Just three weeks after commissioning the USS Zumwalt, the U.S. Navy has admitted it is canceling ammunition specially developed for the ship's high-tech gun systems because the rounds are too expensive. The guns, tailor made for the destroyer, will be unable to fire until the Navy chooses a cheaper replacement round.

The Zumwalt-class destroyers were conceived in the late 1990s as the first of a new generation of stealthy warships. The radar signature of the 610 foot long warship is that of a 50-foot fishing boat, making the Zumwalts great for getting in close to an enemy coastline and then using the 155-millimeter Advanced Gun Systems mounted on the front of the hull. The guns were designed to fire the advanced Long Range Land Attack Projectile, a GPS guided shell with a range of 60 miles.

The result would have been a destroyer that could rain shells down on enemy targets incredible accuracy, clearing a path for U.S. Marines as they advance inland. Alternately, they could strike targets such as terrorist training camps, military bases, and other static targets. The two Advanced Gun System howitzers are fed by a magazine containing 600 rounds of ammunition, making it capable destroying hundreds of targets at a rate of up to ten per minute.

Here's how the Advanced Gun System was supposed to work.

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Now the U.S. Navy is admitting that the LRLAP round is too expensive to actually purchase, leaving the nearly $4 billion dollar destroyer's guns high and dry.

According to Defense News, the LRLAP round costs $800,000—or more—each, making the rounds prohibitively expensive. The Navy blames the rise in cost on the fact that the Zumwalt class went from a planned 32 ships to just 3, drastically cutting the number of LRLAP rounds it was going to purchase.

A May report by US Naval Institute News estimated each LRLAP round to cost between $400,000 to $700,000. For context, the smaller Mk. 45 5-inch gun, standard on Navy destroyers and cruisers, fires an unguided round with a range of 21 miles. Each round costs between $1,600 and $2,200.

The LRLAP round was developed by Lockheed Martin. In 2001, the director of Lockheed's guided projectiles division claimed the LRLAP would cost "less than $50,000 each." Even factoring in inflation, the rounds have ended up costing nearly twelve times as much.

According to Defense News, the U.S. Navy is considering alternatives to LRLAP. One is the Excalibur GPS-guided artillery round. First developed for Army howitzers, contractor BAE Systems has come up with a naval version that can hit targets out to 26 miles. Excalibur costs about $68,000 each—which coincidentally is the same as Lockheed Martin's 2001 estimate for the LRLAP, adjusted for inflation.

Another option is to get rid of the Advanced Gun System entirely and go with railguns. The Navy has been planning to build the third Zumwalt-class destroyer, USS Lyndon B. Johnson, with railguns—provided the technology was mature enough. It may just be worthwhile to send the first ship back to the shipyard to be refitted with railguns, and delay the second ship so it can be fitted with railguns from the get-go.

A third option would be to get rid of the guns and devote their space to missiles. The Zumwalt-class was developed during a period when the U.S. Navy didn't face the prospect of fighting other navies on the high seas. In a search to remain relevant, the Navy developed the Advanced Gun System, which has zero capability to target other ships. In the nearly two decades since the Zumwalt class was proposed, the Chinese and Russian Navies have undergone a period of expansion, and their respective governments have grown more aggressive.

The Zumwalt-class destroyers have only 80 vertical launch missile silos, the least of any U.S. Navy destroyer or cruiser class. Under the missiles-only alternative, the Zumwalts could swap both guns for even more silos. These silos could house SM-6 long range anti-air missiles, Evolved Sea Sparrow short range anti-air missiles, Tomahawk cruise missiles, and the new Long Range Anti-Ship Missile. Replacing the AGS with a field of silos could give the Zumwalts up to 200 missile spaces, more than any other ship in the Western world.

According to USNI News, the U.S. Navy wouldn't talk about LRLAP costs as late as last May. The Navy has known it wasn't getting 32 Zumwalt-class destroyers since 2008—the better part of a decade. Why it has taken this long to announce it would not be buying ammunition for a $22.5 billion dollar weapon system—which was specifically developed to use that ammunition—is a mystery.

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Kyle Mizokami

Kyle Mizokami is a writer on defense and security issues and has been at Popular Mechanics since 2015. If it involves explosions or projectiles, he's generally in favor of it. Kyle’s articles have appeared at The Daily Beast, U.S. Naval Institute News, The Diplomat, Foreign Policy, Combat Aircraft Monthly, VICE News, and others. He lives in San Francisco.