sun shade

A space sunshade or sunshield is a parasol that diverts or otherwise reduces some of the Sun's radiation, preventing it from hitting a spacecraft or planet and thereby reducing its insolation, which results in reduced heating. Light can be diverted by different methods. The concept of the construction of sunshade as a method of climate engineering dates back to the years 1923, 1929, 1957 and 1978 by the physicist Hermann Oberth. Space mirrors in orbit around the earth with a diameter of 100 to 300 km, as designed by Hermann Oberth, are intended to focus sunlight on indiviual regions oft he earth’s surface or deflect it into space so that the solar radiation is weakened in a specifically controlled manner for individual regions on the earth’s surface.
First proposed in 1989, another space sunshade concept involves putting a large occulting disc, or technology of equivalent purpose, between the Earth and Sun.
A sunshade is of particular interest as a climate engineering method for mitigating global warming through solar radiation management. Heightened interest in such projects reflects the concern that internationally negotiated reductions in carbon emissions may be insufficient to stem climate change. Sunshades could also be used to produce space solar power, acting as solar power satellites. Proposed shade designs include a single-piece shade and a shade made by a great number of small objects. Most such proposals contemplate a blocking element at the Sun-Earth L1 Lagrangian point.
In 1989, James Early proposed a space-based sun-shade to divert sunlight at the planetary level. His design involved making a large glass (2,000 km) occulter from lunar material and placing at the L1 point. Issues included the large amount of material needed to make the disc and also the energy to launch it to its orbit.

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