During the last decade, the number of rockets that have reached space has only increased year after year , until 2021 became the year with the most launches in history, with 135 successful launches , surpassing even the golden age of the The first space race, in which the United States and the Soviet Union competed for dominance in space. This has been largely due to the rapid development of reusable rockets by different companies in the private sector. SpaceX stands out among them, responsible for more launches than the Russian agency or other private companies, but there are also other companies with important developments such as Blue Origin, Virgin Galactic, Arianespace or Rocket Lab
The reuse of these rockets allows a considerable reduction in launch costs , making access to space and low Earth orbit more profitable for more nations and private companies. With this increase in space traffic, however, comes a new concern: the pollution resulting from all this activity . Until now, the space industry has been able to avoid these considerations, since its dozens of annual launches could not be compared to, for example, the millions of annual flights that make the aviation industry responsible for more than 2% of the CO2 emitted to the atmosphere each year .
But that is the only thing that makes them less of a problem: their small number, because each launch can be tens or hundreds of times more polluting than a transoceanic flight , and because their contamination occurs in places in the atmosphere that were previously ignored. The same has been studied by the team from the University of Nicosia, in Cyprus, led by researchers Ioannis W. Kokkinakis and Dimitris Drikakis. They have studied the effect of a rocket launch on the concentration of carbon dioxide (CO 2 ) and nitrogen oxides (NO and NO 2 ) . Specifically, they have used the data corresponding to a SpaceX Falcon 9 rocket for their models. This has been due to data availability rather than personal preference.
They have studied the contamination of the atmosphere up to approximately 70 kilometers high , verifying that it is considerable, in contrast to that of commercial flights, which barely exceeds 10 kilometers from the earth’s surface. This contamination at higher altitudes causes gases to be introduced in concentrations much higher than those given naturally, causing processes that we still do not understand enough . When ascending a rocket on its way to low Earth orbit, they calculated that at low altitude, the added carbon dioxide was much lower than the ambient concentration, but that above 40 kilometers of height these concentrations equaled , reaching proportions of 30 to 1 for heights of about 70 km. In other words, when a rocket crosses the upper layers of the atmosphere, it emits, due to the burning of its fuel, about 30 times more CO2 per cubic kilometer than it already had before the passage of the rocket .
This significant increase is dispersed over time, with carbon dioxide falling little by little to lower altitudes , although if the rate of space launches were to increase sufficiently, the dispersion could be overcome, increasing CO2 concentration over time. at this height . This can heat these areas of the atmosphere, bringing currently unknown effects on the rest of the atmosphere. In addition, the amounts of carbon monoxide and water vapor introduced at this altitude, although less than carbon dioxide, are enormous compared to natural concentrations, which are practically 0% .
In addition to the gases these rockets directly deposit, they can also cause the creation of other compounds of concern. For example, the high temperatures reached in the flare that drives the rocket can cause, especially at low altitudes, the heating of the surrounding gas to temperatures sufficient (about 1000 ºC) to generate nitric oxide (NO) and nitrogen dioxide ( NO2) . These compounds contribute to the appearance of phenomena such as toxic fog (known as smog in English) that covers large cities and acid rain . It also affects atmospheric ozone . The levels at which these nitrogen oxides are produced could be high enough to pose a direct risk to human health if the rate of space launches increases.
All these effects have hardly been studied until now , because the contamination due to the space industry was rather anecdotal, however in the near future when we may see hundreds or even thousands of launches a year, this will be a problem to be taken into account . into account and a new challenge for those who develop this technology. There are already some proposals for much more energy-efficient launches, although they tend to be more science fiction. With the development of new materials, new technologies, and with the increasing profitability of space, there may be developments to make this a greener industry .
References:
I. W. Kokkinakis et al, 2022, Atmospheric pollution from rockets, Physics of Fluids 34, 056107, https://doi.org/10.1063/5.0090017
