Solar shield concept would tether asteroid to reduce launch weight

The idea of using a solar shield to deflect a portion of the Sun’s energy away from Earth has been around for many years, generally tabled as a method for mitigating global heating. Gravitational forces dictate that a huge amount of mass would be required to counterbalance the shield and keep it in position, preventing solar radiation pressure from blowing it away.  However, this scale would make launching the device impossible with current technology.

István Szapudi, from the University of Hawaiʻi’s Institute for Astronomy, has proposed using captured space material – either Moon dust or an asteroid – to act as the counterweight for a solar shield. According to Szapudi, this would enable scientists to use much lighter material for the shield itself, reducing launch weight by a factor of 100. His paper, “Solar radiation management with a tethered sun shield,” is published in Proceedings of the National Academy of Sciences.

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

Szapudi began with the goal of reducing solar radiation by 1.7 per cent, an estimate of the amount needed to prevent the continued 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, roughly 100 times lighter than previous estimates for an untethered shield.

While this number is still far beyond current launch capabilities, only one per cent 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. Today’s largest rockets are only capable of lifting around 50 tons per launch, so Szapudi’s method would still be extremely challenging, requiring several hundred launches as well as the linking of the shield material and captured asteroid. However, according, to Szapudi, it is not in the realm of the impossible.