Sonar provides much closer look at USS Hatteras, a Civil War relic off Texas coast
GALVESTON, Texas — The remains of the only Navy ship sunk in the Gulf of Mexico during Civil War combat now can be seen in 3-D sonar images from the gulf's murky depths, revealing details such as a shell hole that may have been among the ship's fatal wounds.
The high-resolution images of the 210-foot, iron-hulled USS Hatteras are being released this month to coincide with the 150th anniversary of the battle where the ship was lost.
Besides the shell hole, they show previously unknown details like a paddle wheel and the ship's stern and rudder emerging from the shifting undersea sands about 20 miles off the coast of Galveston.
“This vessel is a practically intact time capsule sealed by mud and sand, and what is there will be the things that help bring the crew and ship to life in a way,” said Jim Delgado, the project's leader and director of maritime heritage for the National Oceanic and Atmospheric Administration's Office of National Marine Sanctuaries.
“You can fly through the wreck; you're getting a view no diver can get,” Delgado said.
The Hatteras had sat mostly undisturbed and unnoticed from January 1863 — when a Confederate raider sunk the ship and took most of its crew prisoner — until its discovery in the early 1970s.
Recent storms shifted the sand and mud where the Hatteras rests 57 feet below the surface, exposing more of the ship. So archaeologists and technicians, racing to beat any potential seabed movement that could conceal the Hatteras again, spent two days in September scanning the wreckage by using sonar imaging technology for the first time at sea.
Divers used the 3-D gear to map the site in the silt-filled water where visibility is from near zero to only a few feet.
The water's murkiness does not affect sonar technology like it would regular photography equipment. Sonar technology produces computer-colored images by analyzing sound waves bouncing off objects.
“We have very crisp, measurable images that show the bulk of the steam machinery in the engine room is there,” Delgado said. “Some of it is knocked over, been toppled, which suggests we probably have 60 percent of the vessel buried.”
Also revealed were platforms for the ship's 32-pounder guns, named for the size of the cast-iron shell the cannon delivered, and the bow.
The imaging plots the paddle wheel shaft, which appears to have been bent when the ship capsized, and damage to engine room machinery, including the shell hole that likely helped doom the ship, Delgado said.
The 1,126-ton Hatteras was built in 1861 in Wilmington, Del., as a civilian steamship, according to the Navy Historical Center. The ship was purchased by the Navy that year, commissioned at the Philadelphia Navy Yard and assigned to join the blockade of the Florida coast to keep vessels from delivering supplies and war weapons and ammunition to the Confederacy.