Original subtitles

[Josh Gates] To prove a controversial theory,

Explorers Club member Thor Heyerdahl attempts to cross

thousands of miles of open ocean on a simple balsa wood raft.

Will his impossible voyage end with vindication, or at the bottom of the Pacific?

The first extraterrestrial car is custom-tuned to dodge a lunar gauntlet

on its way to a discovery that rewrites the story of earth's origin.

[astronaut over comms] Okay, Jimmy, let's go to work.

[Josh] A miracle plane burning no fuel

flies club member Bertrand Piccard around the globe.

As long as the wind doesn't snap it in two.

And a Roaring '20s airship braves polar storms,

carrying a club legend to the top of the world.

Leave it to The Explorers Club to show

that the real drama isn't always reaching the finish line,

but surviving the ride.

-Fire. -[explosion]

Welcome to the world-famous Explorers Club.

For over 100 years, this has been a gathering place for trailblazers.

The people who dare to venture higher, further, and faster.

As a member of this exclusive club,

I'm bringing one-of-a-kind access to its archives...

This is incredible!

...artifacts...

[Josh] Oh, my word.

...and my fellow explorers.

This is actual lunar dust. Unbelievable.

The expeditions planned here have tested the boundaries of human possibility.

Its flag has flown on death-defying voyages into the unknown

that forever changed our world.

These are the greatest adventures of all time.

These are...

...TalesFrom The Explorers Club.

The most amazing part of some Explorers Club expeditions

is not the destination, but the journey.

Sometimes because the destination is so extreme

that it demands a means of transport that doesn't yet exist.

This was the challenge facing Norwegian ethnographer Thor Heyerdahl 75 years ago,

when he came to the club and used this very globe

to plan a mission many warned him was suicide.

Heyerdahl's proposed journey stretches nearly 5,000 miles.

And although he has the club's support, his expedition

is the result of an academic dispute with a former club president.

Let's back up a bit, and this'll all make sense.

The year is 1945.

For a decade, Heyerdahl has been obsessed with answering

one of history's greatest riddles.

Few places on earth are more isolated than Polynesia,

the vast, triangular area of the Pacific Ocean

extending from Hawaii to Easter Island to New Zealand.

The Polynesians have occupied the islands there for 1,000 years,

but where did they originally come from? How did they get there?

The scholarly consensus is that they came from the West,

from Asia, on outrigger canoes.

But Thor questions that conclusion.

Reexamining the evidence, he's developing a radically different theory.

He's convinced that the solution to the mystery

lies thousands of miles away from where experts claim, in South America.

In 1937, Heyerdahl had visited the Polynesian Island of Fatu Hiva,

and was struck by apparent similarities between Polynesian traditions

and those of indigenous South Americans.

According to myth, Tiki, the father of the Polynesian tribes,

led his people to their remote islands from a mountainous land beyond the sea.

Thor sees a link between this myth

and an Andean legend about a king called Kon-Tiki,

who fled West over the ocean to escape his enemies.

Beyond this parallel, Thor's evidence is spotty.

But he believes that the mountainous region is Peru,

and that the Polynesians are descendants

of an ancient South American population predating the Inca.

But how could anyone, with only Stone Age technology,

make the 5,000-mile voyage from South America to Polynesia?

Heyerdahl believed that the indigenous inhabitants of what is now modern-day Peru

built and sailed seaworthy rafts made of balsa wood as early as the 6th Century.

The same type of rafts that Spanish conquistadors described in their journals

1,000 years later.

But making a seaworthy raft is one thing.

Navigating it 5,000 miles across the Pacific Ocean

to a cluster of islands you don't even know are there is something else.

So, how did Thor explain that?

Heyerdahl's answer is hiding in plain sight.

He believes that two natural forces in the Pacific

can propel a rudimentary wooden raft over a massive distance,

right to Polynesia's doorstep,

even without the ability to meaningfully steer or navigate.

The first is the trade winds, the persistent winds blowing East to West near the equator.

[wind blowing]

The second is the Humboldt Current, a powerful flow of cold water

moving North along South America's coast, then West all the way to Polynesia.

