♪ ♪ ♪ ♪ NARRATOR: 250 miles overhead, traveling 17,000 miles per hour... ...longer than a football field... ...the weight of a fully loaded jumbo jet, one of humankind's greatest feats of engineering.

The International Space Station.

KWATSI ALIBARUHO: It is, to date, the largest structure that we have built in space.

♪ ♪ And it's a peacetime structure.

(man speaking on radio) NARRATOR: The I.S.S.

is the longest continuously inhabited structure in space.

A one-of-a-kind laboratory.

WENDY LAWRENCE: It's a place where you could do scientific research in a very unique environment, that of microgravity.

♪ ♪ NARRATOR: But to reach this point required a construction project like no other.

Pieces built across the globe.

MICHAEL LÓPEZ-ALEGRÍA: They don't get put together until they're in space traveling at 17,000-plus miles per hour.

♪ ♪ NARRATOR: And it's the most dangerous place humans have ever attempted to live and survive.

CHRIS CASSIDY: In a space mission, the bad guy is the environment.

The environment is trying to kill you.

♪ ♪ NARRATOR: Outside the thin metal walls, a merciless vacuum, extreme temperatures, and a long, long way to terra firma.

LUCA PARMITANO: You are constantly at risk of dying for a multitude of reason.

♪ ♪ ROBERT CURBEAM: The systems to keep us alive there are working pretty much at the limit of physics.

♪ ♪ MIKE FINCKE: We're always asking ourselves, "What's the next worst failure?

What could go wrong next?"

We need to be able to handle those things when they happen, because in space, it will happen.

♪ ♪ NARRATOR: This is the extraordinary story of building the I.S.S., a perilous endeavor requiring ingenuity, vision, and, at times, nerves of steel.

♪ ♪ "Operation Space Station: High-Risk Build."

Right now, on "NOVA."

♪ ♪ ♪ ♪ NARRATOR: February 10, 2001.

250 miles above the surface of the Earth.

Astronauts Tom Jones and Robert "Beamer" Curbeam prepare for an extravehicular activity.

A spacewalk.

Just over two years into construction of the International Space Station, the structure is far from complete.

The space shuttle Atlantis has brought up a new component: the laboratory module Destiny.

Tom and Beamer need to connect vital life support systems to enable astronauts to live and work in the lab.

They are working in a lethally dangerous environment, and suddenly, something goes wrong.

♪ ♪ A coolant valve fails, spewing toxic ammonia crystals into the vacuum of space.

CURBEAM (over radio): I'm getting a lot of ice.

WOMAN: Mm-hmm.

CURBEAM: There's ammonia all over the place.

NARRATOR: Years of training mean Beamer remains calm, but it's a serious problem.

JONES (over radio): Need a hand, Beam?

CURBEAM: Yeah, I am going to need one.

BOB CASTLE: We don't know exactly what the leak rate was, but I knew we didn't have long.

NARRATOR: The next few moments will determine the fate of a $150 billion multinational space endeavor... JONES (over radio): Hey, Houston, Atlantis.

Do you copy?

We're having a hard time with the leak.

NARRATOR: ...shape the future of human spaceflight... MAN (over radio): Stand by, uh, we're discussing, uh, next steps.

NARRATOR: ...and, critically, determine whether the astronauts live or die.

♪ ♪ Constructing a high-tech science laboratory in the harsh, unforgiving environment of space, hurtling around the Earth at 17,000 miles per hour, might seem like a crazy thing to do.

But a structure as big and complex as the International Space Station could never be launched fully assembled.

♪ ♪ It meant a massive engineering challenge: connecting modules in low Earth orbit by hand.

♪ ♪ It's the culmination of years of planning that began shortly after the Cold War space race... ...when East and West space programs had competed to demonstrate technological superiority.

(device beeping, man talking on radio) ALIBARUHO: So many of the earlier programs were fueled not just by science, but they were fueled as much by geopolitical competition.

NARRATOR: In the end, the Soviets lose the moon race, so they pivot toward something more enduring: a long-term human presence in space.

Setting out to master living and working in orbit, in 1986, they launch Mir, the world's first modular space station.

(crowd shouting and cheering) But by the early '90s, the chaotic collapse of the Soviet Union had dealt a serious blow to those ambitions.

