Man on Mars: Mission to the Red Planet Horizon

EXPLOSIVE BLAST

Ignition.

Mars, the Red Planet.

We've long wondered if it's harboured life.

Some have dreamt of walking on its surface.

More than four decades after they landed on the Moon,

NASA are now imagining a two-year ride across space...

..to Mars.

The scorecard of Mars is at best 50/50.

It's tough to get there.

If you think about putting humans in harm's way, it's a tough job.

To do it, they need new rockets on a new scale...

A new way of surviving in space...

..and a new breed of astronauts...

Think about a mission to Mars. What is it? Is it outdoor stuff,

or is it confinement?

And then I see somebody that says, "I have a stamp collection,

"I do a lot of reading, I enjoy watching movies."

And I'm thinking, "That might be good for confinement."

To finally go to Mars would be the fulfilment

of one of our grandest dreams.

I long for a time when I can actually walk out of my back yard,

stare at space, spot Mars, and actually think,

"There are humans on Mars, right now, and we helped put them there."

But is this ultimately a dream NASA can really deliver?

Right now on Mars, there is an object the size of a car,

roaming about on the surface.

It was sent across vast voids of space

to this harsh and rocky planet.

And now, every day, it opens its eyes upon on another world,

trawls the surface for signs of life

and sends back images like these.

Now NASA want to go a stage further

and put a group of people up here with it.

And so the man who masterminded the landing of this rover

is now part of a team trying to work out

if humans can safely be sent to join it on Mars.

Mars is a tough place to get to.

It's a scary, expensive and risky proposition for robots.

When you think about putting a human in harm's way,

you've got to double down on your engineering

to make sure that everything goes right.

The simple truth is that much of the technology they'll need doesn't yet exist.

People get, I think, confused by the technologies on Star Trek.

And perhaps in 400 or 500 years from now,

we'll have those kinds of technologies available.

But for the present time, if we want to do space exploration,

there are risks.

And the longer the mission, and the farther away we go,

then the higher the risks are going to be.

The history of previous, unmanned, missions provides little comfort.

So Mars is a risky place to go.

Early attempts - Mariner 3 and Mariner 8,

almost everything the Soviets tried to put there,

the Mars Polar Lander in '99 - all these missions have failed.

The scorecard of Mars is at best 50/50.

So as NASA set their sights on a manned mission to Mars,

can they pull it off?

The scientists and engineers at NASA are returning

to the business they're famous for -

transforming a fantastical idea into a precise set of engineering plans.

These are the people who must face, and overcome,

every problem involved in sending human beings

56 million kilometres from Earth.

Everything from stopping them from going mad with boredom,

to dealing with years of human waste.

It's quite a challenge.

And the team must begin at the beginning, by escaping planet Earth.

If anyone should ever ask you to build a spaceship to go to Mars,

then, like any craftsman,

you first have to find a space to work in.

This vast hangar, once home to key parts of the Apollo rockets

and Space Shuttle, is where a rocket that'll one day

go to Mars will take shape.

Ricardo Navarro is clearing the decks

so that assembly of the rocket can begin.

It's so much larger than what we did here before. So much taller.

The best way to assemble something this complex and this big

is to assemble it vertically.

You generally want to build like you fly.

So they start at the bottom, with the fuel tanks.

This is as high as we can go using the elevator. The rest is on foot.

It's hard to tell with this big of a space

how big the actual vehicle's going to be, the rocket.

But you can actually already see some signs emerging.

You can see that blue circle forming.

That is the actual diameter of the rocket.

So you can imagine something of that diameter, all the way up

to about ten feet below where we are right now,

being the actual size of the hydrogen tank.

Even at this height, we cannot contain the entire rocket.

The rocket is called the Space Launch System, or SLS.

And this building can only accommodate half of it.

So far, very little of the SLS exists beyond the drawing boards,

save for one part that's already under construction.

Here, in New Orleans, they're building the first section

of this monster rocket - the fuel tanks.

Lead engineer Todd May has come to see the first completed section.

And this is what it's like to be inside a rocket.

