Dear friends,
Here's a unique idea! If global warming triggers abrupt climate change it maybe possible to shade the Earth with a space sunshade!
This may sound like a rather off-the-wall idea, but the brain behind it is that
of a brilliant University of Arizona astronomer named Roger Angel. He is a University of Arizona Regents' Professor and one of the world's foremost minds in modern optics. He directs the Steward Observatory Mirror Laboratory and the Center for Astronomical Adaptive Optics. He has won top honours for his many extraordinary conceptual ideas that have become practical engineering solutions for astronomy. This is NOT a man whose ideas we should dismiss lightly.
I hope I have your attention now. It isn't every day that you read about a
space umbrella. :-))
Professor Angel is working to find a way to cool the Earth if there is a crisis.
A crisis would be, for instance, if it becomes clear that our Earth is
certain to suffer disasterous climate change within ten or twenty years.
Angel presented his idea to the US National Academy of Sciences last April and
won the NASA Institute for Advanced Concepts grant in July to allow him to do
further research. His collaborators on the grant are from the Massachusetts Institute of Technology, the Steward Observatory and even include the Director of the NASA Ames Research Center.
Professor Angel is currently getting ready to publish his first detailed
scholarly paper on the subject entitled "Feasibility of cooling the Earth with
a cloud of small spacecraft near L1". (An orbit aligned with the sun is called
the L-1 orbit.)
A constellation of trillions of small, free-flying spacecraft would fly a
million miles above the Earth into this L-1 orbit aligned with the sun.
This cloud of spacecraft would be made of a transparent film filled with small
piercings. Each little flyer would be 2 feet in diameter and 1/5000 of an inch
thick, and would weigh about one gram. That is only as much as the weight of a
large butterfly.
The little flyers would use "MEMS" technology mirrors as tiny sails that tilt, to hold the flyer's position in the orbiting constellation. The flyer's transparency and steering mechanism would prevent it from being blown away by radiation
pressure. Radiation pressure is the pressure exerted by sunlight itself.
This mass of tiny flyers would form a long, cylindrical cloud, with a diameter
about half that of Earth, and about 10 times longer. Approximately 10 percent
of the sunlight passing through the 60,000-mile length of the cloud pointing lengthwise between the Earth and the sun would be diverted away from our planet. Sunlight would be uniformly reduced by about 2 percent over the entire planet. This would be sufficient to balance the heating from a doubling of atmospheric carbon dioxide in Earth's atmosphere.
Other researchers have proposed alternatives for cooling the planet. For
instance, using aerosol scatterers in the Earth's atmosphere.
The idea of a space shade at L-1 to deflect sunlight from Earth was first
proposed in 1989, but these earlier ideas were for bigger, heavier structures that would have had to be manufactured and launched from the moon. We aren't going to be able to progress to the ability to do that in time. Back in
1989, almost 18 years ago now! I'm shocked that it's only now that many citizens here are awakening to the perilous possibilities.
Professor Angel said "I wanted to make the sunshade from small "flyers", small,
light and extremely thin spacecraft that could be completely assembled and launched from Earth in stacks of a million at a time. When they reached L1 they would be dealt off the stack into a cloud. There's nothing to assemble in space."
The total mass of all the fliers would be 20 million tons. A conventional chemical rocket launch costs $10,000 per pound, which is too expensive. Angel
recommends using a way developed by Sandia National Laboratoaries for electromagnetic space launches, which could cost as little as $20 per pound.
The sunshade could be deployed by 20 electromagnetic launchers launching a stack
of flyers every 5 minutes, for ten years. The electromagnet launchers would ideally run of hydroelectric power. In the worst-case environmental scenario it could be done with coal-generated electricity and each ton of carbon used to make
the electricity would mitigate the effect of 1000 tons of atmospheric carbon.
Once outside of Earth's atmosphere and gravity the flyer stack would be steered
to the correct orbit by solar-powered ion propulsion. This is a new method proven in space by the European Space Agency's SMART-1 moon orbiter and NASA's Deep
Space 1 probe.
Angel says "The concept builds on existing technologies. It seems feasible that
it could be developed and deployed in about 25 years at a cost of a few trillion dollars. With care, the solar shade should last about 50 years. So the average cost is about $100 billion a year, or about two-tenths of one percent of the
global domestic product."
He added "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."
Some of you are only about 15 years old now. You may well think of a career in
one of the many fields that exist and will come into existence to reverse man's
effects on global warming. In 25 years time you'll only be 40, and at the peak of your ability, experience and careers. You could very well find yourself
greatly needed to save humanity.
This article has been adapted from a press release of November 3, 2006 released
by University of Arizona.
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