Will Musk’s Starlink satellites lead to Kessler syndrome?

Over the course of the 2020s and 2030s, the evening sky and the quantity of area that surrounds the Earth are each poised to develop into very totally different than they’ve been for all of human historical past. As of 2019, all of humanity had launched an estimated whole of between 8,000 and 9,000 satellites, the place roughly 2,000 of them have been nonetheless lively again then, principally in low-Earth orbit. As many firms now scramble to supply worldwide 5G protection from area — led most prominently by Elon Musk’s and SpaceX’s Starlink, which has by far essentially the most satellites — humanity is now starting to enter the period of satellite tv for pc mega-constellations.

As of immediately in 2023, nevertheless, there are almost 9000 lively satellites, with lively Starlinks making up the overwhelming majority of them: 4755 out of the 8647 lively satellites, or 55% of them. Whereas media protection has largely targeted on just one detrimental impact to this point — the injury that these satellites have already prompted and are nonetheless inflicting to astronomy — there’s a second consequence that may very well be much more disastrous over the long-term: Kessler syndrome. With tens and even tons of of 1000’s of satellites in orbit, a single collision might set off a sequence response. With the realities of photo voltaic flares, coronal mass ejections, and different types of area climate, the period of mega-constellations might usher in a brand new kind of pure catastrophe, making Earth’s orbit impassable to all future space-based missions.

low-earth orbit satellites

Over 100 thousand human-made objects—95% of them “area junk”— occupy low and medium Earth orbit. Every black dot on this picture reveals both a functioning satellite tv for pc, an inactive satellite tv for pc, or a large-enough piece of particles. The present and deliberate 5G satellites will vastly improve each the quantity and the impression that satellites have, and lift the potential for Kessler syndrome.

Credit score: NASA/Orbital particles program workplace

The concept of Kessler syndrome is a straightforward one: if there are too many satellites round Earth, an unlucky collision between any two of them might create sufficient particles that one other collision turns into inevitable. Though there may be not widespread settlement on when that time might be reached, it’s well known that higher numbers of bigger satellites vastly will increase this danger. With Starlink alone proposing a complete of 42,000 satellites in three totally different orbital shells and lots of different firms engaged on following go well with, the hazard of Kessler syndrome is poised to extend by orders of magnitude over the present decade: the 2020s.

In prior years, satellites have been launched into orbits that have been tracked and knowable, with occasional collisions solely occurring attributable to inactive satellites whose orbits have been decaying attributable to atmospheric drag. With mega-constellations, nevertheless, the motions of those orbiting satellites will now not be manually managed by people who find themselves persistently monitoring them for collision avoidance. Quite, synthetic intelligence has now entered the image, absolutely automating the collision avoidance drawback. Whereas many look upon this as an amazing function, in actuality, it poses a novel and catastrophic hazard to all of our present area exploration and area science missions, from Earth-monitoring satellites to planetary exploration and extra.

starlink satellites

A simulation of the complete community of Starlink satellites when the primary batch of 12,000 satellites are up. (Though petitions have been filed for tens of 1000’s extra, by Starlink and likewise by different business gamers.) This community will present near-total world protection, repeatedly, with 5G speeds and low latency occasions. Whereas delivering high-speed web globally is a noble objective, destroying ground-based astronomy, astrophotography, and posing a danger to the way forward for our area infrastructure needs to be reckoned with as extraordinary collateral injury.

Credit score: SpaceX/Starlink

With so many objects in orbit on the identical altitude, synthetic intelligence might be required to be able to always leverage the on-board thrusters to perform three primary targets:

  1. to make sure the proper, steady spacing of the satellites to supply the required web protection,
  2. to spice up any satellites that have the consequences of orbital decay, compensating for the drag of Earth’s environment,
  3. and to carry out any mandatory boosts or orbital alterations to keep away from collisions with different satellites, together with different members of the identical megaconstellation but in addition every other satellites or spacecraft that move by means of these orbital shells.

