A new study published in the journal Earth’s Future has examined the climate impact of rocket launches and re-entry in 2019, and estimated the future impact of projected space tourism scenarios based on the recent billionaire space race.
The experts found that the black carbon (soot) particles emitted by rockets are nearly 500 times more efficient at holding heat in the atmosphere than all other sources of soot combined, thus leading to a stronger impact on the Earth’s climate.
Moreover, since pollutants emitted by solid-fuel rockets – together with the re-entry heating of returning spacecraft – are very harmful to stratospheric ozone, space tourism may soon lead to a significant depletion of the upper stratospheric ozone layer in the Arctic in spring.
“Rocket launches are routinely compared to greenhouse gas and air pollutant emissions from the aircraft industry, which we demonstrate in our work is erroneous,” said study co-author Eloise Marais, an associate professor of Physical Geography at the University College London (UCL).
“Soot particles from rocket launches have a much larger climate effect than aircraft and other Earth-bound sources, so there doesn’t need to be as many rocket launches as international flights to have a similar impact. What we really need now is a discussion amongst experts on the best strategy for regulating this rapidly growing industry.”
The scientists used a 3D atmospheric chemistry model that incorporated data on the chemicals released from all 103 rocket launches in 2019, combined with future projections of space tourism entrepreneurs such as Virgin Galactic, Blue Origin, and SpaceX, which aim to provide regular space travel opportunities for wealthy individuals.
The analyses revealed that the kerosene and hybrid synthetic rubber fuels used by these rockets will have a major impact on global warming. Moreover, when soot particles are directly injected into the upper atmosphere, they will have a significantly greater effect on the climate than other soot sources, being 500 times more efficient at retaining heat.
Finally, under a scenario of daily or weekly space tourism rocket launches, the impact on the stratospheric ozone layer will likely undermine the recovery experienced after the implementation of the Montreal Protocol in 1987, which banned the use of a variety of substances known to deplete the ozone layer.
“There is still a lot we need to find out about the influence of rocket launch and re-entry emissions on the atmosphere – in particular, the future size of the industry and the types and by-products of new fuels like liquid methane and bio-derived fuels,” said study co-author Robert Ryan, a research fellow in Geography at UCL.
“This study allows us to enter the new era of space tourism with our eyes wide open to the potential impacts. The conversation about regulating the environmental impact of the space launch industry needs to start now so we can minimize harm to the stratospheric ozone layer and climate,” he concluded.