What is a ship? What is a boat? Can't tell the difference? How much do you know about ship classification?

In the big family of warships, there are many members, such as: missile boats, torpedo boats, minesweepers, landing craft, submarines, supply ships, frigates, destroyers, cruisers, battleships and aircraft carriers... But have you noticed a detail if you are careful? Some are called "ships" and some are called "boats". Is there a difference between the "ships" we usually talk about?

Indeed, we usually call ships with a displacement of more than 500 tons "ships", and those with a displacement of less than 500 tons "boats" , but the protagonist we are discussing today is a special case. Regardless of their tonnage, they are all called submarines. Next, let's talk about this small family of submarines, see how they are classified, and what roles different submarines play.

▲An aircraft carrier battle group that doesn’t like to fight alone (picture from the Internet)

If the members of the submarine family are divided only by power, there are actually two sisters. The eldest is an older and "seasoned" conventional-powered submarine , or you can simply understand it as a "non-nuclear powered submarine", which mainly uses diesel engine + electric motor hybrid propulsion, or diesel-electric combined full-electric propulsion, or diesel-electric combined + AIP (air-independent propulsion system, such as Stirling self-circulating engine, fuel cell, etc.) full-electric propulsion, and is in service in almost all navies of the world.

The other is the nuclear submarine that makes everyone "feel powerful without knowing why", which uses nuclear power - generating heat energy through nuclear fission reactions, and then using the heat energy to generate steam to drive the turbine and then drive the propeller.

Compared with conventional powered submarines, nuclear submarines have indisputable advantages in terms of endurance, combat index and maneuverability, so they have developed extremely rapidly in recent decades. However, due to reasons such as complex technology, high prices and displacement limitations, they are currently only seen in the navies of six countries, including the United States, Russia, Britain, France, China and India (leased from Russia).

Given that nuclear submarines and conventional submarines each have their own strengths, there is really no need or possibility for nuclear submarines to completely replace conventional submarines in the foreseeable future.

▲The USS Connecticut, a Seawolf-class attack submarine (picture from the Internet)

When it comes to displacement, as the name suggests, it is actually the weight of the same volume of water displaced by the volume of the submerged part of the ship. Although submarines are not divided into "submarine" and "submarine ship" based on their tonnage, the size of the family members does have differences, so they are divided into: large submarines, medium submarines, small submarines and pocket submarines.

Unlike surface ships, submarines have more displacement indexes because submarines not only have states when sailing on the surface, but also states when underwater and semi-shallow.

Usually we use the normal displacement of submarines on the water as the classification standard for submarine types: the displacement of large submarines is usually more than 2,000 tons . Most of them are nuclear submarines, but some conventional submarines are also included, such as Russia's "Kilo" class, Japan's "Soryu" class, Germany's "216" class, China's "039B" class, etc. Because they have strong self-sufficiency, endurance and weapons and equipment, they can stay away from their bases and cruise in the deep seas of the world's oceans waiting for opportunities.

▲The daunting US "Ohio" class strategic nuclear submarine (picture from the Internet)

The displacement of medium-sized submarines is between 600 and 2,000 tons . Although their performance is inferior to that of large submarines, they are relatively cheap and have a short construction period, so they are deeply favored by developing countries. They can also perform missions in mid-sea and even far seas.

Small submarines are much smaller in size, with a displacement between 70 and 600 tons . Being smaller in size, their capabilities are naturally much weaker, but fortunately they are small in size, flexible and maneuverable, have low self-noise, are inexpensive and easy to mass produce. They are a good place to show their prowess in shallow offshore waters or narrow seas and rivers.

▲The French SMX-22 offshore submarine with a displacement of only 480 tons (picture from the Internet)

Submarines with a displacement of less than 70 tons are collectively called miniature submarines, which are mainly used to attack enemy bases, conduct reconnaissance and sabotage activities, and undertake rescue missions for crashed submarines.

▲British pocket submarine during World War II (picture from the Internet)

The tasks performed by submarines are very wide, so there are also classifications of submarine types according to their missions, such as: strategic submarines, tactical submarines and special submarines.

Simply put, strategic submarines mainly perform strategic missions and usually carry nuclear missiles, so they are also called ballistic missile nuclear submarines. Their huge explosive power is enough to destroy the enemy's fixed military, political, industrial, transportation centers and other strategic targets, so as to fundamentally destroy the enemy's ability to launch and maintain war.

▲Russian Typhoon-class strategic nuclear submarines with enough bombs to destroy a country (picture from the Internet)

Tactical submarines mainly perform specific combat missions, so they are also called attack submarines (including attack nuclear submarines). The weapons commonly used are torpedoes and cruise missiles.

▲The USS Hampton (SSN-767), a Los Angeles-class attack submarine (picture from the Internet)

Special submarines are, of course, used to carry out special operations. For example, there are "radar submarines" equipped with high-power radars to interfere with the enemy's radio communications and radar work, while guiding their own aircraft and providing them with return signs; "mine-laying submarines" that are specifically responsible for underwater minelaying; "transport submarines" responsible for transporting fuel, weapons and ammunition and landing special forces; and "training submarines" used for submarine crew training...

▲A mine-laying submarine specially used for mine-laying during World War II (picture from the Internet)

In addition, submarines are classified according to the weapons and equipment they carry (torpedo submarines and missile submarines), or according to the structure of the hull (single-hull submarines, semi-hull submarines, double-hull submarines, and single- and double-hull hybrid submarines).

With the diversification of submarine missions and the continuous advancement of science and technology, I believe that the submarine family will continue to expand. Let us wait and see!