A 1.2m autonomous sailing vessel developed by UK maritime technology company Oshen has completed the first fully unaided autonomous crossing of the Atlantic, winning the Microtransat Challenge after 127 days at sea.
C-Star PC13 crossed the finish line east of Barbados on 13 September, having departed Gran Canaria on 7 May.
The vessel covered 2,926 nautical miles (5,400km), navigating trade winds and shipping lanes without intervention from the Oshen team.
The Microtransat Challenge requires entrants to cross the Atlantic without assistance once underway, with teams unable to influence the vessel’s decisions or alter its course. Boats are also limited to 2.4m in length, restricting the space available for solar generation and onboard systems.
The fully autonomous prize had remained unclaimed for 16 years, with more than 30 attempts made since 2010 by organisations including Shanghai University, France’s École Navale and the US Naval Academy.
PC13 was Oshen’s third attempt. Its first crossing attempt in 2023 ended after 20 days, while a modified vessel launched from Plymouth in 2025 sailed for 277 days and covered around three quarters of the Atlantic before losing its sail in heavy seas.
Oshen’s C-Stars are designed as autonomous sensor platforms for applications including defence, subsea cable and pipeline monitoring, illegal fishing detection and oceanographic research.
The vessels can operate individually or in fleets, collecting up to 2 million data points per day covering variables including sea surface temperature, air temperature, pressure, humidity, salinity and water density. Their navigation software assesses wind speed and direction, currents and battery levels to maintain position or sail to pre-selected destinations.
The company has previously deployed C-Stars in severe weather conditions, including a September 2025 NOAA mission during which C-Star PC8 entered the eyewall of Category 5 Hurricane Humberto and survived 10m waves and winds exceeding 240km/h.
PC13 did not encounter a hurricane during its Atlantic crossing, but passed through the developing low-pressure system associated with Storm Dolly on 28–29 August.
“We are thrilled to have finally completed the Microtransat. Even in the final hours, after so many days at sea, we weren’t certain that PC13 would reach the designated finishing zone. It is a great result and a fantastic validation of all the effort the team has put into making C-Stars the world’s most capable sail-powered USV,” said Anahita Laverack, CEO and co-founder of Oshen.