(crowd chanting) LAWRENCE: There was a concern at the time that some of the Russian scientists who had expertise in the area of developing nuclear weapons might take that expertise to other countries.

(crowd shouting) NARRATOR: To avoid a dangerous new arms race, America has a radical idea to keep Russian scientists engaged in peaceful work: a collaboration with huge ambition.

LAWRENCE: The Soviet Union had been our enemies.

We had been trained to go to war against them.

But now, suddenly, new tasking.

They're not enemies anymore, they're partners.

(camera shutters clicking) NARRATOR: In 1993, the United States, Russia, Japan, Canada, and several European nations agree to merge their human spaceflight programs into a collective effort... ...the International Space Station.

ALIBARUHO: It's huge, and it's got so much technology, and it's got so many moving parts.

LÓPEZ-ALEGRÍA: There are modules being built all over the world, in different countries with different languages, different alphabets, different measuring systems.

♪ ♪ NARRATOR: A Russian-designed life support module based on Mir will form the anchor.

Over time, it will be extended with 15 more modules.

MIKE FINCKE: We had to figure out how to put Soviet designs with these American, Japanese, European design together, and then we couldn't even test them together on the ground.

LÓPEZ-ALEGRÍA: They don't get put together until they're in space, traveling at 17,000-plus miles per hour.

MIKE FINCKE: And they had to work the first time, and that only works on these science fiction shows, not really in real engineering.

LAWRENCE: Building and assembling things that have been built in numerous countries around the world, sometimes using different measurement systems, what could go wrong?

(laughs) NARRATOR: 15 nations collaborate across a complex construction schedule.

The ambition for this orbiting station is unprecedented.

LAWRENCE: We very quickly realized, we don't speak each other's languages very well, but we do have a language in common: the language of spaceflight.

♪ ♪ NARRATOR: It will require more than 40 missions to piece together its many modules.

Exterior trusses to provide structural support.

Radiator panels to dissipate heat.

And around an acre of solar panels to power the station.

All of which must be carefully assembled in microgravity by astronauts working in one of the harshest environments known to humankind.

ANNOUNCER: Main engines start.

Six engines up and running.

And liftoff.

The International Space Station is underway.

NARRATOR: The bold venture kicks off on November 20, 1998, from Baikonur Cosmodrome in Kazakhstan.

A Proton-K rocket carries the Russian component Zarya, meaning sunrise, into orbit.

ANNOUNCER: And liftoff of the space shuttle Endeavour.

NARRATOR: 16 days later, the U.S.

Unity module joins Zarya.

(man speaking Russian on radio) NARRATOR: But it's not until 20 months later, with the arrival of Zvezda, which means star, that life support systems and living quarters are finally added.

On November 2, 2000, the I.S.S.

welcomes its first residents... MAN: The first crew of the International Space Station has reached their home.

NARRATOR: ...NASA astronaut Bill Shepherd and cosmonauts Yuri Gidzenko and Sergei Krikalev, marking the beginning of continuous habitation onboard the orbiting outpost.

Three spacewalks the following month configure power systems and add a framework of trusses to support the station's solar arrays and radiators.

But things are only just getting started.

MAN: Great news, Mario-- go for docking.

NARRATOR: The space station's early success is followed by a sobering truth: building a home in orbit is as dangerous as it is ambitious.

And with every new addition, the risks grow.

♪ ♪ Its next module, Destiny, an American-built laboratory, will lay the foundation for U.S.

scientific research aboard the station.

Its installation falls to two first-time spacewalkers, TOPGUN pilot Robert "Beamer" Curbeam and Tom Jones.

MAN (over radio): The thermal cover is down, so you can go ahead and egress.

JONES: I think it's a great day to go and do a spacewalk.

So, uh, Beamer, when you're ready... CURBEAM (voiceover): When you're first starting and you're going out the hatch, your first thought is, "I want to make sure that I get this right, that I do everything right."

NARRATOR: While their crewmate Marsha Ivins uses the shuttle's robotic arm to maneuver the 16-ton Destiny module into position, the spacewalking pair will assist with its attachment to Unity and integration with the rest of the station.

This is when the game starts, and you've got to be serious about it.

It's time to go to work.