To keep it light, it's made out of aluminium,

using a design inspired by nature.

This is an iso-grid pattern. It looks a little like honeycombs.

You know, bees are pretty smart.

We make this this way to actually keep most of the strength

of the material while being able to remove 90% of the weight.

Keeping the weight down is imperative,

because this seven-metre-high slab is just one of many

which will make up the overall rocket.

Now, to make a core of a rocket,

you actually have to have the equivalent of ten of these tall.

You have a hydrogen tank, which is the equivalent of five of these,

plus a dome on either end. And then the liquid oxygen tank,

which is two of these with a dome on either end.

The core, when you're finished, is two thirds of a football field long.

By the time you add the interim upper stage,

it's taller than the Statue of Liberty.

This giant piece of metal will be useful for just moments.

So, to give you a sense of what's going on through launch,

this section, which is filled with rocket fuel,

is pouring it out through the engines very quickly.

Just one section like this would empty in about a minute.

This is the only piece of the rocket that exists right now.

But before it can be tested in 2017,

millions of other parts will be made to join it.

July 1969. The launch of Apollo 11.

The mission - to leave Earth and carry three men

in a 30-ton capsule...

..a distance of 385,000 kilometres...

..and to be the first to step on the surface of a body other than Earth.

It was a phenomenal feat.

And the whole experience took little more than a week.

CHEERING

But Mars is a very different proposition to the Moon.

Lying 56 million kilometres from Earth,

Mars is over 140 times farther away.

With current technology, a return journey

would take around three years,

and require a team of four to eight astronauts.

Anyone who thinks this is Apollo with bigger rockets

needs to think again.

Because this is a mission that will take man, for the first time,

out of Earth's orbit, leaving its protection far behind.

Stennis, Mississippi.

This is the place where every single rocket engine

that NASA has ever built has been tested...

from Saturn V to the Space Shuttle main engine.

Today, Mission Control are setting up for a full-power burn

of one of their latest models.

Gary Benton, who's in charge of rocket testing,

has come to oversee the burn.

SIREN BLARES

The one-minute siren. So we're within a minute now.

We're getting close. My heart's beating pretty fast right now.

I've got some adrenaline rushing through me.

And there'll be more once it cranks up here in a few minutes.

We're off!

An engine like this will be just one of six

which will help propel the SLS into orbit.

Looks like a safe shutdown.

So when the time comes to test the much bigger SLS rocket,

it must be at the largest stand they have.

Like so much in the mission to Mars,

they'll be standing on the shoulders of NASA's previous missions,

borrowing and re-purposing the best from Apollo and the Shuttle.

-How's it going, man?

-It's going good.

-All right.

B Stand was built over 50 years ago

for the testing of the Saturn engines that carried the Apollo missions to space.

-You can't walk round there, cos there's so many people.

-Right.

Gary and his team will be reshaping and upgrading this stand

so that it can cope with the next generation of rockets.

This is the same crane that we used to lift those Saturn V four-stages

and we're going to use the very same crane to lift the SLS four-stage

and place it in this facility, anchor it down really good.

Firing off about two million pounds of thrust.

And that's going to be the biggest test we've done out here

since we did the Saturn V.

There's a palpable sense of excitement here

because for the first time in decades,

they're thinking of using these rockets to send PEOPLE

beyond Earth's orbit.

For now, this is NASA's best vision of what a rocket

bound for Mars would look like.

'Eight, seven, six, five, four...'

But if you're going all the way to Mars,

a single rocket of this size is not enough.

NASA estimates that they will need at least seven launches

to get all the equipment they need up into space.

The fuel, the food, the Mars Lander -

all will need to be launched into Earth's orbit

and then assembled in space, much as the Space Station has been.

Only then will it be ready to leave Earth's orbit.

But there's an uncomfortable truth about the journey ahead.

Since they can't carry enough fuel for the full distance,

they need to rely on Mars's gravity to pull them in.

It's called the slingshot effect and it means that once they're off,

there's no turning back.

Anyone who's willing to leave the safety of Earth behind

needs to be a very particular type of person.