This final level is completely important. Any two orbits on the identical altitude at all times have two factors the place they’ll cross, the place satellite tv for pc drift makes such a collision inevitable, given sufficient time. Solely by having the satellites right their very own programs in real-time can the operators of those satellites guarantee a collision-free state of affairs, and that can solely work with uninterrupted, 100% steady uptime of those collision avoidance programs.

simulated satellite strike PHILOS-SOPHIA

This simulated collision between a small cubesat and a proposed satellite tv for pc (the Massive Observatory For X-ray Timing) reveals the facility of even a small object to wreck or destroy no matter it impacts. With typical relative orbital speeds of ~10 km/s or so, the particles created is at huge danger for impacting different satellites as effectively.

Credit score: ESA/Fraunhofer Institute for Excessive-Velocity Dynamics

That’s why the present plan of mitigating satellite tv for pc collisions comes together with a doubtlessly catastrophic state of affairs: what if the satellites are rendered non-responsive by some occasion? If fixed orbital corrections are wanted to be able to keep away from collisions with different satellites, the worst factor that would occur can be a state of affairs that paralyzed the satellites and made them unable to reply to not solely the unreal intelligence programs on board, however to any instructions despatched to them: even handbook instructions.

This isn’t some science-fiction horror state of affairs, however one thing as inevitable because the Solar itself: area climate. Occasions like photo voltaic flares, coronal mass ejections, and even the plain previous photo voltaic wind all ship charged particles away from the Solar. Once they occur to get despatched on their method in the direction of planet Earth, our floor is protected by our world’s magnetic discipline and our environment. The hazard to people or any organic organism is basically zero, with the biggest impact that generally happens being a spectacular wanting auroral show. Even when the magnetic fields of the Solar and Earth are aligned in such a method that big numbers of charged particles impression our planet, the higher environment is dense sufficient that none of those photo voltaic wind particles will strike people, vegetation, and even birds within the skies. The danger to dwelling creatures is basically zero.

earth sun magnetic magnetosphere

The Earth’s magnetic discipline sometimes shields us from the charged particles that the Solar emits, however when magnetic connection happens from the Solar’s discipline to the Earth, particles can get funneled down across the polar areas, making a spectacular auroral present, and probably additionally a geomagnetic storm if different circumstances are met.

Credit score: NASA/GSFC

However in area, even in low-Earth orbit, the environment provides no safety, and our planet-wide magnetic discipline provides no assure of redirecting these particles away from no matter satellites could also be current at any altitude: in geosynchronous orbit, medium-Earth orbit, or essentially the most densely populated area of all, low-Earth orbit. In keeping with NOAA:

“Photo voltaic Energetic Particles (energetic protons) can penetrate satellite tv for pc electronics and trigger electrical failure. These energetic particles additionally block radio communications at excessive latitudes in throughout Photo voltaic Radiation Storms.”

Proper now, the Solar is progressively approaching the height of its periodic photo voltaic cycle. On timescales of 11 years, the variety of sunspots — which correlates immediately with the chances of flaring exercise and coronal mass ejections — goes from basically zero (a quiet Solar) to photo voltaic most and again to zero once more. Again in 2018-2019, we have been simply leaving the earlier photo voltaic minimal. However now, sunspots, photo voltaic flares, and different area climate occasions are on the rise, with the following most anticipated to happen in 2024 or 2025 and one other photo voltaic most headed our method each 11 years after that.

NASA NOAA sunspot solar cycle 25

Since we first started observing the Solar and monitoring sunspots, there was a particularly common 11 yr cycle for the variety of sunspots noticed all year long. The twenty fifth photo voltaic cycle has now arrived, and whereas its peak isn’t anticipated to reach till ~2024-2026, the energy of the present photo voltaic cycle (crimson curve) is exceeding predicted expectations (blue curve).