Heyerdahl's commitment to a theory rooted in blind faith is astounding.

But is the voyage he's proposing even remotely possible?

My fellow Explorers Club member, expedition filmmaker Trevor Wallace,

has some perspective on Thor's seemingly improbable theory.

He has sailed the same waters, and cataloged the same islands

that gripped Heyerdahl's curiosity.

Heyerdahl's theory is that ancient South Americans

are rafting West across the Pacific to these islands.

Technically speaking, is this even possible?

Technically, yes. I think most people would, would say,

you have a current, you have the Humboldt Current

that's coming out from South America and pushing towards Polynesia.

-[Josh] Right. -[Trevor Wallace] And you have trade winds.

So you put a sail up on anything that floats,

and hypothetically, it could get there.

But it goes against all conventional knowledge.

-Right. -Like, you know, the Polynesians

were the wayfinding voyagers.

-Yeah. -Whereas, South Americans,

they were not a voyaging culture.

Right, those were rafts in a lake environment.

-Yeah. [laughing] -Yeah. Right?

Yeah. You know, they could have been transporting

heavy, monolithic stone structures.

-Sure. -But are they voyaging over ocean?

-No. -Probably not. [laughing]

-So this didn't really make a lot of sense. -Right.

[Josh] In 1946, Heyerdahl confidently presents his theory

to America's leading anthropologists.

Thor.

Who instantly reject it.

The most eminent is Explorers Club member

and former club president Herbert Spinden.

I'm sure this makes sense to you.

He tells Heyerdahl that his evidence is weak,

and that he's ignoring a wealth of linguistic data linking Polynesia with Asia.

You know, the Polynesian language has parallels.

But in Asia. Not in South America.

And the idea of ancient Peruvians sailing 5,000 miles

across the Pacific on simple rafts?

-[sighs] -This is the way they traveled. I know it.

-Now, look... -Damn it, Herbert, I know I'm right!

All right! Let's see how far you get

going from Peru to Polynesia on a balsa raft.

Please.

This final dig, intended to slam the door on their dispute,

will provide the fuel that propels Thor into Explorers Club history.

Heyerdahl preps an audacious voyage

that will take him and a crew of five other Scandinavians across the Pacific.

The idea of marooning themselves on a homemade raft

on the world's largest ocean sounds like a rejected pitch forCastaway 2,

especially since only one of them has any experience at sea.

Heyerdahl himself has never learned to swim.

But the line between insane and inspired can be a fine one.

In Peru, Thor's team builds their unique raft,

based on the descriptions of the Spanish conquistadors,

using only materials available to ancient South Americans.

The plan is called everything from irresponsible to preposterous.

But Heyerdahl's confidence is unshaken.

He's challenged nature since boyhood,

once shocking his parents by venturing alone

into the icy Norwegian wilderness with only a sleeping bag.

As his raft takes shape, the crew dubs it the Kon-Tiki,

after the Andean legend.

Nine balsa logs comprise the 18' by 45' base,

held together by hemp ropes.

The deck is covered by a latticework of bamboo.

In the center is a bamboo cabin.

At the stern, a steering oar.

The mast is made of rock-hard mangrove.

The main square sail bears a likeness of the sun god.

The Kon-Tiki is straight out of the 6th Century,

a vessel without a nail, rivet or screw.

It set sail from Peru on April 28, 1947.

The only modern gear they bring are a navigational tool called a sextant,

a hand-cranked radio, and a 16 millimeter camera.

Filming an expedition as it happens. Great idea, Thor. I owe you one.

In the first weeks of the voyage, the crew has harrowing encounters

with marine creatures in the Pacific.

They become the first people to cross paths with a living snake mackerel,

after it washes aboard at night into a crewman's sleeping bag.

They attract the attention of a whale shark that nearly upends the raft.

From there on out, the shark encounters pick up steam,

as Heyerdahl unwittingly stars in his own Shark Week special decades ahead of schedule.

Riding the Humboldt Current, the Kon-Tiki travels Northwest,

passing below the Galapagos Islands,

before the current dips to the South and continues West.

