Mars Curiosity rover success depends on 'crazy' landing

 

Project architect Adam Steltzner explains how the Mars Curiosity rover is expected to land on Mars (animation is courtesy of Nasa)

"The average person on the street thinks it's crazy. Even the team that's working [on] it - sometimes we think it's crazy."

Adam Steltzner is responsible for getting Nasa's $2.5bn Curiosity rover mission to the surface of the Red Planet on Monday 6 August.

This mobile Mars Science Laboratory (MSL) should bring about a revolution in our understanding of the geological history of the planet… provided it can land safely.

Steltzner and his team have devised a breathtaking approach to the problem that involves a rocket-powered crane.

"It's so ambitious, it's so audacious, it's so unconventional. It doesn't feel like there's a lot of shelter," he tells the BBC's Horizon programme.

"You can't say, 'Oh, I'm doing what they did before and, oh, it just didn't work out; I didn't get lucky'.

Find out more

"No, we're not doing what we did before. We're doing something completely novel, hanging it way out there. You feel exposed."

But although Steltzner admits to the odd moment of panic in the middle of the night, he and his team actually have high confidence they can pull this one off.

"Reasoned engineering thought," he says, will get them through the white-knuckle ride that is entry, descent and landing - or EDL.

This is how the drama will unfold.

Start Quote

When the rover's wheels touch the ground... they must be moving no more than about 1m/s.”

End Quote

The 900kg rover will approach Mars enclosed in a protective capsule - the biggest capsule Nasa has ever used, bigger even than the Apollo Command Module.

It will arrive at the top of the atmosphere travelling 20,000km/h.

All that energy has got to be dumped. When the rover's wheels touch the ground six-to-eight minutes later, they must be moving no more than about 1m/s.

What scares the uninitiated most perhaps is the complexity of it all.

It starts with very precise navigation through space.

If the rover has any chance of reaching its equatorial target of Gale Crater, it must first hit an "entry keyhole" in the sky just a few kilometres across.

Curiosity - Mars Science Laboratory

MSL (Nasa)
  • Mission goal is to determine whether Mars has ever had the conditions to support life
  • Project costed at $2.5bn; will see initial surface operations lasting two Earth years
  • Onboard plutonium generators will deliver heat and electricity for at least 14 years
  • 75kg science payload more than 10 times as massive as those of earlier US Mars rovers
  • Equipped with tools to brush and drill into rocks, to scoop up, sort and sieve samples
  • Variety of analytical techniques to discern chemistry in rocks, soil and atmosphere
  • Will try to make first definitive identification of organic (carbon rich) compounds
  • Even carries a laser to zap rocks; beam will identify atomic elements in rocks

As the capsule thunders downwards, it ejects ballast blocks to move its centre of gravity and tilt its angle of attack.

This will give the vehicle lift. And with the aid of thrusters and some dead-reckoning, the entry capsule will fly a path through the upper atmosphere.

The underside of the capsule will get hot as it pushes up against the Martian air - the heat shield will experience temperatures above 2,000C.

More ballast blocks are then ejected to straighten the vehicle before, at 11km altitude and with the descent velocity now reduced to 1,400km/h, the capsule deploys a supersonic parachute.

This immense canopy will open instantaneously and must absorb an impulse of almost 30 tonnes.

Half a minute later, what is perhaps the most important event occurs - the separation of the heat shield.

Unless it comes off, Curiosity's descent radar cannot see the ground.

"The radar is fundamental," says Matt Wallace, the flight system manager on the project.

"You have to land softly or else you'll break the rover. To land softly, you have to know how high you are, obviously, from the ground. But more importantly you have to know how fast you are going - both vertically and horizontally.

"It's a pulsed-Doppler system and has the benefit of being extremely accurate in both velocimetry and altimetry, and it's very hard to fool."

The parachute will further slow the fall to about 450km/h, and it's at that point, at an altitude of about 1.5km, that we see the so-called "crazy" stuff.

A "sky crane" holding the rover drops away from the parachute, using thruster rockets to further slow its descent as it heads down towards the surface.

At just 20m above the ground, the sky crane hovers and lowers the rover down to the surface on three nylon cords.

Once the wheels make contact, the cords are cut, and the crane flies away to crash at a safe distance. Steltzner and his crew can breathe again.

All of this is automated; it's all pre-programmed. Earth and Mars are so far apart (250 million km) that communications links endure a 14-minute delay. Mission Control cannot intervene as if this were some online computer game.

