First completely private launch of the ISS has just taken place, but it also has a negative component

(ORDO NEWS) — The Axiom-1 mission to send four private astronauts to the International Space Station is the first of many missions planned by NASA to expand the ISS for commercial use in what is being called the low Earth orbit economy.

The commander of the Axiom-1 mission categorically stated that this is not an example of space tourism, since the crew has been trained, and biomedical research is planned as part of the mission.

The crew members – all males between the ages of 52 and 71 – reportedly paid $55 million (£42.3 million) for the ticket, an amount that would no doubt fund a massive biomedical research program here on Earth. But beyond the ridiculous price of a ticket, I’m concerned about the potential environmental impact of such space travel.

For the flight, a SpaceX Falcon 9 Block 5 rocket is used, on top of which is the crew in the Crew Dragon spacecraft. The rocket consists of two stages: a reusable upper stage, which contains most (about four-fifths) of the fuel and which is returned to Earth for reuse, and a discarded second stage.

Before returning to Earth, the launch vehicle reaches an altitude of about 140 km (87 miles). The energy needed to deliver a spacecraft to the ISS comes from a combustion reaction between rocket kerosene and liquid oxygen, which releases environmentally hazardous by-products.

Rocket launches and the return of reusable components release air pollutants and greenhouse gases into multiple layers of the atmosphere. In the middle and upper atmosphere, they can persist for years compared to equivalent pollutants released on or near the Earth’s surface, which persist for a few weeks at most.

This is because fewer chemical reactions or weather events are required to wash pollutants out of the middle and upper layers.

Potent contaminants

The kerosene fuel used by the SpaceX Falcon rockets is a mixture of hydrocarbons made up of carbon and hydrogen atoms. They react with liquid oxygen to form carbon dioxide (CO2), water vapor (H2O), and black carbon or soot particles that are emitted from rocket exhaust.

CO2 and H2O are powerful greenhouse gases, and black carbon particles are very efficient at absorbing the sun’s rays. This means that all these chemicals contribute to the warming of the Earth’s atmosphere.

Nitrogen oxides (NOx), reactive air pollutants, are also formed during launch due to very high temperatures causing a binding reaction between normally stable nitrogen and oxygen molecules. NOx is also produced when reusable rocket components return to Earth due to extreme temperatures resulting from friction against heat shields as they fly through the mesosphere at an altitude of 40-70 km.

When these particles come into contact with the ozone layer (in the stratosphere), they convert ozone into oxygen, depleting the fragile shell that protects the planet from harmful ultraviolet radiation from the Sun.

Although the total CO2 emissions from this launch will be small compared to those of the global aviation industry, the emissions per passenger will be about 100 times greater than those of a long-haul flight.

Soot emissions are also much less than those from the aviation industry, but in the middle and upper atmosphere, soot has a 500 times greater warming effect than at levels closer to Earth. This is partly because there are generally no clouds and little to no aerosols competing with soot to absorb the sun’s rays.

The potential for building industrial and commercial networks in low Earth orbit was compared by the Axiom co-founder to the early days of the Internet, which is now a near-common technology.

Expanding on this analogy to imagine an equally high level of access to the economy of low Earth orbit, rocket launches are likely to become much more common than the 146 launches achieved in 2021.

Such a scenario would significantly change the Earth’s climate and undermine our significant progress in restoring the ozone layer. At the very least, research is urgently needed to assess the implications of a flourishing economy in low Earth orbit for our planet below. The Conversation


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