SCOTT KELLY: You know, being in space for a year... it's a really long time.

[ticking] I often would tell myself, "Hey, no matter how long I think I've been up here, eventually I won't be."

[laughing] But this study with my brother and I is really important right now because it will help us get to Mars someday.

JESSICA MEIR: NASA is very much on what we call a journey to Mars.

JEFFREY KLUGER: The next generation of astronauts will be the Apollo generation of the 21st century.

JESSICA: Ooh, there it goes!

[splash] VICTOR GLOVER: If we're going to send someone on a mission that could be 500 days, then we need to know that when you get back, you're going to be healthy.

JESSICA: The next question, I think, as a human species, is what is the next step toward furthering our presence in the solar system in our universe?

♪ SCOTT: I think that's our future: learning to live and work in space, on the Moon, Mars, and someday possibly beyond our solar system.

♪ ♪ SCOTT KELLY: I got Misha behind me.

He's waking up, too.

[laughs] MIKHAIL KORNIENKO: Early morning.

[laughing] SCOTT: A year is a long time.

It's a long time to be in space.

It is not an easy place to live for that period of time.

I'm done.

[laughs] MILES O'BRIEN: Going the distance to a year is significant, because we're talking about, you know, time frames that would get you to Mars.

SCOTT: I even said to Misha, about halfway through the flight, "Hey, if we were going to Mars, we'd be arriving right now."

That's good.

MARK KELLY: My brother went in there knowing full well, hey, this is a big challenge.

You know, where he said this has been an incredible experience... SCOTT: Oh, man.

MARK: I think he was also ready for the experience to come to an end.

♪ JEFFREY KLUGER: Returning from space under a parachute has never been a precise business.

You need the largest, emptiest expanse of nothing to aim for.

For the Americans, this has always meant the Atlantic and Pacific Oceans.

For the Russians, it means the vast, desolate expanse of Kazakhstan.

[engine rumbling] ♪ SCOTT: I would like to relinquish command of the International Space Station to my friend and colleague here, Tim Kopra.

NASA REPORTER: On the Soyuz craft, Sergey Volkov sits at the center seat.

To his left, NASA's Scott Kelly, and then that leaves in the right seat Mikhail Kornienko.

[woman speaking Russian] The one-year crew members will have completed over 143 million miles around our globe.

Coincidentally, a journey to Mars would be right around 140 million miles.

WOMAN ON RADIO: 3, 2, 1.

[men speaking Russian] WOMAN OVER RADIO: CC7 is illuminated.

Copy.

[toasting in Russian] [laughing] [man speaking Russian on radio] ♪ AMIKO KAUDERER: You're confident.

We're gonna land, and it's gonna be great.

But you know that there's always things that we just don't really talk about, but they're back there.

They're, they're back in your mind.

There is a time the Soyuz capsule is coming back through the atmosphere that we lose comm, and no one knows where the capsule is exactly.

SCOTT: There's fire all around your head.

It gets hot in there, and it's crazy.

NASA REPORTER: All of the search and recovery helicopters are on their way to the landing zone.

[beeping] SCOTT: Right before the chute opens is when you start really hearing the air outside, really hitting the atmosphere hard.

When it opens, it definitely gets your attention.

[rumbling] Feels like you've kind of lost control.

[rumbling] [clattering] [radio chatter] NASA REPORTER: The SAR teams do have visual of the capsule, Soyuz craft descending under parachutes.

♪ Search and recovery forces moving in on the Russian MI-8 helicopters, as well as all-terrain vehicles.

[applause and cheering] NASA REPORTER: All the recovery personnel from NASA and Roscosmos converging out there in Kazakhstan around the capsule.

♪ [men speaking Russian] [breathing deeply] SCOTT: The crisp coldness of the air is quite refreshing.

Not only fresh, but not space station smell to it.

[laughs] KLUGER: The 340 days Scott Kelly and Misha Kornienko spent in space is less than 50% of what an even brief mission to Mars would be.

[man speaking Russian] The one-year mission will not end with Scott and Misha Kornienko's landing.

They will be studied closely and in depth for the next year.

SCOTT: Air is great.

I don't know why you guys are all bundled up.

KLUGER: That's knowledge that will enable us to protect the next generation of people who will be the generation that will return to deep space.

♪ SCOTT: When I became an astronaut, we were the class that was gonna go to Mars.