Credit score: NASA/NOAA

There’s an amazing hazard to satellites at any time when this kind of area climate, of energetic charged particles product of both naked protons or extra complicated atomic nuclei, impacts them. Energetic protons, once they move by means of the electronics parts of a satellite tv for pc, can:

  • induce currents,
  • trigger electrical shorts,
  • and may fairly simply trigger varied varieties of electrical failure.

If this occurs to a satellite tv for pc spontaneously, the place no precautions have been taken previous to the area climate occasion impacting them, they are going to be unable to regulate their course totally: through synthetic intelligence or every other means. If they can not modify their course, the query of any two of those satellites colliding turns into a Russian roulette-like sport of likelihood, the place there are prone to be a sequence of near-misses earlier than the inevitable — an in-space collision between two of them — happens. With sufficient satellites and sufficient time, this can’t be prevented with out extra mitigations, given the bounds of present know-how and infrastructure.

The worst-case state of affairs, and this state of affairs will get worse with each new, large satellite tv for pc that goes up (and each single Starlink satellite tv for pc of all generations is “massive” by this metric), is that every collision will create new particles, growing each the probability and frequency of in-orbit collisions. The nightmare state of affairs of Kessler syndrome is that briefly order, doubtlessly simply weeks or months after the primary collision, the area round Earth will develop into a particles discipline, with a major share of current satellites getting destroyed by the sequence of impacts that can happen.


A 20 minute interval displaying the closest strategy of two orbiting satellites in area. Notice that, about as soon as per minute, two satellites come inside ~2 kilometers of each other, with many satellites coming even nearer than that. Because the variety of satellites will increase, the danger of satellite tv for pc collisions rises in a short time. At current, the variety of lively satellites in low-Earth orbit is greater than double what it was on this 2021 graphic.

Credit score: Moriba Jah/EAS 2021

At current, each area catastrophe that’s occurred in human historical past, together with collisions between satellites and likewise failed missions which have exploded or malfunctioned as soon as already in area, signifies that there are maybe up to some hundred thousand items of area particles the scale of your fingernail or bigger. These are already hazardous to our current satellites and area exploration operations, with one in every of them having colliding with the Worldwide Area Station only a few years in the past, cracking a window within the course of.

Journey the Universe with astrophysicist Ethan Siegel. Subscribers will get the e-newsletter each Saturday. All aboard!

However the state of affairs can be very totally different with tons of of 1000’s of enormous satellites in low-Earth orbit. Beneath these circumstances, a single collision between two massive satellites might set off a catastrophic chain response like humanity has by no means seen. Briefly order, the variety of items of area particles might rise into the tens of thousands and thousands, impacting satellites not solely in low-Earth orbit however in medium-Earth orbit as effectively.

The primary firm whose communications satellites trigger such a catastrophe would doubtless impression each different communications firm’s satellites, to say nothing of navy and scientific satellites presently in orbit. Not solely will satellite tv for pc know-how develop into an impossibility for no less than a long time and maybe a number of millennia, till the orbit naturally clears, however all “routine” area launches will essentially come together with an unlimited gamble.

solar flare

A photo voltaic flare from our Solar, which ejects matter out away from our father or mother star and into the Photo voltaic System, can set off occasions like coronal mass ejections. Though the particles sometimes take ~3 days to reach, essentially the most energetic occasions can attain Earth in below 24 hours, and may trigger essentially the most injury to our electronics and electrical infrastructure: each on the floor in addition to our area/satellite tv for pc infrastructure.

Credit score: NASA/Photo voltaic Dynamics Observatory/GSFC

The best hazard that the Solar poses to Earth immediately is a large-scale coronal mass ejection, which — if it heads proper for us with the unsuitable magnetic discipline orientation — might result in a wide-scale electrical disaster that would knock out energy grids all around the Earth, beginning fires and inflicting trillions of greenback in injury to our infrastructure.

