The US Navy's most expensive destroyer, the Zumwalt-class destroyer, could be losing its revolutionary 155mm deck guns, as the Navy has yet to find suitable ammunition .

The new ship class has also faced engineering, engine, and electrical problems, and recent photos suggest it may be losing some of its stealth.

The Navy plans to incorporate the Zumwalt into the fleet in 2021 as a platform that can strike land targets and other ships.

With a high-voltage electrical system, the ship is a top candidate for futuristic weapons systems like railguns and lasers.

The Zumwalt-class destroyer, the largest and most advanced surface combatant in the world, was built to be a silent killer, but the revolutionary warship has faced a string of setbacks during development — including the embarrassing problem that its supergun still does not work right.

The two 155mm guns of the Advanced Gun System on the Zumwalt, intended to strike targets farther than 80 miles away, are ridiculously expensive to fire, as a single Long Range Land Attack Projectile costs almost $1 million. Procurement was shut down two years ago, leaving the Zumwalt without any ammunition to fire.

That's not the only problem — the gun also lacks the desired range, Breaking Defense reported Wednesday.

The Zumwalt departing from Bath, Maine. REUTERS/US Navy/Handout via Reuters

"We just cannot get the thing to fly as far as we want," Vice Adm. William Merz, the deputy chief of naval operations for warfare systems, told the Senate Armed Services seapower subcommittee Tuesday, explaining that the Navy may do away with the guns entirely if it can't develop effective and cost-efficient ammunition, according to Breaking Defense.

The Navy "will be developing either the round that goes with that gun or what we are going to do with that space if we decide to remove that gun in the future," he continued.

"The ship is doing fine, on track to be operational in 2021 in the fleet," he said, adding that the Zumwalt-class destroyer remains a "very capable platform with or without that gun."

Read more: Step aboard the USS Zumwalt, the largest destroyer the US Navy has ever built

The Zumwalt at the naval station in Newport, Rhode Island. AP Photo/Michael Dwyer

The Zumwalt-class destroyers were expected to serve as multi-mission ships, focusing primarily on land-attack and naval gunfire support missions with secondary anti-ship and anti-aircraft mission capabilities.

The Navy saw the ship operating in coastal areas and supporting ground troops, but that mission was changed late last year, according to The Diplomat.

The destroyer will now serve as a surface strike combatant, relying on a diverse arsenal of anti-ship and anti-air missiles capable of being launched from 80 Mk 54 Vertical Launch System cells, which Merz said were larger than those of other surface ships, creating more options for armaments.

The Zumwalt, however, has fewer missile cells than the Arleigh Burke-class destroyers and the Ticonderoga-class cruisers, which have 96 and 122 missile launch cells that can carry interceptors, cruise missiles, and rocket-launched torpedoes.

It appears that the Navy intends to force the Zumwalt through the development process and then sort the rest out later.

"We determined that the best future for that ship is to get it out there with the capability that it has and separate out the Advanced Gun System, leaving everything else in place," Merz said, according to Breaking News.

The Zumwalt passes spectators at Fort Popham at the mouth of the Kennebec River in Phippsburg, Maine, in 2015. AP Photo/Robert F. Bukaty, File

But the gun is apparently not the only problem when it comes to the Zumwalt.

The ship has been steadily becoming less and less stealthy as the Navy settles for bolt-on components — including satellite communication antenna systems mounted on the sides and the high-frequency vertical antenna bolted on the top — amid efforts to cut costs.

The Drive spotted these problems on one of three Zumwalt-class destroyers in the works. (There were initially supposed to be more than 30.) The publication speculated that these non-low-observable features would negatively affect the stealth capabilities of the ship, which was initially built to be as stealthy as a fishing boat.

These potential detriments were not visible on earlier versions of the Zumwalt-class destroyers.

The Zumwalt heading down the Kennebec River. AP Photo/Robert F. Bukaty

The Zumwalt-class destroyers have also experienced serious engine and electrical problems during development. Nonetheless, the ship's twin Rolls-Royce MT30 gas turbines and advanced technological systems make it a candidate for future railgun and directed-energy weapons.

"She is going to be a candidate for any advanced weapon system that we develop," Merz said Tuesday, according to Breaking Defense.

The Zumwalt's primary competitor is China's Type 055 Renhai destroyer.

A Type 055 Renhai-class cruiser. REUTERS/China Stringer

Though the Chinese warship is not as technologically advanced as the Zumwalt, which remains unmatched, the Renhai destroyers are equipped with 112 VLS cells able to fire HHQ-9 surface-to-air missiles, YJ-18 anti-ship cruise missiles, CJ-10 land-attack cruise missiles, and missile-launched anti-submarine torpedoes, according to the South China Morning Post.

The missions vary a bit, as the Type 055 is expected to serve as an air-defense and anti-submarine warship, one that could escort Chinese aircraft carriers.