I never actually thought that was a realistic thing.

But the most recent astronaut class could be.

I hope they are.

♪ ASTRONAUT: Right here?

♪ PHOTOGRAPHER: All right, everybody move closer together.

♪ Everybody smile for me.

[laughs] ♪ JESSICA MEIR: I remember the first time that we put on this blue flight suit, and that's kind of this iconic image that I'd always seen growing up.

You take that step back and think, "I'm actually an astronaut."

Uh, the bladder's kind of catching behind my heel there.

MAN: You want to pull it back out and start again?

JESSICA: Uh, no, I think it's gonna-- They might call us astronauts now, but we haven't even gone to space yet.

MAN: You slide in there easily.

That's awesome.

JESSICA: The astronaut candidate training period takes about two years.

Yeah, then they actually stop calling you an astronaut candidate, and they call you a real astronaut.

MAN: Lights on one.

JESSICA: They don't really want to flatter us with that title when we first get here.

We have to kind of prove ourselves first.

♪ The NBL is the Neutral Buoyancy Lab.

And that is what NASA really came up with as the closest approximation toward how we can train for spacewalks.

I am in position.

MAN: You guys are fast.

[Jessica laughs] And, Tom, you're headed over to ESP2.

TOM: OK. MAN: And, Jessica, you're headed over the top.

JESSICA: OK, copy.

Thank you.

♪ [splash] ♪ KLUGER: We have been looking for and training astronauts about since 1957, 1958.

MILES O'BRIEN: The space program began with top guns.

Almost all of them had several sorties in combat scenarios, flying fast jets, flying them higher.

KLUGER: What you needed were people who knew more than anything else about flying unproven vehicles in unexplored places.

[explosion] [crash] ♪ O'BRIEN: This was in the heat of the Cold War.

This was, uh, you know, Sputnik had launched, and the U.S. was in a frenzy to catch up.

VICTOR GLOVER: The time they were selected in, socially, in this country, was very different.

They were all guys, and they were all about the same age.

[applause] You may not have had a whole lot of folks like me that even had an opportunity to apply.

ANNOUNCER: 3, 2, 1.

[indistinct announcement] ASTRONAUT: Roger.

The clock is operating.

We're underway.

[crackling] JESSICA: Oh, there it goes.

♪ VICTOR: The most overwhelming feeling when I think about that legacy is just how awesome it is to be a part of it, you know.

O'BRIEN: Compare the Mercury 7 to Class 21.

I mean, really.

VICTOR: There is a reason that they picked us.

And I think personality and the psychological screening has obviously become more important.

[engine starts] The T-38s enable us to do what we call spaceflight readiness training.

VICTOR ON RADIO: Confirm he said taxi to 1-7?

JESSICA: He did say 1-7.

VICTOR: OK. JESSICA: We have to work together as a team and make quick decisions.

If we make the wrong decision, our lives can really depend on it.

[roaring] NASA...[indistinct] up to one 6,000, direct...[indistinct] VICTOR: If we head toward Mars, you're gonna be away from the planet for a while.

[roaring] JESSICA: You want to make sure you're there with people that you get along with well, and you know how to deal with their idiosyncrasies.

But it's probably going to be a bond that really will last, you know, for the rest of your life.

VICTOR: All right, 2,000 feet.

Here we go.

I love breaking over the water.

Coming left.

♪ ♪ ♪ [cheering and applause] SCOTT: You got bigger!

MARK: She's almost as big as Sammy.

You sore?

A little bit?

SCOTT: Yeah.

A little bit.

TERRY VIRTS: How's the dizziness?

SCOTT: A little dizzy.

MAN: Does it feel like a year?

SCOTT: Uh, yeah.

[laughing] [applause] SCOTT: Oh!

Over a year.

♪ [slap] This is crazy.

♪ Oh...man!

That feels good.

AMIKO: Welcome home!

Back to Earth.

SCOTT: You know, I've served the government for 30 years.

AMIKO: Well, I have a towel.

SCOTT: And I feel very strongly about space.

I think it's important.

I would never rule out flying in space again, but I think it's probably unlikely.

♪ [typing] JESSICA: Sometimes people ask, "Why were you interested in becoming an astronaut now?

I thought NASA closed."

♪ A lot of people really had that perception, when the space shuttle retired, that we weren't even flying in space anymore.

