The Rocket Fuel of the Future May Be More Environmentally Friendly

The commercial space industry is growing exponentially, and experts are looking for ways to make it more sustainable.

May 22, 2024 3:00 PM

Space shuttle rocket launch in the clouds with stars to outer space. Space on background. Sky and clouds. Spaceship flight. Elements of this image furnished by NASA

(Credit: dima_zel/Getty Images)

Newsletter

Sign up for our email newsletter for the latest science news

There’s a reason why high achievers are commonly told to “shoot for the stars” — space travel is far from a simple task. While once an ambitious goal, limited to government entities that had the funding and technology to execute major launches, commercial launches are dominating outer space today, giving rise to a relatively new, rapidly growing industry.

“I would say many of the trends we're seeing in the space industry, from increased satellites in orbit to decreasing payload sizes, can be explained by the rapid commercialization of space,” says Jeff Gardner, a senior writer at The Space Foundation.

The Cost of Commercial Space Launches

While space tourism missions launched by companies like Virgin Galactic have attracted lots of attention, the majority of commercial launches involve the deployment of GPS satellites and other Internet infrastructure into orbit, facilitating digital communication on Earth.

Gardner says he’s seen a major uptick in commercial space launches since 2020. And according to a 2024 report from the World Economic Forum, the commercial space economy could grow to a value of nearly $1.8 trillion by 2035.

Such rapid technological advancement can come at a cost: Emerging research has shown that rocket fuel emissions can have stark environmental impacts, and experts are starting to grapple with how to balance growth with sustainability.

“Right now, It's the wild west out there. There is no regulation, and companies can decide how many launches to make,” says Kostas Tsigaridis, who researches aerosols and their impact on the atmosphere at Columbia University. “But this is not sustainable into the future.”

How Do Rocket Fuels Produce Carbon Emissions?

When the U.S. began investing in space travel in the 1950s, the globally-recognized rocket fuel of choice was kerosene. It’s cheap, stable and easy to store, and was familiar and accessible to most of the world’s spacefaring nations at the time.

However, kerosene has drawn recent criticism due to its inefficiency. Rocket fuel engines that use kerosene produce power by burning carbon to produce carbon dioxide. While kerosene is relatively cheap and accessible, it’s also hard to achieve full oxidation, or convert all of this carbon into carbon dioxide. This can lead to the release of hazardous particulates.

“One of the least oxidized forms of carbon is black carbon,” Tsigaridis says. “[These atoms] are just not volatile enough to go into a gas phase. So they remain in the particulate phase.”

How Black Carbon Impacts the Environment

Black carbon is more common than you might think it is — you might see it, for example, coming from exhaust released by cars or trucks on the highway. What makes black carbon particularly harmful in rocket fuel, however, is what Tsigaridis describes as the “height of injection.” When these particulates are released in lower parts of the atmosphere, they’re swept away more quickly by precipitation. But when released into the stratosphere, several kilometers above the Earth’s surface, they can survive for much longer.

Black carbon also absorbs light and heat, meaning it can cause ozone depletion when released in the stratosphere. Today, it’s known as one of the primary causes of global warming, perhaps second only to CO2 as the main driver of climate change.

The increasing commercialization of the space industry has led to more launches per year. There were 41 successful launches in January and February 2024 alone, marking “the fastest launch cadence [since the start] of the Space Age," according to a report by the Space Foundation. By May, SpaceX had already launched its 50th mission of the year.

Yet kerosene still remains the industry’s default fuel, so with more launches come more black carbon emissions. According to a 2022 study by the NOAA, continued black carbon emissions at a rate of 1,000 tons per year could warm the stratosphere by over 2.5 degrees Fahrenheit in the next several decades.

And because most space launches are now being carried out by private companies, it’s becoming more difficult to cut down on the number of launches per year through domestic or international policy.

Greener Fuel Alternatives

Seeking more efficient alternatives, Tsigaridis and Gardner say experts in the field have begun exploring rocket fuel types beyond kerosene that may produce less particulate matter.

One solution could be switching to methane fuels rather than kerosene. It’s much easier to oxidize than kerosene or other hydrocarbons, which makes it more efficient, says Tsigaridis — but any hydrocarbon-based fuel will still produce some black carbon. If the industry does switch from kerosene to methane as its default fuel, it would likely be in the distant future.

“The only realistic way to create a rocket fuel that does not produce any black carbon, is to not use carbon at all,” Tsigaridis adds.

Liquid hydrogen is another popular fuel option that has long been used in both public and private space launches, from the iconic Apollo 11 mission that took a man to the moon in 1969 to NASA’s recent Artemis mission. It’s much better in terms of air quality — but producing liquid hydrogen can be a very fossil-fuel intensive process that poses some engineering challenges.

Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article: