MrConclusion
Contributor
OK, so the problem with ultra-light and/or ultra-high-pressure tanks is weight shift and buoyancy. Well then...
How about a very light, high pressure tank, designed to be neutral when filled. (Something designed for 4500 to 7500 psi, for example.) The trick would be that the "bottom" of the tank is designed as a piston. The tank body becomes variable volume if you can drive the piston up or down.
As the diver uses air, the tank pressure isn't allowed to drop. Rather, the piston rises, reducing tank volume and maintaining pressure. If you allow water to enter the area below the piston, the weight shift would be minimal as air is consumed. The position of the piston would indicate how much air is left, father than using an SPG.
In fact, the tank itself could be used as a BCD by either compressing or relaxing the piston.
How about a very light, high pressure tank, designed to be neutral when filled. (Something designed for 4500 to 7500 psi, for example.) The trick would be that the "bottom" of the tank is designed as a piston. The tank body becomes variable volume if you can drive the piston up or down.
As the diver uses air, the tank pressure isn't allowed to drop. Rather, the piston rises, reducing tank volume and maintaining pressure. If you allow water to enter the area below the piston, the weight shift would be minimal as air is consumed. The position of the piston would indicate how much air is left, father than using an SPG.
In fact, the tank itself could be used as a BCD by either compressing or relaxing the piston.