Billionaire businessman Jeff Bezos will launch with three crew members aboard a New Shepard rocket on the world’s first unattended suborbital flight from Blue Origin Launch Site 1 near Van Horn, Texas on July 20, 2021.
Joe Skipper | Reuters
The space industry is taking off after decades of stagnation.
Driven primarily by the rapidly evolving space programs of Elon Musk’s SpaceX and China, the world experienced 114 orbital launches in 2018 – the first three-digit number since 1990. This year, the orbital launches are slated to be for the first time since the 1970s. And that count doesn’t include the recent suborbital tourism trips of Jeff Bezos’ Blue Origin and Richard Branson’s Virgin Galactic.
Between NASA planning to return to the moon, SpaceX building a massive “mega-constellation” of internet satellites, China manning a space station, and suborbital companies sending crews of tourists to the edge of space, launches could soon become a daily occurrence will.
But will the new space boom have its price on the planet?
“While we obviously need space launches and satellites, when you think about things like space tourism, you think about the environmental impact,” says Ian Whittaker, lecturer in space physics at Nottingham Trent University in the UK
Researchers are trying to figure out how the Earth might respond to stronger clouds of smoke from rocket exhaust by examining the total mix of carbon dioxide, soot, alumina, and other particles that are collectively emitted by a spreading variety of rockets.
So far, the fledgling space industry is not seriously threatening the environment and likely has room for growth. However, it is unclear whether that will change as the new space race accelerates.
“I don’t think we know enough at this point to pinpoint exactly what this future should look like,” said Martin Ross, atmospheric researcher at The Aerospace Corp. “We just don’t have this information yet.”
Effects on carbon dioxide and climate change
As the world grapples with the move away from fossil fuels, the rise of a new industry – especially one with huge clouds bubbling out from powerful engines – could seem unsettling.
Most rockets emit more planet-warming carbon than many airplanes. A few minutes of weightlessness on the Virgin Galactic spacecraft will leave a carbon footprint comparable to flying business class across the Atlantic, and an orbital launch of SpaceX’s upcoming fully reusable spacecraft will emit as much carbon dioxide as one continuously flying an aircraft for about three years, according to a back-of-the-envelope calculation by Whittaker.
A spokesman for Virgin Galactic said the company is “exploring ways to offset carbon emissions for future customer flights.” While SpaceX didn’t comment directly on carbon emissions, Musk has endorsed a carbon tax policy. Blue Origin has said its New Shepard missile uses carbon-free fuels like hydrogen and oxygen.
But there are far more commercial airplane flights than space launches – 39 million versus 114 in 2018 – too many for the space industry to catch up in even the most ambitious of scenarios. Today, rockets together consume about 0.1% as much fuel as airplanes, which makes their CO2 emissions compared to a rounding error.
Whittaker points out, however, that such calculations neglect the unknown, but likely substantial, carbon footprint of producing, transporting, and cooling the tons of fuel used in space launches
“While it doesn’t coincide with aviation, it’s still a great add-on,” he says.
To achieve carbon neutrality, he hopes the industry will follow Blue Origin’s lead and use carbon-free fuels as well as greener operations by producing fuel locally from renewable energy sources.
What missiles leave in the atmosphere
“If CO2 isn’t in the action, it’s the particles,” says Ross, who has spent decades studying the environmental impact of takeoffs.
The glowing flames that shoot out of a rocket’s engines indicate that when the vehicle burns, soot is produced, technically known as “black carbon”. Any rocket that burns carbon-based fuels like kerosene or methane injects these particles directly into the upper reaches of the atmosphere, where they are likely to circulate for four to five years.
There the growing layer of soot looks like a fine black umbrella. It absorbs solar radiation and effectively prevents sunlight from reaching the planet’s surface, much like proposed geoengineering schemes designed to temporarily cool the earth might work. Shiny alumina particles emitted by the solid rocket engines of NASA’s upcoming Space Launch System and China’s Long March 11 vehicle make the phenomenon worse by reflecting sunlight.
The effects of this unintended experiment are unknown – except that they could be significant. A simple 2014 simulation by Ross and a colleague found that the primary cooling effect of dozens of rocket launches is already consistent with the warming effect of carbon dioxide released by millions of commercial flights.
That’s not to say that the aerospace industry is offsetting the environmental impact of flying. Infusing the atmosphere with novel particles has complex effects, says Ross. For example, their rough model showed that rocket launches cooled some locations by 0.5 degrees Celsius, while they heated the Arctic by more than 1 degree Celsius. And the simulation didn’t try to include side effects, such as whether takeoffs would create clouds or kill. More sophisticated modeling could show that exhaust particulate matter exacerbates overall warming, says Ross.
Other emissions and ozone
Space launches also worry some researchers because rockets emit their exhaust gases directly into the stratosphere, home to the protective ozone layer that blocks harmful ultraviolet light.
Most solid rocket engines emit alumina particles and chlorine gas, which promote chemical reactions that break down ozone into molecular oxygen. SpaceX and Blue Origin have switched to liquid fuels, which are typically less harmful but still contain by-products, including water vapor and nitrogen oxides, which can break down ozone during the years they circulate in the upper atmosphere.
“They’re not harmless,” says Eloise Marais, an atmospheric researcher at University College London. “They have an impact on the atmosphere.”
Marais is working on a prediction of how the current portfolio of rocket fuels could thin the ozone layer in the not too distant future. She has explored the impact of current launches and a speculative scenario where space tourism is proving popular and reliable enough to support a few suborbital launches a day and an orbital launch every week.
The calculations need to be reviewed before release, Marais says, but preliminary results suggest that while today’s launches have little impact on ozone, a booming space tourism industry could begin to change that.
“The effect is big enough that we could worry if the industry grew beyond what we speculate,” she says.
How often the companies will start in the future remains uncertain. Virgin Galactic hopes to operate 400 flights a year at some point. SpaceX envisions Starship competing with commercial airlines to move passengers back and forth between major cities in less than an hour.
Balancing space advances with environmental concerns
Access to space has revolutionized weather forecasting, communications technology, and researchers’ ability to understand how human activities have changed the Earth’s climate. It has also enabled space-based facilities like the International Space Station and a fleet of space telescopes to conduct transformative basic research.
In the future, a thriving space industry could enable practical projects from clean, space-based solar power to asteroid mining, as well as support the search for life in the solar system and other scientific endeavors.
Researchers like Ross don’t want to stop this progress. Rather, they hope to make this possible by identifying potential environmental problems early on. Today’s embryonic space industry is largely harmless, and Ross suggests that an environmental research program could help keep it that way even at maturity.
Stratospheric aircraft could scan rocket clouds directly to learn exactly what they are spewing out, while satellites and ground-based observatories monitor the atmosphere for short-, medium- and long-term effects of take-offs. There is also the unknown effects of obsolete satellites “burning up” and throwing tons of metal particles into the upper atmosphere. Supercomputers could run extensive simulations to determine what levels and types of space activity can be safely conducted.
“We want to avoid a surprising future,” says Ross. “We would like to say that the space industry can now move forward sustainably.”