The derelict Russian satellite Cosmos 2251 had been aimlessly spinning around Earth for nearly 15 years when, in 2009, it slammed into a functional Iridium telecommunication satellite at 26,000 miles per hour.

This collision sprayed an estimated 200,000 centimeter-sized bits of debris into orbit around Earth. Another 3,200 broken pieces from the crash were much larger, at 10 centimeters or greater in size. Each of these objects hurtling around Earth became instantly weaponized. They now threaten to pierce, damage, or destroy any other satellites unlucky enough to be in their way.

This debris, fortunately, hasn't yet collided with any other working satellites.

But scientists warn about the potential for a domino-like effect occurring, where just one collision could precipitate many more. Such an event, called the "Kessler Syndrome," was proposed in 1978 by astrophysicist Don Kessler, a former senior scientist for orbital debris research at NASA.

If the chain reaction were to occur, vast regions of valuable orbital space would become unusable collections of mangled debris.

Forty years after he first came up with his theory, Kessler says that there are about 5,000 satellites orbiting Earth, most of which are dead chunks of metal. Only about 1,700 of these satellites are currently in use.

The chain reaction Kessler warned of has not yet come to pass, but now the Elon Musk-founded company SpaceX has detailed plans to launch almost 12,000 satellites to orbit, according to applications filed with the Federal Communications Commission (FCC). The ambitious proposal, to beam down fast internet from space, is called Starlink.

And if this grand fleet of satellites is realized, SpaceX would have to face the unparalleled challenge of making sure these satellites don’t exacerbate Earth’s space debris problem, and at worst, advance a cascading, irreversible reality filled with space junk.

“It is unprecedented,” said Kessler in an interview. “The sheer number, that’s the problem.”

Lightning fast internet, but at what cost?

A SpaceX spokesperson declined to comment on the exact number of satellites the company is planning to launch, but an FCC public notice, dated August 12, 2017, states that “SpaceX also proposes to add a very-low-Earth orbit NGSO [non-geostationary orbit] constellation, consisting of 7,518 satellites” to the previous application of 4,425. If realized, this grand number would total 11,943 fuel-carrying satellites, each weighing nearly 900 pounds.

SpaceX successfully launched the first two demo Starlink satellites into orbit as a test last month.

First two Starlink demo satellites, called Tintin A & B, deployed and communicating to Earth stations pic.twitter.com/TfI53wHEtz — Elon Musk (@elonmusk) February 22, 2018

It appears likely that the U.S government will soon approve the full Starlink constellation. Last month, FCC Chairman Ajit Pai urged his four fellow commissioners to approve the SpaceX application, saying that the satellite constellation could “unleash the power of satellite constellations to provide high-speed internet to rural Americans.”

Once a satellite becomes antiquated or simply stops working, the ideal thing to do — to clear it out of space — is to let Earth’s atmosphere gulp it up and vaporize it. Satellites in a low enough orbit — around 300 miles above Earth or less — will gradually get pulled down into Earth’s atmosphere. Called atmospheric drag, this often happens naturally, or a satellite (if it has fuel) can be thrust into an orbit where atmospheric drag can take hold.

SpaceX plans for over 7,500 of its Starlink satellites to orbit about 200 miles above Earth, where the atmosphere can eventually destroy them. But over 4,000 will orbit over 700 miles, more than 1,000 kilometers, above Earth, far from reach of natural destruction.

“That’s a serious problem," said Alice Gorman, who studies orbital debris and space archaeology at Flinders University in South Australia, in an interview. “One-thousand kilometers [620 miles] is far too high for stuff to re-enter quickly.”

And the longer thousands of satellites are in space, the higher the chance for collisions — which could validate Kessler’s warning.

SpaceX's satellites could lead to more junk

Most satellites and debris occupy lower orbits than 1,000 kilometers, but that doesn’t mean the SpaceX satellites wouldn’t be threatened by other fast-traveling wayward debris.

“They’re assuming that above 1,000 kilometers it’s almost empty and we won’t run into problems, but that’s not the case,” said Kessler.

He cites an infamous 2007 incident wherein the Chinese launched a test missile at a derelict weather satellite. The missile hit its target, spraying a cloud of shrapnel into a wide range of orbits, including those where SpaceX proposes to fly.

SpaceX’s vice president of Satellite Government Affairs, Patricia Cooper, appears aware of the space debris problem and has publicly stated intentions to mitigate it — though no details have been provided.

“As a company, we are deeply committed to maintaining a debris-free environment in space, and our satellite system has been thoughtfully designed to meet or exceed all existing requirements for safety of operation in space and upon de-orbit,” said Cooper at the Senate Committee on Commerce, Science, and Transportation in October 2017.

“SpaceX is designing our satellites to maneuver thousands of times in their lifetime,” she added.

This means the Starlink satellites will likely carry fuel that could, in theory be used to deorbit them when the time comes. But this, said Gorman, “is like a double-edged sword.”

Fuel might make satellites maneuverable, but it also increases chances for explosions, she said.

Keeping space safe from our junk

Ultimately, the responsibility of keeping space usable, safe, and environmentally healthy probably shouldn’t be the duty of one ambitious company. SpaceX doesn’t have dominion over space — the world’s nations do. But there are no debris laws designed to keep busy parts of space safe.

“There are no binding laws or agreements that require the management of space debris,” said Lisa Ruth Rand, who studies the histories of science and technologies at the University of Wisconsin-Madison.

Without such agreements, if anything is going to persuade Elon Musk’s space venture to responsibly mitigate the debris from thousands of satellites, “it’s the incentive of norms,” said Rand.

“Ultimately if he’s going to be in space, he wants other people to keep space clear, so he should too,” she said.

A European Space Agency concept that proposes catching large pieces of space debris with nets and then bringing them towards Earth's atmosphere. Image: European space agency

On top of that, Musk wants people and governments to like his company, buy his satellite internet, and continue to use his relatively reliable rockets. Littering space isn’t a good business model.

“It’s bad publicity,” said Kessler.

Will it work?

Musk has said he wants Starlink up and running sometime around 2024. There’s little question SpaceX can achieve this. Unlike other telecoms planning to doing similar things — like OneWeb and Iridium — SpaceX has its own rockets, making it all the easier for the company to launch satellites on its own.

The question now becomes: How much demand will there be for broadband beamed from space? Perhaps a lot, if fiber cable infrastructure is still lacking in many places outside of cities.

But still, that's not a sure thing.

“I’d be curious about the voices of people who don’t have the internet,” said Rand. “Innovation for innovation’s sake is sexy, but it’s not clear anyone is going to adopt it.”

Although he’s often criticized for his visionary plans, Musk also follows through with a lot of them: There’s a Tesla Roadster in deep space; the 27-engine Falcon Heavy that launched on its first go; and Tesla — for all its production woes — sells more all-electric vehicles than anyone in the U.S.

Starlink, then, could very well arrive soon — along with its potential for exacerbating an ever-growing orbital debris problem.

“We have to ask some questions that we haven’t had to think about before,” said Gorman.

Maybe it's past time we start thinking up some answers.