Rough Roving: Curiosity's Wheel Damage 'Accelerated' 157
astroengine writes "Despite the assurances that the holes seen in Mars rover Curiosity's wheels were just a part of the mission, there seems to be increasing concern for the wheels' worsening condition after the one-ton robot rolled over some craggy terrain. In an upcoming drive, rover drivers will monitor the six wheels over some smooth terrain to assess their condition. "We want to take a full inventory of the condition of the wheels," said Jim Erickson, project manager for the NASA Mars Science Laboratory at NASA's Jet Propulsion Laboratory, Pasadena, Calif. 'Dents and holes were anticipated, but the amount of wear appears to have accelerated in the past month or so.' Although the wheels are designed to sustain significant damage without impairing driving activities, the monitoring of the situation is essential for future planning."
Please pray with me for Curiosity's wheels. (Score:4, Funny)
Dear Lord, Father in Heaven, we pray together for the safekeeping of Rover Curiosity's wheels. Although it may be a tool of science, and its discoveries a complete threat to religious doctrine everywhere, she is but a rover on a mission of Peace and Goodness. In your ever forgiving heart, please bless her wheels with durability and robustness.
Amen.
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And he is before all things, and by him all things consist. --Colossians 1:17
Perhaps God will inspire the Chinese ... (Score:1)
In this age, whatever failure the other parties has met with is the lesson that one picks up.
The lesson whereby the failure of Nasa to better equip the Curiosity's wheels against abrasion / wear and tear may mean that the only country left on this world that has the will and the financial might to forge ahead with their space aspiration (China) surely benefit.
I bet if they are to send up any more space equipment (rover, dune buggy or whatever) they will put more emphasis on the parts that might face the iss
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"I bet if they are to send up any more space equipment (rover, dune buggy or whatever) they will put more emphasis on the parts that might face the issue of wear and tear / abrasion / friction."
I have to wonder: who chose aluminum as the material for the wheels in the first place? I'm not a mechanical engineer but just off the cuff that strikes me as a remarkably bad choice.
Aluminum has little resilience. If it strikes something hard (especially something hard and pointy) it's going to bend, and not rebound. This is pretty much a given. Make it thin enough to be lightweight and it's also going to puncture or break.
It sure seems like a gross waste of resources to give it a long-life nuclear p
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That's like saying that "all beer tastes like piss", or "all food tastes like shit." There is a huge variety of grades and strengths of aluminium and aluminium alloys. Some are, as you say, quite brittle ; some are tremendously strong and have high (and very well understood) fatigue lives (I'm thinking particularly of aircraft skin alloys ; I'm sure there are others.
I'm not a materials scientist, but a practical geologist. Every year I see the stunned look on drilling enginee
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Where in the hell did this "NASA is dead" meme start? It keeps popping up every few years. Yeah, it's underfunded. Have you written your elected officials? They're the only ones who can do anything.
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May I be allowed to get back on topic? NASA's website doesn't have the "OH, SHIT!!" factor. [nasa.gov]
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Who are you talking to?
You know, talking to yourself may be a symptom of an underlying disorder. Have you talked with your psychiatrist lately?
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It seems there is a moderator lacking a sense of humor, I thought it was funny.
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Don't worry about it, anyone can get mod points. There's no sense of humor test in there at all. Well, except on Slashdot's part where they're giving me 15 mod points at a time now. :)
Some people get really bent over their invisible friends, so even if they had a sense of humor, they lose it entirely. As long as they don't insult Gozer, I think we'll be ok.
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Why would finding life be a threat to religious doctrine? What religion?
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Amen.
B.women.
C.other.
Re: Please pray with me for Curiosity's wheels. (Score:3)
That joke doesn't work if you pronounce Amen correctly.
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That joke doesn't work if you pronounce Amen correctly.
Not all of us are from Bahston. Potato, potahto, fuck off, snob.
Re: Please pray with me for Curiosity's wheels. (Score:2)
It's Latin. You don't get to use English pronunciation with it.
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It's only Latin if it comes at the end of a sentence spoken in Latin. Likewise, "cough" is an English word unless it's in a sentence spoken in German.
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Cough isn't even a word in German...
Amen is a Latin word, and not an English word of Latin origin. While pronouncing it the English way is accepted by laymen, it's not the proper pronunciation. Amen is a word which is used in many different languages too.
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Amen is a word which is used in many different languages too.
