Space weapons are weapons used in space warfare. They include weapons that can attack space systems in orbit (i.e. anti-satellite weapons), attack targets on the earth from space or disable missiles travelling through space. In the course of the militarisation of space, such weapons were developed mainly by the contesting superpowers during the Cold War, and some remain under development today. Space weapons are also a central theme in military science fiction and sci-fi video games. Space-to-space weapons The Soviet Almaz secret military space station program was equipped with a fixed 23mm autocannon to prevent hostile interception or boarding by hostile forces. This was the first and so far the only weapon to be fired in space. The Soviet unmanned Polyus weapons platform was designed to be equipped with a megawatt carbon-dioxide laser and a self-defense cannon. Earth-to-space weapons Anti-satellite weapons, which are primarily surface-to-space and air-to-space missiles, have been developed by the United States, the USSR/Russia, India and the People's Republic of China. Multiple test firings have been done as part of recent Chinese and U.S test programs that involved destroying an orbiting satellite. In general, the use of explosive and kinetic kill systems is limited to relatively low altitude due to space debris issues and so as to avoid leaving debris from launch in orbit. Strategic Defense Initiative On March 23, 1983, President Ronald Reagan proposed the Strategic Defense Initiative, a research program with a goal of developing a defensive system which would destroy enemy ICBMs. The defensive system was nicknamed Star Wars, after the movie, by its detractors. Some concepts of the system included Brilliant Pebbles, which were Kinetic Kill Vehicles, essentially small rockets launched from satellites toward their targets (a warhead, warhead bus, or even an upper stage of an ICBM). Other aspects included satellites in orbit carrying powerful laser weapons, plasma weapons, or particle beams. When a missile launch was detected, the satellite would fire at the missile (or warheads) and destroy it. Although no real hardware was ever manufactured for deployment, the military did test the use of lasers mounted on Boeing 747s to destroy missiles in the 2000s, however these were discontinued due to practical limitations of keeping a constant fleet airborne near potential launch sites due to the lasers range limitations keeping a small number from being sufficient. The tests took place at Edwards Air Force Base. Space-to-Earth weapons Orbital weaponry Orbital