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In all of World War Two, the world used about 5 megatons of explosives.

Now, this is a Trident II missile, capable of carrying 12 nuclear warheads together equivalent

in power to about 5 megatons of explosives.

A single American Ohio Class submarine can carry 24 Trident II missiles.

A single submarine can carry a devastating, catastrophic, inconceivable amount of firepower.

While in reality due to arms reduction treaties and practicality these boats often carry far

less than their maximum armament, submarines can still creep up anywhere, undetected, ready

to unleash their firepower, more powerful that the entire arsenal of some countries,

in an instant.

Submarines are different in purpose to some other elements of a navy.

While an aircraft carrier, for example, is intended to be big, foreboding, and noticeable

as a means to display a nation's power to the world, submarines are meant to to be unseen,

undetected, an invisible, silent force that could or could not be anywhere at any time.

In a way, submarines almost serve a purpose of psychological warfare—an enemy can never

know for sure whether a submarine is looming off its shore.

While dozens of countries operate submarines, the most powerful and often largest of these

boats are those capable of firing ballistic missiles carrying nuclear warheads.

Only six nations are confirmed to have these submarines—The US, UK, France, India, Russia,

and China.

In addition, analysts have found evidence suggesting that North Korea and Israel also

each have nuclear-missile capable submarines.

Nowadays, there are essentially two different types of military submarines with two different

missions.

The attack submarine, the more common kind, is generally smaller and, in combat, attacks

other close-range targets like ships using torpedoes, shorter range missiles, and other

armaments.

The other, often larger type of submarine are those ballistic missile submarines which

essentially serve the purpose of being a mobile, hidden launch platform for nuclear missiles.

The idea is that, as a stealth launch platform, a country's submarines would survive any

nuclear first strike and therefore be able to retaliate against an aggressor.

Ballistic missile submarines are therefore crucial to the idea of mutually assured destruction—if

anyone attacks with nuclear weapons, assuming those attacked had nuclear weapons that would

survive a strike and they retaliated, both the attacker and those attacked would be destroyed.

Therefore, many consider these nuclear missile equipped submarines to actually be a form

of nuclear deterrence—they say they reduce the likelihood of others using nukes since

they assure their subsequent destruction.

Considering that these submarines might survive when a country and its government do not,

they therefore need the independent authority to use their missiles.

While other operators likely have similar setups, it's known that the UK's four

ballistic missile submarines each have a letter locked in a safe instructing their commander

on what to do if the UK is wiped out by a nuclear strike.

These letters are written by each prime minister at the beginning of their term and destroyed,

unread, at the end.

Each PM essentially has to chose which of the four potential options they want to instruct

the sub commanders to do—nothing, to place themselves under the command of an ally like

the US or Australia, for the commander to use their judgment, or to retaliate and launch

nuclear missiles at the attacker.

Of course, what gives submarines their stealth is the blanket of water.

American Ohio class submarines are publicly known to be able to go down as deep as 800

feet or 250 meters.

In reality, it is believed they can go much further.

As soon as a sub surfaces, though, their stealth is lost especially in today's era of satellite

tracking.

Therefore, it is important that submarines can stay underwater for long periods so that

that can dive underwater on one side of the world and make their way to the other undetected.

Of course, almost all of the world's ballistic missile equipped submarines are nuclear powered

meaning they have virtually unlimited range.

These boat's reactor cores only need to be swapped every few decades.

In addition, most submarines have oxygen generators and desalinators so, like nuclear-powered

aircraft carriers, the only thing that really limits how long they can stay deployed is

their food supply.

How it works on American nuclear subs, which work similarly to those of other countries,

is that each boat has two fully staffed crews at any given time—the Blue and Gold crews.

The Blue crew will first man the boat while on patrol which lasts, on average, 77 days.

The different submarines different patrols are scheduled so that there are always submarines

deployed.

Despite this long patrol period, in the US Navy at least, submarines are actually known

to have the best food of any vessel.

Some say it's because submarines are small—the chef has nowhere to hide if a meal is bad.

It more likely has to do with the fact that submarines get a higher food budget than other

vessels.

Food is important to morale especially considering submarine duty is one of the Navy's toughest

jobs.

Of course, fresh food can only last, at most, two weeks, so the meal quality deteriorates

as the weeks go by.

Eventually, the only ingredients left are canned, dried, or frozen.

The sign of food quality deteriorating does mean that the end of patrol is coming at which

time the first crew, the Blue crew, would take the boat back to either its home port

or a allied overseas port.

The Gold crew will then arrive and then both crews will work to complete a turnover, restocking,

and maintenance period of 25 days.

Then, the Blue crew will fly home for vacation and subsequent training before the cycle repeats

again.

Most crew members keep this cycle going for years on end.

Submariners even live their days in cycles as well.

They work eight hours on then have sixteen off to train, conduct maintenance, work out,

eat, and sleep.

Now, to get a sense of the scale of the largest of these submarines, here's a Boeing 747-400

and here's an American Ohio-Class submarine.