Also pushed by the trade winds, the raft averages more than 55 miles per day.

A month into their voyage, the crew has already sailed 1,200 miles.

But at this point, Thor discovers a horrific problem.

The Kon-Tiki is riding lower in the sea.

-This is not a good thing? -Yeah, I mean, the whole reason he chose balsa wood

is because it's incredibly buoyant. But it's also porous.

That was one of the fears all along.

And a lot of his critics were saying, oh, it's gonna fill up with water and sink.

So when it starts to ride low, they're thinking, oh, wow, it's really happening.

Right. And I have to imagine these guys are terrified by this?

-There's no lifeline for them. -Right.

And I mean, for Heyerdahl in particular, he was fully committed.

The guy couldn't even swim, so, [laughing].

-Which, by the way, is the craziest part of this. -Yeah. Yeah.

Like, maybe some swim lessons before the trip? Something?

Because there is no, to your point, like, there's, they, they're not calling AAA.

-No. -Nobody's coming.

-No. -This raft goes in the water, you're dead.

As an experiment, Heyerdahl cuts off a piece of the Kon-Tiki's wood.

What will happen to it if he casts it adrift?

[wood splashing in water]

Oh, God.

In a flash, their expedition is no longer an adventure, but a pending catastrophe.

How long do we have?

Days. Maybe a week.

[Josh] This is Explorers Club Flag Number 123.

It was given to Thor Heyerdahl for his epic voyage aboard his balsa raft, the Kon-Tiki.

Critics were certain the Kon-Tiki, its crew, and this flag

would never be seen again.

And a month into their journey, when the raft appeared to be sinking,

Thor feared they were right.

But then, he discovered that a twist of fate weeks before they set sail

had saved them all.

There is a treasured piece in the Explorers Club archives

that can explain what happened with a little help from club archivist Lacey Flint.

So this is an old piece of wood.

A very old piece of wood. Actually, it's not that old. Uh, it's only from 1947.

It's a piece of the actual Kon-Tiki.

-An actual piece of the Kon-Tiki raft? -Mmm-hmm.

An actual piece of the raft. Yes, absolutely.

And it is light as a feather. This is balsa wood.

Balsa wood. Really light weight, really porous.

Um, it's actually what you use to make model airplanes with.

So this is what's absorbing water

and causing the raft to sit real low in the water.

[Flint] Yeah, absolutely.

[Josh] But the Kon-Tiki doesn't sink.

[Flint] The Kon-Tiki does not sink, and...

-So, why? -That's because they were using fresh balsa wood.

So the initial plan was to just buy some balsa wood when they got to Peru.

-Right. -Serendipitously, turns out, no balsa wood logs.

So they actually have to go to the Ecuadorian Jungle,

chop down their own logs, and then fashion the raft.

-Okay. -And the reason this is important

is because those logs still had fresh sap in them.

And that sap is what's filling in all these porous gaps here,

and helping them to float.

And if they had sourced the balsa wood from Peru, what would have happened?

Really probably would have filled with water, and it would have sunk.

Wow.

[Josh] Satisfied that they won't be swimming to Polynesia,

the crew of the Kon-Tiki sails on.

Three months pass with no land in sight.

Then, on the 101st day of their voyage, they finally spot an island on the horizon.

It is Rangiroa, 475 miles East of Tahiti.

The date is August 7, 1947.

It's the moment Thor and his crew have been praying for.

Beautiful.

[Josh] But when they draw within sight of the island's beach, their hearts sink.

Just below the ocean surface, a massive coral reef blocks their path.

The coral is as sharp as razorblades, and stretches for miles.

Land is in sight. They're right there. And between them and safety is this coral reef.

So what can they do?

They can't do anything. As a drifting vessel, they're at the mercy of the ocean.

The big problem is that the Kon-Tiki was not meant to be maneuverable.

-Right. -And so, like, they're not getting around the reef,

they're going straight into it, and they just have to hold on

and hope that they don't get torn to shreds.

