Curiosity landing is in a week

http://mars.jpl.nasa.gov/msl/participate/

by huhtenberg • 14 years ago

91 37 14 years ago

mars.jpl.nasa.gov

stevewilhelm• 14 years ago

The simulated video of the Curiosity landing makes it seem very complicated and prone to failure.

Wondering what full scale prototypes where built and what testing was done.

chadr• 14 years ago

from Wikipedia... "The landing sequence alone requires six vehicle configurations, 76 pyrotechnic devices, the largest supersonic parachute ever built, and more than 500,000 lines of code."

flexd• 14 years ago

They check for a few more error cases than the average project I guess, hehe.

  am looking forward to seeing it land successfully!

Regardless of how it lands though, it should be exciting to watch.

trafficlight• 14 years ago

How do you even test for something like this?

wolf550e• 14 years ago

http://www.jpl.nasa.gov/events/lectures_archive.cfm?year=200...

jeffbarr• 14 years ago

You may find this paper interesting:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/2009000...

"Mars Science Laboratory: Entry, Descent, and Landing System Performance"

There's another paper floating around (that I can't seem to find) that evaluates and compares all of the alternatives to show why they decided to go with this particular configuration.

mturmon8• 14 years ago

I can find several papers in IEEE Aerospace Conference proceedings, but they are not available in free form online. This is a shame, because the government owns the copyright.

ballooney• 14 years ago

It's very difficult to recreate mars on earth sufficiently (without bonkers expense) to thoroughly test at full scale, but there are some interesting ways you can get close.

For example, the parachutes that will be used on Mars deploy at a certain dynamic pressure, ambient pressure, mach number and mass ratio (the ratio of the payload mass to the mass of the air entrained by the parachute). All of these factors quite significantly affect the magnitude and the shape of force vs time profile of the parachute as it opens.

You care about this because the maximum force that a parachute generates is when it opens, higher than the equilibrium force it would generate under the same conditions, so that's the number you need to do the stress calculations on the entire landing system (and every gram is costing the tax payer a lot, so you can't really afford to just over engineer it to save some analysis).

You also care about this because at one ambient pressure a parachute might oscillate and corkscrew, at another ambient pressure it might form a stable glide (this has a lot to do with where the centre of gravity is of the payload and the air entrained by the payload). If you have a computer vision system calculating landing sites on your lander, you really don't a wobbly 'chute.

So, deploying in a wind tunnel isn't much use as that's at sea level pressure. You also can't really have more than a single-digit percent blockage of a wind tunnel by the test article (in cross sectional terms) otherwise the results are off because the air velocity round the parachute has to increase to maintain the mass flow through a smaller area. Big windtunnels are rare and expensive, big ones that'll do transonic and supersonic basically don't exist, big wind tunnels that will do transonic and supersonic at low pressures (Mars's atmosphere being about 1% the density of Earth's) just don't exist.

But we can do useful things on earth. Our atmosphere density decreases as you get higher to almost nothing. So at some point between sea level and space we can find at altitude that has the right ambient pressure. You can get a model of your lander, tow it above that altitude, to an altitude that you have calculated so that when you release it it will reach (in free-fall) the right mach number at the pressure-matched altitude.

This is done at full scale but it's still very expensive, requiring huge helium balloons over big ranges.

I was involved in a project which did exactly this, but on the cheap at sub-scale, when I was a student. If you're interested you can read the paper here: http://www.cusf.co.uk/CUSF_AIAA_2011.pdf

Of course, that's just the parachute!

As for the sky crane, there is no way to frame it that doesn't make it look extremely ambitious, it is. However, recall that the Mars Phoenix lander of 2008 used steered retrorockets to land successfully: http://en.wikipedia.org/wiki/Phoenix_(spacecraft)

Recall secondly that the Spirit and Opportunity landers used a deploying tether to lower the airbag system away from the retrorockets. Step 8 on this page: http://marsrover.nasa.gov/mission/tl_entry1.html

So, you can argue that the bits have been tested before on Mars, but of course putting them all together into a single system is a challenge in itself.

