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Comment by bernardlunn | Hacker News Reader

Anybody know how dead ones are recycled or is it junkyard in space?

"Recycled"? None.

Deorbited: quite a few. Depends on orbital altitude. Low-earth orbit satellites generally deorbit by themselves eventually, but at the upper range of low-earth orbit that can take a few thousand years unless they are intentionally deorbited.

In geosynchronous orbit, nothing is ever deorbited, it's too costly in terms of fuel. They are instead raised in altitude a few hundred klicks to get them out of the way.

There is a junkyard for GEO i.e 360000km orbit. But there are now concepts and companies coming up to solve the junk problems for the 500-2000km orbits - https://www.bbc.com/news/science-environment-56420047

Like any other externality that isn't constrained by regulation, the problem is raging out of control.

https://www.bloomberg.com/opinion/articles/2021-04-17/space-...

random question for anybody that can answer:

for satellites that are scheduled to be "deprecated," can we use a different rocket to gently nudge them out of orbit and have them float off into space? even if you nudge them at something super low velocity like 100MPH into a direction, presumably it would continue floating endlessly at 100MPH until it would hit something?

i'm guessing the building a separate "rocket that nudges dead satellites out of earths orbit" is extremely expensive?

"I'm guessing the building a separate "rocket that nudges dead satellites out of earths orbit" is extremely expensive?"

Yes, at least as expensive as launching the original satellite, if not more (because it has to have the ability to intercept).

Also, just adding a little nudge doesn't really help. It changes the orbit slightly, but it isn't like an additional 44 meters per second (which is what 100 mph is) of velocity is going to make the derelict spacecraft achieve escape velocity. You'll just change the shape of the orbit some. You need to add an additional ~ 3300 m/sec (7400 mph!) in velocity to get to escape velocity.

Decreasing the velocity, such that the derelict eventually de-orbits and burns up in the atmosphere is typically much less expensive. A few hundred m/sec would probably do it, but it depends a lot on what orbit the derelict starts in.

It doesn't work like this. If you nudge something in a circular orbit by 100MPH, in general it moves into a very slightly higher, lower, or more elliptical orbit. For a typical satellite in LEO, the size of the "nudge" you need to get it to "drift away" is comparable to all the rocket fuel that went into getting it there in the first place.

That isn't right, since all you have to do is lower the orbit until it hits the atmosphere, and let that do all the work. A Space Shuttle deorbit burn was ~90 m/s, versus the 7,600 m/s that the ISS moves at. (With even more lost to drag, gravity, etc, getting there.)

The ISS is in a relatively low orbit at ~400km altitude, geostationary satellites are up at 35,000km and have basically zero drag.

If you give a satellite a shove, it will end up on a slightly higher or lower (or eccentric) orbit depending which way you shove. It won’t keep floating off endlessly into space unless you shove it with enough energy to get to escape velocity.

You would deorbit the sat and let it burn up into the atmosphere. In orbit, you can't really "drift off into" space like you're saying here.

I seriously recommend investing in a copy of Kerbal Space Program. There is no better way to gain an intuitive grasp of orbital mechanics.

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