There are only about 45 active astronauts right now, and so it's still a little bit crazy for me to, to believe that, that I'm actually one of them.

♪ But my heart was really in the biological sciences.

So that's what really led me to my other career, my previous career as a scientist.

For my PhD, I studied the physiology of organisms in extreme environments.

♪ So, I became interested in an animal called the bar-headed goose.

I raised twelve goslings.

This is the species of goose that migrates twice a year over the tallest mountains of the planet.

And in doing so, they experience oxygen levels that are only about a half of what we experience here at sea level.

How do they really power that when there isn't that much oxygen to extract from the air up there?

♪ There are a lot of parallels to the work I did as a physiologist that hopefully I'll be able to start contributing to the human spaceflight program as well.

WOMAN: Ooh, Maya, will you get the cabbage, the purple cabbage behind you?

It's on the bottom shelf.

[laughing] VICTOR: You know, this job is risky.

And while we go through painstaking efforts to minimize those risks, if we head toward Mars, you take risk.

I need you to practice good knife handling, OK?

But you know, I mean, that space is better left with just, it's uncertain and who knows?

So why stress?

Good job, team, good job!

Good job.

[jet roaring] When you have reached a point in your professional and personal journey where you don't really want to give up that current situation, that's probably about when NASA's looking for you.

MAN: Whoo!

[roaring] VICTOR: I joined the Navy while I was in college.

I graduated and went to Officer Candidate School, learned to fly.

I flew the F-18.

My first squadron, I took part of Operation Iraqi Freedom, and I flew a couple dozen missions in combat there.

That's what I was focused on, is, is being a CO of a fighter squadron.

The Navy had invested quite a lot of time in me, and my career in the Navy was very special to me, is very special to me.

And so I absolutely was not looking forward to walking away from that.

♪ It was a bittersweet moment to be able to come here.

Hey, Mr. Dickson.

MR. DICKSON: How's it going?

VICTOR: Good, how you doing?

MR. DICKSON: Doing all right.

VICTOR: But it was an opportunity that you just can't refuse.

Here we go.

Here.

This is cool.

Never been across this line.

♪ JESSICA: Orion is a new spacecraft that NASA is building right now.

And it is the spacecraft that we will fly humans in in order to go back to the Moon, to Mars, any kind of deep space mission.

♪ It looks comfy.

VICTOR: Is it bigger than a Soyuz?

JESSICA: Absolutely.

JULES SCHNEIDER: It looks the same as the Apollo capsule, but when you compare what was on Apollo and what we have, it's just completely different.

NUJOUD MERANCY: Orion is a very key part of the ultimate architecture, which is the safe way for the crew to get to space, off the Earth, and back home again.

The Orion capsule is about the volume of two minivans.

What you can do in that space is you can take the four crew safely to and from space easy, but it also serves as sort of a mini habitat.

♪ JESSICA: NASA is very much on what we call a journey to Mars.

The Space Launch System is the rocket that will launch the Orion capsule.

KLUGER: It will have more lift than the rockets that went to the Moon.

MAN: 3, 2, 1...fire.

[boom] ♪ VICTOR: That thing's gonna go farther than any human-rated vehicle has ever gone.

[pop] [splash] And we're gonna fly people in it.

Maybe one of us.

JULES: Hopefully.

VICTOR: Hopefully, yeah.

This is real.

This is not a PowerPoint drill.

[roaring] KLUGER: We are now passing on this torch to the next generation of people who will be the generation going beyond low-Earth orbit.

Going to deep space.

Going to Mars.

♪ SCOTT: Coming back, it was harder than I thought.

It's not just you readapting to life on Earth; it's about the people that are important to you on Earth readapting to life on Earth with you back.

I would've paid like $100 for this sandwich in space.

If someone would've floated this in the middle of the module, there would've been a riot.

AMIKO: Mm-hmm.

I hate to use the term that, you know, we just picked up right where we left off, because we certainly didn't, but yet it just feels like home to me.

Just being next to him when I hadn't had that for an entire year.

It doesn't feel odd, awkward.

It feels, it feels just right, actually.

Hey, let's sit down and eat dinner.

MARK: All right, so how about I propose a toast?

After 500 billion miles traveling around the planet at the speed of light, and 340 days in space... and how many gallons of your own urine drank?

SCOTT: Well, it's not my urine.

It's everybody's urine.

[laughter] MARK: So it's great, great, great to have you back on Earth safely and on time.

