Thousands of satellites are launched into low orbit. It could harm the ozone layer.
Thousands of small satellites are being launched into the “lower orbit” of space, just above the stratosphere, by companies like Spacex, Oneweb, Amazon’s proposed Project Kuiper and more - devices that can provide internet service among other uses. Because the number will soon reach many tens of thousands, concern is growing among atmospheric scientists about how they may harm the protective ozone layer that shields life on Earth from dangerous radiation from the sun.
Most of these low-earth-orbit satellites, sometimes called LEO constellations, are propelled by rockets that are fueled by kerosene.
The satellites are mostly made of aluminum and contain numerous electronic parts, batteries, carbon fiber, epoxies and metals, including titanium, cadmium, lithium, nickel and cobalt - materials that may contribute to ozone depletion as they continuously disintegrate in space and descend into the stratosphere.
A recent report published by the U.S. Government Accountability Office said at least 5,500 such satellites are in orbit, but it also questioned why these systems are not subject to environmental scrutiny by the Federal Communications Commission, which licenses such systems in the United States, even as the agency is reviewing applications involving tens of thousands of new satellites.
The United States isn’t alone. In 2021, the United Nations’ International Telecommunication Union received radio frequency applications for various systems worldwide that, if all approved, could total more than 1 million new LEO satellites.
In response to the GAO report, the FCC said its requirements for evaluating environmental concerns are based on the National Environmental Policy Act of 1969 - which doesn’t cover these systems. “How NEPA applies to new activities in an outer space environment is a novel issue,” FCC spokesman Will Wiquist told The Post in an email.
Historically, there has been global concern over substances that destroy stratospheric ozone. In 1987, the historic Montreal Protocol greatly restricted the use of chlorofluorocarbons worldwide, after those chemicals, used since the 1920s for refrigeration, air-conditioning, foam and aerosol spray cans, were found to deplete ozone after rising into the stratosphere.
Before that, similar concerns were raised in the 1970s regarding supersonic jets, such as the Concorde, which released ozone-destroying emissions directly into the stratosphere, where they flew.
Kerosene produces black carbon, commonly known as soot, which absorbs solar radiation, and would, in large emissions, exert a warming effect on the stratosphere, according to Christopher Maloney, a research scientist at the National Oceanic and Atmospheric Administration.
“This stratospheric warming can in turn impact ozone chemistry,” Maloney told The Post. He recently published a paper on the topic along with fellow NOAA scientists Robert Portmann and Karen Rosenlof, and Martin Ross of the Aerospace Corp., a California-based nonprofit research facility.
The science “is very clear” that stratospheric black carbon emissions could lead to ozone depletion, said Ross, comparing the effect to a “thin black umbrella that shades the Earth’s surface and warms the stratosphere.”
While jet aircraft also use kerosene, Ross notes that soot from airplanes dissipates within a few weeks.
But black carbon from rocket engines lasts years. Rockets also emit black carbon directly into the stratospheric ozone layer, whereas most jets fly lower in the stratosphere, below the ozone. Finally, Ross points out that rocket engines produce black carbon at much greater magnitude per kilogram of fuel burned than airplanes - up to a factor of 1,000.
“There is currently an estimated 1 gigagram (Gg) of black carbon emitted into the stratosphere from rockets every year,” said Maloney, “but by 2040, if space traffic increases as proposed, there could be as much as 10 Gg (10,000 metric tons) released per year.”
There’s also concern about emissions during reentry.
LEO satellites have a life span of about five years, yet little thought has been given to what happens during reentry.
“The end-of-life disposal mechanism for geosynchronous satellites is to put them in a graveyard orbit and not think about it,” said Ross. “The end-oflife disposal for these large, lower-orbit constellations is to dump them into the atmosphere.”
An estimated 50 to 90 percent of LEO satellites’ mass will disintegrate into an array of chemicals and metals. Aluminum breaks apart into alumina, which reflects sunlight.
This too, could cause ozone loss, by creating a “white umbrella” that cools the Earth, and by providing surfaces for ozone-depleting chemistry to flourish, said Ross.