Commercial space travel could exacerbate our air pollution problems
Leaving our atmosphere sounds like a trip, but it comes at a cost to the planet
Potent pollutants
The kerosene fuel used by SpaceX Falcon rockets is a mix of hydrocarbons, composed of carbon and hydrogen atoms. These react with liquid oxygen to form carbon dioxide (CO₂), water vapour (H₂O) and black carbon or soot particles that are released from therocket exhaust.
CO₂ and H₂O are potent greenhouse gases, and black soot particles are very efficient at absorbing the sun’s rays. That means all these chemicals contribute to warming the Earth’s atmosphere.
Nitrogen oxides (NOx), reactive air pollutants, also form during launch due to very high temperatures causing a bonding reaction between usually stable nitrogen and oxygen molecules. NOx is also produced when the rocket’s reusable componentsreturn to Earth, due to extreme temperatures produced by friction on its heat shields as they whizz through the mesosphere at 40km-70km.
When these particles make contact with the ozone layer (in the stratosphere), they convertozone to oxygen, depleting the fragile sheath that protects the planet from the sun’s harmful UV radiation.
Although total CO₂ emissions from this launch will be small in comparison to those from the global aircraft industry, emissions per passenger will be around100 timesthose from a long-haul flight.
Soot emissions are also much less than those from the aircraft industry, but when released into the middle and upper atmosphere, soot has a warming effect500 times greaterthan at levels closer to Earth. This is in part because there are typically no clouds and few to no aerosols competing with soot to absorb the sun’s rays.
The potential opportunities of creating industry and trade networks within low-Earth orbit have been likened by an Axiom co-founder to the early days ofdeveloping the internet, now an almost universally accessible technology. If we extend that analogy to imagine similarly high levels of access to the low-Earth orbit economy, rocket launches are likely to become far more common than just the146 launchesachieved in 2021.
Such a scenario would substantially alter Earth’s climate and undermine our significant progress in repairing the ozone layer. At the very least, research is urgently needed to assess the consequences of a flourishing low-Earth orbit economy for our planet down below.
This article byEloise Marais, Associate Professor in Physical Geography,UCL, is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
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