SpaceX’s Rockets Are Tearing Too Many Holes In The Sky Worry Astronomers

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SpaceX’s Falcon 9 rockets, which have flown nearly 90 times this year, are now causing astronomers to worry about the impact that they are making on the Earth’s ionosphere. After launching its payload into space, the Falcon 9 fires up its Merline engines to reorient itself and reduce its speed for landing on land or in the sea. Similarly, after the second stage has finished its mission, it also fires up its engines to return to Earth.

These engines create holes in the ionosphere, a layer of charged gas surrounding the Earth that plays a crucial role in satellite communication. These holes generate red light, which can further affect astronomy and astronomers’ efforts to study the sky.

SpaceX’s Second Stage Falcon 9 Creating Holes In The Sky During Return To Earth

SpaceX’s Falcon 9 is the world’s only reusable medium-lift rocket, and while the first-stage booster lands on Earth after most missions, the second stage is not recovered. After a mission, once the Falcon 9’s second stage has delivered its payload, the rocket fires up its Merlin vacuum engine to reduce its altitude and burn up in the atmosphere, sometimes weeks after its launch.

The ionosphere starts from 60 kilometers from the Earth’s surface and extends as high as 300 kilometers. It is one of the highest regions of the atmosphere, and after it, only one additional layer is present before the vast emptiness of space begins. Within the ionosphere, several layers are ‘ionized’, which is scientific speak for charged particles. Particles within the ionosphere are energized due to their height, which leaves them exposed to the Sun’s radiation. This radiation also helps humans on Earth since it helps radio waves travel further.

An ionospheric hole was made by the Falcon 9 rocket, according to Stephen Hummel of McDonald Observatory. Image: SpaceWeather

Now, according to Stephen Hummel of the University of Texas’s Austin Laboratory, the Falcon 9 second stage is making holes in the ionosphere. Exhaust from a rocket can remove the charge from the ionospheric particles to create an empty area. As part of its descent journey, the second stage fires up its Merlin engine roughly an hour and a half after launch. The engine’s exhaust is made up mostly of water vapor, carbon dioxide and carbon monoxide. Hummel explains to Spaceweather that since the Falcon 9 second stage’s engine firings take place higher in the ionosphere, it makes large holes due to a lack of overall atmospheric density.

While the researcher is uncertain about the effects of these holes on astronomy, he is worried that once SpaceX steps up its launch cadence, they could become more common than they are now. However, other researchers are excited, since the rocket launches allow them to properly observe ionospheric deionization.

2023 has seen SpaceX set a new record when it comes to the number of launches, and with one month remaining, the firm still has some way to go before calling it a day. It is also developing the Starship rocket in Texas, and should Starship become operational, then it will fly in higher numbers than the Falcon 9 flies right now. SpaceX has also drawn criticism from astronomers about its Starlink satellites blocking the night sky, and the firm has responded by introducing upgrades on the spacecraft to prevent any reflections.

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