Back in the days of Apollo 11, picking a crew was straightforward.

It was clear who had the right stuff.

Neil Armstrong, Buzz Aldrin and Michael Collins

were the cream of US supersonic flight.

They were drawn from the elite world of fighter and test pilots.

And with that came supreme hand-eye co-ordination and physical daring.

But these may not be the same skills you'd need to go to Mars.

I noticed that a lot of the astronauts were of the old school.

"I hunt, I fish, I ski,

"I climb mountains, I climb trees..."

You know, lots of outdoor stuff.

But think about a mission to Mars. What is it?

Is it outdoor stuff or is it confinement?

And then I see somebody that says, "I have a stamp collection,

"I do a lot of reading, I enjoy watching movies."

And I'm thinking, "That might be good for confinement!"

Dr David Dinges is interested in how you select a crew

and safeguard their psychological welfare in space.

And the key issue is really understanding who's going to develop

a problem and when will it develop? Will all the crew develop it?

How do we detect it? How do we prevent it to begin with?

To date, the only answers come from a Russian study -

an Earth-bound simulation of the approximately 520 days

in isolation it would take for a return trip to the Red Planet.

As the Russian study was gearing up, Dr Dinges set himself a challenge.

Could he use his expert knowledge to anticipate

who would fare best in confinement?

In the Mars 520 mission I watched the crew intensively.

I wanted to see them during the maelstrom of media attention

before they went in to the chamber and how they interacted

in that environment.

And body posture, where they were looking, what they said.

When they went in, he made his prediction.

And I made notes and I wrote down a variety of things.

I made predictions - and this is true - I sealed it up in an envelope

and put it in the drawer and waited till the mission was over.

In this footage, released by the European Space Agency,

the astronauts look well.

But by the end, deep troubles were brewing.

The bottom line is that out of six people who went,

only two didn't have significant behavioural problems

of one kind or another.

A couple of them experienced insomnia.

One experienced some depression. Another was more socially isolated.

But the two I predicted would make it just fine made it just fine.

Like the Apollo missions, the Russian study was all-male.

But what if NASA were to shake up this tradition?

I suspect we're going to find there are some areas women have

a slight advantage. In some areas men have a slight advantage.

Bone loss or radiation. And so I think a mixed crew is likely.

The agencies want to show that the astronauts represent humanity, right?

And that's a reasonable thing to do.

NASA hope to launch the mission in 2033.

So the astronauts who'll get to go are probably still at school.

If you were among those astronauts on board,

you'd sense the major physical challenge immediately -

a lack of gravity.

It's a problem faced every day on the Space Station

but, so far, no-one has spent more than 15 months in low gravity.

But if you were on your way to Mars, you'd be away for twice that time.

For the scientists the question is, how do you understand

the long-term effects of weightlessness here on Earth?

-Good afternoon! Time for lunch.

-Lunch, already?

-Yes. Isn't it amazing how time flies?

-Let's eat!

-Bon appetit!

Welcome to the weird, horizontal world of Frank and Daniel.

They've volunteered to spend 70 days in a row lying down,

as part of an ongoing study on the effects of weightlessness.

That's because the closest thing to zero-G conditions

here on Earth is to lie in bed.

But that's much harder work than it looks.

The second morning waking up from the bed-rest,

you kind of, you know, want to try to normally sit up like you normally do,

but then you bring the lamp down to you to turn on your lights.

You don't go up to the lamp. It's a little difficult.

Yeah, taking a dump here's not too pleasant!

But, you know, what can you do? You've got to do it.

It's not too bad, you know.

I guess I can finally say I know how to use one of our bedpans!

HE LAUGHS

You should try it. It's a good experience!

HE LAUGHS

-Hey, Frank, how is it going?

-It's been pretty good, you know.

-You're on bed-rest day 28!

-That's correct.

Yeah, so how was it when you first went head down?

Dr Roni Cromwell is running the trial,

which overall has 27 subjects.

So we get people from all walks of life.

We've had people who are between jobs,

that are looking for something to do.

We've had people that wish they had been able to be an astronaut

and since that couldn't happen, they wanted to do the next best thing.

