But somehow it survived both the Navy bureaucracy and a broadside barrage to become one of the most celebrated ships in the world. Its designer and crew were the 19th-century celebrity equivalent of astronauts. Long after the ship sank in a storm off Cape Hatteras, N.C., the turret remained a cultural icon: an “armored tower” in Melville’s poetry, an image on book covers and film posters, a shape reproduced in items from toys to refrigerators.

Now the original turret, which was recovered from the ocean floor nine years ago and placed in a freshwater tank to protect it from corrosion, is on display again. It has been temporarily exposed to the air so that it can be scraped clean — very carefully, in front of museum visitors and a live webcam — by a team of researchers at the U.S.S. Monitor Center of the Mariners’ Museum here in Newport News. The team expects to have nearly all the barnacles and sediment removed by the end of this month, giving the public a new look at the dents from the Confederate cannonballs and shells that would have sunk any ordinary ship of its day. Then the turret will be submerged again in fresh water for 15 more years, until enough ocean salt has been removed from the metal to allow it to face the air permanently.

The more that researchers examine the turret and about 1,500 other artifacts from the Monitor, the more impressed they are with its designer, John Ericsson. Besides the 360-degree rotating turret, there were dozens of other patentable inventions in the ship, including a new type of compact engine and a new toilet that could be flushed below the waterline.

“What makes the Monitor so remarkable is that she’s almost a stealth vessel because all the systems except the ordnance are below the waterline,” said Anna Holloway, the curator at the Monitor Center. “Keeping the engine safe from attack was a big breakthrough. Not only did Ericsson create this radically new type of vessel, but his designs were so nearly flawless that foundries and contractors from around the Northeast could fabricate the parts, and they all fit together when the ship was assembled in Greenpoint. It boggles the mind.”