Like it or not, the mega constellations are coming. By the end of 2020, SpaceX plans to launch about 1,000 satellites in its Starlink constellation, singlehandedly increasing the number of active satellites in orbit by half. One of their competitors, OneWeb, intends to launch more than 400 satellites of its own in the same period, while other companies have similar plans for additional large constellations soaring aloft in the near future. And as the number of active satellites skyrockets, so too does the potential for severe adverse effects on our planet's orbital environment. "If you don't take action now, then you will be as responsible as those who have not taken care of climate change," says Kai-Uwe Schrogl, chief strategy officer for the European Space Agency (ESA).

A new and lucrative standard in global connectivity is the impetus for these sprawling swarms of spacecraft. Blanketing our planet in satellites to beam high-speed Internet to any location on Earth around the clock could banish the days of struggling with spotty Wi-Fi and cellular connections, while also transporting the estimated three billion people who are currently offline into the digital age. If these companies are successful, the entire world could be suddenly interlinked as never before, with the Internet becoming truly omnipresent for essentially every human on the planet.

Achieving this goal requires some heavy lifting, in its most literal sense. U.S.-based SpaceX plans to launch at least 12,000 satellites, with the possibility of lofting another 30,000, based on recent filings from the company. U.K.-based OneWeb hopes to orbit about 650 satellites, possibly increasing to almost 2,000 in the future, and U.S.-based Amazon is planning for more than 3,000 satellites in its Project Kuiper constellation. Other companies and nations, including China, also have their eye on developing similar constellations, with rough estimates suggesting there could be more than 50,000 satellites in total added to Earth orbit in the coming decades.

How to best manage this massive outpouring of satellites remains an open question. The roughly 2,000 active spacecraft orbiting Earth already have to dodge each other, as well as errant, defunct satellites and smaller pieces of space debris. The advent of mega constellations will require a huge increase in such "collision avoidance maneuvers." According to Bill Beckman, director of NASA programs at Boeing, speaking last week at the International Aeronautical Conference in Washington, D.C., such maneuvers could swell from a current average of three a day to about eight an hour. "We're going to have a massive increase in the number of satellites in orbit in a very short space of time," says Alice Gorman, a space archaeologist at Flinders University in Adelaide, Australia. "There are quite a few unknowns and there's quite a lot of optimism that I think isn't justified."

There are currently no strict international rules or regulations that dictate how a company operates such constellations in orbit, and regulators have struggled to cope with the rapid development of mega constellations. "Clearly this has never been regulated at this level before," says satellite expert Joanne Wheeler from Alden Legal in England. Each company, however, must have its plans scrutinized by a national regulator in order to be allowed to operate in Earth orbit. In the U.K. this is handled by the U.K. Space Agency (UKSA), which conducted a thorough analysis of OneWeb's proposal but did not provide specifics on their analysis. In the U.S. these reviews are handled by the Federal Communications Commission (FCC), which requires companies to provide both collision risk analyses and proposals to safely remove their satellites from orbit.

SpaceX, in one of its FCC filings, said its active Starlink satellites had at most a risk of collision of just 0.000000303 percent with any objects larger than 10 centimeters if one of them failed immediately after launching into an initial orbital altitude of about 350 kilometers. "Because SpaceX has invested in propulsion for its satellites, collision risk is considered to be zero (or near zero)," the company noted in one document sent to the FCC, although it did not provide collision risk analysis for failed satellites at their operational height of 550 kilometers. SpaceX has touted the automated collision avoidance capabilities of its satellites to dodge other objects, although this system did not operate in September and caused a close call with a European science satellite called Aeolus owing to a "bug" in the Starlink e-mail communication system. That bug, according to a SpaceX spokesperson, "has been fixed."

A satellite's malfunction need not only occur shortly after launch, however—a failure could come at any time in its mission. "My concern with these big constellations is the [overall] failure rates," says Glenn Peterson, a senior engineering specialist at the Aerospace Corporation near Los Angeles. "If a satellite fails, they can't bring it down any more." In its own filing with the FCC, Amazon was asked to project the potential collision risk of its Project Kuiper constellation if up to 15 percent of its satellites failed, a high but not unfathomable number. U.S.-company Iridium Communications, which launched a constellation of 95 satellites into orbit in the 1990s, found that 30 percent of those satellites failed. If 15 percent of Amazon's satellites failed in orbit, the company has estimated a 17 percent chance that one of them would collide with a piece of space debris—potentially breaking apart to create more space debris and raise overall collision risks. (Amazon declined to provide a comment for this story.)

The worst-case scenario, in which satellite collisions create a runaway feedback loop of ever-greater amounts of space debris, is known as the Kessler syndrome. "I think if you have 100,000 satellites in [low-Earth orbit] a Kessler syndrome is a real possibility if you have multiple screw-ups and collisions," says Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics. "More likely is that you get to a point where there's so much debris whizzing around that you have to maneuver so frequently that these constellations are no longer practical."

SpaceX, OneWeb and the FCC, which has authorized more than 13,000 satellites in the past two years alone, say they are taking these concerns seriously. "The FCC will ensure responsible operations through the licensing process and through regulations, including any new regulations adopted in the orbital debris rule-making proceeding," a spokesperson for the agency said. SpaceX's spokesperson, meanwhile, says any of its satellites that fail at lower orbits will "burn up in the Earth's atmosphere within one to five years." The company, however, also has plans to operate satellites at significantly higher altitudes of 1,150 kilometers where orbital lifetimes for failed satellites can be hundreds of years. OneWeb, too, intends to send satellites to such higher altitudes but also says it is working with experts to draw up plans for sustainable practices such as robotic servicing to de-orbit defunct spacecraft.

Astronomers have also raised concerns about constellations on their observations of the universe. The initial batch of SpaceX's Starlink satellites shone surprisingly bright in the night sky at dusk and dawn, and by some calculations these satellites, in addition to OneWeb and Amazon's proposals, could hamper observations. "We could be seeing up to 140 of these satellites at any given point of time 30 degrees above the horizon," says Cees Bassa, an astronomer from the Netherlands Institute for Radio Astronomy, who recently modeled the impact of mega constellations on the night sky. "Astronomy will [still] be possible, we will just have to learn to deal with many satellites passing through our observations, and they may ruin some observations."

Although regulators and organizations are already embroiled in discussions of how to cope with mega constellations, by the time any international agreement emerges, it might be too late. Holger Krag, head of the Space Debris Office at ESA, says they are developing an automated system to help satellites avoid collisions, but it will not be ready until 2023, by which time thousands of satellites will likely have already launched. "We need to develop [the technology]," Krag says. "It's one of our proposals for the ministerial council of ESA [in late November]."

Chris Johnson from the Secure World Foundation says that although there are undoubtedly some benefits from these mega constellations, we should not blindly rush to launch them. "They definitely are something to be concerned about," he says. "The risk is not worth the reward at the moment." In the event of a Kessler syndrome, parts of Earth orbit could be left essentially unusable for the foreseeable future, burdening our descendants with yet another planet-encompassing mess. "If we don't act wisely now, that will have an impact on the generations that want to use space in the future," Krag says. With launches set to come thick and fast in the next year, the window to act is rapidly diminishing.