Roni ensures that all the subjects are kept with their heads tilted

six degrees down, which best emulates the effects of space.

And by tipping them six degrees head down tilt,

we see the headward fluid shifts,

that is similar to what astronauts experience in space as well.

And by doing that we can then study the mechanism for these changes

as well as develop countermeasures to mitigate these changes.

A typical day starts with breakfast in bed...

..and a shower...in bed.

After lunch, tests...in bed.

My favourite part!

Today, they're investigating a mission-critical problem -

why astronauts often lose their appetite in space.

During weightlessness, body fluids flow into the head

and scientists believe this may affect the airflow.

So they're measuring the size of Frank's nasal cavity,

to look for swelling which might restrict

his sense of smell and taste.

Daniel is slightly luckier.

He's among the 50% of subjects who are selected

to occasionally escape bed to study the effects of exercise.

It can be a little bewildering.

The reason for optimising the exercise programme

is to find the best sort of recipe for the exercise that's needed

to preserve muscle and bone in our astronauts.

Exercise has long been known as a means of staving off

loss of bone and muscle mass in space.

Because the effects of this can be devastating.

These astronauts, just landed from the Soyuz capsule in 2013,

are too weak to even stand, let alone walk.

On a mission to Mars, the effects would be even more pronounced.

After all, it's a much longer journey.

But there'll be no-one on Mars to carry them away.

The astronauts must be able to step out of the capsule

and onto the Martian surface by themselves.

Scientists are realising that exercise alone, however optimised,

is not enough.

If humans are ever going to be strong enough to explore

the Martian surface, they'll need some other help

to keep them fit for the adventure ahead.

You may never even notice it, but millions of years of evolution

have finely tuned your body to conditions on planet Earth,

so that cells in your muscle and your bone simply can't grow

without the force of gravity acting on them.

So Dr Randall Urban is looking for something that can stimulate

muscle and bone growth, in the absence of gravity.

And he's turned his attention to a chemical

that's well known for building your body.

Well, testosterone is a very interesting hormone

and it seems to be primarily responsible for protection of bone

and protection of muscle.

Dr Urban is working with the bed-rest study.

He's giving regular injections of testosterone

to half of the subjects who are exercising.

But it's a double-blind study,

so no-one knows who's getting the testosterone and who isn't.

We see that one of the exercise groups is doing much better

than the other exercise group.

In our minds, we think that may be the testosterone group

which is showing that benefit.

Daniel doesn't know whether he's received the testosterone or not.

He'll just keep on running

and having his bone and muscle mass monitored, until his 70 days are up.

The results of the study will help determine whether astronauts

travelling to Mars will take doses of testosterone

to keep their bones and muscles strong.

But that raises an interesting question.

What if some of those astronauts are women?

When we use testosterone in women we have to be very concerned

about the side effects which actually will cause them

to develop male characteristics.

We would have to be figuring out ways to deliver testosterone

in low enough doses that you wouldn't get

any of those other characteristics in the women.

It remains to be seen whether testosterone can be given to women,

not to mention a group of competitive men in a confined space.

But the health risks of travelling to Mars

don't just threaten the body.

Perhaps the greatest challenge of all is in the mind.

Ignition.

Imagine you're one of the astronauts and you've now been on board

for several months, in the same small place,

with the same few people.

You've played all the games on your tablet

and the view out of the window never changes.

You may start to feel a little bored. Perhaps a little glum.

And this is important, not just because it's nice to be happy.

Having a functioning team on a spaceship

can be a matter of life and death.

If you become depressed in space flight,

if you develop a poor interaction style or you become socially

isolated because something's wrong and your brain can't cope

or your behaviour's off, or you become cognitively impaired,

then you pose a risk for yourself

and the rest of the crew and the mission.

These problems occurred in the past with Shackleton, with Nansen,

with Amundsen, with all the great expeditions.

They remain fundamental problems.

One solution being tested by Dr Dinges and his team

is to use the spacecraft's on-board cameras

to watch over the astronauts day and night.

I want to review, sort of, what we've got. OK, so get position.

