theatre ballistic missiles. Pebbles was modified, but doing so raised its weight and cost; the original design called for around 10,000 missiles and would cost $10 to $20 billion, but by 1990 the cost for 4,600 had ballooned to $55 billion. Fighting in Congress through the early 1990s led to Pebbles' cancellation in 1993. History Smart Rocks There are a wide variety of stories about the origins of Ronald Reagan's Strategic Defense Initiative. According to one often repeated tale, it was Reagan's viewing of Alfred Hitchcock's Torn Curtain that did it. Edward Teller instead pointed to a talk he gave on the topic of BMD in 1967 that Reagan attended. Others point to Reagan's visit to the Cheyenne Mountain Complex in 1979; there he saw the systems that could detect a Soviet launch and then track their warheads. When he asked what they could do in that situation, the answer was "launch our own missiles." Whatever the source, Reagan was convinced that Mutual Assured Destruction (MAD) was ridiculous, dismissing it as the international equivalent of a suicide pact. Reagan asked Daniel O. Graham, his military advisor during the 1980 presidential campaign and former director of the Defense Intelligence Agency, to look for possible solutions. At first, Graham proposed a system of manned space fighters, but the idea was quickly dismissed. Next, he revived the 1960s Project BAMBI to be the basis of a new system he referred to as Smart Rocks. This concept used "battle stations" in low Earth orbit, each carrying several dozen small missiles similar to a conventional air-to-air missile. The platforms would carry advanced sensors to detect and track Soviet ICBMs as they launched, and then launch its missiles and guide them until the missile's own infrared sensors picked up the ICBM. As the ICBM rocket engine was extremely bright in infrared, even a very simple interceptor missile could successfully track them. As the interceptors were relatively small and carried a limited amount of rocket fuel, they could only attack ICBMs within a limited range of the stations. This meant the stations had to be in low orbit, to keep them close to their targets. At these altitudes, the stations moved at speeds around compared to the surface of the Earth. At that rate, any given station would spend only a few minutes over the Soviet Union. To ensure there were enough stations in the right locations