UH astronomer’s innovative solar ‘umbrella’ idea could help fight climate change

There is a clear connection between the rapidly warming Earth and wildfires like the deadly fire that destroyed historic Lāhainā, with nearly 100 people confirmed dead on Maui and likely more to come. Much of the island is suffering from moderate or severe drought.

The National Oceanic and Atmospheric Administration supported a 2021 study that found climate change, including increased heat, extended drought and a thirsty atmosphere, isn’t just the key behind the increased number and intensity of wildfires in the western United States, it’s the main reason.

“Our world needs climate action on all fronts — everything, everywhere, all at once,” said United Nations Secretary-General Antonio Guterres in an Associated Press story from March.

Scientists around the globe are working on myriad ways to reduce the effects of climate change, including István Szapudi, an astronomer at the University of Hawaiʻi Institute for Astronomy, who has devised a novel idea to lessen the amount of sunlight hitting our planet.

In a paper titled “Solar radiation management with a tethered sun shield” recently published in Proceedings of the National Academy of Sciences, Szapudi proposes placing a sort of umbrella in a near gravitationally stable region of space between Earth and the sun along the sun-Earth axis, combined with a captured asteroid as a counterweight, that would shade the planet from a fraction of our star’s rays.

He was working on a space ship propulsion idea and read a paper about solar sails, spurring him to look into sun shades.

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

Solar shields have been brought to the table before to help in the battle against climate change, but most have been fiscally unfeasible and beyond current launch capabilities because of the weight of a massive enough shield to do the job and the necessary components to balance gravitational forces and stop solar radiation from simply blowing it away, like a solar sail instead, even using the lightest materials available today.

“You need to move the shade toward the sun to balance the pressure with gravity,” Szapudi said. “As you move the shade toward the sun, you need a bigger shade for the same gain. In the end, there is a minimum weight at an optimal position for shade to be in balance. That weight is more than 10,000 times more than the total humanity put in orbit in history.”

Today’s largest rockets can only lift about 50 tons into low Earth orbit.

His solution is a lighter weight shade connected to a ballast, a bit like a parachute. The longer the tether, the less weight will be needed for the same shade.

Szapudi’s creative idea innovates in two ways.

The tethered ballast, or counterweight, would be used instead of just a massive shield, which would make the shield’s total mass more than 100 times less than what has been previously proposed. Using a more lightweight material as the actual shield would also decrease its mass.

The use of an asteroid as that counterweight also would help avoid having to launch such a heavy payload from Earth. Most of the structure also could be built in space. It’s even plausible parts such as the tethers and shield could be built in orbit.

Szapudi proposes using graphene, one of the strongest and lightest materials known, for the shield and tethers. The price of the material also should drop within the next decade, making the cost of the project more feasible.

The remaining total of the shield structure’s mass, about 99%, would come from the asteroid — or even lunar dust — that would be used as the counterweight, further reducing the expense and time to deploy than previous shield designs. Szapudi suggested using the Pan-STARRS observatories on Maui, which already seek out near-Earth objects, to choose the best object as the counterweight.

The asteroid or lunar dust would have to be moved into place, and the shield and support structure could be deployed using conventional rockets.

The ultimate goal behind Szapudi’s idea would be to reduce solar radiation bombarding Earth by 1.7%, the estimated amount necessary to prevent catastrophic rise in global temperatures. His solar shield concept would be modular and reversible. With sufficient resources, it could even actively help control the planet’s temperature.

But any project of this kind would need to proceed cautiously to measure its effect on Earth.

Even though Szapudi’s concept would reduce the weight of the shield and ballast to about 3.5 million tons, also about 100 times lighter than previously proposed untethered shields, it’s still beyond existing launch capabilities. But about 35,000 tons of that weight would be the shield itself, which is the only part that needs to be launched from Earth.

With today’s technology, Szapudi’s approach to solar radiation management is within the realm of possibility. He admitted, however, additional research and development on how to manipulate an ateroid or lunar dust into place; the development of the tether tech, which would be similar to that needed for space elevators; and the shield and support structure design are needed.

That doesn’t mean we have to wait. Szapudi said engineering studies and research could be done within decades to create a workable design if humanity would put in the necessary resources.

“We are at a point when we start to feel climate change, and scientists say the Earth is approaching several irreversible tipping points,” Szapudi said. “All ideas to mitigate climate change should be investigated. Only geoengineering can reverse the adverse affects in a relatively short time.”

He added that humans could stop using fossil fuels today, but the carbon dioxide produced by their use would remain in the atmosphere.

“Only space-based geoengineering is is safe, modular and reversible on short time scales,” the astronomer said. “Therefore, this idea could be part of the solution.”