intercontinental missiles, the highest altitude (apogee) reached during free-flight is about . The re-entry stage begins at an altitude where atmospheric drag plays a significant part in missile trajectory, and lasts until missile impact. Re-entry vehicles re-enter the Earth's atmosphere at very high velocities, on the order of at ICBM ranges. Types 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: Air-launched ballistic missile (ALBM) Tactical ballistic missile: Range between about Theatre ballistic missile (TBM): Range between Short-range ballistic missile (SRBM): Range between Medium-range ballistic missile (MRBM): Range between Intermediate-range ballistic missile (IRBM) or long-range ballistic missile (LRBM): Range between Intercontinental ballistic missile (ICBM): Range greater than Submarine-launched ballistic missile (SLBM): Launched from ballistic missile submarines (SSBNs) Most current designs have intercontinental range with a notable exception of Indian operational SLBM Sagarika and K-4 as well as North Korea's currently operationally deployed KN-11 which might not have intercontinental range. A comparable missile would be the decommissioned China's JL-1 SLBM with a range of less than 2,500 km. Tactical short- and medium-range missiles are often collectively referred to as tactical and theatre ballistic missiles, respectively. 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 (though the U.S. is evaluating the idea of a conventionally armed ICBM for near-instant global air strike capability, despite the high costs). Quasi-ballistic missiles 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. They include anti-ship ballistic missiles. 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. List of quasi-ballistic missiles