Crewed and uncrewed space flight doesn’t create a large percentage of the Earth’s carbon emissions. In 2018, Everyday Astronaut reported that rocket launches made up just 0.0000059% of the world’s carbon emissions. To contrast, the energy required to run commercial buildings makes up 25% to 40% of the world’s carbon emissions.
But we’ve never had more rockets going into space than we have today. Thanks largely to the efforts of Elon Musk’s SpaceX, rockets launched 180 times in 2022, the highest amount ever. SpaceX alone sent a Falcon into orbit once every six days on average, according to Nature.com.
As SpaceX intends to ramp up to not hundreds but thousands of launches per year, the environmental effects will increase. That’s why it’s essential to offset carbon emissions or make greener rockets.
Just How Bad Is Rocket Fuel for the Environment, Anyway?
Rockets don’t make much of an impact when you compare them to other causes of greenhouse gases, including travel by plane or car.
“I think we can guess that rockets won’t be a huge impact on the environment, and they probably won’t stand out as a sole source of new problems,” Darin Toohey, professor at the University of Colorado Boulder’s Atmospheric and Ocean Sciences, recently told Inverse.
However, the real impact depends on the rocket fuel. This is where some companies are making great strides while other organizations may be left in a cloud of dust – or toxic vapors.
Rockets of the Past: Solid Fuel
Rockets developed by NASA contractors, which have been used for decades in the space shuttle program, use solid hydrogen propellant for the side boosters and a combination of liquid oxygen and liquid hydrogen for the main boosters. Solid rocket exhaust contains hydrogen chloride, which is recognized to be toxic.
NASA has experimented with supercooled liquid hydrogen as a fuel for the Artemis I mission, which seeks to send U.S. astronauts back to the moon.
However, when the Orion spacecraft and Space Launch System (SLS) successfully launched in November 2022, it used solid rockets for the side boosters and liquid oxygen and liquid hydrogen for the center booster.
SpaceX Seeks Greener Fuel
It’s no secret that the founder of SpaceX and electric vehicle manufacturer Tesla seeks eco-friendly solutions whenever possible. Tesla has sold more E.V.s than any other manufacturer in recent years, reducing carbon emissions on roads by 5.0 million metric tons in 2020 alone.
SpaceX rockets use either kerosene and methane as primary fuels, oxygen as the main oxidizer, and nitrogen and helium as pressurizers and for cold gas thrusters. Robert Schuh, a graduate of the University of Stuttgart with a B.Sc in Physics, said on Quora of SpaceX rockets, “The main pollutants are water vapor and CO2. CO2 is very problematic, but only in massive amounts.”
The Merlin rockets that power Falcon 9 rockets rely on kerosene, but the Raptors used in Starship are powered by methane – and that methane could be even greener in coming years.
Green Hydrogen International, an energy start-up in South Texas, is seeking to produce more than 2.5 billion kilograms of green hydrogen, which can be used to create methane-based rocket fuel for nearby SpaceX launches out of Starbase in Boca Chica, Texas.
Orbex Experiments with Carbon BioFuel
Meanwhile, private space company Orbex based in the U.K., seeks to reduce its carbon footprint of launches by 96% using reusable rockets powered by biofuel.
Sutherland Spaceport, currently being erected on the North Coast of Scotland to host Orbex Prime launches, will be the first spaceport worldwide “committed to being carbon-neutral, both in its construction and operation.”
So far, however, the company has yet to launch its Orbex Prime space vehicle, designed to shuttle small satellites into low earth orbit.
Reusable Rockets, Greener Solutions
Of course, emissions from rocket launches aren’t the only aspect of space travel that increases the carbon footprint. When conventional rockets touch down on the ocean floor, they disrupt the natural environment and may release residual propellants into the water.
SpaceX’s reusable rockets, on the other hand, don’t create such waste. And, because the company can use them many times, the carbon footprint per launch is smaller since you don’t have to use energy to create a new rocket each time.
Similarly, Orbex seeks to launch reusable rockets soon and to offset emissions the rockets and their launch operations produce.
For the first time in decades, the future of space travel seems not just bright, but green.