A ballistic missile is a missile that follows a sub-orbital ballistic flightpath with the objective of delivering one or more warheads to a predetermined target. The missile is only guided during the relatively brief initial powered phase of flight and its course is subsequently governed by the laws of orbital mechanics and ballistics. To date, ballistic missiles have been propelled during powered flight by chemical rocket engines of various types.
The first ballistic missile was the A-4, commonly known as the V-2 rocket, developed by Nazi Germany in the 1930s and 1940s under direction of Wernher von Braun. The first successful launch of a V-2 was on October 3, 1942 and began operation on September 6, 1944 against Paris, followed by an attack on London two days later. By the end of World War II, May 1945, over 3,000 V-2s had been launched.
A total of 30 nations have deployed operational ballistic missiles. Development continues, with around 100 ballistic missile flight tests (not including those of the US) in 2007, mostly by China, Iran and the Russian Federation. In 2010 the US and Russian governments signed a treaty to reduce their ICBMs over a seven year period (to 2017) to 1550 units each.
A 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.
Ballistic missiles can be launched from fixed sites or mobile launchers, including vehicles (transporter erector launchers, TELs), aircraft, ships and submarines. The powered flight portion can last from a few tens of seconds to several minutes and can consist of multiple rocket stages.
When in space and no more thrust is provided, the missile enters free-flight. In order to cover large distances, ballistic missiles are usually launched into a high sub-orbital spaceflight; for intercontinental missiles the highest altitude (apogee) reached during free-flight is about 1200 km.
The re-entry stage begins at an altitude where atmospheric drag plays a significant part in missile trajectory, and lasts until missile impact.
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