WOMAN: Cheers.

WOMAN: Welcome home.

MAN: Welcome home.

[glasses clinking] ♪ VICTOR: If we're going to send someone on a mission that could be 500 days, then we need to know that when you get back, that you're gonna be healthy.

Any opportunity that we have to find out what a human is gonna go through being in space for a year, we needed to learn from Scott's mission.

♪ SCOTT: Gravity, uh, definitely gives you a beat-down when you get back.

My joints, my muscles are really, really stiff and sore.

And my skin-- you know, my back and the back of my arms and my legs-- everything that touches any kind of surface just became completely like, inflamed, like, um, almost like a, uh, hives.

And it was simply because, you know, my skin had not really touched anything for a year.

You have clothes on, but the clothes really are just kind of lightly brushing against you.

It was almost like an allergic reaction to any kind of pressure.

And that lasted for, I don't know, like a week.

KLUGER: We don't know what the long-term biomedical risks are when you spend a year in space.

SCOTT: I also had like flu-like symptoms.

Achy, confused, delirious-- such that if I hadn't been in space for a year and didn't know where this was coming from, I would've went to the emergency room.

My feet still bother me some.

I didn't walk on 'em for a year.

[laughs] MARK: Ooh, this is pretty interesting.

This is what your toe looks like after a year in space.

This is pretty disgusting.

Well, my brother called me up and said, hey, you know, one of his space station science people.

MAN: How are you doing?

MARK: Pretty good, yeah.

They started floating the idea around about doing some studies because we are identical twins.

He thinks I'm my brother.

[man laughs] So that way I can get in.

Otherwise I'd have to pull out my ID.

And unfortunately, it's expired.

When we were little, we had like our own secret language.

And we did almost everything together.

You know, I remember laying in bed one time in the morning and talking to my brother about how we were gonna build an airplane in the backyard.

You know, we, just at five or six years old, we figured, like, we have the skill to do this.

Obviously, we didn't.

We didn't get very far with the airplane, or later with the spaceship.

Last time I did this, somebody was going out the hatch.

PHOTOGRAPHER: Could you stand right here and look at him, please?

CHRISTOPHER MASON: The twin study's an extraordinary opportunity.

Working with twins gives you a perfect genetic experiment.

As a geneticist, I wish everyone had a twin on Earth or in space, but in this case, we were just lucky.

♪ KLUGER: Two men with identical genomes, identical careers.

You send one man to space for one year.

SCOTT: I just did my saliva samples.

[beep] Saliva bag number 2.

[beep] KLUGER: You track the other man living an earthly life for that same one year.

Subtract the differences... that's what space did.

SCOTT: These are ice bricks to keep our samples cold when we return 'em back to Earth.

So we're clear.

JOHN CHARLES: By analyzing the samples that have come back from the space station, we hope to understand where spaceflight has its most fundamental effects on astronauts.

♪ KLUGER: This will be an experiment that will go on in depth for a year, and in further research forever, for the life of both astronauts.

WOMAN: And close your eyes.

MASON: In this study, we actually will be examining every aspect you can possibly look at so far in physiology.

MARK: Do some MRIs and ultrasounds.

They did a stand-up MRI yesterday.

It was like torture.

♪ Woo!

You know, we figured out I've spent 40 hours in that machine.

I have to give urine and stool samples.

Here's this.

That's done.

One of my favorite things to do in the world: collect one of those samples.

SCOTT: I got to go do some science in the bathroom.

I'll be right back.

MARK: So what are we looking at there on my eyeball?

WOMAN: Your retinal artery and vein.

MARK: How's it look?

WOMAN: Looks like the eye of an American hero, sir.

MARK: As long as it looks better than my brother's eye.

His is probably, after a year in space, it's probably all shriveled up and decaying.

WOMAN: Blink, blink.

SCOTT: Yeah, you don't want to get to Mars and be, be blind.

That wouldn't be good.

[crinkling paper] I did this so many times in space, it's not even funny.

MAN: So, uh, does the blood still flow the same way in space?

SCOTT: Uh, no.

Fluid behaves differently.

MAN: Does it come faster or slower?

SCOTT: Uh, I don't know.

[laughs] ♪ MAN: Is that enough light?

SCOTT: Yeah.

♪ There we go.

They have more genetic information on my brother and I than they do of any other people.

Ever.

