A conventional submarine can be thought of as the inverse of an airship, in that it controls its depth rather than its height by adjusting its buoyancy. But much like their topside counterparts, these dirigibles of the deep are relatively big, slow, and clumsy. By contrast, a submersible vehicle designed like a helicopter, but that pushes water upward instead of air downward could potentially provide superior maneuverability underwater, in a much smaller and technically simpler form factor.

The aquacopter could be weighted at the surface to be slightly positively buoyant, then derive its (negative) lift from a rotor. The rotor could be powered by a small engine, or even solely by human power. Of course, without some sort of buoyancy compensation, maximum depth would be limited, but as long as the craft is designed to remain positively buoyant at all times, it would fail relatively safely in the event the engine (or the engine's legs) gave out underwater.
-- ytk, Apr 29 2011

an "aircopter" with its rotors on bottom http://www.aviastar...er_helicovector.php
[pocmloc, May 08 2011]

Small submersibles have near-neutral bouyancy, and very small ballast tanks which are not cumbersome. Whether any such craft has ever sunk to its doom due to failure of its ballasting system, I do not know.

Also, the rotors would need constant power, and would be vulnerable to damage or entanglishment.

[-], sorry.
-- MaxwellBuchanan, Apr 29 2011


When I was little and experimented with model submarines, there were two systems used. The expensive and complex way was to fit the model with ballast tanks etc. to trim its bouyancy. The cheap way was to make the model float low in the water, and then angle the vanes so that its forward movement made it submerge. More like an aero-plane than a helico-pter, though.
-- pocmloc, Apr 29 2011


If you've only got a bit of positive buoyancy to work out then all you need is a rock with a rope on it. But [+] for thinking.
-- FlyingToaster, Apr 29 2011


I think this idea is great. Submarines are unbelievably expensive. I think this takes part of the reason for the expense away.

Engine failure is not fatal.
-- Zimmy, May 08 2011


I assume the rotor would be on the bottom, pulling the sub down, not on the top, pushing it down. I've never seen an "aircopter" with its rotors on bottom.
-- sqeaketh the wheel, May 08 2011


//Engine failure is not fatal.//

If you were deep enough and your engines failed, wouldn't the sudden change in pressure be dangerous?
-- nomocrow, May 08 2011


If it holds an internal pressure of 1atm, I don't see why a rapid ascent would cause any problems. But it still doesn't make sense.
-- MaxwellBuchanan, May 08 2011


That's what they said about all of the great inventions.

With the exception of the coin stamping machine, of course.
-- ytk, May 08 2011


Doesn't make sense due to the astounding inefficiency?

We would be so happy, me and you. No one there to tell us what to do...

Squeketh, the Harrier.
-- Zimmy, May 11 2011


// in that it controls its depth rather than its height by adjusting its buoyancy//
It was looking quite good up to that point.
You realise this is baked by small ROVs?
-- AbsintheWithoutLeave, May 11 2011



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