Rough Roving: Curiosity's Wheels Show Damage 78
astroengine writes "In a recent batch of images beamed back to Earth from Mars rover Curiosity's MAHLI camera, obvious signs of wear and tear could be seen in the 'skin' of the robot's wheels. Considering Curiosity is only 281 sols (Mars days) into its mission and roved less than a kilometer after landing, surely this doesn't bode well? Fortunately, there's good news. 'The wear in the wheels is expected,' Matt Heverly, lead rover driver for the MSL mission at NASA's Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News. 'We will continue to characterize the wheels both on Mars and in the Marsyard, but we don't expect the wear to impact our ability to get to Mt. Sharp.'"
Fun fact (Score:5, Interesting)
There's a fun fact about the wheels of Curiosity. They spell out "JPL" in Morse Code in the sand of Mars. :)
Re: (Score:2)
I wonder if this impacts the strength of the wheel any with all those dashes, perhaps just saying hi would make them more durable.
Re: (Score:1)
"I WAS HERE!"
Re: (Score:1)
Should have gone with Michelin. Because so much (money) is riding on your tires.
Re: (Score:2)
Re:Fun fact (Score:4, Informative)
The sections where added to be used to to visually measure the precise distance between drives.
source:
http://www.nasa.gov/mission_pages/msl/news/msl20120829f.html [nasa.gov]
Re: (Score:2)
The addition of holes is very interesting and I'd be interested to hear the rational for incorporating such sections into the wheels.
To drop any sand or grit out once per revolution. You wouldn't want it to build up.
Re: (Score:2)
Re: (Score:3)
I learn something new today. Thanks !
BTW, looking at the picture ( @ http://upload.wikimedia.org/wikipedia/commons/3/37/Curiosity_wheel_pattern_morse_code.png [wikimedia.org] ) I am totally surprised at the sheer thinness of Curiosity's wheel !
How can they expect Curiosity to last long with such thin wheel ??
Re:Fun fact (Score:4, Insightful)
Because the project managers were given criteria. 1. it had to last for X months... 2. it had to be under X kilos. Which do you think was a harder goal? I think it's pretty obvious. Making things that last forever is easy. Making things that are light is easy. Making things that are both? Little bit more difficult.
Re: (Score:1)
Really look at the wheels; they are actually a very well designed machine component. The main design strengths are graceful degradation (inherently long working life), and an excellent balance of material conservation/functionality . A breakdown follows:
1. The center ribs of the wheel are the first structural element, transmitting the forces exerted on the wheel to the hub.
2. The treads are thicker material that provide several functions: provide traction, transmit the forces from the wheels' skin to the c
Re: (Score:2)
Lss Schwab (Score:2)
If they find a Les Schwab center to fix the tires, we'll know there's no intelligent life on mars.
Re: (Score:2)
Out there in Mars, that rover's more likely to find a Charles Schwab center and end up owing a consultant money.
Re: (Score:2)
>Out there in Mars, that rover's more likely to find a Charles Schwab center and end up owing a consultant money.
$7.95 per turn of the wheel, in either direction.
Re: (Score:2)
Quick someone figure out the cost per revolution of a wheel if the rover only completes the primary mission...
Please
Wheel wearing (Score:5, Informative)
These wheels aren't like your normal car wheels. The very thin atmosphere means that the soil is more like lunar soil than Earth soil. Atmospheric erosion tends to smooth out sand particulate so it has a rounder shape -- it is less sharp. Lunar soil is incredibly corrosive. Think of all the problems our troops had operating in Iraq with their equipment, now multiply that by a hundred. It's like walking on microscopic needles. Martian soil isn't quite as bad, thanks to having had an atmosphere at one point, and retains a minimal one now, but it's still inhospitable.
The rover was designed with multiple wheel-sets to operate independently, and the wheels themselves designed to wear somewhat more gracefully in the face of these obstacles. But yes, they're going to look ugly fast.
Re: (Score:1)
Despite its thin atmosphere, Mars regularly experiences massive sandstorms, so there should be plenty of erosion going on.
Re:Wheel wearing (Score:4, Insightful)
I think you are confusing abrasive with corrosive.
Re: (Score:1)
Oh, my apologies. I didn't look at your username before I called you 'sir'. I was initially going to go for a Dr. Strangelove reference but changed it at the last moment. Sorry about that, no insult was intended.
Re: (Score:1)
Oh, my apologies. I didn't look at your username before I called you 'sir'.
He's a girl in training; he won't be a girl until he graduates.
Re: (Score:3)
Rough Landing (Score:1)
Re:Rough Landing (Score:5, Insightful)
Re: (Score:1)
Re: (Score:1)
Re: (Score:2)
But if you look at the pictures more closely, it looks like the dents were formed from the interior side of the wheel. I am not sure how terrain could cause that to happen.
Me either. I just hope it's not some innate metallurgical or manufacturing flaw that would cut the mission short.