Exactly my point. In Spanish it would be pronounced "ah main", since the A is always "ah" and the E is always "A". Pronounced like that it's a Spanish word.
NASA is an ugly place for a grading curve. (Score:2, Insightful)
As A poor young man driving a $500 '73 Ford Pickup, I remember carefully monitoring oil consumption, water level, and tread wear on the five dollar maypops I could afford to put on my baby's feet.
It is common knowledge that NASA has one initial too many for the Brobdingnagian budget, but I was poor as two Mongolian goat herders.
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So, were you driving that truck on Mars?
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Future planning? (Score:1)
...the monitoring of the situation is essential for future planning
They mean when the rover is near it's death, they pause it, and send more rovers. After they get like 8 up there, they'll fight them, like on BattleBots. You know, get Mars ready for humans and their wars.
...the monitoring of the situation is essential for future planning
We all know that those rovers are up there cutting up large rocks and stacking them into pyramidal shapes that regulate the atmosphere in preparation for humans to arrive, only to try to cover up the pyramid's real identity so that the future race of beings don't know their real history.
...the monitoring of the situation is essential for future planning
obligatory fu [xkcd.com]
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As part of planning to send people to the other planets, I am surprised that they do not try to figure out a way to get something back from the landers. I would think that seeing how the materials held up to the conditions it went through would be important data to have.
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Nothing much, really. A number of the Apollo missions left the Earth's magnetic field, and nothing spectacular happened.
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They weren't up there for the year it would take to get to Mars, radiation is a bitch. That said, Buzz Aldrin is 83 with no sign of cancer so who knows?
cheapest return mission is about $4B (Score:2)
The latest proposed sample mission would invovle three sub-missions; (1) A lander-rover to collect the rockets; (2) a lander-
Next time... (Score:1)
they should not go with Pirelli...
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snap!
It always sucks to get tire damage (Score:2)
that gets you stranded in a bad neighborhood.
Rough rovin', or rovin dirty? (Score:1)
Maybe the wheels are just dirty?
They see me rovin'
They hatin'
Amazing machine! (Score:2)
I don't get all the people bashing the design?
Just think how long the rover has been on Mars - far longer than ever expected. It has a few dings in the wheels. Amazing machine!
Should we call those photographs ... (Score:2)
selfies [wikipedia.org] ?
Hasn't it already met most of its goals? (Score:1)
It does raise an interesting question though. Due to the cost of getting stuff there, should future missions include repair robots to reuse or recycle the stuff already on site?
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Yep, just give it to the highest bidder for equally shitty work.
Actually, most of the rover was built in-house.
Re:Typical (Score:5, Informative)
The thinness of the rovers wheels isnt so much about saving money as it is about saving weight.
Every ounce the wheels dont weigh is another ounce for science equipment or batteries.
So im sure they made them absolutely as thin & lightweight as they thought they could get away with.
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So im sure they made them absolutely as thin & lightweight as they thought they could get away with.
Missed it by that much.
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Agent 86
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The thinness of the rovers wheels isnt so much about saving money as it is about saving weight.
Every ounce the wheels dont weigh is another ounce for science equipment or batteries.
So im sure they made them absolutely as thin & lightweight as they thought they could get away with.
...and every ounce the probe doesn't weigh is another few hundred pounds saved in fuel for the launch vehicle.
This is reflected in the amount of power the Voyager probes put out - not even enough to power a digital watch, yet we're still getting science from them. The legwork is done on Earth, with vast arrays of massive radio telescopes gathering and filtering the signals. To put out enough power for an amateur radio astronomer to be able to pick out of the cosmic background... we'd probably have had to la
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That's the #1 reason. If we had infinite thrust with no fuel consumption, we could put up ... well, some really cool stuff. Spacecraft wouldn't need to be concerned with stuff hitting them, if they could put a mile of dirt around a steel reinforced concrete floating bunker. :) And we'd probably have a few Stanford Torus' or Bishop Rings in orbit already.
Looking at the design, and the images, the front left wheel is ac
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Yeah, let's just toss out a few instruments and batteries so we can have wheels that last 5 instead of 3 times the planned driving distance.
Gotta love armchair engineers.
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In terms of total mass, yes they are.
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So? Was there an arbitrary weight limit? What's a few more pounds for proper tires? Was there some reason that it had to be exactly 1,980lb? I find that very hard to believe. Cars have proper tires, at first what look like bicycle tires but they get bigger and heavier so do the tires and suspension. Buildings get taller, so they have foundations to support them. I think that is common sense. We can have our heavier cars loaded with more gizmos and the tires are designed to handle that and extra cargo, so wh
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Yes, it's called a launch vehicle. This isn't Star Trek where you can touch your nipple and talk to the blind guy in the engine room to whip you up a magical force field to float that shit up into space.