Centre yourself.

Dr Dinges and his team are using new facial recognition software,

and its success hinges on identifying telltale signs

in the face, which betray what the mind beyond is really thinking.

Number one, for just tracking purposes, the jaw line really helps.

You, know where the face is oriented.

Number two, we need the lips because the lips tell a lot about frowns,

smiles. And then we need the eyes.

The eyes are hugely expressive in humans.

Chris, give us just neutral here.

And just, you know, think about just work

or whatever you're doing, and nothing particularly important.

Now give me a positive.

OK? A small smile, nothing big.

Just a small joke, there you go.

And now don't be so dramatic with the negative but definitely show me

something negative, like you're annoyed that somebody's...

You don't have to show sadness. Try and give me some anger.

There you go, bingo.

It's not just emotion.

Another important state of mind in space

is how much concentration you have.

We discovered that the most reliable measure, better than brainwave,

was speed of the eyelid closure,

the levator palpebrae muscle in the eyelid.

And that's what these little green boxes are tracking,

and as we get more tired, no matter what we're doing,

the speed of the eyelid blink slows.

Now, it's only slowing in 100, 200, 300 thousandths of a second

so it's almost not visible to a human, but in this case

the computer can measure it with a great deal of precision.

And that means you're highly likely to have a lapse of attention,

to have either a microsleep or fail to respond

in a timely manner to something you're monitoring.

And that's why this is so valuable, because now we know your emotion,

and we know if you're tired or fatigued from inadequate sleep,

sleep loss, circadian desynchrony on the spacecraft.

But is it overkill to design a machine to do a job

so instinctive for humans?

You could argue, "Well, can't a human just do it, then?"

Are you serious?

Is a human going to actually look at, you know, every 30 seconds

or a minute, a face constantly for a 17-month mission? It's not realistic.

Better to have a machine do it, with an algorithm,

then it feeds it back in aggregate. Then a human can say,

"Give me that section of the mission right here,

"and give me this astronaut,"

"and what's going on here? Cos we saw a big spike here".

But what this research cannot answer is the question that might

keep a would-be Mars astronaut awake at night.

What if you or one of your crew members DID break down?

How would you deal with it?

You can't step outside to calm down.

It's a frightening thought.

One we've never faced before.

Thankfully, life in space is not all rumination and introspection.

There are everyday, practical issues to attend to.

How do you keep yourself clean? Tidy? Healthy?

How do you cope with the barest necessities?

Here we are at the throne!

Number two, right here.

I'll show you.

But you see, it's pretty small so you have to have pretty good aim.

And this guy right here... is for number one.

People always ask about toilet paper.

"What do you do with toilet paper? What kind of toilet paper do you have?"

We have gloves, just because sometimes it does get messy.

We have some Russian wipes, which are a little bit coarse

if you like the coarse type of toilet paper.

We have Huggies, erm, just for any clean-ups.

You know, we were all babies once and this sort of helps.

And, of course, you do have your privacy. There's a little door.

But once you've closed that door and flushed the handle,

what happens next?

How do you deal with years of waste, with no plumbing and no sewers?

Here in Tucson, Arizona, Taber McCallum,

a specialist in space life-support systems,

is dealing with the nitty-gritty of this question.

And in space, he believes what comes out

must be inextricably linked to what goes in.

So one of the most important things we need to stay alive

is drinking water.

And people consume about two litres a day of drinking water,

so for a 500-day mission, that's a ton of water. Four crew,

that's four tonnes of water you'd have to bring with you,

so we have to drink the same water over and over again.

Taber is into recycling in a big way.

What we have is a sample of today's urine

and then we put that urine on one side of a special set of membranes.

Similar to the way plants essentially treat water for us

by transpiring the water through the membrane of the cell,

the water then goes in on one side of the membrane,

travels from molecule to molecule,

and at the other side of the membrane, evaporates away.

So it's a process of hydration and dehydration,

and in that process of the membrane we selectively only get water.

He's hoping to reclaim 98% of drinkable water

from the crew's urine.

