# Feasibility of external convertible surface to submersible nacelle

First of all, I am studying to major in mechanical engineering, taking some electrical classes on the side so the math and CAD aspects I haven’t tried this concept on.

I’ve been playing around with a pressure-sealed nacelle that can fold over a system, providing better hydrodynamics. It would be mechanically sealed like an outer submarine hatch, held closed by water pressure when underwater. It would allow quick deployment of said system, as it would be a convertible pressure hull.

From the perspective of a more experienced naval engineer, would such a system be feasible? What aspects would make it impractical?

Weird but interesting and begs the question, why? This brings to mind the image of an underwater “Pac Man” swallowing an oddly shaped machine.

If better hydrodynamics is the goal then why not just start with a lower drag “system” form to begin with? Where does the folding nacelle live when not in use? Doesn’t that by itself add drag in addition to functional complexity, weight, volume, and entrained mass?

Why pressure proof? If the “system” is designed to operate underwater isn’t it already wet and designed to withstand the ambient pressure where it works? Unless there is some compelling reason to protect the contents of the “system” from increased pressure, the use of simple and inexpensive pressure compensated or dry spherical housings enclosed by a lightweight fairing seems like the more practical solution.

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“Convertible”?
As ‘convertible cars’, with a folding top (or a removable hard top)?

When diving deeper than a few feet, there will rapidly act tremendous compression forces on the system.
The greater the vehicle’s volume part at surface pressure, the more difficult it will be to handle these forces.
It is much doubtful, whether any convertible system could handle this.

Yes, a hard top at the same appropriate thickness as the rest of the pressure hull, shaped to blend into the rest of said hull to distribute the pressure evenly. It would also have mechanical seals in place, designed so that water pressure holds it down as depth increases.

The associated technologies are submersible seaplanes of variable purpose, submersible ambush gunboats. Hydrodynamics is one goal, though there’s also the issue of large surface based weapons integrated into pressure vessels (Surcouf for example).

The nacelle would fold behind the system when surface, and for some designs would function as a windshield for the submarine sail. For a submersible seaplane, you can have a high visibility cockpit enclosed by the nacelle before submerging, that would fold above and behind the cockpit.

As for why it would be pressure proofed, it’s more to allow the system to be prepared in advanced of surfacing for ambush tactics while simultaneously allowing rapid deployment. With dry spherical housings, the entire system would have to fit through the door of said housing, taking up internal volume.