Some Basic Information about Underwater Propulsion Vehicles
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.
The meaning of range can be explained in three situations, and these are the restricted quantity of breathing gas that can be carried, the rate of breathing gas consumed under exertion, and the time limits stated by the dive tables in order to avoid decompression sickness of 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. The design is made in such a way that the diver is not harmed by the propeller, the diving equipment, or the marine life, and that the vehicle cannot be accidentally turned on or run away from the diver, and it has to remain neutrally buoyant while use in 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. DPV accessories, if mounted on the accessory board of the DPV can make the vehicle more useful underwater. 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.
The operation of DPV requires more than situational awareness than mere simple swimming since its operation requires simultaneous depth control, buoyancy adjustment, monitoring of breathing gas and navigation.
There are several types of DPV, and the most common type is that which tows the diver while holding onto the handles on the stern or bow. This so called tow-behind scooters are most efficient with the diver placed parallel to and above the propeller wash.
Another type of DPV is called manned torpedoes which are fish-shaped vehicles where one or more divers can sit astride 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.
As DPVs get bigger, they now turn into the big vehicle called the submarines. There are also small submarines called wet subs, where the pilot’s seat is flooded that then requires the diver to wear diving gear.