>"The best efficiency demonstrated in a magnetohydrodynamic drive to date was 1992 on the Yamato-1, a 30-m (100-ft) vessel that achieved 6.6 knots with an effic

>"The best efficiency demonstrated in a magnetohydrodynamic drive to date was 1992 on the Yamato-1, a 30-m (100-ft) vessel that achieved 6.6 knots with an efficiency of around 30% using a magnetic field strength of approximately 4 Tesla," said Susan Swithenbank, PUMP program manager in DARPA’s Defense Sciences Office. “In the last couple years, the commercial fusion industry has made advances in Rare-Earth Barium Copper Oxide (REBCO) magnets that have demonstrated large-scale magnetic fields as high as 20 Tesla that could potentially yield 90% efficiency in a magnetohydrodynamic drive, which is worth pursuing. Now that the glass ceiling in high magnetic field generation has been broken, PUMP aims to achieve a breakthrough to solve the electrode materials challenge." 90% efficiency now vs 30% then. How do they prevent magnetic detection of the submarine? Magnetometers are used to search for submarines. 20 Tesla field is next level.