That's a significant improvement from the 75%

currently recycled on the Space Station.

But Taber has also set his sights on solid waste.

There's two issues with solid waste.

One is there is water in that solid waste that we'd like to extract,

but even if you didn't bother to extract that water out, what

am I going to do with bags of solid human waste for a year and a half?

You've got to stabilise it somehow, that it won't produce

lots of gases and smell bad and ferment and who knows!

So some people keep suggesting,

"Why don't you just blast this waste into outer space?"

One of the more interesting reasons not to is that we'd end up

at Mars with a cloud of waste around the spaceship.

It's not going anywhere. It's already on the trajectory that we're on.

So you really want to keep all that stuff away from the spacecraft

and make good use of this material.

It's good material - we just have to figure out how to use it.

For some reason I can't get any of the lab techs interested in this project!

It may seem trivial, but a mission to Mars will only become

a practical reality if these problems,

that all of us take for granted in our Earthly lives, can be solved.

But imagine the recycling of waste was sorted.

And imagine your body and mind could be kept strong.

If you were on the way to Mars,

there would still remain one powerful threat to your survival.

Radiation.

Just how much radiation you, as an astronaut, would be exposed to

was quantified by the recent Curiosity mission.

And they found it to be several hundred times more intense

than on Earth.

And that's a problem.

So one important factor of, actually, life on Earth

and how we were able to evolve is that we're protected

from the radiation of galactic cosmic rays

and from the radiation of the sun by the magnetic field of the Earth,

which is caused by the iron core of the Earth.

That magnetic field creates a protective shield around

our planet called the magnetosphere, which deflects radiation.

The more dangerous solar particles don't get through

so that we, mostly, receive only life-giving sunshine.

But out in space, everything is different.

Out here, the bubbling surface of the sun occasionally builds

to a huge explosion.

These solar flares throw out massive bursts of radiation

and high-energy protons, which might damage your DNA,

causing mutations and cancer later on.

Fortunately, there's a way of dealing with this - shielding.

Jeff Cerro is investigating the best materials to absorb radiation.

So we're looking at taking a garment and filling it with water,

which you see a first concept of here.

This astronaut with a water wall built into his wearable garment.

So this is something that you fill for an event and you're not really

charging the system the penalty of carrying all this mass.

You need the water anyways for drinking, for contingency water.

So it gets protection. It may be a different form

but with a lot less mass penalty to it.

Doubling up on function using materials that would be

on board anyway is an idea that Jeff is enthusiastic about.

We're trying to look at protecting astronauts using the logistics

which we already have on hand, so there's food,

items that we have in these bags that unfold to form a wall.

If you put a wall against the outside surface, you're trying to place

all these items between the astronaut and radiation you've got outside.

So the more items you can put between him and that,

you know, you attenuate the radiation,

the safer he'll be during this 36-hour solar particle event.

So, we've tried with food, we're trying to use water

but we're trying to use items that you're going to have on board the station anyways.

But there's an even bigger problem...

Another source of radiation that's even more damaging -

galactic cosmic rays.

Galactic cosmic rays are high-energy particles

spewed out from supernovae - exploding stars.

Their effects are pernicious.

By affecting the growth of brain cells, they can induce memory loss

in an astronaut after just six months in space.

But to shield a crew from radiation such as this

is currently impossible, so they have to look for other answers.

The best solution is to have people who are less

susceptible to their effects, or get there more quickly, so the lower

time in exposure is going to result in a lower risk to the crew members.

So the "right stuff" for a Mars astronaut might not just be defined

physically and psychologically, but also genetically.

There's a theoretical possibility as well that we could find some

genetic markers of people who are less susceptible to

the kinds of damage that occur during radiation.

It's too early in any of our research programmes to be able to

speculate on that, but it's certainly a theoretical possibility,

and it's one that we'll be investigating over the next few years of our programme.

But, for now, the stark reality is there is no obvious solution

to the problem of surviving space radiation.

At the moment, this is one of the great unknowns of a mission to Mars.

But assume you've escaped the radiation

and the mission is on track.

