Submersible

Retired modern submersible Star III of Scripps Institution of Oceanography

A submersible is an underwater craft which needs to be transported and supported by a surface vessel or platform. This distinguishes submersibles from submarines, which are self-supporting and capable of independent operation.

There are many types of submersibles, including both human-occupied vehicles (HOVs) and uncrewed craft, variously known as remotely operated vehicles (ROVs) or unmanned underwater vehicles (UUVs). Submersibles have many uses including oceanography, underwater archaeology, ocean exploration, adventure, equipment maintenance and recovery, and underwater videography.

History

See also: Submarine § History

The first recorded self-propelled underwater vessel was a small oar-powered submarine conceived by William Bourne (c. 1535–1582) and designed and built by Dutch inventor Cornelis Drebbel in 1620, with two more improved versions built in the following four years. Contemporary accounts state that the final model was demonstrated to King James I in person, who may even have been taken aboard for a test dive. There do not appear to have been any further recorded submersibles until Bushnell's Turtle.

The first submersible to be used in war was designed and built by American inventor David Bushnell in 1775 as a means to attach explosive charges to enemy ships during the American Revolutionary War. The device, dubbed Bushnell's Turtle, was an oval-shaped vessel of wood and brass. It had tanks that were filled with water to make it dive and then emptied with the help of a hand pump to make it return to the surface. The operator used two hand-cranked propellers to move vertically or laterally under the water. The vehicle had small glass windows on top and naturally luminescent wood affixed to its instruments so that they could be read in the dark.

Bushnell's Turtle was first set into action on September 7, 1776, at New York Harbor to attack the British flagship HMS Eagle. Sergeant Ezra Lee operated the vehicle at that time. Lee successfully brought Turtle against the underside of Eagle's hull but failed to attach the charge because of the strong water currents.

Operation

Apart from size, the main technical difference between a "submersible" and a "submarine" is that submersibles are not fully autonomous and may rely on a support facility or vessel for replenishment of power and breathing gases. Submersibles typically have shorter range, and operate primarily underwater, as most have little function at the surface. Some submersibles operate on a "tether" or "umbilical", remaining connected to a tender (a submarine, surface vessel or platform). Submersibles have been able to dive to over 10 km (33,000 ft) below the surface.

Submersibles may be relatively small, hold only a small crew, and have no living facilities.

A submersible often has very dexterous mobility, provided by propeller screws or pump-jets.

Technologies

Different basic technologies used in the design of submersibles.

Single atmosphere submersibles have a pressure hull with internal pressure maintained at surface atmospheric pressure. This requires the hull to be capable of withstanding the ambient hydrostatic pressure from the water outside that can be many times greater than the internal pressure.

Another technology called ambient pressure submersibles maintains the same pressure both inside and outside the vessel. The interior is air-filled, at a pressure to balance the external pressure, so the hull does not have to withstand a pressure difference.

A third technology is the "wet sub", which refers to a vehicle that may or may not be enclosed, but in either case, water floods the interior so underwater breathing equipment is used by the crew. This may be scuba carried by the divers, or scuba carried by the vessel.

Buoyancy control

During underwater operation a submersible will generally be neutrally buoyant, but may use positive or negative buoyancy to facilitate vertical motion. Negative buoyancy may also be useful at times to settle the vessel on the bottom, and positive buoyancy is necessary to float the vessel at the surface. Fine buoyancy adjustments may be made using one or more variable buoyancy pressure vessels as trim tanks, and gross changes of buoyancy at or near the surface may use ambient pressure ballast tanks, which are fully flooded during underwater operations. Some submersibles use high density external ballast which may be released at depth in an emergency to make the vessel sufficiently buoyant to float back to the surface even if all power is lost, or to travel faster vertically.

Deep-diving crewed submersibles

Main article: Deep-submergence vehicle

Ictineu 3 is a crewed submersible with a large semi-spheric acrylic glass viewport and is capable of reaching depths of 1,200 m (3,900 ft).

Some submersibles have been able to dive to great depths. The bathyscaphe Trieste was the first to reach the deepest part of the ocean, nearly 11 km (36,000 ft) below the surface, at the bottom of the Mariana Trench in 1960.

China, with its Jiaolong project in 2002, was the fifth country to send a person 3,500 meters below sea level, following the US, France, Russia and Japan. On June 22, 2012, the Jiaolong submersible set a deep-diving record for state-owned vessels when the three-person sub descended 6,963 meters (22,844 ft) into the Pacific Ocean.

Among the most well-known and longest-in-operation submersibles is the deep-submergence research vessel DSV Alvin, which takes 3 people to depths of up to 4,500 metres (14,800 ft). Alvin is owned by the United States Navy and operated by WHOI, and as of 2011 had made over 4,400 dives.

James Cameron made a record-setting, crewed submersible dive to the bottom of Challenger Deep, the deepest known point of the Mariana Trench on March 26, 2012. Cameron's submersible was named Deepsea Challenger and reached a depth of 10,908 metres (35,787 ft).

Commercial submersibles

Private firms such as Triton Submarines, LLC. SEAmagine Hydrospace, Sub Aviator Systems (or 'SAS'), and Netherlands-based U-boat Worx have developed small submersibles for tourism, exploration and adventure travel. A Canadian company in British Columbia called Sportsub has been building personal recreational submersibles since 1986 with open-floor designs (partially flooded cockpits).

A privately owned U.S company, OceanGate, also participated in building submersibles, though the company fell under scrutiny when their newest submersible imploded underwater with no survivors.

MROVs

Small uncrewed submersibles called "marine remotely operated vehicles" or MROVs are widely used today to work in water too deep or too dangerous for divers.

Remotely operated vehicles (ROVs) repair offshore oil platforms and attach cables to sunken ships to hoist them. Such remotely operated vehicles are attached by an umbilical cable (a thick cable providing power and communications) to a control center on a ship. Operators on the ship see video and/or sonar images sent back from the ROV and remotely control its thrusters and manipulator arm. The wreck of the Titanic was explored by such a vehicle, as well as by a crewed vessel.

See also

• Bathyscaphe – Free-diving self-propelled deep-sea submersible
• Bathysphere – Unpowered spherical deep-sea observation submersible lowered on a cable
• Benthoscope – Unpowered spherical deep-sea observation submersible lowered on a cable
• Diving bell – Chamber for transporting divers vertically through the water
• Diving chamber – Hyperbaric pressure vessel for human occupation used in diving operations
• Hawkes Ocean Technologies – American marine engineering firm
• Midget submarine – Submarine under 150 tons
• Narco-submarine – Submersible used by drug smugglers
• Personal Submersibles Organization
• CSS David – Confederate States Navy torpedo boat
• Pisces V – Deep-submergence vehicle
• Remotely operated underwater vehicle – A tethered underwater mobile device operated by a remote crew
• Semi-submersible – type of vessel which can partially submergePages displaying wikidata descriptions as a fallback
• Submersible drilling rig – Vessel floated to site and lowered onto the seabed for drilling
• Timeline of diving technology – Chronological list of notable events in the history of underwater diving equipment
• Titan submersible implosion – 2023 maritime disaster
• Underwater acoustic positioning system – System for tracking and navigation of underwater vehicles or divers using acoustic signals
• Welfreighter – British midget submarine of the Second World War

Sources

• Polmar, Norman (2008). "Bathyscaph". World Book Online Reference Center. Retrieved 26 Jan 2008.