♪ ♪ JONES (over radio): Beamer, K bolts are complete.

You have a go to head on to the lab.

CURBEAM: Roger that.

NARRATOR: One of their primary tasks is to connect Destiny's coolant lines to the space station's cooling system to regulate the onboard temperature.

Heat doesn't dissipate in space the way it would here.

It just stays there.

And if it just stays there, you're gonna probably overheat whatever you have.

♪ ♪ NARRATOR: Every 45 minutes, as the I.S.S.

orbits the planet, its exterior is exposed to direct sunlight, raising its temperature to a blistering 250 degrees Fahrenheit.

Then, as the station slips into the Earth's shadow, the temperature plummets 500 degrees to minus 250.

♪ ♪ To combat these wild temperature extremes, the space station's cooling system uses loops of mechanically pumped fluid.

(liquid flowing) Inside U.S.

modules, circulating water transfers heat to an external loop filled with liquid ammonia.

Which then passes through three waffle-shaped panels on the station's exterior to radiate the heat into space.

It's this pressurized ammonia loop that Robert Curbeam needs to connect to Destiny.

JONES (over radio): Beamer, as soon as, uh, you get, uh, on the lab, you're going to be removing the four fluid caps, checking for ammonia crystals.

CURBEAM: Okay, great.

NARRATOR: The pressurized system keeps the ammonia in liquid form.

Any crystals forming around pipes or connections are evidence of leaks.

At Johnson Space Center in Houston, lead flight director Bob Castle keeps watch over Tom and Beamer.

CASTLE: When he's got the suit on, Bob's completely fine.

But one or two breaths of pure ammonia and you will very likely die within minutes.

Everyone watches the systems on the station and on the shuttle to make sure that everything is still working the way it should be.

NARRATOR: While the team knows what's expected of them, in space, any number of things can go wrong.

CURBEAM (over radio): Hold on.

I've got a little bit of ammonia coming out of there.

Some ice crystals.

(voiceover): When I actually removed the hose, I saw a lot more crystals growing all around the two orifices.

And I knew I had a problem.

(over radio): I'm getting a lot of ice.

WOMAN: Mm-hmm.

CURBEAM: There's ammonia all over the place.

NARRATOR: An automatic shut-off valve has failed.

JONES (over radio): Need a hand, Beam?

CURBEAM: Yeah, I am going to need one.

I felt like I was working in a blizzard, because there was so much ammonia coming out.

CASTLE: Beamer immediately reported, "Oh, it's spewing all over the place."

And then my counterpart Andy Algate said, "We see the accumulator going down."

JONES (over radio): Hey, Houston, Atlantis-- do you copy?

We're having a hard time with the leak.

MAN: And stand by, uh, we're discussing, uh, next steps that we need to do.

NARRATOR: Without its coolant, the Destiny module would be uninhabitable, potentially jeopardizing the entire mission of the space station.

ALIBARUHO: That heat must be ejected from the spacecraft eventually, or else you will burn up the spacecraft and the people inside of it.

♪ ♪ CASTLE: We don't know exactly what the leak rate was, but I knew we didn't have long.

NARRATOR: Beamer needs to find the shut-off valve upstream and turn it off.

CURBEAM: I did find very quickly that it was going to be a lot harder than I thought.

NARRATOR: The valve is stuck.

When I tried to close it, it didn't close.

I tried again-- it didn't close.

They said it was gonna be about 25 pounds of force.

I can tell you-- I've spent a lot of time in the gym-- it was not 25 pounds of force.

It was much, much more.

I tried to close it again.

And finally, after four or five tries, I got to close it.

JONES (over radio): You just pulled the bail?

CURBEAM: Yes, and that stopped the leak.

JONES: Very good, Beam.

Good idea.

NARRATOR: Mission Control breathes a sigh of relief.

With the leak stopped, the astronauts can connect Destiny's cooling lines to the station.

(radio static hisses) The I.S.S.

is safe.

JONES (on radio): What's next?

NARRATOR: But now Beamer is covered in toxic ammonia.

CASTLE: Sooner or later, he's gotta get out of the suit.

And sooner or later, he's gotta come back in the cabin and, and expose the outside of the suit to his crewmates.

Who are not interested in dying horrible deaths.

