• Question: as my profile says i love marine related stuff and wanted to ask how do submarines cope with the immense water pressure?

    Asked by billytheshark to Alex, Ali, Kerry, Philip on 19 Nov 2014.
    • Photo: Alison Thomson

      Alison Thomson answered on 19 Nov 2014:

      They have extremely strong hulls, and the inside is pressurised to combat the pressure outside. The reason they’re cylindrical shaped is so that the pressure is spread out around the whole structure, and not concentrated on one point. It’s only actually the submarines that have people inside them that need to be pressurised – the mechanical ones don’t have to be pressurised to the same extent!

    • Photo: Alex Pool

      Alex Pool answered on 19 Nov 2014:

      Great question. So they get round this by making the shape as cylindrical as possible as that’s really strong. Then they give it a really thick hull. But that only does so good and the submarines can only go so deep before the pressure is too high.

      We have robotic submarines that don’t have air on the middle and they’re able to go much deeper with cameras.

    • Photo: Philip Ratcliffe

      Philip Ratcliffe answered on 20 Nov 2014:

      Well, first of all remember that scuba divers with proper equipment can go down 200m or even 300m – they have to be very careful though to come up very slowly. The point is that if the pressure is equalised inside (for example in your lungs) then you don’t feel the pressure outside. That’s also because your cells are mainly water and water is virtually incompressible, so they don’t get deformed either.
      The same holds for a submarine: if we pressurise inside then there’s no real problem – again they have to be careful to depressurise slowly. Also, of course, the hulls are made of steel and the shape is rather cylindrical, which is almost the best shape to withstand outside pressure. The so-called bathyscapes that can go down really deep are usually more or less spherical, which is even better.

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