[Josh] After 4,300 miles, the six men

are just a few hundred yards from their goal.

But they're staring death in the face.

Why don't we just land?

We can't just land, okay? The coral will tear this raft apart.

Let's just swim for it.

We can't just swim, either. The coral will tear us apart.

Listen. We have to stay on this raft.

As the Kon-Tiki washes toward the reef,

the crew's radio man makes contact with a HAM radio operator in New Zealand.

His last, hurried words: "50 yards left, okay, here we go. Goodbye."

All the crew can do now is brace for impact.

A fortuitous swell throws the Kon-Tiki into the shallows beyond the breakers.

The cabin and mast break apart.

Hanging onto the logs, every member of the crew

is able to stagger onto land, largely unharmed.

The island is uninhabited, but one radio transmission later,

help is on the way.

The flag of Norway, and below it, the flag of the Explorers Club,

welcome envoys of a neighboring Polynesian island.

Against all odds, defying all reason, Heyerdahl's voyage is a success.

Today, the Kon-Tiki resides in a Norwegian museum.

In recent decades, most experts have become more convinced than ever

that Heyerdahl's migration theory is invalid.

DNA evidence shows almost conclusively that Polynesia's earliest settlers

came from Asia, not South America.

Still, a flicker of doubt remains.

One DNA study has revealed that several Polynesian populations

bear a genetic signature traced to Native South Americans.

And critics can no longer claim that the epic sea voyage Thor envisioned

was impossible.

To make a journey many believed was delusional,

Kon-Tiki logged over 4,000 miles across the Pacific.

But another unique vehicle of exploration proved that distance isn't everything.

After all, it traveled only 17 miles,

just far enough for the men onboard to find a treasure

that would change our understanding of how our planet was born.

And the really cool part is, they didn't do it on earth.

The date is July 25, 1971.

At Cape Kennedy in Florida, the crew of Apollo 15,

David Scott, Jim Irwin, and Explorers Club member Al Worden,

attend a final briefing on the eve of their liftoff.

All right, guys. TLI is scheduled for T-plus two hours.

As on all Apollo moon flights, they'll be carrying

a downsized version of the Explorers Club flag,

trimmed down to save space and weight.

Apollo 15 marks a huge turning point in America's space program.

To this time, it's been about beating the Russians.

Now, it's about solving the riddle of our solar system's creation.

NASA knows that the moon is a galactic time capsule.

Its rocks hold clues to its origin.

But the rocks retrieved from missions before Apollo 15 don't offer the best evidence.

They come from areas chosen for their flat terrain, tailor-made for safe landings.

The Apollo 15 astronauts will land in a geologically rich area,

rimmed by mountains and canyons.

Their goal is to learn about the moon's origins by finding its oldest rocks.

The Mount Hadley Delta should be a rich site.

And Spur Crater. I like our chances there.

Agreed.

They're told to keep a special lookout

for a white, crystalline rock called anorthosite,

since some of the scientists believe

it could be the remnants of the moon's primordial crust.

But to cover their search zone effectively,

they'll need greater range than any previous mission.

What's the distance from our landing site to Delta L, though?

It is three miles.

In the past, lunar astronauts only explored areas the size of a football field,

never straying farther from their landers than they could safely walk back

in case of an emergency.

Apollo 15 has the solution.

A very American solution. A car.

Its official designation is the LRV, for Lunar Roving Vehicle.

[NASA narrator] The LRV. A spacecraft with wheels.

[Josh] The rover is a 460-pound electric go-kart.

Every part has been whittled down to its lightest, most efficient iteration.

Max speed, eight miles per hour.

There is no steering wheel or foot pedals.

-Just a joystick. -[mechanical whirring]

Each wheel is independently driven by a quarter-horsepower motor.

Its builders have literally reinvented the wheel,

creating wire mesh tires with titanium treads.

On top of all that,

it folds up like a beach chair

for easy storage in the Moon lander's descent stage.

The lunar rover pre-dated Mike Massimino's 18-year career as a NASA astronaut.

But he's always been moonstruck by its colorful history.