"What's a few more pounds for proper tires?"
I eagerly await your formulation for flexible rubber or plastic that can survive the vacuum of space for months, then the harsh unfiltered UV on the surface of Mars and wild swings of temperature as the wheel turns between
Re: Really? (Score:1)
Would 5 grams of TiN ceramic coating really have impacted launch so terribly, AC?
Because they really only need about .0005 inch thick coating of the stuff outside the existing design part to radically increase the surface wear characteristics of the solid wheel design they already have.
We've solved the problem with mechanical erosion a long time ago on CNC cutting tools, where tolerances tighter than a nuns's cunt prevail, and where graceful transition on surface friction over tool life is a must to preserv
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See my posting above concerning the erosion of diamond-coated drill bits by chalk (trigonal calcium carbonate). Diamond is hard, sure. And tough. But Chalk can be much softer, and tougher.
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Make that 100 drops of water. 20 drops per gram.
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"I eagerly await your formulation for flexible rubber or plastic that can survive the vacuum of space for months, then the harsh unfiltered UV on the surface of Mars and wild swings of temperature as the wheel turns between light and shadow."
Ahem... effective and robust wheels to survive those conditions -- at a pretty darned good rate of speed, with 2 human passengers -- were built about 40 years ago for the lunar rovers.
How quickly we forget.
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Yes, it's called a launch vehicle. This isn't Star Trek where you can touch your nipple and talk to the blind guy in the engine room to whip you up a magical force field to float that shit up into space.
They had to lift all of that to MARS, dude. Try dragging a 1985 Honda Civic up Mt. Everest 50 million times. Then tell me you wouldn't toss out the spare tire in the first 50 feet.
So, what, it takes infinitely more energy for an extra few mm of sheet metal to launch that thing? A launch vehicle the size of the moon for slightly thicker tires versus the one they initially used? Apparently the Atlas V was used, and from what I am reading it is very much capable of launching the rover with a few more pounds/thicker tires and still grossly overpowered to deliver the payload. Also I never said anything about changing the tires to rubber or plastic! But alas I am just a armchair internet e
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It looks like those wheels have a Type III Anodizing. That's pretty wear resistant. You are talking about TiN coating on steel or carbide cutters. There is a bid difference. This doesn't look like wear but puncture damage. A coating isn't going to protect against that.
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Wasn't it "aerospace engineers" working in non-metric units that lost the Mars Climate Orbiter [wikipedia.org]?
I don't think NASA would employ someone still working in inches.
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Re: Really? (Score:1)
The wheels aren't showing signs of fatigue, they are showing erosion damage. More wheels means increased contact surface, and greater wear rates.
The better idea is to put a generous coating of a hard ceramic on the wheels, like TiN. (Titanium Nitride.)
There is no compelling reason why they couldn't coat the wheels with TiN after machining them, and before assembling them. It gets applied in a vacuum chamber, and can be precision applied with a vapor deposition process.
A coating just .0005 inches thick would
nope (Score:1)
"More wheels means increased contact surface, and greater wear rates."
Well, no.
The controlling variable with respect to vehicle mass vs. number of wheels is the pressure resolved on the wheel. Pressure is force/area. So having more wheels (of the same geometry, of course), means lower pressure loading, which means lower erosion. It can be a very nonlinear effect if the increase in load bearing area drops the pressure below a plastic deformation threshold.
From a simple wheel erosion POV, more wheels = lower
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"Eight or twelve smaller wheels might be a good idea for the next similarly-sized rover."
No. The diameter of the wheels has a very large effect on the terrain the vehicle can navigate without strain or damage.
To illustrate: ride a bike with a 28" wheel over a sidewalk curb. Then try the same thing on a skateboard with 3" wheels. See how far you get.
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Please record this result. I do not wish to repeat the experiment..
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Maybe they should have less scientists over there at NASA and more people with common sense who can raise their eyebrows.
Yes, that's exactly what they should do. This is, of course, if by "common sense" you mean common knowledge of the terrain on Mars. I'm sure that there are lots of non-scientists with such, as you say, "common" sense.
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The thing I'm wondering about is why they didn't use something stronger than aluminum like titanium -- lighter too!