Spirit and Opportunity set unrealistic expectation (Score:5, Insightful)
Since those 2 rovers outlasted their expected mission life by a factor of 20ish, everyone now expects every science mission to do similar. When they last for the amount of time they were engineered for people are disappointed. That's the danger in overachieving and the reason people feel compelled to use their full budget each year - if they're frugal for a year people expect that they'll be able to do the same every year and cut the budget. Some aspects of human nature stink.
Comment removed (Score:5, Interesting)
Re:Spirit and Opportunity set unrealistic expectat (Score:4, Insightful)
I remember seeing a video where they did the math and for a 3 month stay on the ground and round trip from here to there you'd have needed a ship bigger than the empire state building
Your "math" is incredibly bad. Read any book on Mars from Zubrin and become educated.
What you are overlooking is that one human in one day could day about 100x the total research done so far by all of the rovers combined. What doesn't make sense is to continue to send very expensive robots to learn less and less... we've reached the point where we simply need to send humans to really study the place.
Why are you so focused on Back? (Score:2)
sure, humans would be productive, but orbital mechanics, assuming current and near term rockets, means that you're still looking at 8-9 months on the way out there, and 8-9 months on the way back plus the year or more on the ground while you wait for Mars to get back
Back back back back back.
It's pretty damn obvious at this point there is no "back" for the first people going. When you ignore that part, especially having to launch from the surface, the whole trip is far simpler and cheaper even if you plan f
Re: (Score:2)
But for the same cost as sending a human on a round trip to Mars you could build a fleet of rovers. Design and testing is a significant part of the cost so building extra rovers lowers the average cost dramatically.
A human can do 100x more in a day? For the same cost I'd bet you could send may more than 100 rovers and explore a much larger area of Mars.
Re: (Score:2)
Perhaps the most important reason for humans to go exploring is because the only way to learn how to live in space is to do it.
Re: (Score:3)
So robot bodies are durable but slow, human bodies versatile but fragile...
can't we send zombies?
Re:Spirit and Opportunity set unrealistic expectat (Score:4, Funny)
Dude, relax, it's just science fiction. There was no caretaker, and no one was pulled into the Delta quadrant.
Re: (Score:2)
Glad it's expected. (Score:4, Funny)
Otherwise, it's a hell of a long wait for the AAA. And who's going to to stand there next to the rover with their card?
Mass and Weight are different (Score:5, Interesting)
From the article:
This sounds an idea from the same people that brought us the Mars Climate Orbiter crater.
The problem with this is that Curiosity weighs 342kg but masses 900kg. Scarecrow weighs and masses 342kg. Whatever Curiosity weighs, it hitting a rock at 1m/s is still 900 newtons of force. Scarecrow hitting a rock at 1m/s is 342 newtons. The fact it drove 12km and has serviceable wheels does not make me feel better.
Re: (Score:1)
The same force from gravity is exerted on Curiosity's/Scarecrow's wheels. I would think that, rather than impacts, would be the bulk of the wear and tear on the wheels.
Re:Mass and Weight are different (Score:5, Insightful)
Whatever Curiosity weighs, it hitting a rock at 1m/s is still 900 newtons of force. Scarecrow hitting a rock at 1m/s is 342 newtons.
Stop accusing NASA scientists of not understanding their job when you don't remember basic physics.
F = m * a, not F = m * v. In this case a is the acceleration due to gravity. In addition, mass is measured in kg, weight is measured in Newtons, because weight is a force. The newtons are exactly the same between those two rovers.
Re:Mass and Weight are different (Score:4, Interesting)
F = m * a
Look it's right there, force equals *mass* times acceleration. On earth, Scarecrow is 342kg * 1g when stationary. On mars Curiosity is 900kg * 1mars-g *when stationary*. Sure the vertical force on the tires is the same when standing still, but what about the force required to stop 342kg vs 900kg of inertia if you hit a large pointy rock at 1m/s?. In this case, with the same initial velocity, the acceleration would be the same but the force experienced by Curiosity's tires would be ~3x larger (ignoring any shock absorption).
Re: (Score:3)
Sure the vertical force on the tires is the same when standing still, but what about the force required to stop 342kg vs 900kg of inertia if you hit a large pointy rock at 1m/s?
Who says the rover is stopping when it encounters a rock? Either the 342 kg one or the 900 kg one? The same amount of force will stop both, but the force will need to be applied for longer in the 900 kg rover. The term you're looking for is momentum, not force. The 900kg, assuming it's moving at the same speed as the 342 kg one, has more momentum.
Mass would certainly matter if they crashed the rover and transferred all that momentum, assuming they were moving at the same speed as the equivalent one is h
Re: (Score:3)
You do have a point -- I don't agree with some of the other responders who talk about traction forces being smaller as well. Just to make it clear: what you say applies to a cart on wheels, having constant horizontal velocity and approaching a bump in an otherwise flat surface. A larger mass of the cart will result in a larger force
Re: (Score:2)
Scarecrow is 342kg * 1g
Ow, my units!