It will be fascinating to watch, a magnificent achievement if it works, admirably bold either way.

mturmon8• 14 years ago

Here's a translated abstract on supersonic parachute testing for MSL. I was not able to find the full paper online.

http://www.aric.or.kr/treatise/journal/content.asp?idx=11774...

Achshar2• 14 years ago

What will they show in the live feed? It makes me sad we can't have a (near) live feed from the delivery case or even the sky crane. Except for the understandable 19 (or so?) minutes or lag due to speed of light, the bandwidth is not nearly enough. It would have been cool of another level to be able to see the rover landing live, 19 light minutes away.

avar• 14 years ago

It'll most likely be a panel of people explaining what's happening as they get data coming in, shots of the team as they cheer/look nervous, and eventually a bit after the landing there might even be a photo from the martian surface taken by the rover.

At least that's what it's been like on other similar live coverages.

ricardobeat2• 14 years ago

I'm more curious about why can't we have a live feed. We had one from the moon 40 years ago, is bandwidth also degraded by the distance to Mars?

Achshar2• 14 years ago

The moon is relatively (very) close (238,900 miles vs depending on where they are in their respective orbits, mars can be anywhere from 36 million miles to over 250 million miles away from earth), there are good relay satellites for moon and sun never comes in between to disturb incoming signal.

tocomment2• 14 years ago

I don't understand why they need the skycrane. Why did Viking land ok without this complexity? Why can't they reuse whatever they did for Viking?

dag11• 14 years ago

I'm pretty sure one of the reasons is its unprecedented size: http://upload.wikimedia.org/wikipedia/commons/0/0d/Mars_Scie...

raverbashing• 14 years ago

Size + required landing precision

It certainly looks like overly complex. The simplest system, that is, airbags, are unusable because of the size (it's almost like the difference between a big toy car and a regular car)

You probably can't brake it only with retrorockets, and as this mission is aiming to be the most precise landing on Mars ever (and I'm not even sorry for the pun) they need a way to get the lander to an exact location (by deploying it from the crane)

Sharlin2• 14 years ago

People seem to forget/not realize that the EDL (entry, descent and landing) of Spirit and Opportunity had pretty much all the elements that the Curiosity EDL does PLUS the airbags and the airbag cocoon: http://www.youtube.com/watch?v=Ij33yhdGn_g

ddbeck3• 14 years ago

One of the reasons for the skycrane is that it minimizes the area of the Martian surface that will be disturbed by the landing rockets. The skycrane approach moves less surface soil around the landing site (decreasing travel distance to pristine subjects for geological study) and deposits less rocket exhaust (which complicates chemical and biological studies).

NASA has an excellent and free ebook, _When Biospheres Collide_ [1], which goes into great detail about the problems posed by biological contamination (both forward and back). The book dedicates a long chapter to the great lengths taken with the Viking landers to avoid contamination problems. Having read it, I'm not at all surprised NASA is giving alternatives a try.

[1] http://www.nasa.gov/connect/ebooks/when_biospheres_collide_d...

tocomment2• 14 years ago

Why didn't Viking worry about disturbing the landing site?

Also If it can drive why does it matter what happens to the landing site?

mturmon8• 14 years ago

The specific dust factor that is mentioned in the EDL video is dust, kicked up in descent, settling on the instruments within the robot.

Do you have a reference to the contamination rationale playing a role for the choice of a crane for MSL? Because I have not heard that mentioned.

bhickey• 14 years ago

If you're in the area, there's an event at Ames: http://www.nasa.gov/centers/ames/events/2012/ames-curiosity....

larsberg• 14 years ago

In Chicago, the Adler Planetarium is having a 9pm-2am viewing party as well (http://www.adlerplanetarium.org/curiosityparty ).

alex_c• 14 years ago

Why / where exactly does the sky crane fly away after releasing the lander? Is it just to get it safely out of the way?

ceejayoz• 14 years ago

Yes. You don't want it landing on top of the rover, so it flies a predictable path away and crashes.

Curiosity landing is in a week

Related Stories