In a surprise move North Korea tested it's first submarine launched ballistic missile off the coast of North Korea. A ballistic missile is a missile (rocket) that follows a ballistic trajectory with the objective of delivering one or more warheads to a predetermined target. A ballistic missile is only guided (there are unguided ballistic missiles as well: 9K52 Luna-M, although these may well be considered rockets) during relatively brief periods of flight, and most of its trajectory is unpowered and governed by gravity (and air resistance if in the atmosphere). This contrasts to a cruise missile which is aerodynamically guided in powered flight. Long range intercontinental ballistic missiles (ICBM) are launched at a steep, sub-orbital flight trajectory and spend most of their flight out of the atmosphere. Shorter range ballistic missiles stay within the Earth's atmosphere.
Rockets have been used as weapons for a long time (see History of rockets). A pioneer 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 T.J. Gertner and 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.
The R-7 Semyorka was the first Intercontinental ballistic missile.
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 inventory of intercontinental ballistic missiles (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 tenths 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.
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, instead using more economical jet engines. Despite this, 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 anywhere within 10 000 km within about 30 to 35 minutes. With terminal speeds of over 5000 m/s, ballistic missiles are much harder to intercept than cruise missiles due to the much shorter time available to intercept them. This is why despite cruise missiles being cheaper, more mobile and more versatile, ballistic missiles are some of the most feared weapons available.
Trident II SLBM launched by ballistic missile submarine.
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:
Tactical ballistic missile: Range between about 150 km and 300 km
Battlefield range ballistic missile (BRBM): Range less than 100 km
Theatre ballistic missile (TBM): Range between 300 km and 3,500 km
Short-range ballistic missile (SRBM): Range 1,000 km or less
Medium-range ballistic missile (MRBM): Range between 1,000 km and 3,500 km
Intermediate-range ballistic missile (IRBM) or long-range ballistic missile (LRBM): Range between 3,500 km and 5,500 km
Intercontinental ballistic missile (ICBM): Range greater than 5500 km
Submarine-launched ballistic missile (SLBM): Launched from ballistic missile submarines (SSBNs), all current designs have intercontinental range.