jealous? why?
(11.26.2023)
g**gltrad: To carry out its missions, a nuclear submarine must be as discreet as possible. However, despite the innovations developed over recent decades, such a ship is not yet completely silent, because of the cavitation noise produced by its propeller. Depending on this, it is possible to determine its acoustic signature… and therefore to identify it [this is also the work of the “golden ears” of the Navy Acoustic Interpretation and Reconnaissance Center national].
To eliminate this cavitation noise, there is only one solution: do without a propeller... Which would be possible with magnetohydrodynamics [MHD] which, to summarize succinctly, is concerned with the flow of electrically conductive fluids in the presence of a magnetic field.
“The basic principle of MHD propulsion is simple. It involves using electromagnetic forces to propel ships by reaction. These Laplace forces come from the interaction between a magnetic field, created by superconducting coils and electric currents circulating in sea water. Thus, the electrical energy, supplied by generators on board, is directly transformed into mechanical energy [work of electromagnetic forces],” explains Christophe Trophime, in a thesis on this subject.
And the researcher adds: “The advantages of such a propulsion system lie in this concept which makes it possible to eliminate all moving mechanical parts [propeller, mechanical shaft, etc.] and the disadvantages attached to them [cavitation, noise, tightness, etc.]”.
During the Cold War, work on MHD propulsion for ships was carried out in the United States and the Soviet Union. American researchers Stewart Way, Warren A. Rice and O.M. Phillips demonstrated its feasibility, with tests carried out with a scale model of a submersible [3 meters long and weighing 400 kg] in California. However, their research did not go any further, for lack of being able to manufacture coils capable of producing magnetic fields sufficient to reach scale 1. However, the Soviets continued their efforts in this direction, which also gave the writer Tom Clancy the plot of his novel “The Hunt for Red October”.
However, progress made in superconductivity has since changed the situation, with the production now possible of superconducting electromagnets capable of producing magnetic fields of several Teslas.
Thus, at the beginning of 1992, thanks to research carried out by the Merchant Marine University of Kobe [Japan] and with the assistance of Mitsubishi Heavy Industries, Toshiba and Kobe Steel, the Japanese company "Ship & Ocean Foundation" developed the Yamato 1, the demonstrator of an electromagnetic propulsion ship. With a displacement of 280 tonnes for a length of 30 meters, it could sail at a speed of 8 knots, thanks to an MHD accelerator.
This revived the US Navy's interest in this mode of propulsion, particularly for submarines. But, once again, the technology was not yet ripe to consider going further, with the coils needed to produce a sufficient magnetic field still being too heavy for such ships.
However, last June, DARPA, the Pentagon agency dedicated to innovation, relaunched work in this area with the PUMP [Principles of Undersea Magnetohydrodynamic Pumps] project, the properties of mixed oxides of barium, copper and of rare earth [REBCO] having opened new perspectives.
But France is not left out. Indeed, in the 1990s, and like the US Navy, the French Navy was interested in MHD propulsion, the Geophysical and Industrial Flows Laboratory [LEGI, of the National Polytechnic Institute of Grenoble] having been responsible for conducting technological monitoring in this area.
Questioned on this subject by MP [RN] Nathalie Da Conceicao Carvalho,
the Ministry of the Armed Forces recently expressed its keen interest in MHD propulsion.
“The evolution of performance in the field of superconductivity over the last ten years makes it possible to envisage the manufacture of large magnets developing a significant magnetic field [up to 20 teslas]. Equipped with such magnets, naval magnetic propulsion, the theory of which has been studied since the 1960s, is entering the phase of feasibility studies with many potential advantages compared to conventional propulsion,” the ministry first recalled in its response to the parliamentarian.
Also, the Directorate General of Armaments [DGA] is very interested in this, with the launch, in 2018, of “digital” studies carried out in partnership with “specialized laboratories”, which, if not not named, could be the LEGI, the Grenoble Electrotechnical Laboratory [LEG], for the study of superconducting coils, the Center for Research in Mineral Electrochemistry and Process Engineering [CREMGP] and the Laboratory of MAGnétoDYnamique des Liquids and Applications to Metallurgy, which are at the forefront in this field.
Still, according to the Ministry of the Armed Forces, these studies have “confirmed very encouraging overall performances”, to the point that a “roadmap dedicated to magnetic propulsion for a naval application was established in 2022, specifying the financing needs” and that a “first market was launched” in 2023 with the objective of carrying out laboratory experiments.
There is talk of launching other markets in 2024, in order to assess the “feasibility of integrating a high-performance magnet into a demonstrator” and then carrying out “detailed design and development studies of reduced-scale demonstrators ".
“If the application primarily concerns the propulsion of a nuclear submarine, the investments made as part of this project will have repercussions in several civil fields such as the field of fusion or even medical imaging [MRI] », concluded the ministry./
g**gltrad
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