Nevertheless, a sequence of photo voltaic telescopes and observatories provides a possible answer. By monitoring the Solar:

  • from Earth, with observatories such because the NSF’s Inouye Photo voltaic Telescope,
  • from in orbit across the Solar, akin to with NASA’s Parker Photo voltaic Probe and ESA’s Photo voltaic Orbiter,
  • from the L1 Lagrange level, with observatories like NASA’s SOHO and Photo voltaic Dynamics Observatory,
  • and from in orbit round Earth, like with Japan’s Hinode satellite tv for pc,

we will monitor area climate as quickly because it will get ejected from the Solar, assessing the danger to our planet whereas the area climate is on its method, earlier than any satellites are impacted.

solar flare

When a coronal mass ejection seems to increase in all instructions comparatively equally from our perspective, a phenomenon often known as an annular CME, that’s a sign that the energetic particles emitted by the Solar are doubtless headed proper for our planet.

Credit score: ESA / NASA / SOHO

Such a infrastructure, particularly designed for area climate monitoring, can get us as much as three or 4 days of lead time for many area climate occasions, and even ~17 hours of advance discover for essentially the most highly effective, fastest-moving area climate occasions of all. Whereas a coronal mass ejection must possess particular properties to pose a danger to Earth’s infrastructure, satellites in orbit above Earth are in a much more precarious place, and are weak to:

  • coronal mass ejections,
  • photo voltaic flares,
  • and even simply the plain previous photo voltaic wind,

below all kinds circumstances.

So as to be certain that a photo voltaic flare directed at us doesn’t result in Kessler syndrome, the next precautions might forestall an in any other case inevitable catastrophe.

  • When a photo voltaic flare is emitted from the Solar, all mega-constellations of satellites should enter a pre-planned “protected route” orbit.
  • These “protected routes” can be passive orbits which are explicitly designed to maximise the space between satellites for the biggest period of time into the long run.
  • Such an intervention might purchase us, on the very least, years of time till a collision happens: sufficient time that even within the worst-case state of affairs, we might launch an emergency mission to intercept and de-orbit any damaged satellites.

Nevertheless, no such failsafe has been constructed into the infrastructure of any satellite tv for pc megaconstellation from the start, together with for Starlink. There is no such thing as a “protected mode,” and so till one is put into place, working these satellites below the established order will at all times carry alongside a danger of an area climate event-induced collision or chain response of collisions.


The collision of two satellites can create tons of of 1000’s of items of particles, most of that are very small however very fast-moving: as much as ~10 km/s. If sufficient satellites are in orbit, this particles might set off a sequence response, rendering the atmosphere round Earth virtually impassable.

Credit score: ESA/Area Particles Workplace

If we fail to arrange, the one choice we’ll have is to give you a intelligent identify for this easily-avoidable disaster: I counsel one thing like “Flaremageddon” for these functions. Such a pure catastrophe state of affairs turns into simple to ascertain. Think about that it’s 2035, and we’ve got a number of tens of 1000’s of latest mega-constellation satellites up there, whereas on the identical time, a sequence of sunspots seem across the Solar’s equator. A magnetic reconnection occasion happens, launching an X-class photo voltaic flare with a coronal mass ejection proper at Earth. The magnetic discipline of the Solar, relative to Earth, is oriented so {that a} geomagnetic storm happens, knocking out some main electrical grids within the course of.

However in area, a big fraction of satellites get bombarded by these energetic particles from the Solar, inflicting them to develop into non-responsive. 8 days later, the primary satellite-satellite collision happens. Whereas humanity scrambles to reply appropriately, the a second collision happens, triggering the start of a sequence response. By 2037, the Worldwide Area Station is compelled to be deserted, our Earth-monitoring satellites in low-Earth orbit are knocked offline, and the Hubble Area Telescope is destroyed. Tens of thousands and thousands of items of particles then fill low-Earth orbit, making any subsequent launches not possible with out the launch car itself experiencing a variety of impacts from this particles.

It’s a wholly avoidable catastrophe, however until we put together now, upfront of any foreseeable disasters, we run the danger of mortgaging our complete species’ future in area, all as a result of we did not take the required precautions.


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