The lunar rover is kind of crazy to me.

-Yeah, yeah. -It is. It's like...

It's like let's not just go to the moon, let's bring a car up there.

-Yeah. The dune buggy. -Right? A dune buggy.

Who's ever built a car for the moon before?

-Right? -[laughs]

These are the first ones and it's hard enough I would imagine to build a car

-on Earth. Right? -Right.

How do you design a car for the moon, right?

I mean, what are the design challenges here

that they have to meet and figure out?

Uh, anything you do in space is harder.

-Right. -Then what you're... 'Cause you have to account

for things that are at the extreme.

-Especially on the moon for a car. -Right.

You have extreme temperatures, 500 degrees, uh, temperature swings

that this car is gonna have to withstand.

So that's not an easy thing right there.

-Right. -And the terrain is really hostile.

You've got rocks and sharp edges

and lots of dust all over the place.

-It's pretty challenging. -I mean, it's... it's...

-...it is built for that low gravity environment, right? -Yes.

Like, would it work on Earth?

Ah, no. I don't think you'd want it to

because it was so lightly constructed

for the 1/6 gravity of the moon.

You would put your foot right through the floor board

-if you tried it on Earth. -Really?

-Yeah. Wouldn't be workable. -Wow.

[Josh] This lunar hotrod was 17 months in the making.

But NASA contractors had been tinkering with prototypes for a decade.

Everything from a motorcycle,

to a mechanical worm,

to something resembling the Oscar Mayer Weinermobile.

But in the end, GM and Boeing win the job

and produce a state of the art moon buggy.

And since it cost the modern equivalent of $266 million,

NASA thinks it might be wise to give the Apollo 15 astronauts

a little driver's ed.

But to do it right, they have to do something a little crazy.

Transform a piece of Arizona into the moon...

...the hard way.

[man] Five, four, three, two, one.

Fire!

Fifty years ago, the Apollo 15 astronauts

went rock hunting in the world's first extraterrestrial car.

With any luck, I'll be doing some off-roading on the moon in my lifetime,

following in their tread marks.

A half century after designing the LRV,

NASA gave me a sneak peek of the future in a prototype rover.

I took the wheel for my joy ride

on a lunar surface mock up in Houston.

This is officially the coolest 4x4 I've ever been in.

Actually, I guess it's more like a 12x12.

Okay, Josh, I'm transferring control over to you.

-[Josh laughs] -Do a pure twist to your right.

[Josh] Get out of here.

Got a speaker system here. Play some tunes.

[man] Yeah, all the comforts you want in a RV, you want in this.

[Josh] And what about cup holders?

[man] I already got cup holders for ya.

-[both laugh] -[Josh] They're in.

What you just saw was the lunar rover of the future.

To learn how to drive the original in 1971,

the Apollo astronauts needed a lunar test track like the one I navigated

or attempted to navigate.

So, NASA got busy doing a little moon-scaping.

[Josh] Its starting point is this 66-acre field of volcanic cinders

near Flagstaff, Arizona.

To make the rover's driving experience as real as possible,

engineers recreate a specific portion of the moon's terrain.

That means burying explosive charges

to make 426 craters.

All in the same position and of the same size as the ones on the moon.

[man] T minus 10, nine, eight, seven...

[Josh] The fun part is that they're going

to blast the majority of them all at the same time.

[man] ...two, one.

Fire!

[Josh] The result is surgical.

The blown out terrain perfectly mimics an actual sector of the moon's surface.

Making it an ideal obstacle course

for a version of the rover suitable for use on Earth.

The ride in Arizona is a little otherworldly...

...but it's got nothing on the real thing.

The date is July 31, 1971.

History's first extraterrestrial drive is a treat

for astronauts Irwin and Scott.

It works, I think bucking bronco was somewhat of an understatement.

This thing really gave 'em quite a jolty, uh, bouncy ride.

They were bouncing all over the place with this thing.

They had to wear seatbelts, not just for good form,

'cause they would've been thrown away from this thing.

-Right. -If they weren't buckled in, they would go flying with it.

