Here's Why Exploding Satellites Are a Danger to the Space Station

Orbital space is filled with satellites, and they could damage the ISS.

But that's just the beginning.

On Monday, Russia destroyed one of its defunct orbital satellites, creating more than 1,500 pieces of supersonic space debris that posed a serious threat to scientists and astronauts aboard the International Space Station. Since then, NASA made a statement on the anti-satellite (ASAT) incident, confirming that all crew members were unharmed.

But to fully grasp the magnitude of this incident, we need to face the facts: with roughly 7,500 satellites in orbit as of September 2021, nearly 1,500 of which launched this year, we will probably see an event like this again. Especially since, as tensions mount between the U.S. and its allies on one hand, and China and Russia on the other, space war tactics aren't going to stop anytime soon.

Modern satellites use propellants that detonate upon impact

It may seem counterintuitive to imagine tiny fragments of orbital satellites posing a serious threat to the comparably gigantic International Space Station (ISS). After all, if all concerned objects are moving at similar relative speeds to maintain orbit, how can satellite debris achieve sufficient relative velocity to puncture the walls of the ISS? The answer lies in the engineering: Most modern electric propulsion satellites have Hall Effect Thrusters, which use high-pressure propellant tanks. And, when punctured by a high-velocity object (like a Russian missile), they explode, launching thousands of fragments in every direction.

"Satellites using Hall Effect Thrusters, the most common form of electric propulsion systems in use today, are inherently risky in that they use highly pressurized propellant tanks that, if ruptured, would cause a devastating explosion littering the orbital plane with dangerous debris," said CEO Peter Kant of Accion Systems in an email to IE. Among other things, this means that every single ASAT test has the potential to create a fresh batch of deadly space junk debris, since it would effectively detonate any targeted satellite equipped with high-pressure propellants, like a "space bomb."

Space war tactics will likely create more debris incidents

"The space debris can then collide with other spacecraft to create exponentially more space debris in a cascading chain reaction known as the Kessler Syndrome," added Kant in his email to IE. We've seen chain reactions like this on the silver screen, in the film "Gravity", where a lone astronaut survived not only the destruction of a space station, but also a harrowing long-term space-walk to a Chinese crew capsule. But, while a survival story like the movie's protagonist is compelling, it's also unlikely to succeed in reality. Luckily, this time there was no Kessler Syndrome, and no substantial damage was sustained by the ISS from Russia's ASAT test. But the danger posed to orbital space operations is compounded by the sheer number of fuel-filled satellites. "Imagine 3,700 little bombs flying around in space and extrapolate that to 7,000 next year," Kant said to IE. "Then large constellations may contain as many as 30,000 units. That's a lot of little bombs flying around in space."

And we're still working to understand how fast-moving satellite debris behaves in space. Professor Andrew Higgens of Mechanical Engineering at McGill University published a study in 2017 that detailed his work developing "the fastest gun in the world," according to a tweet. In the study, Higgins worked to expand our grasp of how hypersonic debris propagates — which can travel faster than 6.2 miles per second (10 km/s). That's more than 20,000 mph (nearly 36,000 km/h)! And, to make things worse, a company that generates space tracking information for private and public officials released video recreations of space war tactics executed by both China and the U.S. in October. This magnifies the threat of "3,700 little bombs in space" because, with space powers jockeying for orbital supremacy, further tests (or real military space combat) could trigger a global catastrophe, potentially forcing an early abandonment of the ISS, and periodically transforming low-Earth orbit into a cosmic shooting range.