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Releasable buoys for submarines – X-Sub

The surface of the sea forms an impassible barrier for electromagnetic waves. They do not penetrate below the surface. To communicate above the surface, a diving submarine has no other choice than to accept committing an indiscretion: It must rise to periscope level or above the surface for extending its transmission and reception antennas.

To enable submarines operating below the surface, and therefore discreetly, to at least know their GPS position, BMTI has developed a novel concept of proprietary products based on the following principle:

Using a standard air-lock, the submarine releases small buoys that rise to the surface and enable the vessel to communicate. They are connected to the submarine by a thin cable capable of transferring data until its reels are completely unwound. Communications stop once the cable is broken. Then the buoys sink, leaving no trace of their passage.

Several types of buoy have been developed for meeting information exchange requirements:

  • GPS positioning, which enables a submarine to reset its position and transmit and recover ephemeris;
  • information on the position and characteristics of surface vessels navigating in the vicinity of the submarine: The submarine can use an AIS buoy for obtaining AIS mapping of surface vessels in real time, replying to a permanent nautical safety requirement, especially during delicate sighting phases before surfacing;
  • establishing UHF communication: The submarine can operate a phone link and communicate for several minutes with a surface vessel, or an aircraft, or with land via a satellite.

In this way, BMTI can reply to the requirements of all navies, be they French or foreign, as, except in a few cases, submarines are all equipped with this type of air-lock.

Other releasable buoys offering new functions are under study at present to meet permanent evolution in submarine mission profiles.