-I mean, you literally could go flying out of this thing. -You're out.

-That's right. Yeah. -Right.

[Josh] But this is swashbuckling in the pursuit of science.

[astronaut] Okay, Dewey, let's go to work.

[Josh] During their three days on the moon,

Irwin and Scott collect 170 pounds of lunar rocks and soil.

The rare samples will keep geologists busy for decades.

But one treasure hunt in the rover stands above all.

On the rim of Spur Crater,

three miles from their landing site,

Irwin and Scott have found their geological holy grail.

A half pound chunk of anorthosite.

It's a piece of the moon's original crust.

Older than any moon rock ever found.

It comes to be known as the Genesis Rock.

Its geology is eerily similar to rocks from Earth.

Leading to a radical new theory about the moon's origin.

Four and a half billion years ago

when Earth was still a mass of molten magma,

it was blind sighted by a Mars-sized asteroid.

Within a matter of weeks, the debris had coalesced into a single mass.

About a year later, that mass had evolved into the spherical foundation

of Earth's inextricable dance partner, the moon.

The cosmic collision believed to have formed the moon

may have also helped create us.

A moonless Earth would have no or much gentler tides.

Tides were likely a key ingredient to creating life on Earth.

By sloshing together its primordial soup of foundational chemicals.

So the Genesis Rock tells more than just the story of the moon's origin,

it also tells of our own.

Without the lunar rover, the Apollo 15 astronauts would never have found it.

But on its third and final day on the moon,

it still has one pioneering duty to perform.

An historic first to be witnessed live on Earth

by millions of television viewers.

When the Apollo astronauts completed their last drive

in the lunar rover 50 years ago,

they chose a very specific parking spot.

While not the same as parking a car in New York City,

the challenges are comparable.

The rover was about to make history one last time with its dashcam.

[Josh] On the previous three successful Apollo missions,

the astronauts blasted off the moon unseen.

Not this time.

From a distance of 500 feet,

the rover's camera is aimed at the Apollo lander, the Falcon,

as Jim Irwin and Dave Scott prepare for liftoff.

[Josh] The lunar rover was an electric vehicle far ahead of its time.

But when it comes to launching rockets out of the Earth's atmosphere,

they require a lot of fuel.

Let's just say the MPG isn't exactly ideal.

One Explorers Club member had a vision

for environmentally responsible travel

that everyone said was impossible.

Like, you know, flying a plane around the world without a drop of fuel.

Bertrand Piccard set out to make that dream a reality.

The moment when this crazy idea first occurs to Piccard

takes us back to 1999,

when he's on the brink of achieving a different first.

Soaring over Egypt, he and his co-pilot are minutes from completing

the first non-stop, round the world balloon flight,

but their liquid propane fuel is nearly exhausted.

He began with 3.7 tons,

now only 10 gallons remain.

Piccard lands triumphantly,

but his close call ignites a vision.

A world in which man can fly without burning fossil fuels.

He vows to one day make another flight around the world

in a plane powered solely by the sun.

Aviation experts dismiss the idea as fantasy.

But Piccard devotes the next 15 years of his life to realize his dream.

His compulsion to push the limits runs in his blood.

In 1960, his father, Jacques, was the first

to plunge to the ocean's lowest point, Challenger Deep.

Bertrand's grandfather, Auguste, designed the submersible

that Jacques piloted.

Thirty years after gaining fame with his pioneering balloon flights

studying the Earth's stratosphere.

Like many explorers, Bertrand is competitive to the point of obsession.

He doesn't just want to live up to the family legacy,

he wants to take it to new heights.

To assist him, he's recruited former Swiss Air Force fighter pilot Andre Borschberg

and a team of crack engineers.

After years of effort, they've created a radical new aircraft

unlike any ever built.

The Solar Impulse.

The plane holds one pilot.

It has the wing span of a 747,

but weighs the same as a mid-sized car.

The skeleton is carbon fiber.

Three times lighter than paper.

Seventeen thousand solar cells,

each as thin as a human hair,

cover the wing and fuselage.

The energy flows to four 17-horsepower engines.