My favourite number in this drama concerns the quantity of pyrotechnic devices.

These initiate key events, such as the severing of the nylon bridles or the opening of the chute housing.

All must blow - and in sequence - to ensure success. The number is 76.

Step by step: How the Curiosity rover will land on Mars

Aeroshell separates from cruise stage As the rover, tucked inside its protective capsule, heads to Mars, it dumps the disc-shaped cruise stage that has shepherded it from Earth.
Thrusters fired from MSL entry capsule The capsule hits the top of the atmosphere at 20,000km/h. It ejects ballast blocks and fires thrusters to control the trajectory of the descent.
Heat shield Most of the entry vehicle's energy is dissipated in the plunge through the atmosphere. The front shield heats up to more than 2,000C
Parachute deployment The parachute deploys when the capsule is about 11km above the ground but still moving at supersonic speed.
Parachute deployed above rover A key event is the dropping of the heat shield. This permits imaging and radar instruments to monitor the approaching surface.
Final moments before touchdown At about 1.5km above the ground and still moving at 80m/s, the rover and its sky crane drop away from the parachute and capsule backshell
Rover finally touches down Rockets on the sky crane slow the descent to 1m/s. Nylon cords spool the rover to the surface. Untethered, the crane flies to a safe distance and crashes.
Rover on the surface The rover is equipped with a nuclear battery and should have ample power to keep rolling across the Martian surface for many years.

But if all of this does sound a bit crazy, there is purpose.

We've grasped most of all there is to know about the simple geological history of Mars.

To deepen our understanding necessitates taking more sophisticated instrumentation to harder-to-reach places.

That means a bigger rover and a more robust landing system that can put down on the proverbial sixpence.

Consider all the surface missions Nasa has sent to the Red Planet, from the Vikings in the 1970s to the Phoenix probe in 2008.

Each has had a more accurate landing system than its predecessor, but only with Curiosity's EDL technology could you confidently attempt to get inside Gale Crater, one of the deepest holes on Mars.

"Scientists want to go to somewhere rough because that's where the rocks are exposed. The engineers in the past wanted to go somewhere flat where their machines would be preserved," explains Prof Sanjeev Gupta, a Imperial College London-UK researcher on the Curiosity science team.

"But we've now moved on to the next stage. Issues of life and habitability are really locked in the rock record, and to see those rocks you need to go to canyons and mountains - to get the chronology, to see the relationships and understand past climate changes.

"You won't get that on flat plains."

Landing  ellipses
  • Engineers define an ellipse in which they can confidently land
  • Viking's ellipse was 300km across - wider than Gale Crater itself
  • Even Phoenix (100km by 20km) could not confidently fit in Gale
  • Curiosity's landing system allows it to target the crater floor

Curiosity is due to land on Mars at about 06:30 BST (05:30 GMT) on Monday 6 August.

Horizon: Mission to Mars is on BBC Two at 21:00 BST on Monday 30 July

 
Jonathan Amos, Science correspondent Article written by Jonathan Amos Jonathan Amos Science correspondent

More on This Story

Related Stories

The BBC is not responsible for the content of external Internet sites

Comments

This entry is now closed for comments

Jump to comments pagination
 
  • rate this
    +46

    Comment number 27.

    Come on moaners you have to admit it really is great stuff. I woulld rather the £9billion or more spent on the Mclympics had been spent on something like this.

  • rate this
    +6

    Comment number 26.

    11.Rob - ".....billions are been spent to send a geologist to mars to dig rocks. This really annoys me. We should be sending equipment and supplies for a manned mission...."

    You best add a nought to the cost then & start finding NASA the cash to do it......

  • rate this
    -48

    Comment number 25.

    Next time pictures of starving Africans flash up on our TV screens we may like to ponder how much money,time and effort is wasted on things like this.

  • rate this
    +4

    Comment number 24.

    There are many factories running reliably on very complex fully automated systems. Its not such a crazy idea and it has every chance of being a big success. The question is why are we doing it. Because Mars is there or because somehow we dream of finding evidence of life on Mars.

  • rate this
    +7

    Comment number 23.

    I just can't wait to see the headline: "Mars Curiousity successful landing"

    It'll just break my heart if she doesn't make it.

  • Comment number 22.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • rate this
    +12

    Comment number 21.

    This is pretty awe-inspiring to say the least. I wish the NASA team all the very best of luck - fingers crossed!

