Ballistic Missiles

The flight of a ballistic missile can be divided into three phases: boost phase, cruise phase, and descent (terminal) phase. Boost phase begins with the ignition of the missile's booster rocket. The booster lofts the missile at a steep angle, imparting a high speed to the payload before burning out. The payload and booster then separate, beginning the cruise phase. The spent booster falls back to Earth while the payload, starting to lose speed, continues to gain altitude. If the missile is sufficiently long-range, its payload rises above the Earth's atmosphere during cruise phase, where it jettisons its aerodynamic protective shroud and arcs under the influence of gravity. The payload may be a single cone-shaped warhead or a flat "bus" with several warheads attached to it like upside-down ice-cream cones arranged circularly on a plate.

Individual warheads are not propelled downward toward their targets on the ground, but follow ballistic paths determined by gravity and aerodynamics, gaining speed as they lose altitude. Modern reentry vehicles usually feature small external fins or other steering devices that enable them to control their course, within limits, as they fall through the atmosphere; though such maneuverable reentry vehicles (MARVs) are not, strictly speaking, ballistic objects, missiles delivering them are still termed "ballistic" missiles for convenience. Maneuverability increases accuracy; a modern MARV delivered by ICBM or SLBM can land within a few hundred feet of its target after a journey of thousands of miles. Warheads may explode in the air high above their targets, on the surface, or under the surface after striking into the ground.