CURBEAM: I thought to myself, "What are they gonna do with me?"

You know, now that I have this toxin on the outside of the suit.

I knew that the procedure to go back into the spacecraft was going to change, I just didn't know how.

NARRATOR: Tom wipes the toxic crystals off his crewmate's space suit using a brush in their E.V.A.

kit.

CURBEAM (over radio): Concentrate on the right side.

That would be the side that got sprayed the worst.

JONES: Okay.

NARRATOR: But before he can reenter the space station, Beamer must burn the last remaining traces of ammonia off his suit in the baking heat of the sun.

(boy singing in Latin) CURBEAM: The amazing thing about the procedure to help me decontaminate the outside of my space suit was that it gave me the opportunity to just sit in the sun and watch the Earth go by for 45 minutes.

(boy singing) Which was awesome, and it was incredible-- I loved it.

And you see the Gobi Desert, you see all the different parts of Asia, you see the Himalayas to the south, you see a little bit of cloud layer there.

(boy singing) And you just bask in it.

(boy and chorus singing softly) (singing ends) NARRATOR: Over the next four days, undeterred by the experience, Beamer clocks up 12 more hours of spacewalks to ensure Destiny is safely attached.

JENNIFER BUCHLI: The Destiny module is what we refer to as the U.S.

Lab.

It's really our core lab capability.

So, we have freezers, we have different payload facilities to conduct science.

This is sort of the heart of the U.S.

segment.

NARRATOR: Destiny is designed for microgravity research in a variety of fields, from life sciences to materials science and more.

Microgravity is not zero gravity.

The Earth still exerts a pull on the I.S.S.

This pull is what keeps the station in orbit, circling the Earth in constant free fall.

Creating an environment that allows scientists to observe phenomena that cannot be replicated on Earth.

But the instruments on board are also designed to put our own planet under the microscope.

BUCHLI: We have a really unique capability to look down on Earth.

Our orbital path takes us around 90% of the Earth's inhabited surfaces.

So, this is what allows us, over time, to see how the Earth is changing.

♪ ♪ How weather patterns are changing and affecting our environment.

How the forest canopy is changing and the carbon cycle of Earth.

You have these instruments all on the same platform going over the same area.

And so, you get a global picture of the health of what's happening to our planet.

NARRATOR: The new Destiny module not only provides a platform for scientific research, it also increases the habitable volume of the space station by over 40%.

A welcome addition for those building and living on the I.S.S.

After the installation of the Destiny lab module, it was fast and furious.

♪ ♪ NARRATOR: Over the next 21 months, eight successful missions add the Canadian Space Agency's Canadarm 2, a 57-foot-long robotic arm; Quest, which will serve as the primary airlock for spacewalks; the S0 truss, forming the station's backbone; and radiator trusses to help dissipate heat.

All of this made possible by an iconic spacecraft.

♪ ♪ ALIBARUHO: The I.S.S.

could not have been built without the space shuttle.

Full stop.

NARRATOR: But in February 2003, after 16 successful shuttle missions to the space station, disaster strikes.

MAN (over radio): Columbia, Houston-- comm check.

Columbia, Houston-- U.H.F.

comm check.

♪ ♪ ANNOUNCER: Flight controllers here in Mission Control have declared a contingency, as communications was lost with the space shuttle Columbia during its descent from orbit en route to landing at the Kennedy Space Center in Florida.

NARRATOR: After more than two weeks conducting experiments in orbit, space shuttle Columbia disintegrates on reentry, killing all seven crew members.

CURBEAM: Those are my friends, you know?

I knew them personally.

I knew them professionally.

Some of them were in my class.

I miss them every day.

(man speaking on radio) CURBEAM: It caused us to lose seven very incredible people.

And believe me, they were incredible.

(woman speaking on radio) MAN (over radio): This is amazing.

It's really getting, uh, it's really bright out there.

MAN: Yup.

Yeah, you definitely don't want to be outside now.

CURBEAM: The Columbia disaster, we later found out, was due to foam shedding off of the external tank.

NARRATOR: During launch, a falling piece of insulating foam struck the shuttle's left wing, damaging the thermal protection tiles designed to shield it from extreme heat during reentry.

And what that did was, that allowed very hot plasma to get inside of the wing and basically melt the inner structure of the spacecraft.

