3 ms·

I don’t think this is true. Looking at this: https://i.stack.imgur.com/pMchk.jpg https://i.stack.imgur.com/pMchk.jpg from UN, objects above 500km take ~25 years

I don’t think this is true. Looking at this: https://i.stack.imgur.com/pMchk.jpg https://i.stack.imgur.com/pMchk.jpg from UN, objects above 500km take ~25 years to decay from orbit. They reportedly start at 550km, so I wonder how they hope to achieve 3 years of deorbit without active control.

trothamel 5y ago
That's wrong. There were four missions that were deployed to apogees above 300 km, but most are deployed to 250km and below. That means that satellites that fail tend to burn up quite quickly, in a few years. Here's a chart of deployment apogee and perigee. https://twitter.com/planet4589/status/1491256299002155012/photo/1 https://twitter.com/planet4589/status/1491256299002155012/ph...
teraflop 5y ago
That infographic is a very simplified view of a complex subject. Here's a more detailed overview: https://www.spaceacademy.net.au/watch/debris/orblife.htm https://www.spaceacademy.net.au/watch/debris/orblife.htm Bear in mind that Starlink is much lighter and "draggier" than typical artificial satellites. Based on publicly available data, I get a ballpark figure of roughly 20 kg/m^2 for the ballistic coefficient of a tumbling Starlink satellite. Just eyeballing the graphs in the link I provided, that corresponds to a lifetime of something like 2-9 years, depending on solar conditions.
jccooper 5y ago
It depends on density and cross section (and solar flux); a 500km orbit can be 2-30 years, depending. That's all basically still in the "self-cleaning" domain. Being rather dense and flat, I'd expect Starlink to be on the lower end of that range. http://www.spaceacademy.net.au/watch/debris/orblife.htm http://www.spaceacademy.net.au/watch/debris/orblife.htm The Starlink "0.9" batch was launched in May 2019. Most reached operational altitude; those that did not decayed quite early, as expected. Those that remained operational have by now been deliberately dropped, but some 5 seem to have become unresponsive at a more-or-less operational altitude. See dashboard at https://forum.nasaspaceflight.com/index.php?topic=49936.200 https://forum.nasaspaceflight.com/index.php?topic=49936.200 Starlink-43 is the first of those to fully decay, reentering around 26 January. https://in-the-sky.org/spacecraft.php?id=44257 https://in-the-sky.org/spacecraft.php?id=44257 Starlink-24 is probably going to be the slowest of that cohort. It might have a couple years left. https://in-the-sky.org/spacecraft.php?id=44257 https://in-the-sky.org/spacecraft.php?id=44257 Natural decay in <5 years is really quite fast as these things go.

trothamel 5y ago

That's wrong. There were four missions that were deployed to apogees above 300 km, but most are deployed to 250km and below. That means that satellites that fail tend to burn up quite quickly, in a few years. Here's a chart of deployment apogee and perigee. https://twitter.com/planet4589/status/1491256299002155012/photo/1 https://twitter.com/planet4589/status/1491256299002155012/ph...

teraflop 5y ago

That infographic is a very simplified view of a complex subject. Here's a more detailed overview: https://www.spaceacademy.net.au/watch/debris/orblife.htm https://www.spaceacademy.net.au/watch/debris/orblife.htm Bear in mind that Starlink is much lighter and "draggier" than typical artificial satellites. Based on publicly available data, I get a ballpark figure of roughly 20 kg/m^2 for the ballistic coefficient of a tumbling Starlink satellite. Just eyeballing the graphs in the link I provided, that corresponds to a lifetime of something like 2-9 years, depending on solar conditions.

jccooper 5y ago

It depends on density and cross section (and solar flux); a 500km orbit can be 2-30 years, depending. That's all basically still in the "self-cleaning" domain. Being rather dense and flat, I'd expect Starlink to be on the lower end of that range. http://www.spaceacademy.net.au/watch/debris/orblife.htm http://www.spaceacademy.net.au/watch/debris/orblife.htm The Starlink "0.9" batch was launched in May 2019. Most reached operational altitude; those that did not decayed quite early, as expected. Those that remained operational have by now been deliberately dropped, but some 5 seem to have become unresponsive at a more-or-less operational altitude. See dashboard at https://forum.nasaspaceflight.com/index.php?topic=49936.200 https://forum.nasaspaceflight.com/index.php?topic=49936.200 Starlink-43 is the first of those to fully decay, reentering around 26 January. https://in-the-sky.org/spacecraft.php?id=44257 https://in-the-sky.org/spacecraft.php?id=44257 Starlink-24 is probably going to be the slowest of that cohort. It might have a couple years left. https://in-the-sky.org/spacecraft.php?id=44257 https://in-the-sky.org/spacecraft.php?id=44257 Natural decay in <5 years is really quite fast as these things go.