The Strategic Defense Initiative (SDI) was proposed by U.S. President Ronald Reagan on March 23, 1983 to use space-based systems to protect the United States from attack by strategic nuclear missiles. Dubbed "Star Wars," the program was intended to provide an impenetrable shield against incoming nuclear warheads.
Supporters hail SDI for contributing to the fall of the Soviet Union by the strategy of technology. At the October 1986 meeting in Iceland, Gorbachev ardently opposed this defensive shield. The program was abandoned in 1993 under the Clinton administration but revived under the Bush administration as National Missile Defense.
SDI Project and Proposals
Overseen by Drs. Edward Teller and Lowell Wood, the initial centerpiece was an X-ray laser curtain deployed as a satellite powered by a nuclear warhead. This was quietly abandoned and replaced with Brilliant Pebbles — satellite-based mini-missiles. The focus later shifted to ground-based interceptor missiles.
Anti-Satellite Weapons (ASAT)
Anti-satellite weapons are designed to destroy artificial satellites. The US began tests in 1959; the USSR deployed ASAT missiles from around 1976. The USAF revived its ASAT program from 1977, achieving the first successful interception on September 13, 1985 using an F-15-launched missile.
Nuclear and Orbital ASAT
Nuclear ASAT was considered but the Outer Space Treaty of 1967 banned nuclear weapons in space. The USSR developed kamikaze satellites (Istrebitel Sputnikov) from the 1960s. Both countries experimented with directed energy weapons, including lasers and particle beams.
SDI-Era Developments
The initial US plan envisioned 4,600 kinetic interceptors in Low Earth orbit at a cost of $125 billion by 2000. Both countries reduced expenditure from 1989; the USSR discontinued all SDI research in 1992.