We also did this calculation for the catalogue of satellites, trackable debris, and rocket bodies from 2018, before megaconstellations, showing just how much less safe megaconstellations like Starlink have made orbit.
The densest part of orbit in 2018 had a closer than 1km approach a little more frequently than once a day. Now it's more frequently than once every 15 minutes.
How do you summarize how unsafe orbit is? This is where I get to tell you about my new favourite forced astronomy acronym, which I spent quite a while thinking about.
We needed a metric. I originally wanted to do something like "Kessler Countdown" or "Kessler Clock" but this isn't a countdown to Kessler Syndrome, it's just showing how bad things are in orbit, and how quickly they could get worse. So, our name for this metric is...
Collision Realization And Significant Harm: the CRASH Clock!
Collision Realization Anticipating Significant Harm?
@sundogplanets Much more snappy than Kalman (as in filter) Krash Klock!
@sundogplanets
I'm curious if and how this will be mentioned in the SpaceX IPO prospectus...
The CRASH Clock uses the current density in altitude bins (averaged over eccentric orbits) of satellites, rocket bodies, and tracked debris, assuming typical cross sections for each type and orbital speeds. This calculation tells us how long to a collision if all orbital maneuvers were to suddenly stop.
The CRASH Clock is currently* at 2.8 days.
In 2018 it was 121 days.
*This is actually for June 2025 because that's when we ran it. Will update soon!
@sundogplanets Don’t look up.
@sundogplanets
One interesting number to estimate is how long before a crash in the less extreme case of worse orbital determinations (because a database is down or someone is dazzling telescopes), which then could lead to fewer maneuvers being ordered or maybe even to dangerous maneuvers being ordered.
We set up a CRASH Clock website here: https://outerspaceinstitute.ca/crashclock/
Note that this is a probabilistic calculation. A catastrophic collision could happen sooner than 2.8 days of no maneuvers. In our (extremely computationally expensive) collision simulation, just by random chance we actually got the first collision just 3 hours in.
We are currently well inside the Caution Zone. The probability of collisions happening if no avoidance maneuvers occur is >10% in any 24 hour period.
@sundogplanets I think this is a great page to have.
If I could make one totally unsolicited opinion; If there were a way to feature this number more Doomsday clock style for the clicks and publicity of it, since I entirely think it is info that needs to be spread far and wide and get attention.
Thank you for doing the research and keeping us informed.
@sundogplanets, I keep wanting to correct that to manoeuvres… 😬
@sundogplanets What's the expected lifetime of propellant onboard, especially with increased maneuvers required to avoid ever-more-probable collisions? ie, What are the chances that a satellite loses the ability to avoid its neighbors before burning up in the atmosphere?
I also assume that a corollary of this chart is the likelihood of a snowballing chain reaction where one collision creates multiple pieces of uncontrollable (and untrackable?) debris that increase the likelihood of further collisions?
You missed out on calling it the Henny Penny Clock.
This really highlights how incredibly dependent we are on Starlink's continued perfect collision avoidance maneuvers. So far they've done it, but they keep adding more satellites and making it harder.
Other megaconstellations are now launching as well, and they all need to communicate PERFECTLY in order to not crash. Will China talk to Starlink? Will the US gov't secret satellites talk to OneWeb? This is all incredibly important so that we don't destroy LEO.
@sundogplanets How difficult it would be for some other country without access to Starlink (or similar) to deliberately trigger Kessler Syndrome if they find themselves in war with USA?
@sundogplanets I have (sort of) known of and understood the risks of Kessler Syndrome for some time, but wonder how long it would take for the orbits of the fragments in LEO to decay enough to make it a safe place to operate once again - or is the answer "several human lifetimes, if ever"? Will we forever quarantine ourselves behind a blanket of debris, unable to view the universe clearly or to transit LEO safely?
@tompearce49 @sundogplanets I don't think it would prevent space travel or the use of space, only the resource called LEO would be lost for a time that will depend on the height of the orbit.
During that time, it would not be possible to safely place satellites there, but I think it could be relatively safely traversed quickly. Large fragments could be tracked, tiny fragments protected against by micrometeorite shielding.
"In the short term, a major collision is more akin to the Exxon Valdez oil spill disaster than a Hollywood-style immediate end of operations in orbit. Indeed, satellite operations could continue after a major collision, but would have different operating parameters, including a higher risk of collision damage."
This is why I did a poll here about name recognition for Exxon Valdez a few months ago! (You young'uns go read about it because many of you don't know)
@sundogplanets Exxon Valdez was the biggest ecocide crisis when I was growing up. I still remember all the tragic images of the wildlife & waters affected 😔
@sundogplanets Unlike Exxon, they won’t be able to reflag the satellites as Starlink Mediterranean and pretend it’s business as usual.
One of the scariest parts of this project was learning more about Starlink's orbital operations. I had always assumed they had some kind of clever configuration of the satellites in the orbital shell that minimized conjunctions, and we would see the number of conjunctions grow over time in our simulations. But no! It's just random! There's no magic here, it's just avoiding collisions by moving a Starlink satellite every 2 minutes. This is bad.
I'll end with the last paragraph of the paper:
"In addition to the dangerously high collision risks calculated here, we are already experiencing disruption of astronomy, pollution in the upper atmosphere from increasingly frequent satellite ablation, and increased ground casualty risks. By these safety and pollution metrics, it is clear we have already placed substantial stress on LEO, and changes to our approach are required immediately."
2 interviews lined up to talk about the CRASH Clock so far!
And I usually say yes to just about every interview request I get, but I got 1 interview request on a non-urgent, non-time-sensitive astronomy topic late on a Friday afternoon asking to talk today or tomorrow. I think I will have to blow that one off and focus on other things.
@sundogplanets torre canyon for europeans and older readers!
Biggest issue on a collision is IF it cascades by altering expected paths. Shudders.
@sundogplanets Just because this made a neuron fire: Do you know Planetes? It is about people in orbit "picking up the trash" There are mangas and also a great anime series.
