Contra-rotating propellers boost ship propulsion efficiency by over 10 percent compared to conventional designs. Read the full story at 🔗 https://sci.sx/682012081 In this video: How the propellers spin in opposite directions during a test run in the cavitation tunnel at the Norwegian Ocean Technology Centre. Credit: Norwegian University of Science and Technology 📸 Follow us on Instagram for more exciting content https://www.instagram.com/sciencex.physorg/ #MaritimeInnovation #EnergyEfficiency