MARK: Probably take 30 tubes of blood from me this morning.

MAN: OK, squeeze just a couple times again.

That's plenty.

Just like we've done it before.

SCOTT: Man, that's a lot of tubes.

MAN: You're gonna lose a couple pounds here.

SCOTT: If you do it yourself in space, it hurts less than when someone else does it.

And it also saves time.

MAN: We actually used a guide, there was a guide online for, like, intravenous drug users.

Like, junkies have this handbook that they built for themselves on how to stick themselves-- SCOTT: And that's where you got the... here's how you stick a needle in your vein, per the experts.

MASON: In my laboratory, we study the effects of space travel at the very fine-grain genetic level.

At the DNA level, we're looking for mutations, maybe from radiation.

Out in space, you're gonna be, you know, subject to the slings and arrows of radioactive particles from the sun and deep space.

LISA NIP: These particles literally break apart your DNA.

It's not something you feel immediately.

SCOTT: You know, my radiation, the amount of radiation I got in, uh, in space for a year is significant.

NIP: If you are constantly bombarded with radiation, your body ends up not being able to cope with that, and that's when cancer happens.

♪ SCOTT: Now, if that actually happens, then that was a pretty big risk I took.

♪ KLUGER: Astronauts who are going to deep space have a significantly higher risk than astronauts who are orbiting the Earth.

O'BRIEN: When you go out there, there's really nothing to stop radiation from penetrating your body, and you, you know, what can you do?

CHARLES: One option is to go really, really fast, minimizing the amount of time you're exposed to the deep space radiation environment.

Unfortunately, really, really fast means new propulsive technologies that we don't have yet.

They are in the realm of science fiction.

Star Trek and its warp drive is a good example of something that would be really effective, but darn it, it just doesn't exist.

JESSICA: When we eventually go to Mars, it would probably be six to nine months to get there, six to nine months to get back.

You would spend, you know, a year or two on the surface as well.

KLUGER: Mars has an atmosphere, yes, but it's only one percent that of Earth, so you're getting a radiation bath there.

♪ ♪ ♪ LUCIEN JUNKIN: Ross, we are powering up.

And then you're gonna push straight forward on the joystick.

CHARLES: On Mars, radiation exposure to your brain may render you less likely to be successful on a complex task.

♪ MASON: The big concern is you send someone out there with a 75-year life span and they'll only make it to 30 or 35 because they'll just be bombarded with particles and mutated.

♪ JESSICA: I think all of us understand the risk.

You trust that, because of the type of person you are, the training you've received, you'll be able to psychologically deal with those things.

♪ ♪ O'BRIEN: Space is not where we were supposed to be.

We have to figure out how to make that work for us if we're gonna go beyond this planet.

NIP: Since we can't change space, we should probably consider changing ourselves.

♪ KLUGER: Now, this isn't as Frankensteinian as it seems.

MASON: We may be forced to engineer the DNA of the humans going to space so that they can survive.

It's possible to look at your own DNA today and modify individual letters and change your DNA to whatever you want.

We can take clues from life on Earth that we know it's possible to survive radiation.

Deinococcus radiodurans is a notable organism that can survive hundreds of times, even thousands of times more radiation than we can.

Its DNA is just destroyed, but it pieces it all back together, and then can survive just fine.

The idea is that we can actually engineer the human genome to survive similar insults and still be able to reconstruct itself.

[heart beating] There's of course caveats.

What if something goes wrong?

What if you mis-engineer?

There's a lot of heavy responsibility with this idea of tweaking an entire species.

But there's a chance, I think a good chance, that we will have no choice but to slightly tweak and engineer the genome so that it can survive in long-duration space missions.

And to do so would maybe be the ethical thing to do, 'cause sending people to their near-certain death is probably not ethical.

FILM NARRATOR: Why?

Why must man go into space?

Why must he attempt this new and forbidding environment?

CHARLES: Early in the space flight era, there were many concerns about the effects of the space flight environment on astronauts.

O'BRIEN: There was, there was some belief prior to putting human beings in space that we would kind of instantaneously explode.

You know, boom, gone.

♪ Could you see?

Could you talk?

Everybody had a theory.

♪ And there was no way to know except to go, and so that scared people, and so that's why we sent our primate cousins up.

FILM NARRATOR: The minutes are like hours as the countdown is started.

