DSV meaning in Military and Defence ?

A deep-submergence vehicle (DSV) is a deep-diving crewed submarine that is self-propelled. Several navies operate vehicles that can be accurately described as DSVs. DSVs are commonly divided into two types: research DSVs, which are used for exploration and surveying, and DSRVs (Deep Submergence Rescue Vehicle), which can be used for rescuing the crew of a sunken navy submarine, clandestine (espionage) missions (primarily installing wiretaps on undersea cables), or both. DSRVs are equipped with docking chambers to allow personnel ingress and egress via a manhole.

The real-life feasibility of any DSRV-based rescue attempt is hotly debated, because the few available docking chambers of a stricken submarine may be flooded, trapping the sailors still alive in other dry compartments. The only attempt to rescue a stricken submarine with these so far (the Russian submarine Kursk) ended in failure as the entire crew who survived the explosion had either suffocated or burned to death before the rescuers could get there. Because of these difficulties, the use of integrated crew escape capsules, detachable conning towers, or both have gained favour in military submarine design during the last two decades. DSRVs that remain in use are primarily relegated to clandestine missions and undersea military equipment maintenance. The rapid development of safe, cost-saving ROV technology has also rendered some DSVs obsolete.

Strictly speaking, bathyscaphes are not submarines because they have minimal mobility and are built like a balloon, using a habitable spherical pressure vessel hung under a liquid hydrocarbon filled float drum. In a DSV/DSRV, the passenger compartment and the ballast tank functionality is incorporated into a single structure to afford more habitable space (up to 24 people in the case of a DSRV).

Most DSV/DSRV vehicles are powered by traditional electric battery propulsion and have very limited endurance, while few (like NR-1 or AS-12/31) are/were nuclear-powered, and could sustain much longer missions. Plans have been made to equip DSVs with LOX Stirling engines but none have been realized so far due to cost and maintenance considerations. All DSVs are dependent upon a surface support ship or a mother submarine, that can piggyback or tow them (in case of the NR-1) to the scene of operations. Some DSRV vessels are air transportable in very large military cargo planes to speed up deployment in case of emergency rescue missions.