Diver Propulsion Vehicle
Encyclopedia
A diver propulsion vehicle (DPV, also known as an underwater propulsion vehicle or underwater scooter) is an item of diving equipment
Diving equipment
Diving equipment is equipment used by underwater divers for the purpose of facilitating diving activities. This may be equipment primarily intended for this purpose, or equipment intended for other puprposes which is found to be suitable for diving use....
used by scuba
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....
and rebreather
Rebreather
A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where...
divers to increase range underwater. Range is restricted by the amount of breathing gas
Breathing gas
Breathing gas is a mixture of gaseous chemical elements and compounds used for respiration.Air is the most common and only natural breathing gas...
that can be carried, the rate at which that breathing gas is consumed under exertion, and the time limits imposed by the dive tables to avoid decompression sickness
Decompression sickness
Decompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
. DPV's can have military application; an example is the Diver Propulsion Device (DPD) from STIDD Systems in the US.
A DPV usually consists of a battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
-powered electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
, which drives a propeller
Propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
. The design must ensure that: the propeller is caged so that it cannot harm the diver, diving equipment
Diving equipment
Diving equipment is equipment used by underwater divers for the purpose of facilitating diving activities. This may be equipment primarily intended for this purpose, or equipment intended for other puprposes which is found to be suitable for diving use....
or marine life; the vehicle cannot be accidentally started or run away from the diver; and it remains neutrally buoyant
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
under all conditions.
DPVs are useful for long journeys at constant depth where navigation is easy. Typical uses include cave diving
Cave diving
Cave diving is a type of technical diving in which specialized equipment is used to enable the exploration of caves which are at least partially filled with water. In the United Kingdom it is an extension of the more common sport of caving, and in the United States an extension of the more common...
and technical diving
Technical diving
Technical diving is a form of scuba diving that exceeds the scope of recreational diving...
where the vehicles help move bulky equipment and make better use of the limited underwater time imposed by the decompression requirements of deep diving
Deep diving
The meaning of the term deep diving is a form of technical diving. It is defined by the level of the diver's diver training, diving equipment, breathing gas, and surface support:...
.
For many recreational divers
Recreational diving
Recreational diving or sport diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment. In some diving circles, the term "recreational diving" is used in contradistinction to "technical diving", a more demanding aspect of the sport which requires greater levels...
DPVs are not useful. Buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
control is vital for diver safety: The DPV has the potential to make buoyancy control difficult and cause barotrauma
Barotrauma
Barotrauma is physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding fluid...
if the diver ascends or descends under power. Visibility of less than 5 metres makes navigating a DPV difficult. Also, many forms of smaller marine life are very well camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
d or hide well and are only seen by divers who move very slowly and are very vigilant.
Types
Manta-boards
This is an unpowered piece of board (usually square) with two long ropes attached. It is towed by a surface boat. A diver holds onto it and keeps it submerged by holding it at the correct angle like an upside-down aerofoil. It is named after the manta rayManta ray
The manta ray is the largest species of the rays. The largest known specimen was more than across, with a weight of about . It ranges throughout waters of the world, typically around coral reefs...
fish.
Diver-tugs, tow-behind, scooters
The most common sort of DPV is where a diver is towed behind it holding onto one of its two handles on its stern or bow. These types of scooters are efficient because the divers ride in the slipstream of the scooter as opposed to a "ride-on-top" which must be ridden and increases drag, which affects scooter battery burn time. Even more efficient are the tow-behind scooters where the diver wears a harness and backplate or BC with a front crotch-strap D-ring and the scooter is clipped by a bolt snap and tow leash with proper length. This way the diver rides above the slipstream of the scooter while remaining horizontal, thereby minimizing the energy used to move water (bollard pull).Manned torpedoes and similar
These are roughly torpedo-shaped or fish-shaped vehicles that one or more divers (often two) ride. Sometimes they sit astride it. Sometimes it has hollows in its top and the divers sit inside them. One well-known type is the manned torpedo or "chariot" which commando frogmen used in World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. Similar vehicles have been made for work divers or sport divers; as these do not have a warhead, their bow tends to be pointed for better streamlining. One example is the Dolphin which was made on the Isle of Wight (UK) in the 1970s.