NARRATOR: Test simulations back on the ground reveal the devastating impact of this seemingly small, briefcase-sized chunk of foam traveling at high speed.

All shuttles are grounded while a full investigation is carried out, effectively halting construction of the I.S.S.

The only way to reach the orbiting outpost is via Russian Soyuz capsules launched from Baikonur, Kazakhstan.

To conserve vital supplies like oxygen and water on the I.S.S., the crew is reduced from three to just two.

Commander Gennady Padalka from Russia and flight engineer Mike Fincke from the United States form the two-person crew of Expedition 9.

MIKE FINCKE: I grew up in Pittsburgh, Pennsylvania.

It's not a super-wealthy city, but we have all kinds of resources for education.

So, I went to the planetarium, I went to the library, I learned, and I knew that I wanted to become an astronaut.

I met my wife at Johnson Space Center, here at NASA, and like men and women do, we fell in love and we started a family, and I still hadn't flown yet.

And then the opportunity came up.

(people talking in background) RENITA FINCKE: When I married him, I knew that he wanted to go into space.

And so, I was always going to support his dream, even though it was going to disrupt our planning for life on the ground.

NARRATOR: Mike spent eight years training before this mission, a mission scheduled to last six months.

It's been his ultimate ambition, but one that involves personal sacrifice for himself and his wife, Renita.

(baby crying, people talking over radio) RENITA FINCKE (over radio): It's a girl!

Boy, she sounds upset.

RENITA FINCKE: Oh, she's got some lungs on her.

Well, we heard her all the way up here.

RENITA FINCKE: It was about two months into his six-month mission that we had the baby.

NARRATOR: For the first time in history, an American astronaut is in space when his child is born.

It will be four months before Mike returns to Earth to hold his daughter for the first time.

During his absence, she will grow.

But Mike's body will also undergo changes.

While his new baby is developing muscles quickly, Mike's muscles will deteriorate because of microgravity.

Renita and fellow biomedical engineers at Johnson Space Center research ways to overcome this challenge.

RENITA FINCKE: As you're up there longer and using your muscles less, you're going to need to find ways to counteract all the changes that are happening.

NARRATOR: Without exercise, astronauts' muscle mass can fall by up to 50% over a six-month mission.

RENITA FINCKE: We provide crew members with aerobic exercise, as well as resistance exercise.

So, we're able to build muscle as we're exercising, so that we can make sure that everybody is fit for doing what their duties are in space.

NARRATOR: In their role as the station's caretakers, the crew must occasionally carry out physically exhausting work on the outside of the space station.

For Mike and Gennady, this poses an additional challenge, since, for safety, spacewalks require two crew members.

This means leaving the I.S.S.

completely unoccupied during the operation.

MIKE FINCKE: One of our planned spacewalks was to travel to the very end of the space station, which is the very aft end of Zvezda.

NARRATOR: The plan is to install equipment in preparation for the arrival of a cargo vehicle from the European Space Agency.

The two spacewalkers undertake a tightly choreographed procedure.

But no matter how much they plan and practice, in space, there's always room for the unexpected.

MIKE FINCKE: We're always asking ourselves, "What's the next worst failure?

What could go wrong next?"

We need to be able to handle those kind of things when they happen, because in space, it will happen.

♪ ♪ NARRATOR: Two hours into the spacewalk, it does.

♪ ♪ Gennady and I were just working away, doing what we needed to do.

♪ ♪ NARRATOR: But as they worked, they were inadvertently causing a problem.

♪ ♪ MIKE FINCKE: Our space suits were providing a very little bit of momentum towards pushing the space station.

♪ ♪ So, we were actually pushing it to go out of orientation.

(radio crackling) NARRATOR: The two astronauts working at one end of the station have caused the entire structure to tip.

How could this happen?

♪ ♪ The stability of the I.S.S.

and its orientation, or attitude, should be maintained through the use of four gyroscopes.

A gyroscope is a wheel or disc spinning on its axis.

The heavier the disc and the faster it spins, the more stable the gyroscope.

That's because a spinning disc creates momentum perpendicular to the plane of rotation, which makes it resist tipping over.