After being launched in the world's biggest rocket,

you've staved off the weakening effects of zero gravity...

..you've kept yourself sane...

you've managed to recycle everything...

..and you've survived solar flares.

So now, after travelling for over eight months

and across 56 million kilometres of space,

you're finally arriving

at the planet Mars.

Now comes the greatest engineering challenge of the whole mission -

landing.

Dr Adam Steltzner has been set the task of working out

how it'll be done.

He masterminded the audacious landing of the Curiosity rover on Mars in 2012.

I have tried to describe that many times and I fall short.

And I fall short because it pegged my emotion level, you know,

I have a meter... It just buried the needle.

But my career's not over. I'm going try and make something better.

But landing a human crew is a different matter entirely.

So landing Curiosity, a ton,

biggest thing we've landed on Mars to date, a challenge.

But not nearly as much of a challenge as landing humans.

Humans are sensitive, they're delicate, they don't

like a lot of Gs, they like to carry water with them, they're heavy.

So we think that landing humans might be something like

40 metric tonnes, or maybe more.

Once again, with a spacecraft carrying humans,

it's the bigger size that raises challenges.

There's this interesting bit of physics that occurs

as you scale up things.

Imagine scaling up a drop of water.

As it gets small or big,

its weight goes up with the size of it...

Cubed, raised to the third power.

But its aerodynamic drag gets larger

based on its area, which is its diameter squared.

What that means is, the bigger this self-similar thing gets,

the more easily it falls.

Same thing happens with spacecraft.

So if you think about Curiosity,

she came in going very, very fast, slowing down, slowing down,

and eventually making contact with the surface.

The smaller size of Curiosity meant that it was successfully

slowed by aerodynamic drag as it fell.

But scaling up the size for a human lander changes

the physics of landing, radically.

I've got this self-similar shape.

I'm going to not put Curiosity on the surface,

but I'm going to put two Curiositys.

OK, three, four, five, getting a little challenging.

40.

Now, all of a sudden I can't fly that shape. It's the same shape

it was before, it's packed at the same densities of spacecraft,

but now it ends up flying a trajectory

that intercepts the surface of Mars when its moving Mach 20.

Not good.

Perhaps to get really big things to the surface of Mars,

what we need to do is...

..we need to make our shape like this,

which regular rockets look like,

but when we come flying in, we don't put the pointy end in

or the back end in, we come in sideways.

By coming in sideways, the drag on the spacecraft is increased

significantly, slowing the rocket from hypersonic to supersonic.

To slow it down further,

you need something else to push against the gravity of Mars.

It's called supersonic retro-propulsion.

Imagine motorbiking with your mouth open at 60mph.

It's, "Whoa!" It fills your mouth with air

and it's actually sometimes hard to breathe out against it.

Well, that is the challenge of supersonic retro-repulsion.

You're going to light a rocket off into the flow,

but it's going to be supersonic flow.

Well, NASA's working on that.

And it's likely to take those rockets from a supersonic condition

all the way down to the surface.

It's an inventive and daring idea.

But to carry out this manoeuvre calls once more on one

of the sticking points that bedevils this entire mission -

fuel.

Retro-rockets will need a lot of it.

And where that fuel comes from is something NASA will have to solve

if they are ever to reach Mars.

To stand on the planet Mars.

What would be the reality of this centuries-old dream?

Well, the good news is, not a lot of weather on Mars.

It's very dry, it's windy, it can be dusty.

But the bad news is

that when the little weather there does stir the dust,

it can create scenes like this.

These are real images of a dust storm on Mars,

captured by a NASA rover.

When these storms do kick up,

they can go on for months and envelop the whole planet.

It's likely to be a far harsher situation than any astronaut faced

on the lunar landings.

Even on the Moon, conditions weren't easy.

Lunar soil is clingy and caustic - its particles were small enough

to cause a kind of lunar dust hay fever in the astronauts,

and sharp enough to wear though their Kevlar boots.

But no Apollo mission stayed on the Moon for longer than four days,

and they all used their lander as a base.

On Mars, life will be harder.

The dust whipping around in the wind is known to contain carcinogens

and other damaging chemicals called perchlorates.