Re:Really? (Score:4, Interesting)
The thing I'm wondering about is why they didn't use something stronger than aluminum like titanium -- lighter too!
Density of titanium: 4.5
Density of aluminum: 2.7
So no, not lighter.
Re:Really? (Score:4, Interesting)
Re:Really? (Score:5, Insightful)
And tends towards brittleness and is a PITA to machine.
I'm rather sure the nice folks at JPL thought this one through.
Re:Really? (Score:5, Insightful)
I know weight is important and all, but .75mm of aluminium? Really? Maybe they should have less scientists over there at NASA and more people with common sense who can raise their eyebrows.
Yes, every time something goes wrong, let us point out how "stoopid" those scientists are in hindsight and claim that the "common sense" solution would have worked. Of course, it couldn't be that the people there did a lot of simulations, analysis, and decided that 0.75mm was a reasonable (not perfect - nothing is black and white) thickness and the disadvantage of thicker wheels was outweighed by the advantages of thinner wheels.
Yes, the designers took a risk - that is their job. To clearly assess the tradeoffs and come up with a good design that trades off risk and performance at an acceptable level. Something doesn't work out as you expect? Use that knowledge in the next iteration. At one extreme you have a lot of equipment with no wheels, and the other extreme you have just wheels, no equipment. You want to do the designer's job? Go ahead, show me what your "common-sense" analysis of the tradeoffs are - what equipment would you cut for thicker wheels, and back it up with a detailed discussion on how the benefits outweigh the disadvantages.
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I'd say that the material itself is questionable for something designed to roll over rocks. Why not titanium?
Re:Really? (Score:4, Informative)
In reply to the GGP, here's what I would suggest, and why:
(Note, I work in aerospace)
I would suggest a minimum wheel skin thickness of .08 inches (a little over 2mm, it's a standard sheetmetal thickness) made of structural aluminum alloy (say 2025, or 7075, whichever is most electrically compatible with the suspension, given the pesence of perchlorate in the environment. 7075 is probably the better bet between the two, but 6Al4V might be a good choice too.) With a very generous plating of titanium nitride.
To make up the weight, (which would amount to only about 100 grams on the high side, give or take) I would look at using smaller radii on the machined parts of the suspension, using lighter gauge insulation on low voltage data wires in the electrical system, and laternative solder formulations. Also, replacing components that don't experiences constant drive or levering forces with ones made of titanium. (Parts of the arm near the wrist, parts of the camera mast, parts of the outer skin, etc.)
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But is the sheet aluminum even structural? Maybe the mission will finish with just the ribs which make the wheels rigid, but that may be enough.
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That they didn't even give them an abrasion resistant coating tells me that you had beancounters making engineering desicions.
It's the nature of the beast. The launch costs were just shy of $195 million. The mass of the vehicle ended up being 900 kg. That's roughly $215,000 per kg or $100,000 per pound. That's just the ante for putting something on the surface of Mars. Shaving off a mere 5 grams saves you more than $1000 just in launch costs. You then have to add in the testing to make sure the coating actually stays on and such.
Given that this decision didn't actually endanger the mission's success, it was a successful gamble
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But if increased weight was a factor which stopped them from putting in more robust wheels, couldn't they have used something similar to what the Indian mars mission did, and launch the vehicle into a polar orbit, and from thereon, perform a Hohmann transfer?
They could, but it'd require more delta v and result in less payload. Putting the vehicle into a polar orbit is already less efficient because it takes more delta v to do that than to put the vehicle into a near equatorial orbit (especially from India). And then transitioning from that orbit to a Mars transfer orbit (or MTO, the Hohmann transfer you speak of) is another delta v cost.
Instead, launching almost directly (I understand there is a somewhat later boost after the vehicle drops the first stage) t
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still, the coating I would have suggested is well understood to be very chemically compatible with aluminum alloys, and is quite inexpensive.
And it is untested in a Martian environment. It's also worth noting here that Curiosity's tires experience considerable flexing as part of normal operation. A coated saw blade just doesn't see that kind of flexing.
Having said that, if I were running the unmanned Martian exploration program, I would be deploying a large number of much smaller rovers. For example, the Mars Exploration Rovers are proven technology. I would be launching several of them every two years to different locations on Mars using the
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If I were building them I'd CNC cut the outside on a 5-axis mill. There is plenty of support material with no deflection. Then wire EDM the inside out. No cutting forces.
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Ouch, that's a lot of EDM time. I presume the wheels were built to do some deformation, anyway.