Embedded in the I.S.S.

are four huge gyroscopes pointed in different directions, with 220-pound wheels spinning at over 100 revolutions a second, usually enough to keep the whole station from rotating in any direction.

The space station constantly experiences forces, from solar winds or from the Earth's gravity.

If left unchecked, they would cause the space station to tilt or tumble.

The gyros counteract those movements.

But they can only compensate so much.

And they're already close to their limit when Mike and Gennady push the station out of alignment.

So, the space station went into a mode that said, "Look, I can't control myself anymore.

"I'm not out of control, but I'm gonna go into" what we call free drift.

So, the space station just started to drift and point up, point up.

And there we are, and we looked up, and we were in a very unusual attitude, and there was, planet Earth was zooming below.

♪ ♪ NARRATOR: Holding a desired orientation in space is crucial to help keep the station's solar arrays locked onto the sun.

This isn't just about efficiency.

It's about survival.

♪ ♪ MIKE FINCKE: We're completely off the grid, and in order to keep it powered, we're collecting as much solar energy as we can when we're on the light side of the planet.

NARRATOR: When the station slips into darkness, for 45 minutes every orbit, solar-charged batteries become crucial for powering critical life-support systems.

♪ ♪ With the solar panels unable to charge the I.S.S.

's batteries, to conserve power, Mission Control turns off non-essential systems.

♪ ♪ The only way to get the space station back into the correct attitude is with the use of thrusters... ...located exactly where Mike and Gennady are working.

(radio crackling) But there's a new problem.

Gennady and I were working and talking to our, our Russian colleagues on the ground, and all of a sudden, it became very quiet.

(radio crackling, transmission breaking up) NARRATOR: The power-saving protocols have inadvertently cut off all communication between the astronauts and Ground Control.

♪ ♪ (radio crackling) There was no one else to give us instructions.

And Gennady and I said, "Well, what are we going to do?"

NARRATOR: Mission Control has a terrible dilemma.

To restore attitude, they must activate the thrusters.

But with no way to communicate with Gennady and Mike, flight controllers have no idea whether their astronauts are in the firing line.

ALIBARUHO: If a crew member was going to be moving by them, that crew member would be blasted with hot gas or contaminated because the gas that the thrusters used was extremely toxic, extremely, extremely toxic-- deadly.

MIKE FINCKE: We don't want to be anywhere near that action.

If we were there in our space suits when the thrusters went off, we would've experienced the, the thrill of being melted.

NARRATOR: Suspended hundreds of miles above Earth, the two spacewalkers cling to an empty, drifting space station, unsure what to do next.

♪ ♪ As the planet turns slowly beneath them, Mike scans the horizon and spots something that provides a spark of hope against the void.

MIKE FINCKE: We saw where we were going.

We were headed over Greece, and headed north and east, so, we knew we were going to be over what we call a Russian ground site.

(static crackling) NARRATOR: After several minutes of silence... (man speaking Russian on radio) NARRATOR: ...success.

Roscosmos manages to reestablish backup communications.

MIKE FINCKE: We heard Moscow.

They said, "Hey, guys, you know, "the space station is not in good control.

"We need to reestablish control.

"We highly suggest-- in fact, we tell you "to move away from those thrusters.

It's not in your interest to stay there."

♪ ♪ So, we had to go hand-over-hand to move away from the thrusters to be safe from any plume damage or any heat that was being produced.

♪ ♪ NARRATOR: With the pair clear, the thrusters are fired.

♪ ♪ Attitude reestablished.

♪ ♪ MIKE FINCKE: It was a good view.

We got to look at planet Earth as we regained orientation from being pitched up all the way being pitched down.

We got the chance to just sit there and wait as the station regained its orientation.

Then they said, "Okay, we're back to normal work.

"Get back out there and finish your job.

Stop slacking."

(laughs) NARRATOR: On October 23, 2004, after traveling more than 78 million miles aboard the International Space Station, Expedition 9 hands over command of the outpost to the crew of Expedition 10 and makes preparations to return to Earth.

(talking indistinctly) By the end of the mission, I was kind of missing things back on planet Earth.

I was missing my family-- it got bigger while I was gone, we had a baby.

And I knew I had to go back home.

♪ ♪ NARRATOR: For almost two years, I.S.S.

has been in stasis.

