Humanity's satellite habit could end up choking Earth's ozone layer
- Reference: 1719304508
- News link: https://www.theregister.co.uk/2024/06/25/satellite_reentry_ozone/
- Source link:
Constellations of small satellites being deployed for purposes such as broadband coverage typically have a relatively short life span, said to be about five years for Starlink, after which they re-enter the atmosphere and burn up, with replacements sent up to take over their roles.
But researchers at the University of Southern California (USC) say that this leads to the generation of aluminum oxides in the atmosphere, which are known to accelerate ozone depletion. The large number of satellites involved – Starlink alone was estimated to have 6,078 satellites in orbit as of May 2024 – could mean this presents a serious risk.
[1]
A [2]research letter published in Geophysical Research Letters, "Potential ozone depletion from satellite demise during atmospheric re-entry in the era of mega‐constellations," says the demise of a typical 250 kg satellite can generate around 30 kg of aluminum oxide nanoparticles, which may endure in the atmosphere for decades.
[3]
[4]
The researchers calculate that large constellations of satellites may cause over 360 metric tons of aluminum oxide compounds to enter the atmosphere per year, which could lead to significant ozone depletion.
Aluminum is one of the most common materials in satellites, the article says, and reacts with oxygen upon re-entry in the atmosphere to generate aluminum oxide that can interfere with ozone chemistry. A chlorine activation reaction catalyzed on the surface of aluminum oxide particles boosts ozone depletion.
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The effects of aluminum have been known about for some time through studies of the emission of hundreds of tons of such particles from solid rocket motors during atmospheric ascents, but little attention has been paid to vehicles re-entering from low Earth orbit, and none covered the re-entry of satellites, according to the researchers.
They estimate that re-entry by-products may take up to 30 years to settle from the top of the mesosphere into the stratospheric ozone layer. Upon reaching an altitude of about 40 km, aluminum oxides catalyze chlorine activation, which promotes ozone depletion.
This would introduce a noticeable delay between the beginning of the injection process, when orbiting bodies are decommissioned, and the ozone depletion consequences becoming apparent in the stratosphere. As re-entry rates for satellites increase, it is crucial to further explore the concerns highlighted in this study, the researchers assert.
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How worried about this should we be? The short answer seems to be that we don't know, and more research is needed.
Up until now, scientists were confident that the ozone layer was slowly recovering from the damage done to it by chemicals such as chlorofluorocarbons (CFCs), thanks to the Montreal Protocol agreed back in the 1980s.
Last year, a [7]UN-backed Scientific Assessment Panel reported that about 99 percent of banned ozone-depleting substances had been phased out, and said that if current policies remain in place, the ozone layer was expected to recover to 1980 values (before the appearance of the ozone hole) by around 2066 over the Antarctic, and by 2040 for much of the rest of the planet.
[8]Starlink stuffs the internet into a backpack by invitation only
[9]Satellite phone service could soon become the norm
[10]Japan's space junk cleaner hunts down major target
[11]FCC boss wants tighter rules to prevent devastating satellite explosions in orbit
We asked the USC researchers whether the volume of aluminum oxides they expect to enter the atmosphere would seriously impact regeneration of the ozone layer.
They told us that the current study only compares the amount of aluminum oxides generated by satellite re-entry with the natural levels of it in the atmosphere, and they are not in a position to compare this against the effect of other chemicals at the moment, but plan to address this in a future study.
Robyn Schofield, Associate Professor in Atmospheric Chemistry at the University of Melbourne, explained in an [12]article that other researchers studying aerosol particles in the stratosphere had previously detected traces of metals from spacecraft re-entry.
"We don't know what effect this will have," she said. "One likely outcome would be that the aluminium particles seed the growth of ice containing particles. This means that there would be more small, cold, reflective particles with more surface area on which chemistry can occur.
"We also don't know how aluminium particles will interact with the sulfuric acid, nitric acid and water found in the stratosphere. As a result, we can't really say what the implications will be for ozone loss."
