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Spinning Metal Sails Could Slash Fuel Consumption, Emissions On Cargo Ships (sciencemag.org)
sciencehabit shares a report from Science Magazine: U.K. soccer star David Beckham was known for "bending" his free kicks over walls of defenders and around sprawling goal tenders, thanks to a physical force called the Magnus effect. Now, the physics behind such curving kicks is set to be used to propel ocean ships more efficiently. Early next year, a tanker vessel owned by Maersk, the Danish transportation conglomerate, and a passenger ship owned by Viking Line will be outfitted with spinning cylinders on their decks. Mounted vertically and up to 10 stories tall, these "rotor sails" could slash fuel consumption up to 10%, saving transportation companies hundreds of thousands of dollars and cutting soot-causing carbon emissions by thousands of tons per trip.
Rotor sails rely on a bit of aerodynamics known as the Magnus effect. In the 1850s, German physicist Heinrich Gustav Magnus noticed that when moving through air a spinning object such as a ball experiences a sideways force. The force comes about as follows. If the ball were not spinning, air would stream straight past it, creating a swirling wake that would stretch out directly behind the ball like the tail of a comet. The turning surface of a spinning ball, however, drags some air with it. The rotation deflects the wake so that it comes off the ball at an angle, closer to the side of the ball that's rotating into the oncoming air. Thanks to Isaac Newton's third law that every action must have an equal and opposite reaction, the deflected wake pushes the ball in the opposite direction, toward the side of the ball that's turning away from the oncoming air. Thus, the spinning ball gets a sideways shove.
Rotor sails rely on a bit of aerodynamics known as the Magnus effect. In the 1850s, German physicist Heinrich Gustav Magnus noticed that when moving through air a spinning object such as a ball experiences a sideways force. The force comes about as follows. If the ball were not spinning, air would stream straight past it, creating a swirling wake that would stretch out directly behind the ball like the tail of a comet. The turning surface of a spinning ball, however, drags some air with it. The rotation deflects the wake so that it comes off the ball at an angle, closer to the side of the ball that's rotating into the oncoming air. Thanks to Isaac Newton's third law that every action must have an equal and opposite reaction, the deflected wake pushes the ball in the opposite direction, toward the side of the ball that's turning away from the oncoming air. Thus, the spinning ball gets a sideways shove.
Or they could just use old fashioned sails and cut fuel consomption by 100%.
Rotor ships are right up there with Sterling engines, fuel cells, and a lot of other "great ideas" that turn out not to be so great in practice. When a fairly simple technology like this hasn't caught on for over a century, there's probably a good reason for it. My guess is in the case of rotor ships, it's higher purchase price, higher maintenance costs, higher weight, higher center of gravity, vulnerability to high winds, and insufficient savings under real weather conditions.
Oil is not expensive enough. It's just a matter of time.
Oil will be "expensive enough" when something comes along to replace it. We don't burn oil to be assholes to the environment, we burn it because it's the best we got right now. Wind power might replace it, but then so could nuclear power. It's not like nuclear propulsion is a new technology.
I know someone just fainted upon reading the idea of civilian shipping powered by nuclear reactors. We have a choice. We can burn oil, use nuclear power, or leave vital shipping to the whims of the weather. Nuclear powered shipping has been tried before and failed primarily on poor ship design and politics, not for any technical reasons. We've got better reactors now so it's not like they are going to melt down or something.
I've heard of proposals for a lead cooled reactor, where the reactor is surrounded by molten lead. It's probably heavy as fuck but it's in a ship, so no one cares. If there's a problem the reactor is shutdown and the lead solidifies, sealing everything inside. The lead is a neutron reflector, so if it leaks away the reactor cannot function. Probably not a good thing if your coolant leaks away but at that point the ship is likely taking on water, and water makes a good radiation shield. If a leak is detected then shut it down and dump water on it, that will solidify the lead and seal it up. There's other reactor types that could work, but lead cooled has been tried and shown to work. Nuclear powered ships can't be any worse than oil fired ships, can they?
Again it's oil, nuclear, or leaving vital shipping to the whims of the weather. There might be some future alternative but those are our choices right now.
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