With no way of getting new modules up, its completion relies on one crucial factor: NASA's return to flight.

(birds chirping) (helicopter blades whirring) Less than a year after Mike's return to Earth, following an overhaul of NASA's safety practices, the space shuttle program is reinstated, with the first assignment a mission to the I.S.S.

(crowd cheering) On July 26, 2005, the crew of Discovery prepares for STS-114.

(on radio): Okay, Eileen, our long wait may be over.

So, on behalf of the many millions of people who believe so deeply in what we do, good luck, Godspeed, and have a little fun up there.

ZEBULON SCOVILLE: STS-114 was our return to flight after the Columbia tragedy.

We had made mistakes, and we were ready to fly again with the solutions to be able to show that we belonged in space, and we could keep going.

MAN (on radio): Okay, here we go.

ALIBARUHO: The fact is, we had to have the space shuttle to finish building the International Space Station.

NARRATOR: For mission specialist Wendy Lawrence, STS-114 will be her first visit to the I.S.S.

and fourth and final venture into space.

(man speaking on radio) NARRATOR: The flight will carry supplies to the station and prove that the shuttle program is safe enough to continue.

(man speaking indistinctly on radio) We're ready to go.

ANNOUNCER: T-minus ten seconds.

Go for main engines start.

Seven, six, five-- three engines up and burning.

Three... ♪ ♪ LAWRENCE: Main engines lit off, solid rocket boosters lit off.

You literally feel like you're in your slingshot.

You know when you're leaving the launch pad.

♪ ♪ NARRATOR: In the wake of the Columbia disaster, NASA implements a series of new safety protocols: a redesign of the shuttle's external tank to reduce the potential for foam shedding; installation of multiple cameras to cover the launch and check for any anomalies; and an enhanced in-orbit inspection of the shuttle using new cameras and sensors.

♪ ♪ EILEEN COLLINS (over radio): Houston, Discovery.

We have a good plus-X maneuver.

NARRATOR: Discovery reaches orbit, apparently without issue.

LAWRENCE: Flight day two for us was the initial on-orbit inspection.

ALIBARUHO: We used the shuttle robotic arm and the new sensor package to examine the structural integrity of the thermal protection system to see if there was any damage that may have occurred.

NARRATOR: Meanwhile, on the ground, analysts scour footage of the launch and discover several troubling incidents.

♪ ♪ A large bird hitting the shuttle's fuel tank.

♪ ♪ A small piece of thermal tile detaching.

And a large section of foam falling from the external tank.

Could history be repeating itself?

We looked at the side of the vehicle, we looked around our nose cap area, as well.

Didn't see any damage, so we were, like, "Okay.

"Not great to hear that foam came off.

Doesn't look like it hit a critical area."

NARRATOR: The inspection isn't conclusive, though.

They need a closer look.

And to do that, they'll need the help of the I.S.S.

crew and a shuttle maneuver never before attempted.

LAWRENCE: We came to 600 feet below the station.

We basically did a back flip.

NARRATOR: Inside Discovery, commander Eileen Collins initiates the maneuver to pitch the shuttle 360 degrees.

The shuttle was performing what we called the rendezvous pitch maneuver to allow the I.S.S.

crew to take scores of high-resolution photographs.

NARRATOR: The crew onboard the I.S.S.

have a window of just 93 seconds, when the underside is in the sun, to take high-resolution images of the shuttle's heat shield.

SCOVILLE: Those were then downlinked to engineers to be able to look for any damage or misconfiguration of those tiles.

LAWRENCE: As we came out of our back flip, we got to watch space station come up over the tail of our orbiter, Discovery.

And I called that our "Star Wars" moment, because it was just so cool.

It was, like, here's this big spacecraft right next to mine, rising up over the tail.

NARRATOR: While the shuttle crew unloads supplies onto the station, engineers on the ground pore over the images of the shuttle, searching for anything out of the ordinary.

♪ ♪ (camera shutter clicks) SCOVILLE: Engineers identified that there was a small piece of gap filler.

What this is is a piece of fabric that is meant to fill spaces in between the tiles on the orbiter.

This gap filler had actually stuck up into the surrounding area above the outer mold line of the orbiter.

So, there were two of these gap fillers sticking out from in between the tiles on the underside of Discovery.