It is almost 2.5 times longer with a hull circumference far larger than the plane's

fuselage.

But even this is not the world's largest submarine.

That title goes to slightly longer and far wider Russian Typhoon-class submarine.

These are so large that their amenities include a sauna and small pool.

On American and most other submarines, the amenities are more lacking, though.

It's important that submariners have things to do in their down-time considering they'll

spend three months without sunlight in a metal tube, but there just isn't much space.

The mess is really the only open space not devoted to work.

Submarines tend to have gym equipment but it's not usually consolidated in one room—more

often it's just spread out in different nooks and crannies.

On large Ohio-class submarines, a submariners tiny bunk is their only true personal space.

On smaller submarines, like the American Virginia-class, the number of sailors exceeds the number of

bunks so the most junior sailors will have to share bunks—while one works the other

sleeps and vice versa—and there's no true personal space.

Compared to many surface Navy ships, which have phones, frequent mail deliveries, and

even internet, communication to the outside world is limited on submarines.

Each submariner is given an email address that their family can send messages to.

When the submarine is able to receive communications, all these messages are then sent electronically.

Onboard, the messages are all reviewed by a dedicated crew member.

They check through to be sure that no information is being sent that they don't want known

by the sailor.

For example, they might choose to not pass on information of a family death in order

to not affect crew morale.

There's often no way to get sailors off, anyways, so many believe it's better to

leave that news for the end of the patrol.

How submarines communicate, though, is complicated because they do, of course, spend months underwater.

Almost all radio waves can't travel through salt water but submarines do need communications

to receive orders.

Very low frequency radio waves, though, do penetrate water to an extent.

That's why VLF radio forms the core of submarine communication systems.

Different navies have large VLF transmitters—for example, the US has ones in Maine, Washington,

Hawaii, and elsewhere; India has one on its southern coast; and Australia has one in Western

Australia.

These VLF signals are able to penetrate the ocean and be picked up by a submarine as deep

as 60 feet or 20 meters.

One major disadvantage of VLF, though, is that it is very low bandwidth.

It can't even transmit real-time audio signals—the most it can do is about 700 words per minute

in text.

When deeper, some submarines also have the capability to launch buoys to shallower depths

to receive signals.

Submarines also typically can't respond with VLF frequencies since they don't have

large enough transmitters so they have to raise to shallow depths so they can have antennas

sticking out of the water to respond.

It's at this depth that modern submarines will often have quick transmissions with satellites

in order to download and upload information.

There are a few other techniques used less commonly, some new technologies under development,

and some separate systems designed for use when the main systems are compromised, but

VLF radio forms the bulk of communications with most submarines.

But the fact that submarines spend their time underwater in stealth also makes another crucial

element difficult—navigation.

Both GPS and Radar don't work underwater since they use higher frequency waves that

can't make their way through any depth of water.

What does work underwater is Sonar where the submarine essentially generates a sound and

then listens to when and how the sound comes back to map out its surroundings but emitting

this sound makes it quite easy for others to track a submarine.

Therefore, when operating in stealth conditions, submarines can't use active sonar.

Rather, they use an inertial navigation system.

These are essentially systems of accelerometers and gyroscopes that take the last-known accurate

GPS position of a submarine and then tracks the submarines movements relative to that.

It uses this to estimate position but of course, as time goes on from the last reliable reading,

the accuracy of this system diminishes.

24 hours after the last reading, these will drift to only about 1.15 miles or 1.85 kilometers

of accuracy.

Now, this technique combined with the consultation of maps is usually fine since most of the

time the ocean is a big, wide open space but there are a few objects floating below the

surface that submarines could collide with—submarines.

Some modern submarines are so well cloaked that another submarine just feet away might

not be able to detect it.

That's what happened on the night of February 3rd, 2009 when the British Navy's HMS Vanguard

submarine felt a resounding bump while sailing in the East Atlantic ocean.

It had collided with the French submarine Le Triomphant seemingly just by chance.

Luckily they were going at low speed and there were no injuries but, considering both these

subs were both equipped with nuclear warheads, one can only imagine the potential consequences

of a more damaging collision.

Submarines are dangerous—even in peacetime.

They are designed to disappear so, after something does go wrong, they often do just disappear.

Many submarine operating countries have rescue submarines that can hypothetically be used

to save stranded submariners by going down, latching on, and shuttling sailors to the

surface but in practice, these have never really had much action.

Sometimes submarines sink, their systems fail, and nobody can get to them before oxygen runs

out.

As submarines become better at masking themselves submarine tracking technology is simultaneously

advancing.

There's some thought that there will be a time when nothing can hide in the ocean's

depths but until then, submarines are a crucial aspect of any modern navy.

Nowadays, just as they were in World War Two, even traditional, non ballistic-missile submarines

and their torpedos are effective and deadly.

One of the best ways to track submarines is also by sonar equipped submarines so it's

a situation where countries need submarines because others have submarines.

That's why there are still hundreds of them somewhere, or rather, anywhere, ready to strike

at any moment.

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