Could a cloud of two-foot wide sunshades 60,000 miles long save the Earth from a global warming emergency? Roger Angel (Steward Observatory, University of Arizona) has been studying the idea of making the spacecraft out of micron-thick glass weighing one gram per sunshade. That’s the weight of a butterfly for each unit, but we’re talking about trillions of them out at the L1 Lagrangian point, an almost fixed zone in relation to Earth whose mild orbital instability can be overcome by onboard intelligence. Total sunshade mass: 20 million tons.
This article in the Arizona Daily Wildcat has more on the improbable concept and what Angel is doing today:
One of the big problems for the project is getting the total mass of all the sunshades into space…so Angel came up with using electromagnetic force to propel the spacecraft up a two-kilometer launch tube.
The launch tube would have a series of electrical coils that propel the rocket until it accelerates to escape velocity, about 25,000 mph, the speed needed to escape Earth’s gravity.
Hmmm… A two-kilometer tall launch tube would be an architectural marvel but prohibitive in cost, and the electromagnetic liftoff would likely shred the sunshades on the way up. With NASA funding terminated, Angel may not have time to work out these problems; he’s now looking for ways to keep us from having to use sunshades in the first place by tackling global warming here on Earth. If the shades are ever launched, though, don’t expect immediate results. One to two centuries seems to be a realistic figure for dropping carbon dioxide levels and lowering the heat.
ADDENDUM: A better way to put that last sentence would be: “One to two centuries seems to be a realistic figure for lowering the heat to compensate for greenhouse effects.” See Paul Dietz’ comment below.
And note this: Dr. Angel developed this concept as a potential solution to a planetary emergency, not as a final fix. He’s quoted on this in a Steward Observatory news release: “The sunshade is no substitute [for] developing renewable energy, the only permanent solution. A similar massive level of technological innovation and financial investment could ensure that. But if the planet gets into an abrupt climate crisis that can only be fixed by cooling, it would be good to be ready with some shading solutions that have been worked out.”