Context: https://www.bbc.com/news/world-us-canada-65953872
The above titanic submersible that went missing can only send short text messages from the ship to the submersible. From my understanding there is no GPS underwater and radio communication is impossible. How can Navy submarines communicate and navigate while submerged in the ocean but the missing submersible can’t?
In: 121
Water is a really, really effective EM shield so most radio signals can’t penetrate very far at all. Higher frequencies are most affected so submarines often use [Extremely Low Frequency radio](https://en.wikipedia.org/wiki/Extremely_low_frequency) (ELF) for communications.
The catch is that this requires very long antennas to transmit so the submarines can only receive the message – they have to use other means to transmit a signal.
[VLF](https://en.wikipedia.org/wiki/Communication_with_submarines) can penetrate a few 10s of meters so a submarine can receive and transmit with an antenna on a buoy (float) without needing to surface.
The other thing that works well is sound – just like sonar uses sound to locate objects underwater because radar can’t penetrate, you can use sound to communicate directly.
I can’t find anything that says what this sub uses for comms but I’d guess [acoustic](https://en.wikipedia.org/wiki/Underwater_acoustic_communication#Applications)
Latest Answers