Rigid wing sails (bound to the ship) or towing kites (free-flying on a long tether) generate direct thrust from ambient wind. Different operating envelopes than Flettner rotors - wing sails like quartering winds, kites like downwind trades.
DesignWind assist
Installation
Wind + voyage
Displacement
Effective thrust power
275kW
Fuel saved / year
288.8t
CO₂ avoided / year
899.3t
Formula, assumptions, and limits
Wing sails deliver steady thrust over long sea legs; kites pulse but can be 4–8× larger area for similar installed cost. Both suit trades with consistent wind direction - trans-Atlantic, trans-Pacific trade routes - less suited to coastal or monsoon regions.