Contractors reassemble the Coast Guard Cutter Polar Star’s port side hub while the cutter undergoes extensive maintenance at a dry dock facility in Vallejo, Calif., Oct. 3, 2018. The 399-foot Polar Star, build more than 40 years ago, is the only operational heavy icebreaker in the U.S. fleet, weighing 13,500 tons and uses 75,000 horsepower to break ice up to 21 feet thick. Coast Guard photo by Petty Officer 1st Class Matthew S. Masaschi.