The Coast Guard on Tuesday said a fire earlier this month aboard its sole medium polar icebreaker, the cutter Healy, put one of its propulsion motors out of service, forcing the ship to scrub its annual scientific mission to the Arctic and return to port.

The fire broke out on Aug. 18, taking out the Healy’s starboard propulsion motor and shaft while the ship was 60 nautical miles off of Seward, Alaska, where it had embarked 11 scientists earlier that day before beginning its mission to the Arctic.

The Coast Guard said no injuries were reported.

The Healy was delivered to the Coast Guard in 1999 and was built by Avondale Industries in Louisiana. Avondale is now owned by Avondale Marine, a joint venture between T. Parker Host and Hilco Redevelopment Partners.

An electrical fire was reported at 9:30 p.m. and a fire crew disconnected the starboard propulsion motor. The fire was extinguished by 9:56 p.m. The cause of the fire is unknown. Both the starboard propulsion motor and shaft are not operational.

The Healy is transiting back to its homeport in Seattle with the use of its port propulsion motor, a service spokesman told Defense Daily on Tuesday. He said the 420-foot ship had not suffered a major casualty in recent years that rendered it unable to carry out its missions.

The Healy is one of two operational polar icebreakers in service with the Coast Guard. The Polar Star, a heavy icebreaker, performs an annual mission each winter to help resupply a U.S. science mission in Antarctica. The Healy is used for research in the Arctic and for maritime domain awareness and maritime presence operations.

The Healy had already completed a 26-day patrol this summer as part of Operational Arctic Shield, an annual exercise typically focused on maritime domain awareness, partnership building, and demonstrating U.S. presence.

“I commend the crew of the Healy for their quick actions to safely combat the fire,” Vice Adm. Linda Fagan, Pacific Area commander, said in a statement. “This casualty, however, means that the United States is limited in icebreaking capability until the Healy can be repaired, and it highlights the nation’s critical need for Polar Security Cutters.”

The 44-year old Polar Star earlier this year completed its mission to Antarctica, largely without incident. However, in recent years, the ship has suffered major casualties while underway, including an incinerator fire and a leak in a propeller drive shaft during the Antarctic mission in late 2018 and early 2019.

With the Polar Star showing its age, the Coast Guard in 2019 awarded a contract to VT Halter Marine to design and build the first of at least three new heavy polar icebreakers, the Polar Security Cutter. The first PSC is expected to be delivered in 2024.

The fire aboard the Healy will likely fuel the Coast Guard’s and nation’s urgency in recapitalizing its polar icebreaking fleet.

The Healy hasn’t undergone a service life extension program.

On its latest mission, the Healy was slated to conduct the the Arctic Mobile Observing System (AMOS) research effort for the Office of Naval Research. AMOS consists of support recovery and deployment of mobile systems that drive with the sea ice cover within the water column. The spokesman said scientists aboard the Healy have been able to conduct a limited amount of the AMOS mission while transiting to homeport.

A second science mission, the high-latitude Coordinated Arctic Acoustic Experiment involving the recovery of three acoustic mooring deployed by Healy in 2019, was canceled, the spokesman said.