Only the star of the space drama seems unconcerned at the mounting tension around him as he arrives in typical high spirits for his final check-up.

O'BRIEN: Ham was a courageous chimp.

FILM NARRATOR: But what of little Ham?

Has he survived the tremendous shock of takeoff?

Yes.

Remarkable motion pictures made in flight show Ham, bottom screen, playing the game of levers and lights, just as he has been trained to do.

♪ The question on everyone's mind is, "How did he take it?"

And implied in that question is still another: How in the future will man take it?

[chattering] O'BRIEN: You can draw a straight line, dot by dot, from Ham the chimp to Scott Kelly.

[helicopter] SCOTT: Misha and I are the first guys, uh, spending a year on the space station, so we were both involved in experiments to understand better how to keep people alive for longer periods of time in space.

♪ You start doing this right when you get out of the capsule.

♪ The idea is to measure your performance right when you get out of the vehicle, and let's say you landed on Mars, to try to understand what your physical capability is.

You walk with your eyes closed, like, foot to foot, which is hard even when you haven't been in space for a year, especially on this uneven ground of Kazakhstan.

You get on an airplane, the airplane flies to Norway, and you do it there.

WOMAN: Remember, try to, try to go toe to toe.

SCOTT: And then it gets back to Houston, and you do them here again before you even get to go home.

You're doing these tests for weeks.

When do I do this again?

WOMAN: Uh, Wednesday.

SCOTT: What?

Like in two days, Wednesday?

WOMAN: Yes.

SCOTT: Man!

SCOTT: Eventually you're doing them once a month.

Then it's a couple days every six months, which is where I'm at right now.

♪ WOMAN: At 25.

♪ MAN: What is this test measuring?

SCOTT: What, this?

MAN: Yeah.

SCOTT: I don't know.

[laughs] I'm just, I'm just the lab rat.

I'm the guinea pig.

♪ JESSICA: When we eventually go to Mars, it would be about a three-year mission, which is, of course, a long time flying in space.

So as a physiologist, one of the things that I think about a lot is how the spaceflight and microgravity environment affect the human body.

MAN: All right, try to shift your arms out.

Grab on to the--there you go.

Can you push back up?

O'BRIEN: Everything about us is built to live with what we call 1 g, which is the force of gravity here on Earth.

♪ JESSICA: Argos is enabling us to start understanding the real forces that we'll experience in space.

LARRY DUNGAN: We generate weightlessness by, if she weighs a hundred pounds, we provide a force through the lifting cable of 100 pounds.

So, as she moves, we will follow her motions and provide a reduced-gravity environment.

JESSICA: In space, once you get moving, it's hard to stop.

Aaah.

[laughs] You get that real experience as you would in space of, you know, I might start driving a bolt or using the drill, but it's actually going to rotate my whole body like this at the same time.

♪ So, it's a great analogue for space, I think, on many, many levels.

♪ SCOTT: I got to push the button.

Then push that button.

MAN: You do this ten times.

SCOTT: Ten times.

[ding] ♪ [ding] O'BRIEN: When you're in space, you really don't need the skeletal structure that we have built here that is tuned up and ideally suited for gravity.

And so you lose a lot of calcium, a lot of bone.

BOB TWEEDY: In order for, you know, Scott, or anyone, for that matter, who goes on a mission, to come back in good shape and not be at risk, uh, they need to exercise.

And they need to do it a lot.

They need to do it six out of seven days a week.

Let's go down to 20 on the bar height.

My job is to teach crew members before their mission how to use and how to maintain all of the exercise hardware on the space station.

The ARED allows us to lift loads in a weightless environment where we use evacuated cylinders.

It's like a bicycle pump in reverse.

You have to push or pull or stand up against that force of the vacuum.

The exercise hardware we have on a mission to Mars needs to deliver what the hardware on ISS is delivering, maybe even to a greater extent.

However, it's got to be smaller 'cause there isn't the space for the big stuff.

JESSICA: We need to make sure that once we arrive at those places that do have some gravity that we are able to walk around, that we've maintained our physiological integrity, our muscle mass, our bone density.

Wow, that is challenging.

SCOTT: We've had two guys break hips after long-duration space flight.

You need that exercise equipment.

If you broke your hip on Mars, you'd probably die.

♪ That's some embarrassing-looking hat.

KLUGER: Scott's mission is not a glamorous mission, but it's vital to humanity's future in space.

