Ships for Commerce and Exploration
Many types of ships throughout history have been used for both naval warfare and commercial trade. Even in the modern era, part of the job of a navy is to defend a country's commercial shipping industry.
Longship
This is the signature vessel of the Vikings, used for both exploration and warfare (often at the same time, since what the Vikings liked to do when they discovered new communities was raid them.) Longships, often with a fearsome dragon at the prow, used their sails to cross the vast distances of the ocean and their oars to pick up speed, quickly closing the distance between them and their targets. The design was later modified into the knarr, which had fewer oars and focused on long-range exploration. Viking explorer Leif Ericson is known to have reached Newfoundland, Canada, five centuries before the more renowned Christopher Columbus "discovered" the New World.
Junk
The Chinese junk was a sailing ship that remained in use, with modifications, from the 2nd through the 17th centuries. It often compared favorably to its European naval contemporaries. For instance, the merchant junks of the 15th century are estimated to have been six times longer than the Portuguese caravals of the time. Scholars have even speculated that junk-sailing Chinese explorers reached the New World in 1421, which indicates that discovery of America is a crowded field.
Carrack
The carrack was the precursor to the galleon, used by Portuguese and Italian explorers of the 15th and 16th centuries. Like its cousin, the caraval, it was primarily a merchant ship; however, it was equipped with cannons in case it needed to defend itself.
Ocean Liner
The design of these behemoths of the sea has not changed significantly since the days of the Titanic and the Lusitania. They are called "liners" because they stick to a set route and schedule. Ever since the 1960s, with the advent of commercial airlines, they have waned in popularity as carriers of passengers across the Atlantic. Their shipping duties, meanwhile, have been taken over by container ships, which now transport 90 percent of the world's nonbulk cargo, and bulk carriers, which carry nonpacked goods like grain and iron ore.
Oil Tanker
These long ships are indispensable to the world's oil trade. According to How Stuff Works, the price of transporting oil in a tanker is only two to four cents per gallon. However, due to ecologically damaging spills like that of the Exxon Valdez, many countries have imposed regulations that serve to balance between an oil company's profit line and the environment. The Navy uses oil tankers as well, to supply fuel for its missions.
