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After watching a TV show I saw that bubbles originating from underwater can lower the impact damage when something hit it at velocity.

I was wondering if another implementation of this would work.

When deep underwater the pressure on a vessel is massive, apparently the pressure goes increases 14.5 psi every 10 meters. Could surrounding a vessel with small bubbles lower this pressure?

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  • $\begingroup$ Air bubbles around a submerged vessel would in fact lower the pressure on the vessel, and it would also lower the buoyant force on the vessel. This means that the vessel would immediately begin sinking lower if this technique was attempted. At some point, the bubbles would have to be discontinued, but the vessel could well be at a much lower depth by then. Much lower depth means much higher pressure. Practical issues prevent this method from being attempted. $\endgroup$ – David White May 8 '18 at 1:30
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Air bubbles lower impact damage by breaking the surface of water and lowering density of water right near the surface. However small air bubbles at depth would have almost the same pressure as the surrounding liquid. So small bubbles would not lower considerably the pressure felt by a vessel unless there are so much of them as to considerably lower the density of the fluid all the way up to the surface, but this would rapidly exhaust the air reserves abroad the vessel.

There is a phenomenon, supercavitation, when a large bubble/cavity (filled with water vapor) encompass most of a rapidly moving through liquid body, considerably lowering friction drag. Parts of the body inside the bubble would feel only vapor pressure which would be considerably lower than the hydrostatic pressure of the surrounding fluid. However, for the formation of such cavity parts of the body would be exposed to a dynamical fluid pressures even higher than hydrostatic pressure at a given depth.

Current applications of supercavitation are projectiles, some propellers and supercavitating torpedoes, all operating at relatively small depths but potentially it is possible to apply the technology for deep underwater.

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NO the pressure inside most be equal to the pressure outside..... i want to mean that if you look at the bubbles coming out of the water it volume increases because of decrease in the water pressure so the pressure inside the bubble most be equal to outside...

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  • $\begingroup$ So airating the water around a vessel wouldn't ease tension on the vessel? $\endgroup$ – Curtis Hennessy May 7 '18 at 16:57
  • $\begingroup$ It's the total weight of the water (and) air above it, so you'd have to aerate the entire ocean. Note that this does happen in white water--where people who usually float find themselves sinking. $\endgroup$ – JEB May 7 '18 at 17:12
  • $\begingroup$ Air is compressible but their should be massive effect of air pressure in vehicle because the air inside the bubble is balancing the water pressure $\endgroup$ – Sobit Khatri May 7 '18 at 17:16

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