Shading the Earth with a Solar Shield

As the UK Government plans to extract even more gas and oil from the seas around Scotland it appears the ’emergency’ in ‘Climate Emergency’ has not managed to overcome their desire to exploit fossil fuels and make a lot of money.

Scientists around the world are searching for ideas in how to mitigate the effects of the global catastrophe of climate change. Some are thinking not just out of the box, but out of this world.

large triangular shield in front of the sun
Artist’s rendition of the proposed solar shield tethered to an asteroid as a counterweight. Image credit: Credit: Brooks Bays/UH Institute for Astronomy

 István Szapudi, an astronomer at the University of Hawaiʻi Institute for Astronomy, has proposed a novel approach—a solar shield to reduce the amount of sunlight hitting Earth, combined with a tethered, captured asteroid as a counterweight. Engineering studies using this approach could start now to create a workable design that could mitigate climate change within decades. 

One of the simplest approaches to reducing the global temperature is to shade the Earth from a fraction of the Sun’s light.

This idea, called a solar shield, has been proposed before, but the large amount of weight needed to make a shield massive enough to balance gravitational forces and prevent solar radiation pressure from blowing it away makes even the lightest materials prohibitively expensive.

Szapudi’s creative solution consists of two innovations:

  1. a tethered counterweight instead of just a massive shield, resulting in making the total mass more than 100 times less
  2. the use of a captured asteroid as the counterweight to avoid launching most of the mass from Earth.

Szapudi began with the goal of reducing solar radiation by 1.7%, an estimate of the amount needed to prevent a catastrophic rise in global temperatures.

He found that placing a tethered counterbalance toward the Sun could reduce the weight of the shield and counterweight to approximately 3.5 million tons, about one hundred times lighter than previous estimates for an untethered shield. 

While this number is still far beyond current launch capabilities, only 1% of the weight—about 35,000 tons—would be the shield itself, and that is the only part that needs to be launched from Earth.

With newer, lighter materials, the mass of the shield can be reduced even further. The remaining 99% of the total mass would be asteroids or lunar dust used as a counterweight.

Such a tethered structure would be faster and cheaper to build and deploy than other shield designs.

Today’s largest rockets can only lift about 50 tons to low Earth orbit, so this approach to solar radiation management would be challenging.

Szapudi’s approach brings the idea into the realm of possibility, even with today’s technology, whereas prior concepts were completely unachievable. Also, developing a light-weight but strong graphene tether connecting the shield with the counterweight is crucial.

Click on this link to access, Solar Radiation Management with a Tethered Sun Shield,  published in Proceedings of the National Academy of Sciences.

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