Context: 

Recently, a small submersible vessel named Titan, carrying five people nearly 4,000 metres down the Atlantic Ocean to view the 1912 wreckage of the Titanic, lost contact with those at the surface and was found in pieces on the ocean floor  due to catastrophic implosion of its pressure chamber.

More in the news

• The trip was organised by the company OceanGate Inc, which mentions private “crewed submersible exploration” as part of its offerings.
• The Titan, one of three types of crewed submersibles operated by OceanGate, is equipped with a platform similar to the dry dock of a ship that launches and recovers the vessel

About Submersible:

• A submersible is typically a small, uncrewed vessel used for exploration or research, while a submarine is larger and manned, designed for military operations.
• Submersibles are underwater robots that are deployed from the ship to the sea, where they record and collect information from the ocean’s water column and seafloor for scientific analysis. 

Types of Submersibles:

• Remotely Operated Vehicles (ROVs): ROVs are tethered underwater robots used for research, exploration, and imagery collection. 
  • ROVs are tethered to the ship, allowing control signals to be sent and received directly between topside operators and the subsea vehicle. 
• Human-Occupied Vehicles (HOVs): HOVs transport a small team of scientists and pilots directly to the seafloor for a limited amount of time. 
  • Similar to the other submersibles, HOVs are equipped with tools such as lights, cameras, sensors, manipulator arms, and collection instruments. 
• Autonomous Underwater Vehicles (AUVs): AUVs are independent underwater robots used to explore the ocean. 
  • Unlike ROVs, AUVs are untethered from ship, allowing them to complete pre planned missions without direct control from an operator. 
  • Once deployed, AUVs operate on their own, guided by a pre-planned route.

Difference between Submarines and Submersibles:

• Size: Relative to submarines, submersibles are very small and simply constructed, and are only equipped for short-term dives. 
• Power: A submarine can leave port and come back under its own power. A submersible has very limited power reserves and cannot launch itself into the ocean, or come back, on its own. It needs a mother ship that can launch it and recover it. 
• Oxygen supply: Submersibles need oxygen supply in tanks. Most submarines, by contrast, can generate their own oxygen, and might stay submerged for a few months at a time. 

News Source: Indian Express