Submarines have been conceived for many years, but only became practical in about 1900. Submarines have changed a lot in design from their first making which was in the years B.C. This sub was a box held under water with big ropes. New submarines are nuclear powered and can move at a speed of 30 knots and are big war weapons.
The first submarine that could stay under water on it's own and move on it's own was built in about 1620 by Cornelius van Drebbel. It was a rowboat surrounded by leather.
This sub like many subs that were made later had a problem getting air down to the people in the sub. On Cornelius van Drebbel's sub, they had a tube to the top of the water. Other subs had an air supply in the ship that lasted about 30 minutes. New subs can make air out of the sea water.
Getting subs to move is hard. Cornelius van Drebbel's sub had oars. Other old subs had bicycle pedals that turned a propeller in the back of the sub. Newer subs have an engine like a car engine powered by diesel. The engine turns a propeller in the back. The first diesel sub was made in 1906. Modern subs are made of metal hulls in a tube shape. Steel and titanium are used.
The newest kind of sub is the nuclear sub. These have a nuclear reactor that generates heat. The heat makes water turn into steam. The steam then moves past something that turns the propeller in the back of the sub. Nuclear subs can go 400,000 miles underwater without refueling and can stay underwater for up to 6 months.
The way submarines dive and surface is very complicated. The sub has a tank...