that could cause a breakup."

https://spacenews.com/faa-to-complete-orbital-debris-upper-s...

Thanks! I will update my word definitions search to include context keywords instead of ordinary dictionaries :)

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

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")

Aside from light pollution they leak radio signals which is starting to impact our ability to make astronomical observations.

https://en.wikipedia.org/wiki/Starlink#Impact_on_astronomy

It may comfort you to hear that the Starlink satellites are tiny in comparison to the vastness of their orbit – the visualization makes them appear larger than they are, so you can see them clearly – and that they’re low enough that they’ll naturally de-orbit and burn up in the atmosphere after about 15 years even without using their maneuvering thrusters.

They’re providing worldwide rural broadband, and according to the FAA they’re doing so in a way that’s careful and responsible about space debris and collision avoidance. Is disgust truly warranted in this case?

Red zones are “instruments” which isn’t defined, but is apparently surface-based observatories.

Stuff like Space Fence.

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