Receive an email a day with our articles:When it comes to operating a submarine there are certain fundamental factors.And having good power and going unnoticed by potential enemies are two important advantages on the list.A team of researchers from Shanghai claims to have taken a decisive step to advance this double objective.The key lies in a new propulsion system with a pump-jet (pump-jet) that allows greater thrust to be achieved in certain conditions and —what is just as important— reducing annoying and telltale vibrations by more than 90%.When moving around some Chinese submersibles they run into a problem that takes away power and stealth.As the South China Morning Post details, to propel themselves they use a covered propeller with the rotor located inside a conduit that presents certain handicaps.Between the inner face of this structure and the rotor blades themselves there is a small space, an insignificant clearance, but enough for cavitation to be generated inside, bubbles that do double harm to the progress of the submarine: they slow down its progress and reveal its presence.That is the problem that the Shanghai experts wanted to minimize.How?Basically with a new design and making use of a material that has not revealed details.The technicians wanted to tackle the undesirable effects of the pump-jet with a redesign in which the outer edge of the blades splits into the walls of the rotor duct.Result: the tips no longer remain in direct contact with the water, vibrations and noise are reduced in most frequencies and even thrust is gained at slower speeds.Experts calculate in fact that the signals that could give away the presence of the submarine are reduced by more than 90%.Those are at least the conclusions left by the simulations that have already been carried out on the ground.The application is interesting due to the implementation of pump-jet propulsion, incorporated in some important class submersibles such as the Virginia or Seawolf, both from the USA.Also because one of the great problems of the first nuclear submarines of the Asian giant was precisely the noise they generated, which made it easier for other countries to track them.The Chinese are not the first in fact to try to reduce turbulence in the rotors.The great advance of the Shanghai technicians would focus on the key element that clears up the equation: having a versatile sealing material, capable of avoiding the unwanted effects caused by water and at the same time not hindering the movement of the rotor.The details of his proposal, yes, are unknown.So far it has only transpired that they create a seal with fine fibers and that Chinese scientists have also chosen to coat the tips of the blades.Not all are advantages in the system.As the team has exposed in the Chinese Journal of Ship Research, when operating at maximum speed, jet propulsion becomes less efficient.The effect is compensated however in the opposite scenario, with lower gears.The thrust of the device is in those cases about 10% higher.A plus to which is added above all the ability to reduce unwanted vibrations by more than 90%... and noisy.Share China already knows how to make its submarines more stealthy: this system reduces vibrations by more than 90%More Sites You'll LikeSee more articlesSee more videosMore Sites You'll LikeSee more articlesSee more videos