HN Reader

The paper in question is here: https://link.springer.com/article/10.1007/s40295-024-00458-3

It adds to a pretty large body of literature around this subject, the gist of which is "risk is going up, but we don't really have a good way of estimating what that means in terms of actual collision rates".

The current trajectory is that SpaceX proved the commercial and military viability of an LEO megaconstellation, repeatedly lowering their target altitudes and raising their satellite count because of debris and cell size concerns...

And now the rest of the world is trying to catch up in a sort of arms race, and not taking any care about debris concerns. The most tempting orbits are the ones in upper LEO that permit them to launch fewer satellites.

SpaceX are going to end up well under 500km (orbital lifespan: a decade) before things are finished, and they switched to very low orbit staging with SEP spiral out to reach final orbit a ways back.

China's newest constellation Thousand Sails is at an altitude of 800km (orbital lifespan: thousands of years), with a thousand satellites in the works over the next year or so and 14,000 planned, and they're launching them using chemical upper stages designed to explode into a thousand pieces at the target altitude. This is sufficient for Kessler Syndrome all on its own, without counting interactions with anything else up there. A catastropic debris cascade at 800km percolates down to lower altitudes over time and impacts.

We need viable treaties limiting development beyond 400 or 500km and we need them ten years ago.

I don't know how to sell the urgency of this predicament. You can have as many satellites as you want, a million uncoordinated bodies, at 400km because direct collision potential scales with (satellite count / orbital lifespan) ^2 . At 1000km, satellites decay so slowly we are already too crowded; we have already overused the space. We are speed-running the end of the space age and we are doing it to save a small number of dollars and to avoid a small amount of diplomacy.

This is not something we get a do-over on. There is no practical way to collect ton-scale debris at present, no way to track kilogram-scale debris, no practical way to shield pressure vessels against gram-scale debris, and even milligram-scale debris can hit with the force of a bullet. After collisions start occurring at a rapid clip, the mass of potential impactors quickly forms a long tailed lognormal distribution that denies us space for centuries.

We need a Mega-Maid like in Spaceballs to clean up the mess: https://spaceballs.fandom.com/wiki/Mega_Maid

There might be a cool storyline where we have to use enormous ground based lasers to clean up and start again.

Could even look a bit like the iconic Gibraltar WW2 search lights photographs.

As long as it is militarily and commercially viable then the number of satellites will continue increasing, regardless of what academics have to say about collision rates. As per usual this is a coordination problem and in case people have not noticed nations are becoming less coordinated and more insular.

Paper: https://link.springer.com/article/10.1007/s40295-024-00458-3

Anyone have an open link?

I love Sabine Hossenfelder's videos but the audio effects on the transitions are killing me.

The parallels to global warming appear to be close enough that this could be a good area to study what actually changes behavior on a global scale for a global environmental problem. I suspect this is easier to 'fix' mainly because there are fewer entities involved so not a total parallel, but it still might be informative to see when in the crisis arc action actually starts happening and what messaging impacted that timing.

VLEO/LEO is the safest place to put satellites is it not? They'll eventually deorbit themselves if you do nothing, no?

The worst place for space junk is high orbits it would seem like. Earth was wildly visited by an Apollo rocket stage a few years back! That is pretty wild.

My understanding was always that LEO is much less of a Kessler risk due to atmospheric friction - ie: in the absence of active control and regular correction, LEO objects will gradually de-orbit themselves. It's the the higher geostationary orbits that pose the problem.

Positioning a large, armored satellite in low or mid-Earth orbit significantly enhances its strategic value for both offensive and defensive anti-satellite operations. Such a platform could serve as a pivotal asset in maintaining orbital dominance, offering rapid response capabilities to neutralize threats and protect critical infrastructure.

In other words, welcome various "death stars" to keep order against malicious Kessler style attacks, etc.

I would think newer sats will have collision avoidance capabilities and older ones will just crash. Maybe even clean up sats will be developed to collection them

Maybe it's a feature. If you want to build a large spaceship on the orbit you have a problem how to launch all the needed material, but with a lot of garbage already up there, you can just recycle it on spot, everything is already launched.