We could cool down earth with a shield in space tethered to an asteroid

Photo: Pexels/Peter Fazekas

As greenhouse gases accumulate in the atmosphere, the planet continues to warm, making life on it increasingly difficult both on land and in water. Blocking the sun rays could help reduce temperatures and a scientist has a novel solution for that: a solar shield tethered to an asteroid.

As his Solar Radiation Management strategy, István Szapudi, an astronomer at the University of Hawaiʻi Institute for Astronomy, envisions launching a massive shield into low orbit and then tethering it to a captured asteroid to act as a counterweight and stop the shield from drifting away.

“Engineering studies using this approach could start now to create a workable design that could mitigate climate change within decades,” the scientist says regarding his findings that he details in a study.

Although the idea of a solar shield is not new, tethering it to an asteroid is. The latter would provide the weight needed to make a shield large enough to balance gravitational forces and prevent solar radiation pressure from blowing it away.

“One of the biggest hurdles for proposals aimed at blocking a small fraction of sunlight from space is weight. In space, weight translates into unrealistic costs. The preferred location for a sunshade is beyond the L1 Lagrange point toward the Sun, where the solar radiation pressure and gravity of the Earth and the Sun are in balance. Advances in light materials, such as graphene, could produce extremely light solar shades, similar to solar sails,” the scientist writes in his paper.

He got the idea, he says, from umbrellas used by people to shield themselves from sunrays.

“In Hawaiʻi, many people use an umbrella to block the sunlight as they walk about during the day. I was thinking, Could we do the same for Earth and thereby mitigate the impending catastrophe of climate change?” Szapudi notes.

Szapudi wanted to find a way to reduce solar radiation by 1.7%, which is likely 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.”

Currently it would be impossible to launch such a massive weight from earth and only 1% of it, or about 35,000 tons, would be the shield itself. Even the largest rockets today can lift only about 50 tons to low orbit around the planet,

With newer, lighter materials, the mass of the shield can be reduced further while the remaining 99% of the total mass would come from asteroids or lunar dust captured in space to serve as a counterweight. Developing a light-weight but strong graphene tether would also be crucial.

“Such a tethered structure would be faster and cheaper to build and deploy than other shield designs,” the scientist says.