What is an Underwater Propulsion Vehicle
In order to increase the range underwater of scuba and rebreather divers, they use an item of diving equipment called underwater propulsion vehicle, also known as underwater scooter or diver propulsion vehicle or DPV.
Range is described under three conditions, and these are the limited amount of breathing gas that can be carried, the rate at which the breathing gas is used under efforts while diving, and the limited time imposed by dive tables to prevent decompression sickness among divers.
A DPV has some basic components which are a pressure-resistant watertight casing containing an electric motor that is battery-powered, and this drives a component which is the propeller. Some factors are considered in the design of this vehicle, and these are that it cannot harm the diver, diving equipment, marine life, and that it cannot run away from the diver or accidentally started, and the vehicle is to remain neutrally buoyant while being used underwater.
The usual uses of underwater propulsion vehicle are for cave diving and technical diving, where deep diving needs the help to move big equipment and making divers use better of the limited underwater time based on the decompression requirements. There are also DPV accessories that can be attached onto the DPV accessory board and these can make the DPV more useful. Compasses, cameras, lobster sticks, and also spear guns are some of the accessories that can be mounted on to the DPV.
DPV also serves for military applications that include delivery of combat divers and their equipment over distances or at speeds that can be considered as not practicable.
There is more to simply swimming when you operate a DPV, and it requires depth control, being able to adjust buoyancy, being able to monitor the breathing gas, and navigation of the unit.
There are various kinds of DPV, and the most common type tows the diver who holds onto the handles on the bow or stern. The diver of this tow-behind scooter is placed parallel to and above the propeller wash and this makes the vehicle most efficient.
The next kind of DPV is termed manned torpedoes, shaped like a fish, where the one or more divers can sit typically astride on it or in hollows inside.
The next kind of DPV is called a subskimmer which is described as a rigid-hulled inflatable boat, powered by a petrol engine when on the surface, and when being submerged, the petrol engine is sealed and the vehicle runs on battery-electric thrusters being attached on a steerable cross arm.
By now, you would have realized that as DPVs get larger, they gradually become submarines. There is a wet sub, which is a small submarine, where the seat of the pilot is flooded and thus the diver is to wear a diving gear.