New research warns that a single strong solar storm could flip low Earth orbit from busy-but-manageable to unstoppable chain reaction in just a few days, leaving thousands of satellites smashed and future launches at serious risk.
How close are we to losing low Earth orbit?
The study, led by astrophysicist Sarah Thiele and colleagues, paints a stark picture of life in low Earth orbit (LEO) in the age of “mega-constellations” such as SpaceX’s Starlink and other broadband fleets.
These networks rely on vast numbers of satellites flying in tight formation a few hundred kilometres above our heads. Under normal conditions, they are kept apart by constant tracking and tiny course corrections.
Across all mega-constellations, two spacecraft pass within 1 kilometre of each other roughly every 22 seconds.
For Starlink alone, the researchers estimate that such near-misses happen around every 11 minutes. Each of those satellites must carry out dozens of avoidance manoeuvres per year, nudging itself out of the way of other spacecraft or debris.
On paper, this is a highly choreographed traffic system. In practice, it is operating very close to the edge.
The solar storm trigger
What solar storms actually do to satellites
Solar storms start with explosions on the Sun’s surface, flinging out clouds of charged particles. When those particles slam into Earth’s magnetic field, they do far more than create pretty auroras.
The team highlights two key effects that matter for satellites:
- Atmospheric heating and drag: The upper atmosphere warms and puffs up, creating extra drag that slows satellites and shifts their orbits.
- System disruption: High-energy particles can knock out or scramble onboard electronics, including communications and navigation.
That atmospheric expansion makes satellite paths harder to predict. Operators must fire thrusters more often to keep each craft on its assigned track, and then fire them again to dodge other objects whose orbits have also shifted.
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During the intense “Gannon storm” of May 2024, more than half of all satellites in low Earth orbit had to burn fuel for repositioning. That was with operators still in control.
When control is lost
The truly dangerous situation is not just a strong storm, but a strong storm that also severs or degrades communications.
If a satellite cannot receive commands or cannot work out where it is, it becomes a 300‑kilogram bullet travelling at 7–8 kilometres per second. Multiply that by thousands, and the risk rises sharply.
Solar storms can simultaneously distort satellite orbits and shut down the very systems that would normally prevent collisions.
That combination is what turns a stressed but manageable environment into one that could fail suddenly.
The CRASH clock: 2.8 days to catastrophe
To quantify this risk, Thiele’s team designed a metric with an ominous name: the Collision Realization and Significant Harm Clock, or “CRASH clock”. It asks a simple question: once operators lose the ability to steer satellites, how long until a major collision occurs?
Their answer for June 2025 is unsettling:
| Year | Estimated time to first catastrophic collision if control is lost |
|---|---|
| 2018 (pre-mega-constellations) | 121 days |
| 2025 (mega-constellations in place) | 2.8 days |
That change reflects the sheer growth in satellite numbers since 2018. The more objects packed into LEO, the smaller the margins for error.
If control links went dark today, the study finds, there is about a 30% chance of a catastrophic collision within 24 hours.
One such crash would not just destroy two spacecraft. It could generate thousands of high-speed fragments that go on to hit others.
From one crash to a cascade: Kessler syndrome
This kind of runaway chain reaction has a name: Kessler syndrome. First proposed in the late 1970s, it describes a situation where each collision makes more debris, and that debris in turn triggers further collisions.
Kessler syndrome does not unfold overnight. It can take years or decades for the orbital environment to deteriorate to the point where safe launches become nearly impossible. Yet every big collision moves the system a step closer.
What the new CRASH clock shows is that the “seed event” for such a cascade might now be only days away during a severe solar storm that breaks control links.
In other words, the lag between losing control and having a serious, debris-generating crash has shrunk from seasons to a single weekend.
We have seen storms like this before
None of this is based on a far-fetched sci‑fi scenario. The strongest solar storm ever recorded hit Earth in 1859, known as the Carrington Event.
Back then, our technology consisted largely of telegraph wires. Even so, some telegraph offices caught fire and operators received strong electric shocks from their equipment. Today, the same level of solar fury would be hitting a planet wrapped in electronics and wrapped again in satellites.
