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Comment by modeless | Hacker News Reader

If the Starlink satellites all collided, the worst case is that we would have to ditch the space station (which is already planned in a few years) and wait a few years to launch more into LEO. The debris deorbits automatically due to atmospheric drag. And in the meantime we would still be able to launch through the cloud to higher orbits or escape velocity as it wouldn't be dense enough to hit something that only passes though for a couple of minutes.

IMO now that LEO communication satellites are feasible we should ban launching satellites into higher orbits. Collision debris up there is much, much worse because it's essentially permanent. It will not deorbit by itself for thousands of years or more, and there is no plausible way to clean it up even with technology much more advanced than ours.

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There actually is one idea for cleaning up debris in high orbit: You launch tons of very fine powder into the orbits you wish to clear. These orbiting particles create drag on anything up there, so that their orbits degrade much faster. But the because the particles themselves are so tiny, they have a very low ballistic coefficient, and will deorbit quickly.

More: https://caseyhandmer.wordpress.com/2019/10/25/space-debris-p...

That’s a solid idea. Never heard that before. And it really seems like it would solve an otherwise extremely difficult problem.

It would not discriminate though. Everything in that orbit would be taken down - debris and any functional satellites.

You should read the linked post. You can tune the particle size to affect only objects below a certain size.

I'm not sure I believe that operational satellites would be unaffected by sustained bombardment with tungsten particles at orbital velocity (x2 for head on collisions), even if they are 10 microns.

a reasonable concern

If we assume there's some altitude that's so polluted by debris that we need to intervene, it might not have that many functional satellites left. Cleanup the orbit in 1 year might be something the world could agree to if the alternative is waiting 5 years for it to clear up by itself.

Hmm, seems like it would work for 800 km, but maybe not for 1000+ km? Just based on what he says there, which is that each 100 km increase is a factor of 10 in deorbit time, and it's 1 year at 800 km.

It's not just starlink up there, at minimum NRO will be sad and unable to track nuclear weapons and such, the US military will be down a satellite coms systems, and there are probably some people which use starlink for something important.

Yeah it would suck to lose Starlink for a few years. I wouldn't mourn spy telescopes. But most other satellites like weather satellites or ballistic missile detectors or GPS are in higher orbits and wouldn't be affected at all.

My point is that even the unlikely worst case scenario would be limited in time and extent. It couldn't possibly block us from reaching space or last for decades, as some people fear.

> the worst case is that we would have to ditch the space station (which is already planned in a few years)

There is more than one Space Station up there. "Tianhe space station module conducted preventive collision avoidance due to close approaches by the Starlink-1095 (2020-001BK) and Starlink-2305 (2021-024N) satellites on July 1 and Oct. 21 respectively." [1]. Wikipedia also has a long list of planned and proposed space stations.

1. https://www.n2yo.com/satellite-news/Chinas-space-station-man...

a collision can send debris into an orbit with a higher eccentricity. these orbits may not last very long as they would also have a lower perigee.

Even though most of the satellites affected would be other Starlinks, I don't think the many entities with other spacecraft in sub 550km LEO would be particularly delighted to lose them (and the ability to safely relaunch for 5 years)

Satellites in higher orbits do a lot that can't be done in LEO and typically have much lower collision risk (though GEO is fairly crowded). There are plenty of plausible candidate technologies for cleaning up debris, just few practical demonstrations (and even tracking smaller pieces is work in progress)

> Satellites in higher orbits do a lot that can't be done in LEO

This isn't really true anymore. Yes there's a lot of legacy technology still in use and even still being launched, but there's nothing in MEO or GEO that can't be done in LEO with today's technology. Doing it in LEO requires more satellites and better radios, but you get better performance.

The risk of collisions may be lower but the consequences last thousands or millions of times longer...

The consequences of "there's some debris in a little-used MEO orbit for enough decades for it to take for somebody to be bothered to deal with it" are a little less drastic than "the world can't use satellites for 5 years" with the kinds of LEO crashes you'd be encouraging by replacing single satellites in higher orbits with dozens in lower. So even if the unit economics of replacing a geostationary satellite with a constellation large enough to maintain that continuous line of sight from a 500km orbit were acceptable, it would still be the exact opposite of a safety-enhancing move.

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