How is a submarine able to submerge and surface?

Answer 1

Submarines have ballast tanks. The tanks can hold air, or they can be "vented" and water can flow into them and fill them completely. When the tanks are full of air, the submarine is buoyant and floats. When the main vents are opened, the tanks are flooded and the submarine submerges. When the submarine is submerged and wants to surface, air can be injected at high pressure into the ballast tanks to force out water and again make the submarine buoyant and cause it to rise to the surface and float. In practice, when a submarine surfaces, it doesn't use a lot of air from its high pressure air tanks to "blow the ballast tanks" because it takes a long time to pump up the high pressure air tanks again. What happens is that all the ballast tanks are given a "good shot" of high pressure air (a few seconds), and then the planes are used in conjunction with the screw (which some call a propeller) to actually drive a submarine to the surface. Once there, something called a low pressure blower system can be used to finish blowing the ballast tanks (while the high pressure air compressors are running to pump the high pressure air tanks back up). When as submarine is submerged, the trick is to keep in neutrally buoyant and "balanced" or trimmed so that it is "level" in the water (has a "zero bubble"). There are axillary tanks aboard that allow trimming the boat, and that are used to set up neutral buoyancy. When a boat is properly trimmed and neutrally buoyant, it can be moved most efficiently through the water. The planes, which are used to "steer" the ship vertically, will be at zero and the boat will hold its depth with a zero bubble. There is a bit more to this, but the basics can easily be grasped and are covered here. A link is provided to our friends at Wikipedia who have posted an article on submarines, and it contains information on submerging and surfacing. Knowledge there is free, and you can use the post to check facts and learn more.