Something they'd never seen before.

SCOVILLE: The problem with this is, as this reenters the Earth's atmosphere, this could actually cause the smooth flow to hit that gap filler, and then become turbulent, which creates downstream heating and puts extra heat stress on the orbiter tiles.

LAWRENCE: The flow might come back together in a way where it now becomes almost like a blowtorch, and it might burn through one of the thermal protection system tiles.

NARRATOR: This could turn the shuttle into a fireball.

The gap fillers protect the tiles from vibrations on launch, but are not needed for reentry.

LAWRENCE: The decision was made that these two gap fillers really need to be removed before we come back for landing.

MAN (on radio): ...one hour and ten minutes, the I.M.U.

aligned... LAWRENCE: The underside of the space shuttle orbiter was not designed to have astronauts there.

There were no handholds whatsoever.

Really, the only way for us to have done the gap filler removal was to have a crew member on the end of a robotic arm.

(man speaking indistinctly on radio) LAWRENCE: I got to fly the station robotic arm for that E.V.A.

Steve Robinson was on the end of the arm, and I flew him to where no astronaut had ever been before: on the underside of the space shuttle orbiter, beneath the belly.

NARRATOR: Once Steve locates the gap fillers, he must remove them.

ROBINSON (over radio): My brakes set?

MAN: The brakes are on, you're a go.

♪ ♪ MAN: Nicely done, Steve.

♪ ♪ ROBINSON: Okay, that came out very easily.

Probably even less force.

It looks like this big patient is cured.

MAN: Copy that.

NARRATOR: After a two-week, 5.8-million-mile journey in space, on August 9, 2005, Discovery sets off for home.

LAWRENCE (over radio): ...circuit breakers coming back in.

Okay, we did see that... NARRATOR: Only now will the team find out if the fix worked.

ANNOUNCER: Discovery's altitude now 72 miles.

Speed 17,000 miles per hour.

And now all of a sudden, you're coming back to gravity, something you've spent virtually your entire life in, and it's not pleasant.

NARRATOR: The shuttle's immense speed as it reenters Earth's atmosphere superheats the air, tearing molecules apart, creating a plasma.

Temperatures outside soar to a blistering 3,000 degrees Fahrenheit.

ANNOUNCER: As Discovery descends into the atmosphere, it will perform a series of four banks to dissipate speed.

NARRATOR: Well past the point of no return, all the seven crew members can do now is trust that their inspection was thorough and the repair is sufficient.

MAN (over radio): Discovery, Houston.

Energy, ground track, and nav are all go.

Your touchdown is 2600 at 205.

COLLINS: And Discovery copies, thank you.

♪ ♪ Houston, Discovery has the runway in sight.

MAN: Copy runway.

♪ ♪ ANNOUNCER: Main gear touchdown.

Nose gear touchdown.

And Discovery is home.

SCOVILLE: Let me tell you, when Discovery touched down on the runway, we knew that it had been a flawless reentry profile.

There was a sense of both relief and accomplishment of all the teams that had shown that we could again fly the space shuttle safely.

♪ ♪ NARRATOR: With the shuttle program reinstated, construction of the I.S.S.

can now resume.

♪ ♪ Over the next six years, 19 shuttle missions, and 94 spacewalks, numerous parts and modules are bolted onto the International Space Station.

Among them Columbus, a cutting-edge science laboratory from Europe.

The Japanese Kibo laboratory, with an exterior facility to conduct Earth observation, communication, and materials science research.

The Poisk Mini-Research Module 2, Russia's first major addition since 2001.

And the Tranquility module, with its now world-famous observation cupola.

♪ ♪ In May 2011, the I.S.S.

is finally complete, a $150 billion space laboratory.

♪ ♪ LAWRENCE: It was a milestone many, many, many people had been working to to achieve its original goal, which, to be a place where you could do scientific research in a very unique environment, that of microgravity.

MIKE FINCKE: We've opened some of the secrets of the universe, all the way from science and physics to how to work together as humans.

How to plan and overcome difficulties together.

♪ ♪ LAWRENCE: When we humans really want to, we can take that proverbial sword and we can truly beat it into a plowshare.

We can do some pretty remarkable things together, peacefully, for the benefit of all humankind.

♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