Their power output is comparable to the Wright brothers' first plane.

Spare energy is stored in four batteries.

They can be fully charged by the solar cells in six hours.

Allowing the plane to fly at night or under cloud cover.

The date is June 2, 2014.

Piccard's innovative aircraft prepares for its first test flight.

It's nearly as silent as a glider,

but it needs no powered plane to tow it aloft.

Its takeoff speed is a blistering 27 miles per hour.

Usain Bolt could give the Solar Impulse a run for its money.

On the ground at least.

At cruising altitude, its average speed increases to 45.

The Solar Impulse was a marvel of energy efficiency,

but there was a tradeoff.

The craft was so big and light

that it became unstable in anything but perfect weather.

A down draft or up draft could snap the plane in two.

It was no match for rain or turbulence

and banking more than 10 degrees

would throw it into a tailspin.

Despite the risks, Piccard sets out to make history

on March 25, 2015.

The starting point for Solar Impulse's

round the world flight is Abu Dhabi,

the capital of the United Arab Emirates.

The plan is to complete the 26,000 mile trek in 12 legs

with Piccard and Borschberg alternating as pilots.

Borschberg takes the first leg.

Mission control is 3,000 miles away in Monaco,

where meteorologists will monitor weather models to help steer the plane

through corridors of pristine weather.

Borschberg completes the first leg to Oman uneventfully.

But on the second leg en route to India,

Piccard runs into trouble.

[Josh] He can't keep the plane on its assigned heading,

but the issue vanishes as quickly as it appears

and Piccard lands safely.

Bad weather keeps Solar Impulse grounded for extended periods

over the next three months.

By day 111, Solar Impulse has reached Japan

and now faces its ultimate test.

A five day, 5,500 mile flight over the Pacific Ocean to Hawaii.

Borschberg is at the controls.

The dangers have never been higher.

If he hits foul weather, Solar Impulse doesn't have the speed to outrun it.

And over the open ocean, there's nowhere safe to land.

Two days out, Borschberg is faced with a critical problem.

Not with the weather, but with the aircraft.

Its batteries are overheating.

Temperatures approach 122 degrees.

If things don't take a turn for the better,

his only option is to ditch the fragile airplane

and hope help can arrive in time.

Exploration and snowboarding.

Two words you wouldn't necessarily expect to find in the same sentence.

But with the help of a grant from Discovery,

Dr. Connor M. Wood is changing that

with his Explorers Club expedition.

Connor's a PhD in wildlife ecology

and an experienced backcountry snowboarder.

Navigating California's Sierra Nevada mountains on snowboards,

he and his team are deploying listening devices

that will record the mating calls of an endangered species

that spends 30 weeks of every year buried under the Sierra snow,

the Yosemite toad.

For two weeks, just as the snow is melting,

the toads will sing their hearts out.

[toad calling]

Giving Dr. Wood a rare opportunity to gather data.

Enabling him to estimate their diminishing population.

Doing that will help him figure out why the toads' numbers are declining.

And, hopefully, discover a way to save this rare species.

Over the vast expanse of the Pacific,

the Solar Impulse and its overheating batteries

were in danger of crashing into oblivion,

along with Bertrand Piccard's dream and Andre Borschberg's life.

[Josh] Borschberg is at the halfway point

of his five day, 5,500 mile flight from Japan to Hawaii.

Flight level. We're at 5,000 feet.

[Josh] The plane's solar powered batteries continue to run hot

and the project's engineers at mission control in Monaco

can do nothing to cool them down.

Hawaii, the nearest landing site, is still 2,500 miles away.

Fears mount that the batteries are suffering so much abuse

that they can't hold out much longer.

But Solar Impulse powers through day three, then day four.

Getting only brief and restless sleep,

Andre is also running low on energy.

But both man and machine endure.

And on day five, Solar Impulse lands in O'ahu.

[all cheering]

Piccard's engineers determine that the overheating

was caused by excess insulation in the battery compartments.

They also discover that the batteries are damaged beyond repair.

They don't have enough spare cells to replace them.