And there is some urgency to find out. Starlink and other low Earth orbit comms operators alone have plans for tens of thousands of new satellites by 2030, and the total worldwide [13]could be in the millions , according to some estimates. ®
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[2] https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GL109280
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[7] https://www.unep.org/news-and-stories/press-release/ozone-layer-recovery-track-helping-avoid-global-warming-05degc
[8] https://www.theregister.com/2024/06/21/starlink_mini_invitation/
[9] https://www.theregister.com/2024/06/19/satellite_phone_service_could_soon/
[10] https://www.theregister.com/2024/06/17/asia_tech_news_roundup/
[11] https://www.theregister.com/2024/05/30/fcc_chair_sat_debris_rules/
[12] https://theconversation.com/defunct-satellites-burning-up-in-the-atmosphere-could-damage-the-ozone-layer-heres-how-232592
[13] https://www.space.com/million-satellites-congest-low-earth-orbit-study-shows
[14] https://whitepapers.theregister.com/
Plenty of better reasons to prosecute Musk
I would start with unpaid bills from Xitter and move on to all the redundancy payments he has withheld. Complaining that he followed the requirements of the launch licenses by making Starlinks burn up completely in the atmosphere is a bit capricious. For now, how about some research into which is better: complete burn-up or mostly in one piece to the [1]satellite cemetery .
Long term, things will change. Starlink will switch to Starship: more satellite mass to orbit but the second stage of the rocket will be re-usable. That will cut out the current aluminium Falcon stage 2 for every twentyish Starlinks and everything else SpaceX launches (which accounts for about a third of their launches). Currently in second place in terms of mass to orbit is China. China is making a real effort to match Starship. Third place is so far behind that it is currently almost irrelevant. At some point in the distant future Amazon will be launching Kuiper satellites on Blue Origin's New Glenn. New Glenn will dump a large aluminium second stage back into the atmosphere with every launch. Guessing forth place is tricky. The most obvious two contenders are Rocket Lab's Neutron (aiming one step ahead of Falcon 9 with cheaper operations and a very slimmed down stage 2) and Stoke's Nova (fully re-usable but not as huge as Starship).
There are plenty of others but at best their only advantage over Falcon 9 is that the launch fee does not got to Musk. A few customers will pay handsomely for that but the bulk of the market will be significantly cheaper launch than we have now. That will move the costs further from launch and even more towards the cost of the satellites - which are getting bigger as well as more numerous. That might be enough to make in orbit repair/re-use/recycle worthwhile and burning satellites in the atmosphere will be as quaint and old-fashioned as single use rockets.
[1] https://en.wikipedia.org/wiki/Spacecraft_cemetery
Colour me (not at all) surprised. Humans have invented a new method of killing future us. Let me guess, we need new technology to fix the failures of old technology?
"Let me guess, we need new technology to fix the failures of old technology?"
Pretty sure that neither fire nor the wheel will provide us with good ways to solve this particular problem (though they'll be used in the solution I don't doubt)
The whole idea of single projects launching thousands upon thousands of satellites just seems like a bad idea for so many reasons.
Grumble grumble moan moan etc
Who needs an ozone layer?
If all the competing satellite constellations are encouraged then there will soon be enough solid bodies in orbit to block out as much UV as the ozone layer used to.
There may be other side-effects, but we can tackle these as they show up.
The nice thing about low-orbit constellations
Sounds like the sort of thing that can be fixed by adjusting the satellite design; either switching to different materials or a more controlled reentry. Satellites are specifically designed to burn up on reentry; presumably it would be possible to make them not do that and instead aim for a controlled reentry over the ocean.
The nice thing about low-orbit constellations is they're rotated out every six to ten years anyway, so this can be fixed in the next version.
Re: The nice thing about low-orbit constellations
Heat shields are hard (see recent starship reentry flap).
Ok, most satellites will have a much easier time, but....
- The heatshield has mass, which must be launched
- There are always two modes of reentry. With a passively stable heatshield an uncontrolled reentry (due to some failure) is considered pretty risky...
A fair bit of orbital debris ends up as something other than nanoparticles - starting with the debris from batteries dumped from the ISS which hit a Florida house, but I expect other debris may simply be small-but-not-nanoparticles. Assuming it all turns into nanoparticles in the ozone layer is probably unnecessarily pessimistic.
Prosecute Musk for fly-tipping?