Submarines

If you mean in the periscope, two.

It's estimated that Sgt. Lee of the American Continental Army pedalled his TURTLE submarine at about 2 mph in 1776.

A submarine is kept at, or close to, surface air pressure.

A standard viewing device used on a submarine is a periscope.

The number of active duty submariners is always a fluid number, being it's an all-volunteer service of the Navy. The numbers have always been historically small; the Submarine Force typically only comprises about 5-6% of the Navy's overall personnel.

In today's terms (assuming 300,000 active duty sailors), given the number of active submarines, newcon (new construction) boats, those who are in the training pipeline, and those in command / support units, the number is likely between 15,000 and 20,000.

It's important to understand that like most hazardous duty services, there are physical and mental requirements that must be met by all volunteers before actually being allowed to a submariner. The most obvious is claustrophobia; unless you're comfortable being in tight, cramped spaces for weeks at a time without seeing daylight (and most people aren't), being on a submarine crew isn't the best career option.

As miraculous as nuclear submarines are, they cannot sail under continents.

The South Pole is located on the continent of Antarctica, 10% of the surface area of planet Earth.

Submarines will implode very well if they go to a depth past their rated crush depth.

All boats are designed to withstand a lot of PSI on the hull, and most boats are designed so that the hull contracts and expands with depth changes. This ability to flex increases the longevity of the hull, though not all navies build their boats that way.

In addition to hull design (usually spherical or cigar shaped, the best design for pressure), boats maintain a positive air pressure inside while submerged. This is less about pressure on the hull than it is to maintain a vigil on hull integrity; if pressure in the boat drops, it means there's a leak or flooding somewhere, or a hatch not sealed properly.

La Provence, renamed Provence II and used for troop transport in the Mediterranean until the ship was torpedoed and sunk by the German submarine U-35.

Bigger, Deadlier, Faster, more Comfortable.

52 US subs were lost in WWII.

Lithium Hydroxide is the only chemical used to remove Carbon Dioxide (CO2) from the atmospheres of both submarines and spacecraft. For submarines, however, it is only used in emergencies or to augment a failing CO2 scrubber (or replace one that has failed).

Oilers then merchantmen.

David Bushnell built his 'Turtle' in 1776.

The Confederate submarine H.L. Hunley was built in 1863 using a boiler as a template. Having sank twice previously before her historic mission in Charleston Harbor, she was finally placed into service February 17, 1864, the day of the attack on the USS Housatonic, and the day she sank for the final time.

There's at least 51 USN subs resting in the Pacific. One's in the Atlantic. If the question is asking about operational submarines, an exact count would be difficult to obtain, but there are certainly hundreds. Many navies of the world have a submarine force, even if it consists of only one or two subs.

Likely Churchill.

Lord yes. Under extreme surface weather conditions, submerged turbulence can go very deep indeed. I still remember being at sea in 1983, at 400', while a hurricane was passing on the surface (we actually emergency sortied to get out of port before it hit). The turbulence was so bad we were taking 15-20 degree rolls - at 400 feet. Waves can be so high that if you're near enough to the surface, you can actually be brought to the surface under the right conditions. This is also one of the major reasons the Navy switched back to bow planes instead of Fairwater planes, since a boat brought to the surface by weather action has no depth control, the planes being out of the water. Major storms are interesting to say the least.

Yaw and Pitch don't happen as much because submarines are steadied by their keel from bow to stern, but if near enough to the surface pitch can be as bad as roll.

Surfaced submarines transiting in bad weather also experience bad rolls. Modern submarines actually go faster underwater than they do on the surface, and they don't deal well with surface conditions. The worst I ever encountered was a 2 day surface transit to Tampa for a Port visit on a Navy B'day in '85. The Gulf of Mexico is too shallow for a long submerged transit, and we were in the midst of the remnants of a hurricane that had passed through just prior to our arrival. Misery is the best description.

You need a minimum High School diploma or GED for Enlisted service, a 4 year college (accredited) degree for Officer programs.

Regardless of your education, you still need to pass the Navy's entrance exams, which are pretty thorough across all subjects. Its score determines whether or not you get the job you want, or will be scrubbing decks.

It depends on the type of boat (Fast-Attack, Ballistic Missile, Cruise Missile), the mission, and the state of world affairs.

FBM submarines are on a 3 month rotation schedule, since they have 2 crews for each boat; the boat spends 1 month for crew transfer and maintenance, then time for sea trials, drills, etc., before heading to their patrol area for several weeks.

Fast-Attacks typically don't have a set schedule - they can be gone for Monday-Friday ops, gone for 2 weeks, 2 months, 4 months, etc. It just depends on the boat's mission at the time, be it actual operations, certifications, training, etc.

Global affairs can alter a boat's mission time as well, or inclement weather like hurricanes which might require an emergencie sortie (underway) from port to avoid the storm.

But no matter how long you're gone, there's always something to do.....

Just like you do any Navy vessel:

1. Walk down the brow (without tripping or falling overboard into the water).

2. Turn toward the U.S. Flag at the stern of the boat, render a hand salute.

3. Turn toward the Topside Watch (who is typically right at the end of the brow), render a salute, and request permission to come aboard.

3. You present your ID card, and the watch will check your clearance status in the topside watch records. If an escort is needed, he'll call down below for one.

In cases of Flag Officers, the procedure is essentially the same, except the watch will ring the topside bell 4 times (2 bells, pause, 2 bells) and then announce the Officer's arrival. For example, if the Squadron Commander for Submarine Squadron 4 was coming aboard, the watch would announce over the 1mc (general announcing circuit) 4 bells, then "Subron 4 arriving".

Many early attempts to operate submerisibles and submarines led to their sinking, notably the German construction called a Brandtaucher (1850). Its six-man crew attempted to break the Danish blockade of the port of Kiel, but became stuck on the harbor bottom for six hours before they were finally able to abandon the ship.

Observational ones yes, but not those used in the forces. You cant really see that far at depth, so they 'see' using sonar.

They typically run on steam power, using nuclear reactors to create the steam. Prior to the development of the nuclear power systems, they used electric motors through batteries, that were charged using diesel engines. On the surface the diesel also propelled the shafts.

124. Mostly 24 Megaton Warheads.

Ships try to avoid sinking, submarines sink on purpose...