  • rate this
    -20

    Comment number 20.

    Half of all our missions to Mars mysteriously end in failure.
    Haven't you all figured it out yet?

    Think about it. They're getting shot down!

  • rate this
    +8

    Comment number 19.

    Now this is what humanity should be using technology for, looking outward and exploring rather than looking inward and using it to enslave a myopic and naive public.
    my only regret is that the mission concentrates on the geological and not the biological.

  • rate this
    +13

    Comment number 18.

    @4 (tobus)
    What you have to remember is that the BBC (and other mainstream news portals) aren't staffed by boffins. The beeb's own Science/environment page consists mainly of stories relating to penguin poo and left handed bees. Hit a proper site like the Planetary Society Blog for the real story of why landing on a planet with a bit of atmosphere and gravity is so hard. :)

  • rate this
    +11

    Comment number 17.

    As for some answers to questions to date ... why are we exploring rocks instead of preparing for human touchdown? Answer: this is preparing for human touchdown ... we aren't going to test out the prototype landing method with real people. Why so complicated ... ie. the floating sky crane? Turns out given all the variables that this is the safest - most dangerous part is take-off & landing.

  • rate this
    -15

    Comment number 16.

    "...I'm sorry but the rover you are attempting to call is toast, please try again later..."

  • rate this
    -28

    Comment number 15.

    Even if it works, and even if they'd come-up with something WOW, what good was it supposed to do on Earth? We already know a bunch more about deep space than what's cooking right at our front door. Ambitious indeed.

  • rate this
    +12

    Comment number 14.

    As long as all the little motors and explosives work and there are no issues with the nylon cables and the different teams didn't do anything stupid (like one used metric units while the other used Imperial, as has happened before), I think it has a decent chance to work. This is the organization that successfully conducted a manned round-trip to the moon in the 60s. Using primitive computers. Go!

  • rate this
    -52

    Comment number 13.

    I think its pure genius how organisations like NASA invent intriguing ways to distract us from asking essential questions such as "Why on Earth are we sending yet another rock sampling mission to Mars?" Technologically speaking we are 100's of years away from any real chance of transporting humans to/from Mars. This $2.5bn would be better spent on something that actually advances humanity...

  • rate this
    +10

    Comment number 12.

    9 deryk houston - Where do you get the idea NASA doesn't approve of art? The Voyager Golden Records are probably the purest definition of art; utterly useless, never to be seen again by human eyes yet full of symbolism & lacking any pretentiousness.
    They also take great care over their mission logos. The pair from Spirit/Opportunity were a favourite of mine – Duck Dodgers & Marvin the Martian!

  • rate this
    -25

    Comment number 11.

    so let me get this straight, billions are been spent to send a geologist to mars to dig rocks. This really annoys me. We should be sending equipment and supplies for a manned mission not wondering about a silly rock sample. I can't wait for China to start their mission because in the west we are just happy to look at rocks. No one cares just humans to mars. Or even robots for the purpose of colony

  • rate this
    0

    Comment number 10.

    Why do virtually all of the paragraphs in this report consist of only a single sentence? So patronising

  • rate this
    -14

    Comment number 9.

    I'd like to challenge the team to do a very simple drawing on the surface using the wheel tracks of the vehicle. (from cave walls to the surface of another planet.)
    One little wiggly line (sperm) that leads to a small circle (egg).....life on Mars.
    The NASA team says that these missions are about science and art has no place in these very expensive missions.
    I believe that art is everything.

  • rate this
    +48

    Comment number 8.

    So we're landing a rover the same size as a car on another planet 250m km away, using a completely automated system due to the radio time delay all for 1/6th the cost of a sporting event... why is this not bigger news!?
    This will be a brilliant achievement if everything goes to plan, the Mars rovers have been some of the most interesting projects in history; Opportunity has been going for 8 years!

 

Page 7 of 8

 

Features

  • NS Savannah, 1962Nuclear dream

    The ship that totally failed to change the world


  • Ed Miliband takes a selfie at a Cambridge hairdressersNo more photo ops?

    Why is Ed Miliband drawing attention to his public image?


  • Espresso cup7 days quiz

    Which city serves the strongest cup of coffee?


  • Glasgow 2014 quaichs and medalsQuaich guide

    What do the Scottish gifts given to Games medallists symbolise?


  • Malaysian plane wreckage in UkraineFlight risk

    How odd is it for three planes to crash in eight days?


BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.