Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: WEDNESDAY, May 16, 1990 TAG: 9005160288
SECTION: NATIONAL/INTERNATIONAL PAGE: A-1 EDITION: METRO
SOURCE: WILLIAM J. BROAD THE NEW YORK TIMES
DATELINE: LENGTH: Long
It has no moving parts, is virtually silent and promises great reliability at relatively low cost.
The basis for the advance is a tongue-twisting phenomenon known as magnetohydrodynamics, or MHD, in which magnetic fields are used to move water.
There are no moving parts - no motors, no propellers, no gears and no drive shaft. Instead, a superconducting magnet, more efficient and powerful than conventional magnets, exerts a magnetic force on sea water passing through its core, driving water out the back and creating forward motion.
The technology is featured in the movie "The Hunt for Red October," based on the book by Tom Clancy in which an advanced Soviet submarine is hunted by the American and Soviet navies.
In real life, scientists say MHD propulsion might find both military and civilian uses. It might economically power commercial ships and cargo submarines.
And it might pave the way for a new generation of military submarines that are quieter than ever, helping them elude foes.
"It's provocative in its simplicity," said Dr. Michael Petrick, a scientist who directs research on the idea at the Argonne National Laboratory in Illinois. "But there's lots of work that needs to be done to make it viable."
Questions to be answered include both its technical feasibility and utility. So far, the idea has undergone no known large-scale trial, although that is about to change.
Early next year, the Japan Foundation for Shipbuilding Advancement plans to launch a 100-foot-long, prototype MHD-powered ship that will carry up to 10 people. The test is a sea trial for commercial operations.
And the Argonne lab is spearheading a military-sponsored program that centers on a 21-foot-long, 180-ton monster superconducting magnet.
Its trials, confined to the laboratory, are to begin early next year. In a different project, the Navy is considering sea trials for MHD propulsion.
"The marriage of an MHD propulsion system to underwater vehicles is a natural," said Dr. Daniel W. Swallom, who manages the Navy-financed program on the propulsion system at the Avco Research Laboratory in Everett, Mass. His program's goal is an open-ocean test with a remotely piloted vehicle.
The Soviet Union has carried out much basic research on this form of propulsion, but intelligence experts are at odds on whether the Russians are applying the idea to their submarines.
Magnetohydrodynamics involves magnetic fields (magneto) and fluids (hydro) that conduct electricity and interact (dynamics). The phenomenon occurs naturally in the Earth's core, giving rise to the planet's magnetic field.
In MHD propulsion, a pair of electrodes on either side of the thruster pass an electric current through sea water. The process does not work effectively with fresh water because it can carry little current.
At a right angle to the current is the magnetic field generated by the superconducting magnet. The interaction of the magnetic field and the current produces a strong force on the water, moving it through the duct in the center of the magnet. If the polarity of the current is reversed, so is the direction of thrust.
The action is identical to what happens with an electric motor when its magnetic field crosses a bundle of copper wires carrying an electric current, causing it to move and the central shaft of the motor to rotate.
The activity in each case revolves around charged particles. In the motor, the current-filled wires are filled with moving electrons, which carry a negative charge, and are strongly acted upon by the magnetic field.
In MHD propulsion, the electric current flowing through the seawater causes the formation of charged particles, or ions, which in a similar manner are acted upon by the powerful field of the superconducting magnet. It propels both the ions and the seawater.
The direction of the force is at right angles to the matrix formed by the current and magnetic field.
This effect, known as the Lorentz force, was first quantified by the Dutch physicist Hendrik Antoon Lorentz in the late 19th century.
This form of propulsion was conceived and tested in the United States more than two decades ago but languished until the advent of superconducting magnets.
These can be made very powerful and very efficient because, when their coils are cooled almost to absolute zero, they lose no electricity to resistance.
In the late 1980s, Japan became the first nation to publicly embark on a sizable program meant to achieve MHD propulsion. "It's the same old story," said Petrick at Argonne. "The idea evolves in this country but someone else picks it up and runs with it."
Leading the Japanese work is the Foundation for Shipbuilding Advancement, a private concern working with Mitsubishi Heavy Industries, Hitachi Zosen and Mitsui Engineering and Shipbuilding. The foundation is believed to have spent about $31 million on the research since 1987.
"They've gotten the best people from industry, government and the universities to work on this thing," said William J. Andahazy, a staffer on the House Armed Services Committee who was once associated with the American MHD effort.
The Japanese work focuses on the 100-foot ship, whose top speed is to be eight knots. It has two MHD thrusters on two huge fins protruding from the craft's hull, according to a paper by the foundation.
A thruster is made up of six magnetic modules, each fitted with a sea-water duct some 10 inches in diameter.
One thruster assembly is being built by Mitsubishi Heavy Industries, and the other, with a slightly different configuration, by Toshiba Corp.
The Japanese ship is simply a technology test, its small thrusters being relatively inefficient. If the technique is to work commercially, magnets must become lighter, larger and more powerful.
The Japanese work has helped increase American interest in MHD propulsion, although the Defense Department had been studying it for many years.
by CNB