[bell dinging] SCOTT: You get used to it.

It's not... some of it's not fun, like getting electrocuted.

[buzzing] Aaah!

WOMAN: Relax.

SCOTT: Part of the job.

This shows how quickly we can put pegs in little holes.

They have chimpanzees that can do this faster than us.

NASA REPORTER: Scott Kelly has the all-time U.S. record for time in space.

SCOTT: You know, records are made to be broken.

And they all are eventually.

You're doing it for a reason that is larger than yourself.

That'll help us get to Mars someday.

O'BRIEN: There's this expression, "Standing on the shoulders of giants."

You don't get anywhere until you've boot-strapped your way up through the generations and through the innovators and through the people who've tested the limits.

MAN: Rock and roll, Scott!

O'BRIEN: Scott's part of that chain, and it's time now for him to hand it off to the next group.

PHOTOGRAPHER: Picture.

Wanna get a hero shot real quick?

JESSICA: The sense of history, to us as astronauts, it's incredibly important.

♪ When you go to Kennedy Space Center, from anywhere you are, you can see this giant building always looming on the horizon.

VICTOR: Which really hearkens back to the Saturn V rocket and Apollo and when we sent folks to the Moon.

♪ O'BRIEN: The Vehicle Assembly Building opened in 1966.

The high, holy cathedral of space.

♪ It was designed to hold four fully stacked Saturn V rockets, the biggest, bad-ass rockets we've ever built.

And at that time, we weren't even sure we could get to the Moon.

♪ I mean, it's just absolutely symbolic of the hubris of the era.

We don't just need one; we need four.

'Cause we need, we got to have four ready.

You just need four.

'Cause...'cause!

This was the blank check era.

♪ To walk in there, you're in the presence of history, but you're also, we hope, in the presence of the future at the same time.

VICTOR: We're upgrading it to be able to support the entire Space Launch System with Orion.

JESSICA: So the entire SLS will be assembled vertically, all in its entirety, right here.

MAN: Yes.

We'll have different components come in horizontally.

We'll lift them up and over.

And then integrate vertically.

♪ ♪ VICTOR: Being able to stand up there on the edge and just look out, and that view is just, it's amazing.

♪ VICTOR: Launch Pad 39B was a launch pad for the Apollo program.

It was a launch pad for the space shuttle.

It is being renovated to be where we launch the SLS rocket and Orion from.

INTERVIEWER: How long have you been working here?

MAN: Um, off and on since 1985.

JESSICA: But those were the shuttle glory days.

I mean, we were launching all the time.

We were always seeing it on the news, all the launch coverage.

And that's when I think, you know, when we started wanting to be astronauts, right?

♪ [laughing] Now you look like an astronaut.

[laughs] MAN: There you go.

What I'm gonna do is tuck some of your hair inside the neck down here.

VICTOR: Any day you get to put on a space suit is a good day.

Any day that you get to crawl inside of a spacecraft, even a spacecraft mock-up, that's a good day.

Hey, Goose.

JESSICA: Coming in.

VICTOR: Come on in.

♪ ♪ This is when you know you're having a bad day, if you have to fly the vehicle using these.

JESSICA: Survival RCS.

VICTOR: Yeah.

Well, this one right here, that's a very scary switch.

JESSICA: Yes, I see that.

Let's leave that in "safe."

[laughing] ♪ KLUGER: The next generation of astronauts who will go to Mars are going to have an experience that only the Apollo astronauts had.

[cheering and applause] KLUGER: The Apollo 8 crew in 1968 was the first crew to receive the command.

MIKE COLLINS: Apollo 8, you are go for TLI, over.

FRANK BORMAN: Roger.

We understand.

We are go for TLI.

KLUGER: Apollo, you are go for TLI.

What that meant was you are go for trans-lunar injection.

You are go to ignite your engine, travel to the Moon, and surrender to the Moon's orbit.

They were the words that were the kick-off for human exploration of deep space.

FILM NARRATOR: As the world listened and watched, its people were overtaken by a new awareness, an awareness that they were perhaps witnessing the overture to the ultimate destiny of man.

♪ Frank Borman, Bill Anders, and Jim Lovell were about to leave their cradle Earth and face the infinite frontier.

KEN MATTINGLY: Jim, we've just been, uh, looking at your marks with respect to, uh, accuracy, and they figure they're within a couple of thousandths of a degree of the theoretical optimum.

