From Damn Interesting:
But the military masterminds’ most sinister ambitions were embodied in their behemoth Sonnengewehr, or “Sun Gun” projectâ€“ an orbital weapon intended to exact fiery punishment upon the enemies of the Third Reich, forever establishing their dominance over the genetically inferior Untermenschen of the Earth.
The Sun Gun was based on a design originally conceived by Hermann Oberth, a physicist who is widely credited as one of the founding fathers of rocketry and astronautics. In his 1929 book Wege zur Raumschiffahrt, or “Ways to Spaceflight,” Oberth presented a scientific description of a hypothetical manned space station orbiting at an altitude of one thousand kilometers. He detailed potential construction methods using prefabricated sections, described a rotational cycle to produce centrifugal gravity within the station, and outlined a system for periodic resupply missions. Oberth advocated the development of these Raumstations to serve as astronomical observatories and telegraph relays, in addition to Earth-observing activities such as meteorology, search-and-rescue, and military intelligence. What interested the Nazi scientists, however, was his suggestion that a specially engineered 100-meter-wide concave mirror could be used to reflect sunlight into a concentrated point on the Earth. But whereas Oberth’s design had peaceful intentionsâ€“ to use the intense heat to produce electricity with steam turbinesâ€“ the nefarious Nazis envisioned a colossal heat ray which could vanquish humanity.