Re: (Score:3)
That's what's referred to as dynamic acceleration. Rolling along at 1 m/s and then coming to a sudden stop by running into a rock would indeed produce some big accelerations, and the difference in mass between Curiosity and Scarecrow would be pretty significant.
However, the scenario that you and an earlier comment are talking a
1m/s? Are you kidding me? (Score:2)
Sure the vertical force on the tires is the same when standing still, but what about the force required to stop 342kg vs 900kg of inertia if you hit a large pointy rock at 1m/s?.
1 m/s? Are you kidding? Curiosity has a top speed of less than 0.04 m/s on flat ground, it literally crawls along. Force due to gravity will be by far the dominant force on the rover's wheels.
Re: (Score:3)
Curiosity wheel encounters rock. Wheel exerts force to lift itself over rock. To do this, wheel must lift all of Curiosity. Curiosity masses 900kg. Object at rest tends to stay at rest. Curiosity tends to stay at rest. Curiosity wheel has much inertia to overcome to make Curiosity start moving up and then over rock.
You're still incorrect. Yes, the 900 kg rover has more inertia. Inertia doesn't matter as far as how much force is being applied to the wheels, though. It means the same force will be applied as to the equivalent lower mass rover on Earth, and because of its higher inertia the rover on mars will accelerate slower while that same force is being applied.
Write the force diagram yourself. Think about what it takes to move a vehicle on wheels. How much traction do you get? the coefficient of traction times [wikipedia.org]
Re: (Score:2)
Curiosity wheel encounters rock. Wheel exerts force to lift itself over rock. To do this, wheel must lift all of Curiosity.
False. The rocker-bogie system allows the wheels to move vertically with very little problem. Weight is distributed all the wheels equally under normal circumstances. The most that a wheel might experience would be half the weight, and that would only happen if two of the three wheels on the rocker-bogie were off the ground. That's not going to happen because the onboard hazard avoidance and the NASA route planners wouldn't get the rover into such a predicament. So, the most that Curiosities wheels wou
Re: (Score:1)
The force due to gravity is the same, however on impact the forces will be different (or would you argue the force would be zero in space, since a=0?).
If I was the bump in the way, I would far sooner be hit by a 342kg mass than a 900kg one - and similarly the damage I'd inflict on the mass would be less.
Re: (Score:1)
except that Curiosity goes nowhere near 1 m/s... more like a few cm/sec so gravity loads far exceed acceleration loads.
Re: (Score:3)
That distinction is really only revelant in the case of dynamic loading: hitting things at speed, rapid straightline accerelation, or quick turning. Whether Curiosity on Mars or Scarecrow on
What about the landing? (Score:2)
It must have been rougher than normal driving. Can a comparison be made with images taken right after landing?
They did. (Score:2)
the words we choose. (Score:2)
My tire-skin brings all the rovers to the marsyard
And they're like,
Its worse than yours,
Damn right, much worse than yours
I can teach you,
But I'll eat your sols
Wait, what? (Score:2)
So.... (Score:2)
In other news: Car tire worn out. "To be expected" claims manufacturer.
Re: (Score:2)
Punctured from the inside out? (Score:1)
Doesn't anybody find it curious that it looks in one of the shots that the holes go from the inside to out? How is that even possible? I mean, dents on the outside are reasonable but how did the ones (and there are several deep ones) on the inside happen?
Re: (Score:3)
Not really. Work in a garage for a month, you see all kinds of weird damage come in.
And this wheel is basically a cut-open barrel. Punch it on the outside and it makes a dent on the inside. It's rolling across a rocky landscape, after being basically dropped onto the planet. It probably bumps down a lot more rocks than you realise and even more than NASA ever plan, the chances of finding a level surface to wander over that doesn't have a hidden 10cm drop onto rock for at least one of the wheels hidden b
Optical illusion (Score:2)
Could be an optical illusion, all the dents I can see on the images go from the outside in.
Re: (Score:2)
This was my first through.
I mean, the thing does not travel fast enough to warrant getting a stone to punch through from the outside in,
However, look at the "Speed Holes" on the wheel surface, I am sure stones caught caught up IN the wheel and then tumbled down to dent the wheel from the inside out.
I mean, come on, you got big open wheels on a rocky surface, this ain't rocket science.
Can't repeat the blunder... (Score:2)
Don't worry, it's all according to the plan.
Considering the continued cost of maintaining Opportunity (and until not so long ago, Spirit) still running strong many years past expected "expiration date", all new mars rovers have "planned obsolescence" features built in; they are designed to break soon after their planned mission time is past. /tinfoilhat
Typical auto industry (Score:2)
The rover loses 30% of its value as soon as you drive it off the lot. And if NASA tries to trade it in I bet a lot of "damage" will be discovered to drive down the price.