Feasibility study: underwater -500 meters exploration



I am looking for some tips.
I need something to start from with my project: the objective is to explore a cave 500 meters below water surface.
I know it’s a very difficult project; it’s currently just in the phase of feasibility study.
The biggest problem is the low budget. The second big problem is that I don’t yet know HOW MUCH low it is…

What I am trying to figure out is:

  • how much does it cost a 30-40 cm glass/plexiglass spehere capable of tolerating 50 kg/cm2? Where to buy it?
  • how much does it cost a small electric motor capable of pulling a 5-10 kg object underwater at -500m? where to buy it?


A sphere may be problematic with sealing and machining. I would suggest you go with a solid cylinder and mill out separate openings just large enough for your electronics package, lighting and camera. Same thing for your power source. For this depth, you might want to consider building it with a limited life expectancy, rather than a multi use long life unit. What I have in mind are things like sealing your openings with semi permanent Aquaseal or silicone sealant, rather than a quick access gasket or o-ring system.


a cylinder? Can the flat faces tolerate 40 kg/cm2? Or should the cylinder be 2cm in diameter?


end cap sketch.pdf (164.4 KB)
If the upload works, you will see a sketch of the design.The end caps are milled down from a single piece to provide strength. There are 2 o rings on each end cap. One is milled into the interior of the cylinder and the matching OD of the smaller diameter of the end cap. The second o ring is to allow for the compression when you tighten the clamps that pull the end into the cylinder. This o ring also sits in a channel milled into both the cylinder and the end cap.