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Comment by mchusma | Hacker News Reader

Space is massively big. We can easily have a thousand systems like this without getting the density of an airport airspace. We should be trying to put a trillion people in space.

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These orbits aren't that far out, so the volume available to them is actually comparable to that of airspace. However, there are some massive differences. First, in airspace you can easily maneuver and change directions if problems arise. Second, while a collision in airspace is certainly a local disaster, it's limited in scope. A collision between satellites creates a giant scattering of debris with unpredictable orbits. Debris that can stay in orbit for years and years.

Airspace is usually up to flight level 600, or 60k feet. That's around 18km. Starlink flies at an altitude of around 550km, so more than a magnitude higher.

How could the volume between them be in any way comparable?

Uh, because if you wanna talk about the radii of the spherical shells like that, you need to consider the actual radii, namely the distance from the shell to the center of the Earth.

In your example (which is an exaggeration, FL600 isn't really used for commercial flights), airspace goes from 0 to 18 km above the surface of the Earth. The Earth's radius itself is approximately 6400 km. So airspace is the shell between 6400 km and 6418 km. Starlink operates around 6950 km. That's not "an order of magnitude more", it's completely comparable to airspace, so the space available to the satellites scales with the shell's thickness in almost the same way as airspace does.

Think of it this way: the Earth's radius is ~6400km. Starlink orbits less than 10% higher than that.

Depending on the thickness of the orbital shell there might be significantly more vertical space available, but the surface area isn't much bigger at all. (It's actually only ~18% larger[1].)

[1]: https://www.wolframalpha.com/input/?i=%284%CF%80%28radius+of...

The vertical space is significantly larger, about 200km (400km-600km height) for usable latencies (35000km if we’re talking any orbit) vs only 3-4km for commercial flights.

So we should be comfortable with billions.

>Debris that can stay in orbit for years and years.

Just a note on this, The Starlink constellation is in low earth orbit, ~500km. There is still enough atmospheric drag at this altitude that most things will slow down and re-enter & burn up within months, not years.

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