Subskimmers
A subskimmer is a sort of Rigid-hulled inflatable boatRigid-hulled inflatable boat
A rigid-hulled inflatable boat, or rigid-inflatable boat is a light-weight but high-performance and high-capacity boat constructed with a solid, shaped hull and flexible tubes at the gunwale. The design is stable and seaworthy...
(RIB). It is equipped to inflate and deflate itself. When submerged it seals its motor and runs with battery-electric thrusters. Thus it transforms between a fast, light, surface boat and a submerged diver-rider. There are these makes:
- SubskimmerSubskimmerThe Subskimmer is a Diver Propulsion Vehicle which is a form of RIB with an outboard petrol engine. It is equipped to inflate and deflate itself as it runs. When submerged it seals its motor and runs with battery-electric thrusters, which are on a rotatable cross-arm, and is deflated...
. This project was started in the 1970s by Submarine ProductsSubmarine ProductsSubmarine Products Ltd were a diving gear manufacturer with a factory in Hexham in Northumberland in England. It was founded in 1959 by Lt.Cdr.Hugh Oswell....
Ltd. of HexhamHexhamHexham is a market town and civil parish in Northumberland, England, located south of the River Tyne, and was the administrative centre for the Tynedale district from 1974 to 2009. The three major towns in Tynedale were Hexham, Prudhoe and Haltwhistle, although in terms of population, Prudhoe was...
in NorthumberlandNorthumberlandNorthumberland is the northernmost ceremonial county and a unitary district in North East England. For Eurostat purposes Northumberland is a NUTS 3 region and is one of three boroughs or unitary districts that comprise the "Northumberland and Tyne and Wear" NUTS 2 region...
, England and passed through various hands. Its thrusters are on a rotatable cross-arm. "Subskimmer" is a tradename owned by Alphachamp. - Infernus. Infernus is smaller than Subskimmer. They use the word "subskimmer" as a genericGenericized trademarkA genericized trademark is a trademark or brand name that has become the colloquial or generic description for, or synonymous with, a general class of product or service, rather than as an indicator of source or affiliation as intended by the trademark's holder...
term.
Torpedo-shaped with handles near its front end
Some Farallon and Aquazepp scooters have this arrangement and have a raised arm at the rear to support the diver's crotch against the water current.Miscellaneous
- The first commercially available DPV was the Aquazepp built by Josef Rupprecht in Munich. Aquazepps remain popular with cave and technical divers who appreciate the robust build quality and flexibility in customisation of the machines.
- There are DPVs where the diver is held on in some other way. One example is the Protei-5 Russian diver-riderProtei-5 Russian diver-riderThe Protei-5 is a small Russian one-man diver propulsion vehicle often used by Russian commando frogmen. It is battery electric powered, using six non-sealed lead–acid batteries. It clips on under the diver with a clip over each shoulder and one up between his legs. Its casing is aluminium...
where the diver is clamped on top of it; there is a similar Russian DPV called ProtonProtei-5 Russian diver-riderThe Protei-5 is a small Russian one-man diver propulsion vehicle often used by Russian commando frogmen. It is battery electric powered, using six non-sealed lead–acid batteries. It clips on under the diver with a clip over each shoulder and one up between his legs. Its casing is aluminium...
. - There is a DPV called ProteusProteus (disambiguation)-In mythology:* Proteus, a Greek god who is the son of Poseidon* Proteus of Egypt, an Egyptian king in a version of the story of Helen of Troy* King Proteus, a mythical Greek ruler, featured in the story of Bellerophon-Scientific publications:...
made in New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
that is strapped onto the diver's cylinder.
Wet subs
As DPVs get bigger, they gradually merge into submarineSubmarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
s. A wet sub
Wet sub
A wet sub is a type of underwater vehicle that does not provide a dry environment for its occupants. Usually, wet suited scuba divers will ride upon the device , although it can be designed to fully enclose its occupant to provide lower drag...
can be classed as a small submarine where the pilot's seat is naturally flooded and they must wear diving gear. Covert military operations use swimmer delivery vehicles (SDVs) to deliver and retrieve operators into harbors and near-shore undetected. An example is the Multi-Role Combatant Craft (MRCC) produced by STIDD Systems in the US.