Space sunshade

A space sunshade or sunshield can be described as analogous to a parasol that diverts or otherwise reduces some of a star's rays, preventing them from hitting a planet and thereby reducing its insolation, which results in less heating of the planet. This can be of particular interest towards mitigating global warming through solar radiation management. Such shades could also be used to produce space solar power, acting as solar power satellites.

Cloud of small spacecraft near L1

One proposed such sunshade for use towards that effect would be composed of 16 trillion small disks at an altitude of 1.5 million kilometers, otherwise known as the L1 Orbit. A sunshade that blocks 2% of the sunlight, reflecting it off into space, would be enough to halt global warming, giving us ample time to cut our emissions back on earth.



Such a sunshade would have a diameter of 1800 km; it would cost tens of trillions of dollars to get the disks into space. It has been proposed that this would be accomplished most easily with a large railgun or coilgun which fires a capsule containing a million 1-gram shades into space.

Even so, it would still take years to launch enough of the disks into orbit before they have any effect. Thus, if using this technology should become essential, enough time would be needed to implement it.

Roger Angel of the University of Arizona presented the idea for the Sunshade at the U.S. National Academy of Sciences in April, 2006 and won a NASA Institute for Advanced Concepts grant for further research in July, 2006. His team members working on the grant are David Miller of the Massachusetts Institute of Technology, Nick Woolf of UA's Steward Observatory, and NASA Ames Research Center Director S. Pete Worden.

Creating this sunshade in space was estimated to cost in excess of US$5 trillion, thus leading Professor Angel to conclude that "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."

From http://en.wikipedia.org/