A Carrington-level event in the age of mega-constellations could leave operators unable to command their fleets for far longer than 2.8 days.
The 2024 Gannon storm was powerful enough to force mass satellite manoeuvres and cause issues on the ground. Yet by historical standards, it was not the worst the Sun can deliver.
Why mega-constellations make everything harder
Low Earth orbit used to host a relatively modest number of large satellites. Ground teams could track them individually and plan avoidance moves with generous buffers.
The new era of broadband constellations has changed that. Thousands of small satellites fly in shells and planes only a few kilometres apart. Their orbits overlap with older satellites, spent rocket stages and pieces of debris from past collisions and anti-satellite tests.
This congestion drives up the background collision probability. It also forces operators to rely more heavily on automation and real-time data. During a storm, both those pillars can wobble at the same time.
There are trade-offs here. Mega-constellations deliver real benefits: global broadband coverage, improved navigation, rapid Earth observation and support for remote communities. The study’s point is that these benefits come with systemic risk that stretches far beyond a single company or country.
What could be done to slow the CRASH clock?
Thiele and her co-authors focus on the physics and statistics, not on policy prescriptions, but their numbers hint at possible lines of defence.
- Reducing satellite numbers or spreading constellations across different altitudes could ease congestion.
- Mandating better shielding and fault-tolerant electronics would help satellites ride out solar storms without going blind or mute.
- Improving space weather forecasting could give operators a few more hours to raise or lower orbits before a storm hits.
- Requiring reliable end-of-life deorbit plans would slowly trim the background clutter in LEO.
None of these steps remove the risk. They lengthen the CRASH clock, buying time during a crisis. That time could make the difference between a bad storm and a generational setback for spaceflight.
Key terms and ideas behind the warning
Some of the jargon around this research hides simple concepts that shape the debate.
Low Earth orbit (LEO) is the region from roughly 160 to 2,000 kilometres above Earth. Most internet mega-constellations sit between about 500 and 1,200 kilometres. At these heights, orbits decay slowly, so debris can linger for years, yet the atmosphere still has enough drag to be highly sensitive to solar storms.
Atmospheric drag in this context is just friction with thin air. Even at near-vacuum altitudes, tiny molecules act like a very weak brake. When the Sun heats the upper atmosphere, that brake gets stronger, pushing satellites into slightly lower, faster orbits. Those shifts change when and where close approaches happen.
Close approach thresholds are another subtle but important detail. The study uses 1 kilometre as its benchmark. For an object travelling at several kilometres per second, a kilometre is not much room at all. The fact that such near-passes occur multiple times a minute reflects how crowded LEO has become.
What a worst-case week in orbit could look like
Imagine the following chain of events in the late 2020s.
A solar flare erupts from an active region on the Sun, hurling a cloud of plasma toward Earth. Space weather monitors see the eruption and issue a storm watch. Operators begin preparing, but the full impact time and strength remain uncertain.
When the cloud arrives, auroras explode across mid-latitudes. At the same time, the upper atmosphere swells. Tracking radars see orbits shifting. Warning messages for potential collisions spike. Teams scramble to send updated avoidance commands.
Then a subset of satellites, particularly older or more lightly shielded ones, start reporting glitches. Some reboot. Some lose contact. A few go dark. The network that coordinates collision avoidance now has moving objects it can see but no longer control.
On Earth, operators are dealing with power-grid fluctuations and patchy communications just as they most need clean data. For several hours, manoeuvre planning falls behind the pace of orbital change.
Somewhere above, two satellites cross paths at the wrong time, at a relative speed of more than 10 times that of a rifle bullet. The impact shreds both and sends fragments through nearby orbital lanes. Each fleck of metal becomes a threat in its own right.
The study’s CRASH clock is, essentially, asking how long it would take for such a moment to arrive once control starts to slip. In 2025, their answer sits alarmingly close to a single long weekend: 2.8 days.
As mega-constellations expand further, that number could shrink again unless design, regulation and space weather resilience catch up. The orbits above our heads are no longer an empty frontier; they are a fragile, crowded system that can tip from order to chaos faster than most people on the ground realise.
Originally posted 2026-02-10 11:00:06.