It is difficult for submarines and planes to communicate with each other when they are each in their own environment. Above water, radio waves are used for communication, but they are drowned out by liquid, in which sonars and other acoustic systems are much more effective. Massachusetts Institute of Technology has come up with an interface that brings these two different types of communication together.
The system is based on a conventional underwater acoustic emitter, operating at different frequencies to encode logical data. For example, a 1000 Hz wave means "0" and a 200 Hz wave means "1". Such a system can be multiplexed to increase the data transfer rate. When a wave reaches the surface of the water, ripples are created on it, which is fundamentally different from the natural waves of the sea - the fluctuations of the environment are fast and there are a lot of them per unit time. All that remains is to point the radar from the aircraft to this area of water, read the reflected signal and decode it.
The airborne radar operates at frequencies of 30-300 GHz, it is operated by a powerful computer that analyzes each reflected radio beam for power and distance traveled, filters out interference and can direct the radar to keep a given area of water in the sight. The prototype unit passed 500 tests in the pool, including jamming by swimmers, for the most part successfully. We managed to transmit and receive whole phrases, down to the letter.
Scientists have great doubts that this technology will be as effective in a real, rough and salty sea. But even if there is no, and instead of clear, high-speed communication, we will receive only the equivalent of a flashing beacon, then it will be possible to teach the black boxes of aircraft to signal themselves directly from the depths, without waiting for rescuers with underwater equipment to approach the crash site.