Petra Stock
A University of Hawai’i astronomer argues tethering a sun shield to an asteroid would reduce the required mass of the climate geoengineering structure for blocking solar radiation.
Sunshades and space mirrors are a group of climate geoengineering technologies called solar radiation management. These are large-scale, high-consequence technologies for tackling climate change.
The latest proposed design would still exceed current rocket capabilities, and the technology for sufficiently robust tethers does not yet exist, author and astronomer István Szapudi explains in his paper, published in the Proceedings of the National Academy of Sciences.
Szapudi writes “one of the biggest hurdles for proposals aimed at blocking a small fraction of sunlight from space is weight”.
In order to balance gravitational forces and solar-radiation pressure, a sun shield would need to be a minimum weight.
Szapudi’s design proposes tethering the space structure to an asteroid, which would act as a counterweight.
According to the paper, this would reduce the required mass of a solar shade by “up to two orders of magnitude”, with the asteroid supplying the rest.
The design still exceeds current capabilities. The reduced-mass sun shield comes in at around 35 kilotonnes – around 700 times as heavy as a current rocket’s capacity of 50 tonnes.
Multiple tethers would be required to attach the sun shield to the asteroid.
“The shield has enough weight to wreak havoc if it accidentally crashes on Earth,” the paper says.
“If multiple tethers hold the shield, breaking one or two would not create an accident. When down to two tethers, the shield automatically turns away from the solar radiation (like a sail when the rigging breaks), and the counterweight pulls the structure safely toward the Sun. The structure would be lost in the worst case, but the security threat to Earth is negligible.”
The technology for sufficiently robust tethers does not yet exist, the paper says.
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