The Private Space Race Takes A Toll On Planet Earth

5:17 minutes

Night time launch of space shuttle
Black carbon, soot, and other forms of air pollution are released into the air during spaceflight. Credit: Shutterstock

After the SpaceX explosion last month, debris wasn’t the only thing on the minds of Science Friday listeners. The following messages arrived in our inbox after we reported on 3-D printed rockets in March.

It was interesting to hear you discuss 7 space launches in 5 days, and then just moments later the fact that we’re not on track to reduce carbon emissions. My understanding is that rocket launches release huge amounts of carbon and other greenhouse gases. Story idea?—@RevBobIerien, Twitter

Also regarding the 3-D rockets there wasn’t any concern made for space pollution was there? I may have tuned out unhappily before the end. —Juanita H, email

How much carbon do rockets contribute to global warming? —Robert C, email

Very disappointing to hear the report of new “cheaper” 3D-printed rockets are available so that, like fast food pods and big gulps, we can now drop even more cheap **** into the ocean. And, *immediately* following a story about the new report on climate change, what exactly is the carbon footprint resulting from the ability of more people to more cheaply fire rockets into space? —David M, email

Carbon isn’t the big pollutant that comes from spaceflight, says Dr. Eloise Marais, associate professor in physical geography at University College London. Instead, black carbon or soot particles are generated and released directly into the atmosphere, alongside reactive nitrogen and nitrogen oxides.

Dr. Marais joins Ira to talk about how much of an impact increased rocket launches could have on the atmosphere, and how that compares to the auto industry. 

Segment Guests

Eloise Marais

Dr. Eloise Marais is an associate professor in Physical Geography at University College London in London, United Kingdom.

Segment Transcript

IRA FLATOW: Debris isn’t the only environmental consequence of spaceflight. Air pollution comes from rockets leaving and re-entering Earth. With private companies launching rockets more often than ever before for space exploration or tourism, how much pollution is being added to our atmosphere, and is it significant?

Joining me to evaluate this question is Dr. Eloise Murray, associate professor in physical geography at University College London in the UK. Welcome to Science Friday.

ELOISE MURRAY: Hi, Ira. Great to be on your show.

IRA FLATOW: Thank you. You’re welcome. We got a lot of questions from listeners recently– Robert, David, Bob, all writing in to ask how much carbon comes from rocket launches. And I assume that they mean CO2, the greenhouse gas. Can you answer that question for them?

ELOISE MURRAY: Yeah. Not much, especially in comparison to the CO2 that’s emitted from our sources on Earth– so burning of fossil fuels like coal and natural gas, vehicles, ships, a whole host of sources that contribute to CO2 on the ground. The carbon footprint from Rocket launches is quite low in comparison.

IRA FLATOW: What other pollutants are coming from the spaceflight?

ELOISE MURRAY: Yeah. The pollutants that we’re most concerned for in terms of their environmental influence are soot, or black carbon. These are tiny black particles that come from propellants that have carbon in their chemical structure. And these soot particles, because they’re dark, they’re very efficient at absorbing the sun’s radiation. And, in the process, they heat the surrounding atmosphere.

Then there’s also reactive gases that are released that are injected directly into the stratospheric layer– the layer that’s protecting us from harmful UV radiation. And many of them react to with ozone, essentially depleting it– so thinning that layer that’s protecting us from the sun’s rays.

IRA FLATOW: Is it possible to know just how much pollution is coming from rockets?

ELOISE MURRAY: We can calculate roughly what major pollutants are coming from rockets. We have information about the types of propellants that are used. They undergo combustion. And in this combustion process, they typically produce a host of pollutants. And we have some information about the amount of these pollutants that are produced per kilogram of propellant burned.

But of course, with all of these calculations, it’s not a precise estimate. It’s a good enough estimate for us to be able to assess the influence on the environment.

IRA FLATOW: Are there factors that change just how much pollution is occurring during a launch or a re-entry?

ELOISE MURRAY: Yeah. It’s mostly to do with the kind of propellant and the amount of propellant that’s being burnt for the launch process. And then for the re-entry process, a bit of a combination of what’s being burnt and how fast it’s moving through the atmosphere as it burns.

IRA FLATOW: Private companies like SpaceX are able to make and launch rockets at a speed we haven’t seen before. Do you have specific concerns about how these companies operate?

ELOISE MURRAY: Yeah. Especially if Elon Musk’s ambition of having three launches a day, and that’s every day in the year, and that’s just one company, that’s about 1,000 launches per year. And we haven’t quite hit the 200 launches per year mark. So this will be a substantial increase in the amount of rockets that are launched and then the amount of pollutants that are produced as well.

And unfortunately, for something like soot particles, the rockets have an overwhelmingly larger influence on climate than the soot particles that are produced near the surface of the Earth because the soot stays up in the higher layers of the atmosphere for so much longer. The longer it’s there, the greater the effect.

IRA FLATOW: But how much does this really compared to the auto industry or power companies burning coal and oil?

ELOISE MURRAY: We conducted a study where we focused on 2019 rocket launches– and this is before the exponential growth in the number of rockets being launched. And in that study we estimated that the amount of soot that’s produced from rockets is very small in comparison to all other anthropogenic sources, representing something like 0.01%. Really, really small.

But the climate effect in comparison to the other surface sources is 3%. So, considerably larger than the amount of emissions. And the implication there is that we don’t need to grow the rocket industry as much as, say, the number of flights we have to be able to have a similar impact.

IRA FLATOW: Well, that’s very interesting. And thank you for taking time to be with us today.

ELOISE MURRAY: Sure. It was great chatting to you.

IRA FLATOW: Dr. Eloise Murray, associate professor in physical geography at University College London in the UK.

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