Groton ― The Nautilus made its journey back to the Submarine Force Museum on Thursday, after months of repairs and preservation work at the Naval Submarine Base.

Crew members busily worked on the sunny morning to untie the Nautilus from a pier at the base to get the historic ship underway. Two tugboats towed the 319-foot-long submarine down the Thames River to a pier at the museum, where the newly refurbished vessel will reopen to the public next month. Workers standing on the museum pier and in work boats helped secure the vessel in place.

“It was smooth sailing,” said Lt. Cmdr. Derek Sutton, officer-in-charge of the Nautilus, the world’s first nuclear-powered submarine, and director of the Submarine Force Museum.

The purpose of the $36 million preservation project, which began last fall and is in the final stages, is to give the Nautilus a “clean bill of health” for the next 30 years, said Sutton.

“Coming back to the pier here today is the start of that 30 years that she’s going to be able to continue to tell the stories of the bold and courageous sailors that have served on board all submarines throughout the U.S. submarine force history,” Sutton said.

The crew from the Nautilus, along with Electric Boat and the Navy, worked on the preservation project that removed the topside wood decking, blasted and repainted the hull, repaired the ship’s superstructure and cleaned and preserved tanks, according to a news release from the naval base. The Mystic Seaport Museum worked on installing new wood decking. The project also included lighting improvements and additional access points for staff, among other components.

The historic ship was towed to the base last fall for the preservation work. With the return to the museum on Thursday, the final maintenance work will be completed at the museum pier, Sutton said.

The Submarine Force Museum is open through the weekend, but will temporarily close Aug 8-18 for maintenance work on the Nautilus, he said. The museum will re-open Aug. 19, though the historic ship will remain closed until its grand re-opening in September.

A grand re-opening ceremony is slated for 12:30 p.m. Sept. 9, the same day that the Connecticut Maritime Heritage Festival begins. Sutton said the ceremony is open to the public and everybody is welcome and encouraged to attend and be one of the first people back on board the Nautilus after the preservation project is complete.

The Nautilus, which was built at Electric Boat, was launched in 1954 and commissioned that year into the U.S. Navy. In 1958, the Nautilus made history as the first ship to make it to the North Pole.

The ship was decommissioned in 1980 and became a National Historic Landmark in 1982. The ship and museum first opened to the public in 1986, according to the museum website.

The Nautilus underwent a $4.7 million preservation project at Electric Boat in the early 2000’s, the Navy said.

k.drelich@theday.com