Ballistic missile
A ballistic missile (BM) is a type of missile that uses projectile motion to deliver warheads on a target. These weapons are powered only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles (SRBM) typically stay within the Earth's atmosphere, while most larger missiles are exo-atmospheric. The largest ICBMs are capable of full orbital flight. These weapons are in a distinct category from cruise missiles, which are aerodynamically guided in powered flight and thus restricted to the atmosphere.
For self-navigating guided constant-speed missiles, see Cruise missile.Flight[edit]
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.[4]
Ballistic missiles can be launched from fixed sites or mobile launchers, including vehicles (e.g., transporter erector launchers), 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.[4]
When the fuel is exhausted, no more thrust is provided and 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 4,500 kilometers (2,800 mi).[5]
The re-entry stage begins at an altitude where atmospheric drag plays a significant part in missile trajectory, and lasts until missile impact.[4] Re-entry vehicles re-enter the Earth's atmosphere at very high velocities, on the order of 6–8 kilometers per second (22,000–29,000 km/h; 13,000–18,000 mph) at ICBM ranges.[6]
Ballistic missiles 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:
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 in comparison to conventional bomber aircraft.
The following ballistic missiles have been used in combat: