When Blue Origin and Galactic Virgo spear their first respective crewed missions in July, this raised environmental concerns.
“How the billionaire space race could be a giant leap for pollution” The Guardian wrote. “The cost […] will be paid in carbon emissions ”, we read Popular science big title. “Who thinks of the atmosphere? ” demand The hill.
One billionaire who claims to think about the atmosphere is Elon Musk. The CEO claims he is “work on sustainable energy for Earth with Tesla and protect the future of consciousness by making life multiplanetary with SpaceX.”
But is SpaceX’s work to explore the stars undermining Tesla’s work to clean up Earth’s atmosphere? The short answer is, we don’t really know.
Martin Ross, senior commercial launch projects engineer at the non-profit consulting organization The Aerospace Corporation, recounts Reverse that more research is needed in this area.
“The current level of data on rocket emissions does not provide researchers with enough information to fully assess the impact of launches on the global environment,” he said.
Current rocket launches have a negligible effect on total carbon emissions – Everyday astronaut found that they accounted for 0.0000059% of global carbon emissions in 2018, while the airline industry produced 2.4% in the same year.
But the long-term effect is less clear, especially as companies like SpaceX go from hosting 26 launches in a year to 1,000 launches. by rocket in a year.
“I think we can guess that rockets won’t have a huge impact on the environment, and they probably won’t stand out as the only source of new problems,” he added. Darin Toohey, a professor at the University of Colorado Boulder’s Atmospheric and Ocean Sciences, tells Reverse. “But they will add to the growing list of activities that have negative impacts on the environment.”
Here’s what we know so far.
What is the carbon footprint of space travel?
Much depends on the rocket and the fuel it burns to create a thrust.
Eloise Marais, associate professor of physical geography at University College London, said The Guardian in July that she simulated the effects of rocket launches for a decade. She discovered that a rocket launch can produce 200 to 300 tonnes of carbon dioxide.
This largely corresponds to Everyday astronaut calculations. The United Launch Alliance’s Delta IV Heavy, which burns only hydrogen, leads with virtually no carbon. SpaceX Falcon 9 and NASA’s Space Shuttle both produce around 400 tonnes of carbon dioxide per launch.
United States today reported that Blue Origin’s New Shepard emits virtually no carbon dioxide. This is because it uses liquid hydrogen and oxygen as fuel.
The upcoming SpaceX Starship and Super Heavy produce 2,683 tonnes per launch. When adjusted for payload, it produces roughly the same as the Falcon 9: 27 tonnes of carbon dioxide per tonne in low Earth orbit.
Marais noted that these numbers are low compared to global air travel. But air travel produces one to three tonnes of carbon dioxide per passenger. As rocket launch emissions increase by nearly 6% per year, she warned that it would not take long to overtake air travel.
What pollution do rockets produce?
Beyond the carbon emissions described above, it’s important to remember that rockets can emit other gases and pollutants as well.
In a 2020 analysis, Everyday astronaut explained that each rocket will produce varying amounts of pollution. Take the SpaceX Falcon 9: it burns the rocket thruster and liquid oxygen, so it emits carbon dioxide, water vapor, nitrogen oxides, carbon soot, carbon monoxide, and sulfur compounds.
Other rockets produce pollutants like inorganic chlorine and alumina. Some, like the hydrogen-burning Delta IV Heavy, only produce water vapor and nitrogen oxides.
Water vapor has an effect on the atmosphere. In a 2012 article published in the Geophysical Research Journal, the authors observed how the last launch of NASA’s space shuttle in 2011 emitted around 350 tons of steam as it climbed. This created polar mesospheric clouds brighter than 99% of other clouds of this type in the region.
Are reusable rockets better for the environment?
In terms of launch emissions per ton sent into space, reusable rockets are actually worse. That’s because the ship can’t send that much weight into space at once, because it has to save fuel to get back.
Everyday astronaut notes that the SpaceX Falcon 9 can send 15.5 tons to low Earth orbit when reused, but it can launch 22.8 tons if it doesn’t need to return to Earth. This means that a reusable Falcon 9 emits 27 tonnes of carbon dioxide per tonne sent into space, while the non-reusable model emits 19 tonnes.
Of course, that doesn’t take into account the emissions associated with the production of the rocket itself. Reusable rockets will avoid emissions from the manufacturing process.
What is the most environmentally friendly rocket fuel?
It’s hard to say, because every fuel has its drawbacks.
In October, a study from the University of Exeter found that Orbex’s new Prime rocket would have a 96% lower carbon footprint than comparable launch programs. The engine uses biopropane and liquid oxygen.
The study examined direct emissions from launch, indirect emissions from production, and radiative forcing effects of non-carbon dioxide emissions into the atmosphere. He found that an Orbex Prime rocket launch would produce the equivalent of 13.8 tonnes of carbon dioxide.
Do space launches damage the ozone layer?
They tend to do this, but like so many other areas, it needs a closer look.
Ozone is a gas in the Earth’s stratosphere. Oxygen molecules in breathing air are made up of two oxygen atoms, but ozone molecules are made up of three oxygen atoms. The BBC notes that this layer absorbs about 98 percent of the sun’s harmful ultraviolet rays.
Scientists in the 1970s warned that commonly used chlorofluorocarbons, or CFCs, created a hole in the ozone layer. The Montreal Protocol in 1990 banned these ozone-depleting chemicals, but the Radio-Canada notes that the protocol did not cover aerospace.
In 2009, research published in the journal Astropolitics asserted that current rocket launches deplete a few hundredths of a percent of the ozone layer per year.
Toohey, who contributed to the study, claimed at the time that “if left unregulated, rocket launches by 2050 could result in more ozone destruction than ever realized. CFCs ”. Reverse that this statement was made with reference to powder rocket engines containing ammonium perchlorate.
“As far as I know, there are no limits to their use,” he says.
In January 2020, a new article in the Cleaner Production Journal warned that rocket launches moving across the ozone layer are a major concern. He explained that rockets cause ozone loss, but powder rocket engines like those on NASA’s space shuttle cause much greater losses.
Newer rockets that use liquid propellant, like SpaceX’s Falcon 9, cause less ozone loss. These rockets have grown in popularity since the 2009 study. The problem is that most of the studies have focused on solid rocket engines, so more research is needed to understand how they differ.
Can rockets be environmentally friendly?
In terms of carbon dioxide, Musk has indicated he’s thinking about it. In September 2019, he wrote that carbon capture would allow net zero carbon theft in the long run.
In January, Musk announced a $ 100 million in prize money for carbon removal. The four-year XPrize competition, which will end by Earth Day 2025, invites teams to demonstrate a cost-effective solution to removing gigatons of carbon per year.
Of course, carbon dioxide only covers part of the equation and does not take into account other pollutants. Even if Musk captures all of the carbon dioxide in the spacecraft, it will still emit water vapor and oxides of nitrogen. This is a problem with other zero carbon rockets like Blue Origin’s New Shepard.
The problem is, there isn’t enough data or research to understand what rockets do to the environment.
“As atmospheric scientists, we would like to be able to assess what these impacts are likely to be so that efforts can be made to reduce these impacts as launches become more frequent,” said Toohey. “But we lack the rocket emission observations that are needed to do this.”
This might be a small problem at the moment, but as the frequency of rocket launches increases, that could change soon.