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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 tes

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.

deleted 14y ago
[deleted]
chadr 14y 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 14y 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 14y ago
  How do you even test for something like this?
wolf550e 14y ago
http://www.jpl.nasa.gov/events/lectures_archive.cfm?year=2009&month=8 http://www.jpl.nasa.gov/events/lectures_archive.cfm?year=200...
jeffbarr 14y ago
You may find this paper interesting: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090007730_2009006430.pdf 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.
- mturmon 14y 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.
  - trothamel 14y ago
    Unless something has changed, the US government doesn't own the copyright - works they produce are automatically in the public domain. Most journal put wording on the paper to that effect. So if you have access to the papers, you should be able to post them for free somewhere without violating copyright.
    - mturmon 14y ago
      Not quite. They were almost certainly approved by JPL in its role as a FFRDC. The copyright in such cases belongs with the government. What you write would be correct if they went through copyright release at another NASA center like JSC in which the workers are federal employees (I work at JPL.)
ballooney 14y 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 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) 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 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.

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.

deleted 14y ago

[deleted]

chadr 14y 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 14y 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 14y ago
How do you even test for something like this?

wolf550e 14y ago

http://www.jpl.nasa.gov/events/lectures_archive.cfm?year=2009&month=8 http://www.jpl.nasa.gov/events/lectures_archive.cfm?year=200...

jeffbarr 14y ago

You may find this paper interesting: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090007730_2009006430.pdf 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.

mturmon 14y 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.
- trothamel 14y ago
  Unless something has changed, the US government doesn't own the copyright - works they produce are automatically in the public domain. Most journal put wording on the paper to that effect. So if you have access to the papers, you should be able to post them for free somewhere without violating copyright.
  - mturmon 14y ago
    Not quite. They were almost certainly approved by JPL in its role as a FFRDC. The copyright in such cases belongs with the government. What you write would be correct if they went through copyright release at another NASA center like JSC in which the workers are federal employees (I work at JPL.)

ballooney 14y 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 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) 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 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.