The
sun gun or
heliobeam is a theoretical orbital weapon, which makes use of a concave mirror mounted on a satellite, to concentrate sunlight onto a small area at the Earth's surface, destroying targets or killing through heat.
In 1929, the German physicist Hermann Oberth developed plans for a space station from which a 100-metre-wide concave mirror could be used to reflect sunlight onto a concentrated point on the earth.
Later during World War II, a group of German scientists at the German Army Artillery proving grounds at Hillersleben began to expand on Oberth's idea of creating a superweapon that could utilize the sun's energy. This so-called "sun gun" (
Sonnengewehr) would be part of a space station 8,200 kilometres (5,100 mi) above Earth. The scientists calculated that a huge reflector, made of metallic sodium and with an area of 9 square kilometres (900 ha; 3.5 sq mi), could produce enough focused heat to make an ocean boil or burn a city. After being questioned by officers of the United States,
the Germans claimed that the sun gun could be completed within 50 or 100 years.
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