The next flight, Hawaii to San Francisco,

must be pushed back nine months to April,

when the plane will be ready and the weather clear.

During the delay, engineers chill out

by creating a new battery cooling system.

A manually operated two way valve allows

cool air to enter the battery compartment and heat to be released.

The green light comes on April 21, 2016.

Piccard is at the helm.

His three day, 2,500 mile flight goes off without a hitch.

Over the next three months, Solar Impulse continues its epic trek

back towards its starting point in Abu Dhabi.

On July 26, 2016,

Piccard pilots the mission's historic final leg.

Crazy as it sounds, the plane has circled the globe

without a drop of fuel.

Pointing the way to a cleaner, more sustainable future.

And the heir to a family legacy of Explorers Club triumphs

has his own moment in the sun.

The Solar Impulse was tailor made

to help an Explorers Club member fulfill his dream.

A century ago, Roald Amundsen needed his own custom ride for one final shot at glory.

Amundsen had gained fame in 1911

by conquering the South Pole.

By 1926, he was obsessed with becoming the first man to reach both Poles.

But at 54, his dog sledding days were behind him.

He needed a more user-friendly ride.

[Josh] Hope arrives in the form of the era's new marvel, the airship.

Unlike balloons, airships can maneuver in any direction against the wind.

They can also stay airborne longer and carry heavier loads than airplanes.

Sponsored by fellow Explorers Club member Lincoln Ellsworth,

Amundsen purchases an airship from the Italian government called the N1.

The N stands for the last name of its acclaimed designer

and Explorers Club member, Umberto Nobile.

The deal comes with one string attached.

Hungry for glory of their own,

the Italians demand that Nobile will pilot the flight

and that five Italian airmen will join Amundsen's Norwegian crew.

Amundsen counters, rechristening his airship the Norge,

Norwegian for Norway.

The Norge is cutting edge for its time.

A hundred feet longer than a 747,

it's powered by three 230-horsepower propeller engines.

Under its fabric skin, 10 compartments

holding lighter than air hydrogen provide lift.

Sixteen men are aboard and one female,

Nobile's fox terrier, Titina.

On May 11, 1926,

Amundsen, Nobile and Ellsworth

take the Norge aloft at Norway's northern most point,

the island of Spitsbergen.

Seven hundred miles from the North Pole.

Amundsen's goal is not just to reach the Pole,

but continue on to Nome, Alaska.

Achieving the first flight across the Arctic Ocean.

The Norge cruises north at 3,000 feet at 62 miles per hour.

It's 11 degrees below zero,

but the skies are mercifully clear.

After 16 hours, the airship shadow falls on the North Pole.

It's 1:25 in the morning, but at this time of year,

the Pole is bathed in constant sunlight.

There were three nations collaborating on this expedition.

Norway, the United States and Italy.

Nobile had ordered Amundsen and Ellsworth to bring miniature flags

to keep down the weight and volume of the Norge's load.

But the proud Italian didn't let the space constraints hamper him.

The flag he packed for the journey

faced no limitations and dwarfed the others.

They couldn't plant their flags from the blimp,

so they did the next best thing.

They dropped them.

The remaining 1,700 miles of their flight to Alaska is a bumpy ride.

After 71 hours in the air,

they're forced down 63 miles short of their destination, Nome,

in the tiny Inuit village of Teller.

The Norge is dismantled by the crew.

Its parts end up everywhere from Seattle to Rome.

Much of its canvas stays in Teller

where the Inuits use it to insulate their houses.

In 1928, Nobile returns to the North Pole in another airship...

...but crashes.

An international search is launched for the survivors.

Amundsen joins the search.

He takes off from Norway in a biplane with five others.

Then, like Nobile, vanishes without a trace.

Tales of daring adventure after, after all, a mix of triumph and tragedy,

and of explorers inextricably linked with their mode of transportation.

Venturing into the unknown takes more than skill and courage.

Sometimes it requires a very special vehicle.

Custom tuned and ready for adventure.

And when you're travelling to places the Explorers Club members visit,

it's bound to be one wild ride.