Vertical launching system

A vertical launching system (VLS) is an advanced system for holding and firing missiles on mobile naval platforms, such as surface ships and submarines. Each vertical launch system consists of a number of cells, which can hold one or more missiles ready for firing. Typically, each cell can hold a number of different types of missiles, allowing the ship flexibility to load the best set for any given mission. Further, when new missiles are developed, they are typically fitted to the existing vertical launch systems of that nation, allowing existing ships to use new types of missiles without expensive rework. When the command is given, the missile flies straight up far enough to clear the cell and the ship, then turns onto the desired course.

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 Mark 13 single-arm and Mark 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.

The most widespread VLS in the world is the Mark 41, developed by the United States Navy. More than 11,000 Mark 41 VLS missile cells have been delivered, or are on order, for use on 186 ships across 19 ship classes, in 11 navies around the world. This system currently serves with the US Navy as well as the Australian, Danish, Dutch, German, Japanese, Norwegian, South Korean, Spanish, and Turkish navies, while others like the Greek Navy preferred the similar Mark 48 system.

The 3S-14 VLS was developed in Russia and is used in sea-based as well as land-based TEL systems such as the S-400 missile system.^{[citation needed]}

The advanced Mark 57 VLS is used on the Zumwalt-class destroyer. The older Mark 13 and Mark 26 systems remain in service on ships that were sold to other countries such as Taiwan and Poland.

When installed on an nuclear-powered attack submarine, a VLS allows a greater number and variety of weapons to be deployed, compared with using only torpedo tubes.

A vertical launch system can be either "hot launch", where the missile ignites in the cell, or "cold launch", where the missile is expelled by gas produced by a gas generator which is not part of the missile itself, and then the missile ignites. "Cold" means relatively cold compared with rocket engine exhaust. A hot launch system does not require an ejection mechanism but does require some way of disposing of the missile's exhaust and heat as it departs the cell. If the missile ignites in a cell without an ejection mechanism, the cell must withstand the tremendous heat generated without igniting missiles in adjacent cells.

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, particularly when designed around smaller missiles. A potential disadvantage is that a malfunctioning missile could destroy the launch tube. American surface-ship VLSs have missile cells arranged in a grid with one lid per cell and are "hot launch" systems. The engine ignites within the cell during the launch and so requires a way of venting rocket exhaust. France, Italy and Britain use a similar hot-launching Sylver system in PAAMS.