SpaceX Now Valued at $350 Billion Facing Space Debris Problem(II)

By Yibai, Jointing.Media, in Shanghai, 2024-12-26

Retired satellites will continue to deplete the ozone layer

Ozone levels in the stratosphere are in a dynamic equilibrium.The ozone layer acts as a filter for harmful ultraviolet light from the sun’s rays, and it is likely that ozone breaks down into oxygen molecules during this process. However his balance can be disrupted by human activity, such as the release of Freon into the atmosphere. Since 1987, when many countries around the world signed the Montreal Protocol to phase out the use of Freon as a refrigerant, there has been a gradual recovery of the ozone layer.

However, the number of satellites is increasing, and they are becoming a significant source of concern due to their potential to cause pollution. According to the European Space Agency’s Space Debris Office (SDO), there are approximately 3,200 failed satellites as of February 2020, and the number of malfunctioning satellites from just one project, the Starlink programme, may amount to 12-38% of the total number of satellites that have failed over the past 60 years. Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, cross-referenced data from SpaceX and the U.S. government and surmised that about 3% of the Starlink satellites that have been launched so far may have failed.

It is estimated that the total number of satellites planned for future launches will exceed 100,000. This means that the number of failed satellites is likely to be significant, regardless of whether the failure rate is 3 per cent or 1 per cent.

International guidelines recommend that once a satellite has reached the end of its useful life, it should be re-entered into the atmosphere within 25 years to minimise the risk of collision with other satellites.Generally, a satellite is composed of approximately one-third aluminium. When a satellite re-enters the atmosphere, aluminium metal particles produced by friction from the high temperature, high speed airflow react with the surrounding oxygen to form aluminium oxide nanoparticles (AlO). These particles have been found to be chlorine-activated catalysts, which deplete ozone in the stratosphere.

The study indicates that a standard 250 kg decommissioned satellite generates approximately 30 kg of aluminium oxide nanoparticles, which have the potential to persist in the atmosphere for extended periods, potentially decades. The satellites re-entry in 2022 contributed approximately 17 tonnes of alumina compounds, marking a 29.5% increase compared to natural levels. Furthermore, re-entry scenarios involving giant constellations suggest potential annual emissions of more than 360 tonnes of alumina compounds, which could lead to severe ozone depletion.

The number of objects in LEO is set to triple over the next century. Researchers predict a dramatic rise in ozone depletion levels in the coming decades if the problem is not addressed.
Aluminium oxide particles are produced at altitudes in excess of 80 kilometres above ground and take 30 years to reach the stratosphere, 10 to 50 kilometres above ground, where the Earth’s ozone is predominantly distributed.

(To be continued)

Edited by Wind and DeepL
Image:Starlink Satellites over Carson National Forest M Lewinsky | M Lewinsky/CC BY 4.0

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