Sail ships in the 21st century: Why ancient technology remains relevant today

Indian Express

20-05-2025

Two people were killed and at least 19 others were injured after ARM Cuauhtémoc, a sail training vessel of the Mexican Navy, collided with the Brooklyn Bridge in New York City on Sunday (May 18).
In the age of mechanised propulsion, sail ships are somewhat of a novelty today. But modern navies — including the Indian Navy — continue to retain such vessels in their fleets. And amid growing concerns about climate change, they may actually make a triumphant return in the world of shipping.
Unlike the great ships of the line during the Age of Sail, sail ships today are not meant to participate in naval battles. They lack the speed, endurance, manoeuverability, and resilience to participate in modern maritime warfare.
That said, sail ships are excellent platforms to train naval cadets. 'Sail training ships are increasingly being used as basic seamanship and character building platforms by Navies the world over,' according to the website of Goa Shipyard Ltd which has built two sail ships — INS Tarangini and INS Sudarshini — currently in service with the Indian Navy.
This is because sail ships are thought to provide the 'purest' experience of the seas possible.
'In an age of electronic navigation and advanced bridge simulators, nothing can replace the experience of going to sea under sail and feeling the power of the wind and waters that shape one's voyage and sharpen the senses,' wrote Captain Lawson W Brigham (retd). ('Training Under Sail in the 21st Century', Proceedings of the US Naval Academy, 2020).
'Sailing is transformative; it enhances environmental awareness and develops in a person a respect for the sea — fundamental lessons that will last a lifetime,' the former US Coast Guard officer wrote.
According to a 2018 press release by the Indian Navy, 'the primary role' of sail training ships like INS Tarangini 'is to develop character and professionalism, as well as inculcate the qualities of initiative, courage, resilience and esprit-de-corps (meaning group spirit) amongst the Sea Trainees and also impart practical training to them, primarily on navigation, sailing and seamanship.'
These ships also go on lengthy 'goodwill trips' — voyages to foster cooperation and improve relations between different nations. For instance, last November, INS Tarangini conducted a joint sailing exercise with the Italian training ship Amerigo Vespucci off the coast of Kochi. Tarangini has also gone on extensive voyages in the past, most notably a circumnavigation of the globe in 2003-04.
Sail ships — wind-propulsion, to be specific — may soon make a big-time comeback in commercial shipping.
Cargo ships, which carry more than 80% of the world's goods, are mostly propelled by diesel engines. By some estimates, shipping alone accounts for roughly 3% of annual climate change-causing greenhouse gas emissions, similar to the contribution of the aviation sector.
Scientists have long been looking to improve fuel efficiency of cargo ships. And a return to sail has been heralded as one of the most practical ways to cut ships' emissions. This is because unlike other cutting-edge technologies in the play, wind propulsion is tried and tested, and thus significantly more economical to be widely adopted by profit-driven merchant shipping companies.
That said, do not expect modern cargo vessels to suddenly morph into the great Age of Sail-era counterparts.
For one, wind propulsion will not replace but simply augment a ship's mechanical propulsion system. This alone can lead to significant emission reductions by allowing the crew to turn the engine down while still maintaining speed, and thus, meeting critical deadlines.
For instance, in 2024, shipping company Cargill reported that its vessel the Pyxis Ocean, a diesel-powered cargo ship retrofitted with two 'WindWings' — solid sails installed to vertically catch the wind and propel the ship forward — used three tonnes less fuel each day on average, equating to '11.02 tonnes of C02 emissions' saved each day when sails were up.
Moreover, the 'sails' on 21st century cargo ships will look very different from traditional sails. Some designs look more like power kites used in kite surfing. Others, like Pyxis Ocean's WindWings, may resemble airplane wings.
Still others may not be 'sails' at all. One viable, century-old design is the Flettner rotor, designed by German engineer Anton Flettner in the 1920s. Essentially a revolving cylinder mounted on a ship's deck, the Flettner rotor utilises the Magnus effect — same principle that makes a cricket ball swing — to propel a ship forward.
'As the wind flows around the revolving cylinders, the rotation creates an area of high air pressure on one side and lower pressure on the other… [This] pressure differential creates a force at right angles to the wind direction… On a vertical rotor, it helps push a ship forward,' a 2024 article in The Economist explained.
While improvements in the fuel-efficiency of conventional diesel motors and the falling prices of oil had put the development of Flettner motors on the backburner, multiple companies are now looking at this technology to cut their cargo ship emissions.
While widespread adoption of such technologies might still be years away, stricter emission rules in many ports is forcing shipping companies to change as fast as possible.
As the article in The Economist put it: 'If their vessels continue to belch fumes then shipowners will soon find themselves unable to operate within many ports. Though the number of vessels returning to wind power remains small for now, this technology clearly has the wind in its sails.'