In a rare incident on July 18th an American warship firing a missile from a vertical launch tube was damaged when the rocket motor of the SM-2 exploded shortly after launch. The explosion showered the Burke class destroyer USS The Sullivans with fragments and started a small fire on the left side of the ship. That damage was minor and cost about $100,000 to repair. There is no record of any similar accident. The SM-2 was an older rocket that had been kept in service via regular monitoring, maintenance and refurbishment. Those procedures are now being reviewed.
Meanwhile the U.S. Navy was already in the midst of a $100 million effort to design and implement upgrades to the VLS (Vertical Launch System) sealed launch tubes used for a wide variety of anti-ship/aircraft/missile/satellite/land target missiles on its ships. The U.S. Navy has about 9,000 VLS cells on 90 ships. Mechanical and electronic improvement are needed to accommodate or get the most out of new versions of missiles used in the VLS. This accident puts additional emphasis on reviewing safety as well.
Basically a VLS is a square cell that can accommodate the sealed canisters missiles are shipped, stored and fired from. These canisters have a standard electrical and mechanical interface which meshes that of the VLS and fire control systems. So it’s easy to install, store, maintain and fire missiles from VLS cells.
Since the 1980s the United States and later several other nations have adopted the eight cell VLS systems. With this missiles are launched directly from the vertical launch tubes (cells) just beneath the decks of warships. The launch tubes also contain electronic connections that enable the crew to monitor the condition and readiness of the missiles. Most cells contain only one missile, although the smaller Sea Sparrow anti-aircraft missile can fit four to a VLS cell. Since 1982, over 11,000 VLS cells have been installed in nearly 200 American and foreign warships. The most common VLS user is the American Burke class destroyer, with 90 VLS cells. A smaller number of cruisers have 122 VLS cells each. Some of the older Spruance class destroyers got 61 VLS cells.
In the 1980s, there was some debate over the need for an at-sea VLS reloading capability for surface ships. A system was developed, but it meant losing six cells (three for the forward VLS cells and three for the ones aft, in the rear of the ship). This crane system was dropped, so that the ships could use more cells for missiles. Back then, it was believed that any future war would mainly be a series of hard fought initial battles, when every VLS cell counted. It was also found that actually reloading those cells was very difficult at sea and was really only practical if the ships dropped anchor in a harbor or other sheltered space to do the reloading with the help of a support ship.