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Launch of the new US moon rocket SLS in Florida
Photo: JIM WATSON / AFP
The European space agency Esa has just been allocated a significantly increased three-year budget.
Numerous space projects are to be financed with it, including rocket launches - even if the new Ariane 6 will at best fly for the first time at the end of next year.
The problem: rockets for space flights have a measurable impact on the climate.
They produce harmful nitrogen oxides, contribute to the depletion of the ozone layer and accelerate global warming.
The scope of such space flights is still comparatively small, as SPIEGEL reported last year, but experts expect an enormous increase also due to the emerging space tourism that companies such as Space-X, Blue Origin and Virgin Galactic are planning.
"Such space flights are harmful to the climate and a sheer waste of resources just because a few rich people have discovered this as a status symbol," says Knud Jahnke from the Max Planck Institute (MPI) for Astronomy in Heidelberg.
A team led by Robert Ryan from University College London has calculated that three years of space tourism could be enough to produce twice as many climate-damaging emissions as all scientific space missions.
"Rocket launches are routinely compared to greenhouse gas and air pollutant emissions from the aircraft industry, which we prove to be wrong in our work," explains co-author Eloise Marais from University College.
The simulations revealed that soot particles from the burned fuel in the stratosphere are about 500 times more effective at heating the Earth than near the ground.
Although rockets only contribute 0.02 percent of global soot emissions, they already account for six percent of soot-related global warming.
The scientists also take a critical view of the influence of rocket launches, the falling back of burned-out rocket stages and the return of spacecraft on the ozone layer, which protects the earth from aggressive ultraviolet solar radiation.
Increased space tourism would massively increase ozone loss over the northern polar region.
"The only part of the atmosphere that shows strong ozone recovery under the Montreal Protocol is the upper stratosphere," Ryan said.
“And they are the ones who are hit the hardest by the impact of rocket emissions.”
Exhaust plume after takeoff
Ioannis Kokkinakis and Dimitris Drikakis from the University of Nicosia in Cyprus took a closer look at the rocket exhaust plume.
The effects of the combustion products change significantly depending on the altitude, the researchers report in the journal Physics of Fluids.
Because the chemical composition of the air changes, but above all because the density decreases enormously.
At an altitude of up to ten kilometers, the higher air pressure keeps the rocket's exhaust plume together and therefore hot, so that the compounds nitrogen monoxide and nitrogen dioxide can form.
The amount of nitrogen oxides in the rocket trail is so large that it would be harmful to human health.
"We hope that commercial airlines like SpaceX,
Even if the greenhouse gas footprint of scientific space flights is manageable, more and more astronomers are thinking about how their research can be made more climate-friendly.
In a study presented in the journal "Nature Astronomy", experts led by Jürgen Knödlseder from the University of Toulouse examined the CO2 footprint left by the astronomical research infrastructure on the ground.
They estimate the amount of greenhouse gases released into the atmosphere by astronomers' activities at around 20.3 million tons of CO2 equivalent each year. The greenhouse gas potential of other gases such as methane is converted to the potential of carbon dioxide.
Calculated for the individual astronomers, this is 36.6 tons of CO2 equivalent.
If you consider that, according to experts, nature on Earth can only compensate about two tons of CO₂ per person per year, astronomy is currently 18 times as much.
chs/dpa