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Yep and a lot of wire. Nice cut though.
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Interesting, thanks. Wish I had mod points today.
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The internet says that the wheels and suspension are made of aluminum and " fittings made of titanium where ever they are needed"
Obviously cost wasn't an issue, so I'm curious about the alloy of Aluminum they used and why they picked that over lots of other more exotic possibilities.
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"Nothing new there, and sadly, the money pit they are doesn't look to change any time soon."
Find the NASA budget in this chart:
http://www.nytimes.com/interactive/2010/02/01/us/budget.html?hp&_r=0 [nytimes.com]
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I know weight is important and all, but .75mm of aluminium?
It's already been pointed out that the mission and those wheels exceeded the mission parameters. That means that 0.75 mm of aluminum was indeed enough. The common sense, eye-brow raising people are done here.
Your worry IMHO completely misses the point. In the real world, when someone screws up a prototype badly, they just make another cheap prototype which eliminates that failure mode and come up with more advanced and sophisticated screw ups. If 0.75 mm wheels weren't enough, then make the next generati
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Engineer the entire system (Score:3)
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we can barely make WHEELS that survive going 2 miles per hour there!
The rover masses 1000kg so there is 50kg of force on every wheel. Thats pretty substancial, about the same pressure as a mountain bike wheel, and mountain bikers lose a lot of tires to rough terrain.
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I agree. The rover only has itself to blame. It should go on a diet and stop complaining about sore feet.
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how much science has gone in to building the Rover wheels? Mountain bike wheels have been using the same technology for decades - a steel hub, steel spokes, steel rim, and air-filled rubber tyres. With the Mars Rover, they had to think about:
Tyres: no good in such a rarefied atmosphere - they'd explode, that's if they didn't explode on the way. Plus there's no way to stop and repair a puncture. Solids are making a comeback (again), but you run in to weight issues (I know, I've had newtech solids and they ar
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The hand cart on apollo 14 used pneumatic tires at 10 psi. It was probably inflated in a vacuum chamber. Though I think Curiosity is fine with the wheels it has.
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The rover masses 1000kg so there is 50kg of force on every wheel.
Where does it hide the other 14 wheels?
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1000kg mass. 300kg weight. Six wheels, each carrying 50kg.
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500 Newton.
Re:They didn't pack a 3D printer? (Score:5, Interesting)
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Maybe it was anticipated, but the wheels are still expected to survive for the service life of the vehicle.
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Oh okay 500 newton.
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How far has this thing managed to go now? Couple miles?
Tires are stupid anyway. Hey, news flash, PhD eggheads... try these things called "tracks". I'm pretty sure they'll work on Mars...
There would probably be a weight issue with tracks...
Re:Sad. (Score:5, Funny)
Hey man we don't need none of yo science, we got Common Sense Internet Man here, who read 4 sentences on the topic and is gonna design him a better rover than all them eggheads!
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So, umm... who's the idiot(s) here?
It's you, hillbilly.
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there'd be an issue with MPF (moving parts failure) as well, how many moving parts per inch of track? Half a dozen? On a wheelbase of three feet? Couple hundred? The failure of any ONE of which would end the mission.
Probably why they opted for six independent wheels - so the failure of any two on opposite sides would not be a mission ender. On a four wheeled vehicle, the failure of just one wheel would end the mission.
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In my misspent youth, I spent a number of years operating heavy machines, many with tracks. Anything from rubber-tracked skidloaders, to D10 bulldozers... in the Rocky Mountains.
I experienced and saw many tire/wheel failures... but never a track failure. It happens, but it's considerably more rare. Tracks not only provide better traction, better maneuverability, better stability, better slope capability, and lower ground pressure/better flotation, but they are more durable in rough/rocky conditions.
Just
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PhD eggheads... try these things called "tracks". I'm pretty sure they'll work on Mars.
That's a lot of moving parts to go wrong. Doesn't matter here on Earth so much because there are typically tank mechanics within driving range.
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OMG... seriously? Another one?
Think about the whole drivetrain for a moment. Two drive motors instead of six. Steering by differential motor speeds, not steering motors or servos. Etc, etc, etc. Fewer motors, less wiring, fewer joints, fewer electronics, lighter weight all round... in exchange for some more moving parts on a track -- whose parts barely move, and are far less complex than motors, electronics, or steering knuckles. Yes, there are many parts in a track system. SIMPLE parts. It's a SIMP