Engineering -- May The Force Be With You
Using a relatively simple principle, a Japanese group has developed a ship powered by a force called magnetohydrodynamic propulsion. Though mostly impractical now, this system is on the cutting edge of propulsion technology.
KOBE, Japan - There was little fanfare and no speeches as the Yamato 1 - looking less like a watercraft than something Luke Skywalker might pilot against Darth Vader's Death Star - was towed from the dock at Japan's most advanced high-tech shipyard recently.
Then the tow lines were cast off. The Yamato 1, equipped with a revolutionary superconducting magnetic propulsion system never before tested at sea, was on its own.
"We have 1,000 amperes of electrical current," the skipper's voice crackled over the radio. "Speed, 1.2 knots."
And, yes, the 100-foot, 185-ton Yamato - propelled by a futuristic propulsion system that essentially turns sea water into part of an electric motor - was moving,slowly surging against the light chop of Kobe Harbor and into nautical history.
"We have 2,000 amperes of electrical current."
The skipper's matter-of-fact tone sounded distinctly forced as the vessel's superconducting electromagnetic propulsion system cranked soundlessly up to full power and full speed.
"Speed, 6.2 knots." About seven miles per hour, barely faster than Robert Fulton's steamboat Clermont as it chugged 130 miles from New York to Albany in 32 hours in 1807.
This was not a test of speed, however, but of a new technology - a potentially highly energy-efficient, almost totally silent "magnetohydrodynamic" propulsion system, better known as MHD - that many believe will eventually make the piston- and turbine-driven propellers of today's fleets as obsolete as the canvas and rigging of the age of sail.
The Yamato 1 passed with flying colors, with only a faulty alarm light marring an otherwise perfect performance.
"After so many years, we have success," said Seizo Sasakawa, chairman of the research committee of Japan's Ship and Ocean Foundation. "We are proud to be the first to develop this technology, and we will share it with researchers around the world."
However, Sasakawa stressed, generosity has its limits: Japan is flatly opposed to lending its breakthrough to military applications - the focus of most MHD research in the United States. "We want to limit its use to peaceful applications," he told reporters after the first run.
To the exultant scientists, engineers and industrial leaders of the foundation - a consortium that has already lavished eight years of intensive work and $40 million on the project - the maiden sea trial of the Yamato 1 marked a technological leap comparable to the Clermont's historic voyage and the launching of the nuclear submarine Nautilus in 1955.
"We are still in the cradle stage of development, but we produced thrust power, we drove the vessel," said Seizo Motora, chairman of the foundation's subcommittee on hull development.
He acknowledged that the most difficult task lies ahead. "We have to refine and enhance the performance of this technology," he said. "The potential uses are limitless, but we still have a long, long way to go. The crawling infant must find its feet."
The Yamato 1's power system has no moving parts: no huffing motors, no gears, spinning drive shafts or whirling propellers.
MHD ship propulsion is an application of an electromagnetic phenomenon known as the Lorentz force, sometimes described using "Fleming's left-hand rule." When an electric current is passed at right angles through a magnetic field, force is generated in a direction perpendicular to the plane in which the current and the magnetic field intersect.
An electric motor relies on the same principle. A current is passed through coils of wire inside a magnetic field, and the resulting force on the coils causes the central shaft to rotate.
In the Yamato, a pair of electrodes on either side of the two thruster tubes, which run bow-to-stern underneath the ship, set up an electric current in the sea water flowing into the front of each tube. The tubes are surrounded by coils of titanium and niobium that become superconducting when cooled to minus 269 degrees Celsius (four degrees above absolute zero), creating a powerful magnetic field at right angles to the current and forcing the electrically charged water at high pressure out through nozzles at the stern, driving the vessel forward.
Although the Yamato 1 dawdles along at a rate that might fairly be described as sluggish, Japanese researchers see it as the precursor of giant tankers, freighters and other commercial ships that will whisk across the oceans at high speed, unhampered by the so-called "cavitation effect" - the turbulence created by propellers that limits their speed and can even shatter the blades at top speeds.
Daniel Swallom, director of military power and propulsion systems for Textron Defense Systems in Everett, Mass., said research there, which began at about the same time as the Japanese program, is working toward applying the principle to submarine propulsion, where it could make possible a new generation of "stealth" submarines that produce none of the engine and propeller noise that is now used to track submarines. The plot of Tom Clancy's best-selling techno-thriller, "The Hunt for Red October," revolves around an elusive Soviet submarine powered by a water propulsion system, although it relies on a mechanical system, not MHD, to move the water.
Swallom said if Congress approves funding for the project, a small-scale prototype MHD submarine could be ready for testing in about three years. A Navy facility in Newport, R.I., was built to test the MHD concept for ships but has been idle for more than a year, he said.
In Japan, Sasakawa acknowledged that it will take many more years of research and billions of dollars to realize that nation's long-range goal of launching fleets of energy-efficient, fast-moving and silent-running commercial craft and cargo submarines. In theory, such vessels could travel at speeds of 100 knots (roughly 115 miles per hour), reducing the voyage from Japan to North America from two weeks to a few days.
U.S. researchers have scored successes in the new technology in military and corporate test labs, but the short sea trial of the Yamato 1 - the craft cruised the harbor for only half an hour - represented the world's first voyage of an MHD-driven vessel.
"The biggest technological stride they've made," Swallom said of the Japanese vessel, "is they've gone out and done something, rather than generating more paper and studies. In this country, we're still struggling and trying to decide whether to do anything or not."
Superconductors, which carry electricity with virtually no resistance when cooled to ultrafrigid temperatures, use energy very efficiently and are key to the powerful magnetic fields the system requires. At present, the main obstacle to their practical use is size and weight. The MHD propulsion system on the Yamato 1 uses a big metal-alloy superconductor coil that must be cooled with expensive liquid helium carried in bulky tanks. Despite its sleek design, the craft is basically a floating power plant with a small cockpit and space for 10 passengers forward.
With present technology, an MHD drive capable of moving the vessel at high speed would "be so big it would sink the ship," said Sasakawa. "Our next step is to build a ship with much more efficiency and much more speed."
To accomplish this, Japanese researchers are feverishly developing super-strong, super-light composite materials to make smaller superconducting magnets capable of generating greater power and operating at higher temperatures.
"The coil we are using now expands and heats up, which destroys its superconducting properties," said Kensaku Imaichi, chairman of the Ship and Ocean Foundation. "The bottleneck now is how to make and maintain a stronger magnetic field in a drastically (smaller) superconductor. That is dream, and we intend to achieve the dream."
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