The Assassin (Sha ren zhe Tang Zhan)

Today on "Impossible engineering"...

The Virginia class,

one of the most advanced submarines ever built.

To come down the waterfront,

to see these submarines being built,

it is truly a magical thing.

Pushing marine engineering to its limits.

The Virginia class is acoustically

the stealthiest submarine that the U.S. Navy has ever produced.

It took revolutionary engineering...

What we have now on Colorado

really incorporates the latest and greatest

of what's out in industry.

To make the impossible possible.

captions paid for by Discovery communications

Submarines are an invaluable asset to the U.S. military.

After decades of service,

their fleet is in need of an upgrade.

The Navy was looking to a replacement

for the 688 class ships.

They were nearing the end of their useful life.

Similar to a vehicle, it gets wear and tear over time,

and it was time to come up with the newer model.

What designers came up with

is breaking the boundaries of maritime engineering.

What we're looking at

is the 15th Virginia class submarine,

the U.S.S. Colorado.

She's 377 feet long.

She can dive to depths greater than 800 feet.

She can operate at speeds greater than 25 knots.

The Virginia class is one of the most advanced

nuclear-powered fast-attack submarines ever produced

for the U.S. Navy.

At the electric boat shipyard in Groton, Connecticut,

a 15th Virginia class vessel is under construction.

Starting with the first ship of the class,

it took 15-million hours to build that ship.

And with the Colorado,

we brought that cost down to 10-million hours.

That's the kind of effort that's required

to put one of these remarkable ships to sea.

I've served on three classes of submarines,

and by far, the Virginia class is the best-engineered

that I have had the pleasure of serving on.

These technological titans are as long as 26 cars.

Each sub weighs 7,800 tons.

That's 40 blue whales.

They're equipped with an advanced nuclear reactor

and can dive to depths of almost 800 feet

or inch across shallow water with pinpoint accuracy,

thanks to a control room

that's equipped with an automated navigation system.

The pilot can literally dial in

any depth, any speed.

It allows the ship to operate

in much shallower water close to shore.

The combination of stealth, endurance, versatility,

the range is truly a benchmark for all ships.

The engineers of the Virginia class sub

have created a modern marvel,

one that would have been impossible

had it not been for the great innovators of the past.

Humans have been diving to the depths

of our oceans for centuries.

Hmm?

Hello!

Ancient sponge divers used to plummet to the sea floor

using heavy rocks.

They held their breath for minutes on end

to retrieve precious bounty.

In the 5th century B.C.,

Greek diver Scyllis breathed underwater

using a hollow reed...

Hmm?

Allowing him to sabotage the enemy Persian fleet.

Legend has it Alexander the great

used the first submersible craft.

He dove into the Bosporus straits

using a clear glass barrel to spy on enemy sea defenses.

Controlling a vessel underwater was nearly impossible

thousands of years ago.

And today, it's still a huge challenge.

At the David Taylor model basin facility in Maryland,

nautical designers are testing their submersible designs

at the annual international submarine races.

Scores of young engineers from around the world

have brought submarines that they've designed and built

with the goal of becoming the fastest human-powered submarine.

The challenge is go 100 yards

without coming out of the water, touching the bottom,

touching the sides, or any part of the submarine falling off.

100 yards may not seem like much,

but controlling a submersible's buoyancy is no easy feat.

So up and down is a little bit difficult.

Left and right so far has been really good.

I can follow the line.

It's just been a question of keeping the buoyancy right.

Did we make it further than before?

We've got about... Yeah, sort of halfway.

The trim is slightly off.

Like, the controls seem to be working.

The propeller's definitely working.

The key to the perfect submersible continues to elude

even the finest young engineering minds.

But they're getting close,

thanks to an invention created almost 250 years ago

by David Bushnell.

Dr. Rhys Morgan is at the royal Navy submarine museum

Ginosport, England,

uncovering information about a secret weapon

from the revolutionary war.

And this is it... the Turtle...

The first submersible used in recorded underwater combat.

Bushnell's plan for the Turtle

was to sneak up on the British enemy ships

moored in New York harbor.

The vessel had lots of weights in it

to help it sink into the water,

and underneath the base, there was a ballast tank,

which would be filled with water.

And the operator, a man called Ezra Lee,

would pump the water in and out of the tank

to help sink to the right depth.

As the Turtle slips underwater,

its two surface-mounted snorkels seal.

The pilot powers the craft

using a hand-cranked front-mounted propeller.

As he approaches his target, he readies the Turtle's weapon.

The Turtle's weapon, a keg of gunpowder,

was attached to the back of the wooden hull.

As the submarine silently crept up underwater

to the base of the ships,

it would be attached by this drill,

which would be literally hand-drilled

into the base of the ship.

Unfortunately for the pilot, Ezra Lee,

the British fleet had metal hulls.

By sheer bad luck,

Ezra Lee wasn't able to drill into the ship's hull,

so the Turtle was a bit of a failure.

But having said that,

it did set the precedent for submersible combat,

and the principles of ballast tanks and propulsion

still to this day remain on all submarines.

The Turtle can only hold one person.

The U.S. Navy's Virginia class can hold 135 people.

Ships manager Patty McDaniel

is charged with fitting out the 15th Virginia class sub.

One of the challenges with the design

of the Virginia class ships

is all of the services and equipment

that we need to fit into a tight space.

So all through construction, we tried to design having spaces

to put all of the services up in.

One of the other challenges with that is the crew,

when they come out to sea,

these racks are the extent

of the space many of the crew members

have to store all of their items.

So just this thickness deep is what these sailors have

to have all of their clothing and books

and whatever they choose to take out to sea with them.

Tight quarters are a recurring theme on board,

regardless of rank.

This is the wardroom of the Virginia class submarine.

So the wardroom, as you might imagine,

is where the officers gather to eat, among other things.

It's also where a lot of the meetings happen

to discuss all of the ongoings on board the ship.

Interestingly, too,

submarines are very limited on space.

So the table is a large, clear surface.

So this doubles, out at sea,

as if you needed to have an operating table.

Not only can the Virginia class

accommodate more people than the 17th-century turtle submersible,

it can also dive much deeper.

They can reach depths of about 800 feet,

thanks to a system of internal and external ballast tanks.

We have five external ballast tanks

that are normally filled with air

when I'm riding on the surface.

When it is time for us to dive,

we'll open vents on those ballast tanks.

There's grates on the bottom of the ship

that allow water to come in, displace the air,

making the ship

just slightly negatively buoyant.

We then proceed down to the depth

that we want to go to,

and we use internal ballast tanks

to make the ship neutrally buoyant

that then we can progress on our way

whatever depth we choose.

The crew on board the Virginia class

have an abundance of cutting-edge controls

at the firingertips,

one of which is replacing the most iconic feature

in submarine history.