They are also carried by missiles, such as intercontinental ballistic missiles (ICBMs) or submarine-launched ballistic missiles (SLBMs). Some missiles travel to the border of space, and then launch a number of separate nuclear weapons back toward the ground, with each weapon travelling to a different target. This is called a MIRV Warhead, or Multiple Independent Reentry Vehicles. Very large nuclear bombs have been produced, but in practice a weapon with multiple warheads can produce much more damage by attacking more targets.