Naval Defense Through The Utilization Of Natural Buoyancy
The principle behind this system is simple: an airtight container, when forcibly submerged, will return to the surface once it has been freed from restraint. Releasing a submerged object will function much in the same way as releasing a bow-string: the stored mechanical energy of the submersion will be imparted to the projectile.
Through calculation and experimentation, a streamlined object can be devised which will function as a self-propelled torpedo. Streamlining will minimize water resistance and allow travel at high velocity, causing considerable damage upon impact with a surface target.
As a projectile is submerged, the pressure of the water will compress the air inside. This can prove advantageous. Air from a previously submerged tank or diver's bell can be easily added to the projectile to increase buoyancy.
As the projectile rises and outside water pressure is reduced, the expanding air can be directed through a nozzle at the base. This simple propellant should allow a projectile to travel for a considerable distance after breaching the water.
Potential Missile Payload
A blown glass or thin cast-metal chamber can be devised, containing a quantity of appropriate alkaline metal (Sodium, Cesium or the local hydrofulminating equivalent). This module can either be shattered against the hull of a target, or ruptured by the change in pressure as the projectile rises. Exposing the reactive contents to water will have obvious consequences for nearby targets.
For the sake of secrecy and safety, initial experimentation should take place under "haut atemptarie ad domum" conditions. Test projectiles can be submerged either with simple weights or with a sunken pulley and winch system. Any full deployment of the system should take advantage of TRUMP as a method of bringing projectiles and containers of stored air directly from the surface.