What's more, Mars astronauts will be expected to stay for a whole year

before the planets line up for them to take the shortest journey

back to Earth.

So for these astronauts to live and work comfortably on the Martian

surface, they're going to need a new form of protection.

In charge of developing the next-generation spacesuit

is Dr Amy Ross.

So, one of the videos that we watch a lot is the Charlie Duke

dropping the hammer on Apollo 16 video.

He's trying to take a core sample,

he's hitting that core with his hammer, and he just loses the hammer.

He has real trouble retrieving the hammer,

so he just resorts basically to falling on it.

You can see we've progressed quite a ways,

and so our crew members now and our subjects now

can do all of those functional, realistic tasks that you need to do

in a much more normal fashion that didn't scare spacesuit engineers

like Charlie did on Apollo.

Remarkably, spacesuits have changed little since the Apollo days,

and those worn on the Space Station are just as bulky.

So Amy is looking to slim down

and add flexibility in every way she can.

So we have a side bearing which allows you to rotate your shoulder.

And then we have an upper-arm bearing, which you can see here,

that lets you rotate your arm.

Now, in the waist area,

this suit was built so it can allow flexion extension joint,

a waist bearing, and allows them some pretty wide range of motion,

very natural, and you move your waist a lot when you walk

and you don't realise that, so that's a very important joint to have.

And then we can watch him squat...

He can get down to his boots. So he can adjust his boots

when the suit's pressurised.

Can you touch the ground?

And you can see the joints work as he's doing these functional tasks.

Seemingly small developments like this take NASA ever closer

to the prospect of sending humans to Mars.

But from setting up a home on Mars

to knowing how they'll generate enough food and oxygen,

there are many thousands of these steps left to conquer.

And the final unknown is this.

Will the Mars astronauts be able to get home?

When the Apollo astronauts returned, it was to a heroes' welcome.

But for the astronauts going to Mars,

there's rather more uncertainty about their homecoming.

And that's because, as yet, no-one's worked out a way to get them home.

For now, this is a problem that NASA is trying to solve.

I would expect that they would come back.

We wouldn't design a mission unless we were pretty certain

they were going to be able to get back safely. That's one of our objectives.

We want to explore, which means getting there and coming back

and telling us what happened.

We value, in our modern society, life too greatly

to send astronauts on a one-way trip to the surface of Mars,

intentionally, certainly. There are tremendous risks.

The brave men and women who go into the astronaut corp...

take on those risks knowingly.

And sometimes astronauts perish.

Part of planning the mission will be about the risks

NASA are willing to accept.

But that's a delicate balance.

Because the more they aim to protect the astronauts,

the higher the cost and the further into the future

the dream will be pushed.

A momentum is starting to build around a manned mission to Mars.

Not just at NASA, but within other privately owned companies

who may work alongside them or even in competition.

Here at NASA, the scientists and engineers are doing what

they love doing - starting to grapple with problems which,

at first sight, seem unsolvable.

If we committed ourselves to getting to Mars,

we'd BE on Mars. Certainly within a decade.

I believe that we could get there within a decade.

The question is, are we willing to spend the efforts, the resources,

the capital to do that?

And I think the answer is, right now, no.

But maybe sometime in the future.

One reality is dawning.

Given the scale of this challenge,

it's one that no country can tackle on its own.

More likely than not, a Mars mission will be a multi-national mission,

so one political person in one country isn't going to drive the whole thing.

It's going to require a lot of cooperation from countries around the globe.

So this becomes a very interesting challenge,

but one that Earthlings will take on

and not just people from one country.

So the greatest challenge of this mission to put Earthlings on Mars

may not be a scientific or engineering one.

Whichever countries or companies join the undertaking,

it will be ambitious, risky and expensive.

But, above all, their challenge is to re-kindle the dream

of manned space travel...

..beyond our own planet.

What are we doing when we are exploring other worlds,

other planets, our solar system, our universe?

We are engaging in one of the most fundamentally human acts.

We are following our curiosity.

We are more curious than any other creature on this planet.