Space Sunshade May One Day Reduce Global Warming

Global warming is a reality and increasingly itsthey would be dealt off the stack into a cloud.
consequences are upon us. We may think that globalThere's nothing to assemble in space."
warming does not affect us but the fact is it hasAngel proposes to design lightweight flyers made of
already started to have disastrous consequences.transparent film pierced with small holes and would be
Flash floods, droughts, receding icebergs, cyclonestwo feet in diameter, 1/5000 of an inch thick and
are some of the manifestations of global warming.weigh about a gram, the same as a large butterfly.
Although we are aware and worried about it andHe suggests using "MEMS" technology mirrors as tiny
trying our best to control it but no significant impactsails that tilt to hold the flyers position in the orbiting
could be seen.constellation.
Scientists have come up with new strategies toThe weight of all flyers would be 20 millions tons. But
tackle the problem. Now a scientist has suggested anconventional rocket launch system at $10,000 a
ambitious idea to contain global warming. Putpound would be too prohibitive. His alternative would
sunshades in space. That's right. University of Arizonacost only around $20 a pound.
astronomer Roger Angel suggests putting sunshadesHe suggests deploying a total 20 electromagnetic
in space and has detailed his idea in a paperlaunchers launching a stack of flyers every 5 minutes
"Feasibility of cooling the Earth with a cloud of smallfor 10 years. The electromagnetic launchers would
spacecraft near L1" in the Proceedings of the Nationaluse hydroelectric power but even if it uses
Academy of Sciences. He suggests launching acoal-generated electricity, each ton of carbon used
constellation of trillions of small free-flying spacecraftwould reduce the effect of 1000 tons of
a million miles above Earth into an orbit aligned withatmospheric carbon.
the sun, called the L-1 orbit.Once propelled beyond Earth's atmosphere the flyer
This spacecraft would form a long, cylindrical cloudstacks would be steered to L-1 orbit by
and would have a diameter about half that of Earth,solar-powered ion propulsion, pioneered by European
and about 10 times longer. It is suggested that aboutSpace Agency's SMART-1 moon orbiter and NASA's
10 percent of the sunlight passing through theDeep Space 1 probe.
60,000-mile length of the cloud, pointing lengthwise"The concept builds on existing technologies," Angel
between the Earth and the sun, would be divertedsaid. "It seems feasible that it could be developed
away from our planet. This would result in uniformlyand deployed in about 25 years at a cost of a few
reduced sunlight by about 2 percent over the entiretrillion dollars. With care, the solar shade should last
planet and would balance the heating of carbonabout 50 years. So the average cost is about $100
dioxide in Earth's atmosphere.billion a year, or about two-tenths of one percent of
The use of space shade was first mooted by Jamesthe global domestic product."
Early of the Lawrence Livermore National LaboratoryHe added, "The sunshade is no substitute for
in 1989.developing renewable energy, the only permanent
"The earlier ideas were for bigger, heavier structuressolution. A similar massive level of technological
that would have needed manufacture and launchinnovation and financial investment could ensure that.
from the moon, which is pretty futuristic," Angel said."But if the planet gets into an abrupt climate crisis
"I wanted to make the sunshade from small 'flyers,'that can only be fixed by cooling, it would be good
small, light and extremely thin spacecraft that couldto be ready with some shading solutions that have
be completely assembled and launched from Earth, inbeen worked out.
stacks of a million at a time. When they reached L1,