Rocket And Missile System3 ~ WORLD BLOG LOG

Ballistic missile defense

Although ballistic missiles followed a predictable flight path, defense against them was long thought to be technically impossible because their RVs were small and traveled at great speeds. Nevertheless, in the late 1960s the United States and Soviet Union pursued layered antiballistic missile (ABM) systems that combined a high-altitude interceptor missile (the U.S. Spartan and Soviet Galosh) with a terminal-phase interceptor (the U.S. Sprint and Soviet Gazelle). All systems were nuclear-armed. Such systems were subsequently limited by the Treaty on Anti-Ballistic Missile Systems of 1972, under a protocol in which each side was allowed one ABM location with 100 interceptor missiles each. The Soviet system, around Moscow, remained active and was upgraded in the 1980s, whereas the U.S. system was deactivated in 1976. Still, given the potential for renewed or surreptitious ballistic missile defenses, all countries incorporated penetration aids along with warheads in their missiles' payloads. MIRVs also were used to overcome missile defenses.

Maneuverable warheads

Even after a missile's guidance has been updated with stellar or satellite references, disturbances in final descent could throw a warhead off course. Also, given the advances in ballistic missile defenses that were achieved even after the ABM treaty was signed, RVs remained vulnerable. Two technologies offered possible means of overcoming these difficulties. Maneuvering warheads, or MaRVs, were first integrated into the U.S. Pershing II IRBMs deployed in Europe from 1984 until they were dismantled under the terms of the INF Treaty. The warhead of the Pershing II contained a radar area guidance (Radag) system that compared the terrain toward which it descended with information stored in a self-contained computer. The Radag system then issued commands to control fins that adjusted the glide of the warhead. Such terminal-phase corrections gave the Pershing II, with a range of 1,100 miles, a CEP of 150 feet. The improved accuracy allowed the missile to carry a low-yield 15-kiloton warhead.

MaRVs would present ABM systems with a shifting, rather than ballistic, path, making interception quite difficult. Another technology, precision-guided warheads, or PGRVs, would actively seek a target, then, using flight controls, actually “fly out” reentry errors. This could yield such accuracy that nuclear warheads could be replaced by conventional explosives