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A ballistic missile is a missile (rocket) that follows a ballistic flightpath with the objective of delivering one or more warheads to a predetermined target. A ballistic missile is only guided during relatively brief periods of flight, and its trajectory is largely 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 trajectory and spend most of their flight out of the atmosphere. Shorter range ballistic missiles stay within the Earth's atmosphere.
The R-7 Semyorka was the first ICBM.
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 course taken by ballistic missiles has two significant desirable properties. First the long free flight period provides ballistic missiles far greater range than would otherwise be possible for missiles of their size. Powered rocket flight over thousands of kilometers would require vastly greater amounts of fuel, making the launch vehicles larger and easier to detect and intercept. Powered missiles that can cover similar amounts of range 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 across their flight path. It is believed that an ICBM would be able to strike a target anywhere in its range (potentially up to 10,000 km) within 30 minutes. With terminal speeds of over 5000 m/s, ballistic missiles are radically harder to intercept than cruise missiles due to the massively reduced 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.
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:
Short- and medium-range missiles are often collectively referred to as theater or tactical ballistic missiles (TBMs). Long- and medium-range ballistic missiles are generally designed to deliver nuclear weapons because their payload is too limited for conventional explosives to be cost-effective (though the U.S. is evaluating the idea of a conventionally armed ICBM for near-instant global air strike capability despite the high costs).
The flight phases are like those for ICBMs, except with no exoatmospheric phase for missiles with ranges less than about 350 km.
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A quasi ballistic missile (also called a semi ballistic missile) is a category of missile that has a low trajectory and/or is largely ballistic but can perform maneuvers in flight or make unexpected changes in direction and range.
At a lower trajectory than a ballistic missile, a quasi ballistic missile can maintain higher speed, thus allowing its target less time to react to the attack, at the cost of reduced range.
The Russian Iskander is a quasi ballistic missile. The Russian Iskander-M cruises at hypersonic speed of 2,100–2,600 m/s (Mach 6 - 7) at a height of 50 km. The Iskander-M weighs 4,615 kg carries a warhead of 710 – 800 kg, has a range of 480 km and achieves a CEP of 5 – 7 meters. During flight it can maneuver at different altitudes and trajectories to evade anti-ballistic missiles.
China, India & Iran have recently developed anti-ship ballistic missile;