The Apollo 5 mission tested the Lunar Module in a space environment, in particular its descent and ascent engine systems, and its ability to separate the ascent and descent stages. The descent engine would become the first throttleable rocket engine fired in space.
Low Earth OrbitUS-A (Upravlenniye Sputnik Aktivny) were active radar satellites for ocean surveillance. The high power consumtion of the active radar required a nuclear reactor as power source. The satellites were known as RORSAT in the west. The US-AO series consisted of satellites, which tested all the system components but the nuclear reactor. They were battery powered.
Low Earth Orbit