US Navy stealth destroyer Zumwalt's deck guns are basically useless, but it's on its way to get new hypersonic missile launchers

• Destroyer USS Zumwalt has long had problems with its main deck guns, which don't have any ammunition.
• The technologically advanced stealth destroyer is getting something new though.
• The Zumwalt is changing homeports to receive upgrades including a new hypersonic missile system.

The stealth US Navy destroyer USS Zumwalt has been plagued by a wide range of problems throughout its development, including guns that are all but useless, but the ship on its way to do something about it.

After a brief hiccup — an abrupt return to port for unexpected maintenance— the ship departed San Diego, California Wednesday for Pascagoula, Mississippi, home of Ingalls Shipbuilding, part of the major Navy shipbuilder Huntington Ingalls Industries.

The Zumwalt will "receive technology upgrades including the integration of the Conventional Prompt Strike weapons system," the Navy said in a statement, adding that the coming "upgrades will ensure Zumwalt remains one of the most technologically advanced and lethal ships in the US Navy."

During the upgrade period, according to a USNI News report, shipbuilders will remove the impotent twin 155mm Advanced Gun Systems and replace them with missile tubes that altogether are expected to carry a dozen hypersonic missiles, weapons that are still in development and expected to be fielded in the next few years.

The Zumwalt-class destroyers were designed with a land-attack and naval-fire support mission in mind and were armed with a pair of 155 mm deck guns. The problem is that these naval artillery guns do not have any ammunition and haven't for years, and the reason for that is that the ammo is ridiculously expensive.

A reduction in the overall size of the Zumwalt class from a planned 32 ships to just three caused the cost of the ammunition for the guns, the Long Range Land Attack Projectile, to jump to about $800,000 a round. The guns also never acquired the desired range. So, the Navy was forced to rethink the weapons and missions for these destroyers.

Ammunition procurement stopped in 2016, the year the Zumwalt was commissioned, and by 2018, senior Navy officials were publicly considering scrapping the main guns, which is now exactly what the service is doing apparently. 

The sea service is now looking at using the Zumwalt-class destroyers, which include the USS Michael Monsoor and the USS Lyndon B. Johnson, for blue-water surface-warfare and naval-strike missions, and that's where the hypersonic missiles come into play.

The Conventional Prompt Strike (CPS) system is a boost-glide hypersonic weapon system that consists of a two-stage solid-fueled rocket booster to get the missile to a faster than Mach 5 speed and the Common Hypersonic Glide Body (CHG-B), which was jointly developed by the Army and the Navy for their respective hypersonic weapons programs.

Though the term "hypersonic weapon" emphasizes speed, specifically speeds at least five times the speed of sound, many other types of missiles, including regular ballistic missiles, can actually achieve the same if not greater speeds. True hypersonic weapons pose a new and potentially unstoppable threat due to their ability to maneuver unpredictably at these speeds. 

The Navy intends to deploy this capability aboard Zumwalt-class destroyers by 2025 and then on the Virginia-class attack submarines by the end of this of this decade. The CPS, including both the missiles and the launchers, is still in development though, so there is always a very real possibility of delays.