Ballistic missile

A ballistic missile follows a ballistic trajectory to deliver one or more warheads on a predetermined target. These weapons are only guided during relatively brief periods of flight—most of their trajectory is unpowered, being governed by gravity and air resistance if in the atmosphere. Shorter range ballistic missiles stay within the Earth's atmosphere, while longer-ranged intercontinental ballistic missiles (ICBMs), are launched on a sub-orbital flight trajectory and spend most of their flight out of the atmosphere.The earliest form of ballistic missiles dates from the 13th century with its use derived from the history of rockets. In the 14th century, the Ming Chinese navy used an early form of a ballistic cruise missile weapon called the Huo long chu shui in naval battles against enemy ships. A modern pioneer ballistic missile was the A-4, commonly known as the V-2 rocket developed by Nazi Germany in the 1930s and 1940s under the direction of Wernher von Braun. The first successful launch of a V-2 was on October 3, 1942, and it began operation on September 6, 1944 against Paris, followed by an attack on London two days later. By the end of World War II in Europe in May 1945, over 3,000 V-2s had been launched.An intercontinental ballistic missile trajectory consists of three parts: the powered flight portion; the free-flight portion, which constitutes most of the flight time; and the re-entry phase, where the missile re-enters the Earth's atmosphere. (The flight phases for shorter-range ballistic missiles are essentially the first two phases of the ICBM, as some ballistic categories do not leave the atmosphere.)The course taken by ballistic missiles has two significant desirable properties. First, ballistic missiles that fly above the atmosphere have a much longer range than would be possible for cruise missiles of the same size. Powered rocket flight through thousands of kilometers of air would require vastly greater amounts of fuel, making the launch vehicles larger and easier to detect and intercept. Powered missiles that can cover similar ranges, such as cruise missiles, do not use rocket motors for the majority of their flight, but instead use more economical jet engines. However, cruise missiles have not made ballistic missiles obsolete, due to the second major advantage: ballistic missiles can travel extremely quickly along their flight path. An ICBM can strike a target within a 10,000 km range in about 30 to 35 minutes. With terminal speeds of over 5,000 m/s, ballistic missiles are much harder to intercept than cruise missiles, due to the much shorter time available. Therefore, ballistic missiles are some of the most feared weapons available, despite the fact that cruise missiles are cheaper, more mobile, and more versatile.Ballistic missiles can vary widely in range and use, and are often divided into categories based on range. Various schemes are used by different countries to categorize the ranges of ballistic missiles:Throw-weight is a measure of the effective weight of ballistic missile payloads. It is measured in kilograms or tonnes. Throw-weight equals the total weight of a missile's warheads, reentry vehicles, self-contained dispensing mechanisms, penetration aids, and missile guidance systems—generally all components except for the launch rocket booster and launch fuel. While throw-weight may refer to any type of warhead, in normal modern usage it almost exclusively refers to nuclear or thermonuclear payloads. It was once also a consideration in the design of naval ships and the number/size of guns they carried.