A ballistic missile 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 travel outside the atmosphere. The type of ballistic missile with the greatest range is an intercontinental ballistic missile (ICBM). The largest ICBMs are capable of full orbital flight.