Vertical launching system

A vertical launching system (VLS) is a modern type of missile-firing system used aboard the submarines and surface vessels of several navies around the world.

Derived from the launch systems developed for ballistic missiles aboard SSBNs, a VLS forms a scaled-down equivalent for launching cruise missiles such as the Tomahawk and surface-to-air missiles (SAMs) such as the Standard missile.

When installed on a SSN (nuclear-powered attack submarine), a VLS allows a greater number and variety of weapons to be deployed in comparison to using only torpedo tubes. A VLS allows surface combatants to have a greater number of weapons ready for firing at any given time compared to older launching systems such as the Mk-13 single-arm and Mk-26 twin-arm launchers, which were fed from behind by a magazine below the main deck. In addition to greater firepower, VLS is much more damage tolerant and reliable than the previous systems, and has a lower radar cross-section (RCS). The U.S. Navy now relies exclusively on VLS for its guided missile destroyers and cruisers, an advanced Mk 57 VLS system is projected to be used on the new Zumwalt class destroyer, and the older Mk-13 and Mk-26 systems remain in service on ships that were sold to other countries such as Taiwan, Greece, and Poland.

Hot launch and cold launch


Western VLSs have the missile cells arranged in a grid with one lid per cell and are "hot launch" systems, i.e. the engine ignites within the cell during the launch, and thus it requires exhaust piping for the missile flames and gasses, while Russia produces both grid systems and a revolver design with more than one missile per lid, and the People's Republic of China uses a circular "cold launch" system that ejects the missile from the launch tube before igniting the engine. Russia also uses a cold launch system for some of its VLS missile systems, e.g., the Tor Missile System.

An advantage of a hot-launch system is that the missile propels itself out of the launching cell using its own engine, which eliminates the need for a separate system to eject the missile from the launching tube. This potentially makes a hot-launch system relatively light, small, and economical to develop and produce. A potential disadvantage is that a malfunctioning missile could destroy the launch tube.

The advantage of the cold-launch system is in its safety: should a missile engine malfunction during launch, the cold-launch system can eject the missile thereby reducing or eliminating the threat. For this reason, Russian VLSs are often designed with a slant so that a malfunctioning missile will land in the water instead of on the ship's deck. Another advantage of the cold-launch system is its low life-cycle cost of the launching tubes: since the missile's engine ignites outside of the tube, the tube is not subject to extreme heat blast and enjoys a long life span.