Submarines

It depends on the submarine type and hull design.

Older WWI and WWII Fleet submarines were specifically designed as surface ships with limited submergence capability - they primarily ran on the surface with their diesel engines, and submerged using their battery powered electric motors when attacking a surface vessel. This hull design made gave them a lower water resistance on the surface, but much higher underwater. Their speed underwater was almost half of what they could do on the surface.

With modern submarines, the opposite is true. Submarines today are specifically designed for lower water resistance (higher speeds) underwater than they are on the surface. Top speed for most boats on the surface might approach 20 knots, but underwater they can do over 30 knots. The old Russian ALFA class submarines were known to do 45 knots submerged.

Yes definitely. Maybe not military class submarines but there are many public submarine tours that take you under the water to see shipwrecks, sea life etc

They were only capable of going about 50-80 feet under. They were mostly used for spying.

tva

The German Type XXI U-boat had a deep diving depth of 280 meters (919 feet).

As a submarine submerges, it is subjected to a high volume of water pressure, which increases the further in depth the submarine goes. They have to be built to be able to withstand this pressure.

The primary advantage a submarine has over other ships is its ability to submerge and hide.

At the time of the attack on Pearl Harbor, the U.S. Navy had 111 submarines in commission. It commissioned 203 more during the course of the war.

Five midget submarines participated in the attack.

as near as one can figure from somewhat ambiguous ( possibly to confuse outsiders) my l946 Fleet submarine technical manual describes it as a (Surface condition) where the ballast tanks are partly flooded and trimmed down so the boat is almost submerged but not quite and the ballast vents are open. There are no diagrams to explain exactly how this works, but one surmises the general idea. the sub is heavily ballasted but still in surface trim, it is riding low in the water, as if it were heavily laden.For some odd reason this term has never made the scene in action-packed submarine films- unlike Crash Dives, running on the batteries, Green Board- an indication that the electrical connections are ( rigged for dive) all hatches and openings that are normally closed- sealed) and so on. Maybe it was not a very widely-used tactic.

During the American Revolution, the Colonists tried to use a submarine called The Turtle to sink a British warship in New York harbor. The English ship had a metal plate attached to it, and the attack failed.

During the USA civil war, the South, (Confederate States), tried to use submarines to break the Union blockade, but, although they sank one Northern ship, the sub also sank, and it was not worth the effort.

The German use of submarines in WWI, was the first time a country made an effective use of the boats, and from then on, many countries with navies tried to get submarines in the fleet.

The US, Russia, Great Britain, France, China and (recently) India have nuclear submarines.

Propellers need to have very precise shapes, and be kept very smooth, for proper operations, therefore, a corrosion resistant material must be used, regular steel will not do. Brass is a cost effective alternative. More expensive materials may be used if the situation warrants it, for example, stainless steel is used for propellers in very cold waters, where the brass would be rendered brittle.

Steel or titanium

Believe it or not; they're just metal tubes. Unlike surface ships (Carriers, Battleships, Cruisers, Destroyers, PT Boats, Swift Boats, etc.) subs are metal tubes with men inside them.

The Canadian Maritime Forces (MARCOM) currently operates 4 Victoria-class Diesel-Electric submarines. However, noting (like every other major power has already) the limitations and expense of maintaining diesel boats, it has undergone a new program of developing nuclear powered boats. It's estimated the first will be ready within the next 2 or 3 years.

It depends entirely on the size and normal surface displacement of the boat, and the current ballast (fixed and variable) aboard. Most modern boats can have a varied draft between 25' and 35'. The visible portion of any submarine above water is only about 1/5 of it's total size.

Every submarine since Drebbel's first in 1578 has been able to reach the ocean floor. Not all have been able to resurface, though.

For many decades, Submarine optical periscopes have used prisms instead of mirrors, for both reflection and magnification. The simplest way to describe it is 2 telescopes pointed at each other. Prisms are used instead of mirrors because they are more rugged, and unlike mirrors, do not require special coatings to keep them from being impaired by environmental factors.

Traditional periscope masts are very long, over 30' in most cases. They are raised and lowered using the ship's main hydraulic systems. All modern submarines have at least 2 periscopes - one for attack (low profile) and the main periscope, which typically has many other functions built into it. Something that's not well known is that the Navigator can hook a Sextant to a Periscope and get a sunline or star fix if the need were to arise.

More recent newer classes of Submarines (e.g., U.S. Virginia and British Astute classes) use a device called a Photonics Mast which replaces the old optical type periscope system. Since it doesn't have to be contained within the pressure hull or raised/lowered from the Control Room like a traditional scope, it means the Control Room can be located in an area not directly under the sail. Photonics masts are essentially digital camera arrays, which have increased functionality over their optical counterparts, and of course since they don't penetrate the hull, if damaged the chance of a flooding casualty is much less.

The world's first atomic powered submarine was the USS Nautilus.

Though it's largely for morale purposes (most boats operate in depths that if they sank would crush them), the reason for exhaling when escaping from a sunken boat is so that your lungs don't explode.

Sea pressure compresses air in the lungs, and that air expands as the person moves to shallow water. If you don't exhale as you head for the surface, you risk the air expanding in your lungs as the sea pressure decreases, rupturing the lungs and killing you.

It's not just for those in a disabled boat; the technique is also taught to divers in basic SCUBA classes.

It's one thing if you're on the surface and hold your breath and then dive down; in that case, air at sea level is being compressed as you go deeper, and the volume will be the same once you return to the surface. For divers and those in submarines, the air is equalized to the ambient sea pressure at the depth in question, so the air expands as you go shallower.

Submariners are taught how to do this in Submarine School. Though I don't believe they use them anymore, we used to train in the old 100' water towers, where you entered at 100' and then rose to the surface, exhaling all the way.

U. S. submarines in World War II had a top surface speed of around 20-knots. Submerged, their top speed was around 9-knots, although at that speed they would exhaust their batteries after one hour and have to surface to recharge them.

Yes, water exerts pressure on the hull of the submarine.

During WWII the largest submarine was the Japanese I-400 Class sub. It was 400 feet long, displaced 6,000 tons, carried 3 airplanes, and had a complement of 144 officers and men.