MIRACL, SSTS, BSTS, CHECMATE and ERINT -- all were systems designed to take down ICBMs as part of the Strategic Defense Initiative (SDI). The acronyms alone are enough to make your head spin and only hint at how complex and difficult building a missile defense shield truly was and is. Not only did the system have to detect when a missile launch occurred, it also had to track the missiles in flight, communicate that information to the weapons poised to shoot down those missiles, and finally, aim and fire those weapons to score directs hit on fast-moving targets.
To make matters even more complicated, the Soviets could add missile decoys, overwhelm the system by building more ICBMs or even take aim at the defense system itself, incapacitating it before launching a nuclear attack in the first place. And finally, certain technologies were off the table from the start thanks to restrictions outlined in the ABM and Outer Space treaties.
Still, scientists and engineers heading up SDI came up with several promising approaches shortly after the program received funding, and many of them lived up to the "Star Wars" moniker. The press particularly enjoyed focusing on the X-ray laser, a weapon seemingly ripped out of the pages of a science-fiction novel. The laser, proposed by renowned physicist Edward Teller, was designed to orbit the Earth, where it could shoot down multiple Soviet ICBMs simultaneously using power generated by a nuclear blast. Initial testing of the technology provided disappointing results, however. By the late 1980s, the X-ray laser was scrapped, but not before becoming a symbol for the impracticality and expense of the "Star Wars" program.
Other approaches to destroying Soviet ICBMs included so-called kinetic warheads that would collide with ICBMs in orbit and destroy them, satellite-mounted rail guns that were ultimately scrapped for requiring huge energy reserves to operate and the MIRACL laser that scientists hoped to shoot off of ground-based mirrors at moving targets. Critics of SDI are quick to point out how few of these approaches amounted to anything, but in fact, SDI was set up to explore every alternative from the start and pursue only the most promising of the candidates. Unfortunately, even after billions of dollars were spent developing these technologies, SDI had yet to shoot down a single ballistic missile in flight [source: New Scientist]. And before the technologies could be refined and modified to take advantage of ever-increasing computing and tracking systems, the Cold War had ended and "Star Wars" was phased out for a new approach to missile defense.