Captured asteroid secured to solar shield could tackle Earth's rising heat

The concept may seem far-fetched at first, but as you read on, it actually makes sense.
Sade Agard
Sun ‘umbrella’ tethered to asteroid might help mitigate climate change
Sun ‘umbrella’ tethered to asteroid might help mitigate climate change

Brooks Bays/UH Institute for Astronomy 

In the ongoing quest to combat Earth's rising temperatures, an astronomer has put forth an innovative approach—a solar shield combined with a tethered, captured asteroid as a counterweight. 

The research behind this novel concept was recently published in the Proceedings of the National Academy of Sciences on July 31.

The asteroid-solar shield combo

Shading the Earth from a fraction of the Sun's light, known as a solar shield, has been suggested in the past. 

However, the enormous weight required to create a shield large enough to balance gravitational forces and counter solar radiation pressure has rendered the idea impractical due to the high cost of materials.

Stván Szapudi, an astronomer at the University of Hawaiʻi Institute for Astronomy, offers a creative solution featuring two key innovations. 

First, he proposes using a tethered counterweight instead of a massive shield, significantly reducing the total mass by over 100 times. 

Second, he suggests employing a captured asteroid as the counterweight, eliminating the need to launch most of the mass from Earth.

"In Hawaiʻi, many 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 said in a press release. 

Captured asteroid secured to solar shield could tackle Earth's rising heat
Concept image of the 'sun umbrella' in space

Szapudi aims to reduce solar radiation by 1.7 percent — a critical estimate to prevent a catastrophic rise in global temperatures. 

His research found that placing a tethered counterbalance toward the Sun would reduce the shield's weight and counterweight to approximately 3.5 million tons, about one hundred times lighter than previous untethered shield estimates.

Though still beyond current launch capabilities, Szapudi's concept offers hope. 

Better than other designs

The shield itself would constitute only 1 percent of the weight —approximately 35,000 tons — it's also the only part that would need to be launched from Earth. 

Further reduction of the shield's mass becomes feasible with the development of newer, lighter materials.

The remaining 99 percent of the total mass would be composed of asteroids or lunar dust, used as the counterweight. This tethered structure would be faster and cheaper to build and deploy than previous shield designs.

While today's largest rockets can only lift about 50 tons to low Earth orbit, Szapudi's approach brings the idea within the realm of possibility with current technology, unlike prior concepts deemed unachievable.

Another key challenge is the development of a lightweight but robust graphene tether connecting the shield to the counterweight. Success in this aspect is crucial to making this ambitious solar shield concept a reality.

As scientists continue to explore bold ideas to safeguard our planet from the effects of climate change, Szapudi's proposal stands out as a promising avenue worth further investigation.

The full study was published in PNAS on July 31 and can be found here.

Study abstract:

This paper presents an approach to Solar Radiation Management (SRM) using a tethered solar shield at the modified gravitational L1 Lagrange point. Unlike previous proposals, which were constrained by the McInnes bound on shield surface density, our proposed configuration with a counterweight toward the Sun circumvents this limitation and potentially reduces the total mass by orders of magnitude. Furthermore, only 1% of the total weight must come from Earth, with ballast from lunar dust or asteroids serving as the remainder. This approach could lead to a significant cost reduction and potentially be more effective than previous space-based SRM strategies.

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