FILM NARRATOR: Lovell's proficiency in navigating the spacecraft with its onboard optical instruments would eventually earn him the nickname "the man with the golden fingers."

[roaring] KLUGER: This generation's next going to hear the words, "You are go for..." in this case, trans-Mars injection, TMI.

They're going to be the generation that will be the Apollo generation of the 21st century.

♪ JESSICA: So when was the last time you were in this room?

JIM LOVELL: Oh, a long, long time since I've been here.

A long, long time.

♪ BORMAN: Houston, Apollo 8.

How do you read?

COLLINS: We hear you loud and clear, Apollo 8.

BORMAN: Roger.

We're loud and clear.

We're taking pictures of the S-IVB, uh, the post-separation sequence is completed, and we seem to have a high gain.

COLLINS: Give us a clue as to what it looks like from way up there.

LOVELL: Roger.

I can see the entire Earth now out of the center window.

FILM NARRATOR: Scientist, astronaut, engineer, the world... all followed the progress of Apollo 8.

For this was preparation, an advance scout marking the way for those who would follow.

LOVELL: That right there, I'm saying, "Happy birthday, Mother."

It was, uh, her birthday at that time.

WOMAN: Oh, yeah?

Really?

COLLINS: Apollo 8, you are go for TLI, over.

LOVELL: And go for TLI.

FILM NARRATOR: The men of Apollo 8 watch the readouts, the numbers snowballing toward the velocity that would allow the spacecraft to escape Earth's gravity.

LOVELL: When we burned our engine on TLI, we gave the velocity, the total velocity enough to coast all the way to the Moon.

Didn't...it was about close to 24,000 miles an hour.

And then we would accelerate towards the Moon for the final phase.

[roaring] ♪ We looked back at the Earth, and you can actually see the Earth start to get smaller.

And it was like driving into a tunnel and you're sitting in the back seat looking out the back, and you see in the tunnel getting smaller and smaller and smaller as you're driving down inside the tunnel.

JESSICA: Did that personally really change things for you, that first time looking back and getting that perspective?

LOVELL: Yeah, it has.

In some respects, it has, because when I looked at it, I thought to myself, you know, you know, you know, you go to heaven when you're born, because you just think of what you have here.

You got a body with a proper mass to have the gravity, that contains water and an atmosphere, the essentials for life.

You're in orbit around a star or a sun at just the proper distance-- not too far out to be too cold, too close in to be too hot.

Just the proper distance to absorb the sun's energy.

That energy was what evolved life on Earth to begin with.

So, you know, in reality, out there, just 240,000 miles away, which is not much at all, you really see what you have back here.

MISSION CONTROL OFFICER: We've got it.

We've got it.

Apollo 8 now in, in lunar orbit.

There's a cheer in this room.

This is Apollo Control, Houston, switching now to the voice of Jim Lovell.

LOVELL: You are probably in the position now to repeat what you just saw a long, long time ago, because I fully believe that going to the Moon is probably the best thing we should do, and then going to Mars.

Now, whether you're going to go to Mars or maybe your grandchildren will go to Mars... [laughing] VICTOR: Oh, those are good jalapeños, Maya.

MAYA: I put some salt on them.

VICTOR: When we launch EM-2, the first manned mission of Orion, we're gonna send it to the Moon.

I don't mind saying it.

My dream is to walk on the Moon.

But if I don't walk on the Moon, to see the dark side with my own eyes and to see Earth suspended out there in the blackness, I mean, the fact that that's even possible is amazing.

♪ JESSICA: Now that we have spent decades exploring the low-Earth orbit where the space station operates, the next question, I think, as a human species is, "What's next?"

What is the next step toward furthering our presence in the cosmos, in the solar system, in our universe?

SCOTT: When I was backing away from that space station, I was reflecting on the fact that we built this space station in low-Earth orbit... WOMAN ON RADIO: What a beautiful piece of hardware.

SCOTT: The size of a football field.

A million pounds.

I think it's the hardest thing people have ever done.

And I feel very strongly that if we can do this, we can do anything.

As future explorers, I would say if we decide we want to go to Mars, we can go to Mars.

♪ ♪ A Year in Space and Beyond a Year in Space are available on DVD The book Endurance by Scott Kelly is also available.

to order visit shoppbs.org or call 1-800-PLAY-PBS Also available for download on iTunes.

♪