Researchers at the University of Arizona are developing an ambitious space sunshade system that could reduce the sunlight reaching the Earth by 2%, enough to balance the heating effects of the increasing amounts of carbon dioxide in the atmosphere. Composed of trillions of miniature spacecraft, this sunshade would form a cylindrical cloud with half of the diameter of the Earth and a length about ten times longer than that located in an L1 orbit. Anything orbiting at this location remains interposed directly between the Sun and the Earth, allowing the shade to constantly filter the sunlight reaching our planet.
Each individual piece of the sunshade would be made from a thin film pierced with holes imprinted onto a one micron thick plate of glass, be a mere two feet in diameter, and weigh only a gram. Microelectromechanical (MEMS) mirrors would act as tiny sails, aiding in positioning and ensuring that the system as a whole filters out the projected levels of sunlight. The L1 orbit is not completely stable, so minor corrections controlled by these mirrors will be necessary to maintain the sunshade over time.
Despite the small size and weight of the individual components, the sunshade as a whole adds up to approximately 20 million tons; placing that much mass in orbit using traditional chemical rockets would be prohibitively expensive, so alternative launch methods are a necessary element of the project as a whole.
Project director Roger Angel proposes to solve the launch problem by using electromagnetic rocket launchers developed at Sandia National Laboratory in Albuquerque, New Mexico. Even with 20 such launchers, it would take ten years of launching stacks of rockets every five minutes to fully deploy the sunshade system. Once launched out of Earth orbit, the stacks of components would be steered to L1 orbit using solar powered ion propulsion, the same electromagnetic propulsion method currently used in several NASA and ESA projects.
Angel estimates such a sunshade system could be ready for deployment in as little as 25 years and that careful manufacturing and materials selection could grant each component a 50 year workable lifetime. The shade would be expensive, but presents a viable method of cooling the Earth’s temperature if other attempts to mitigate global warming fail or are not sufficient.
TFOT has reported on other innovative technologies designed to reduce greenhouse gases and global warming, including bacteria that produce hydrogen that can be used as a source of clean power, a new material that can reduce the carbon dioxide emissions from power plants, and yachts that spray salty sea water into the air to increase the reflexivity of clouds so they reflect more sunlight back into space.
More information about the space sunshade can be found on an early press release by the University of Arizona and in a follow-up piece in the school’s newspaper, the Daily Wildcat. You can also learn more about the head researcher Roger Angel at his College of Optical Sciences faculty page found here.