When it all begins, we’ll be five days and 12 hours from disaster.
But that unstoppable calamity would unfold over the course of decades.
Some 600km above Earth is a rapidly intensifying cloud of satellites. They’re already indispensable. They enable our smartphones to navigate, research, and think for us. They control remote-controlled farming and mining machinery. They watch the ground to analyse everything from bugs to floods.
It’s big business.
Which is why megacorporations like Elon Musk’s SpaceX and superpowers like China are determined to pump tens of thousands more of these metallic boxes into increasingly crowded space lanes.
Like cars and trucks, each one is an accident waiting to happen.
Unlike cars and trucks, an orbital accident doesn’t end with the initial pile-up.
The wreckage keeps flying. And one prang can cause tens of thousands of others.
It canons around the Earth for weeks, months, years – possibly even centuries.
The odds of them eventually hitting something are high. And every hit adds more ammunition to the orbital cannonade.
Ground-based traffic controllers are struggling to keep up.
The odds of an orbital prang must constantly be calculated for about 14,000 active satellites. This is already complicated by the need to include the paths of 32,000 other objects (dead satellites, rocket debris and collision wreckage) bigger than 10cm.
Most modern satellites now have tiny thrusters.
These are vital.
They’re needed to dodge impending collisions.
Statistics suggest that each of Starlink’s 10,300 active satellites must swerve to avoid an accident an average of 41 times a year. That’s a total of 422,300 near-misses, or one every 1.8 minutes.
So what happens if their traffic controllers go offline?
All it would take is a solar storm. A war. Or a cyberattack.
An as-yet unreviewed study published in the digital science journal arXiv warns a catastrophic crash that could trigger a relentless orbital pile-up: “Our calculations show the CRASH Clock is currently 5.5 days, which suggests there is limited time to recover from a widespread disruptive event, such as a solar storm.”
Traffic snarl
“The number of required manoeuvres continues to increase; temporary lapses in collision avoidance capabilities, whether that be from inaccurate orbital determination or even a small miscommunication between operators in manoeuvre decision-making, will become increasingly catastrophic in their potential consequences,” the study, led by astrophysicist Sarah Thiele, reads.
“We propose a new metric, the CRASH Clock, that measures such stress in terms of the time it takes for a catastrophic collision to occur if there are no collision avoidance manoeuvres or there is a severe loss in situational awareness.”
Put simply, without active and effective traffic control, a serious smash is inevitable.
Low-Earth Orbit (LEO) is a narrow band of space between 400km and 800km high. It is popular for being close to the ground for speedy communications and sharper photos, but high enough to minimise drag from the dregs of Earth’s atmosphere.
The researchers report that LEO is already so crowded that it is experiencing a “close approach” (when one object passes another within a kilometre) every 36 seconds.
An encounter of less than 100m happens every 69 minutes.
And satellite tracking accuracy is measured in the tens of metres.
A LEO satellite generally orbits at about 27,000km/h. Which is why all it took to punch a hole in the Chinese Space Station’s “lifeboat” Shenzhou-20 capsule last year was a 1mm metal shaving.
An estimated 140 million such “untrackable” objects under 10cm in size are cannoning through the space lanes.
Those numbers keep rising.
On April 30, SpaceX fed another 29 new Starlink satellites into the traffic flow. That brings its total for the year to 1200.
More are being launched every month.
Starlink traffic controllers are reportedly having to double the number of satellite evasive manoeuvres every six months. Space operations management is a booming business, with companies such as Australia’s Saber Astronautics needed to chart paths through crowded skies.
“Simulations have shown that altitudes above 600-800 km altitude in LEO are already above the unstable threshold for long-term runaway debris growth,” the study reads.
“Strikingly, given the density and surface area, the main Starlink shell (about 550 km altitude) is also within the runaway threshold, meaning a single collision could
have catastrophic long-term consequences.”
Perfect storm
“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,” the researchers conclude. “Indeed, satellite operations could continue after a major collision, but would have different operating parameters, including a higher risk of collision damage.”
At the heart of the problem is a theoretical scenario first described by NASA scientist Donald Kessler.
Imagine a game of snooker or pot black.
The white ball smashes into an assembly of coloured balls. These scatter, bouncing off the edges and each other – with hopefully the right one going into a pocket.
Now imagine such a “break” without friction. The balls keep moving. They keep colliding.
In space, however, every collision creates thousands of new balls.
“While collisional cascades can take decades to centuries to develop, a single collision could create substantial stress on the orbital environment immediately, even if it does not lead to a runaway,” the researchers warn.
Major collisions (and deliberate destruction) have already happened in orbit.
In 2007, China tested an anti-satellite weapon by destroying the Fengyun 1C satellite. This created a cloud of 3000 trackable objects larger than 10cm, and more than 150,000 of 1cm or more.
A 2009 collision between the Iridium 33 and Kosmos 2251 satellites produced some 1800 pieces over 10cm, and more than 100,000 larger than 1cm.
Every piece is a potential satellite killer. As are the uncountable pieces smaller than 1cm.
Larger pieces can even cause an artificial meteor shower, such as the one triggered by the detonation of a SpaceX Starship rocket in January. That prompted the urgent declaration of a no-fly zone over major air routes, leading to several emergency landings.
“Ultimately, this debris will cause problems for all space launch agencies and private companies, as there is a limit to our ground-based tracking and warning abilities,” Nottingham Trent University researchers warn in a separate document.
“This makes addressing the global governance of space critical. However, it may take several high-cost satellites being taken out of commission, or potentially loss of life, for this issue to be taken seriously.”
