Rough Roving: Curiosity's Wheels Show Damage

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.'"

Comments

Fun fact

[funky49]

There's a fun fact about the wheels of Curiosity. They spell out "JPL" in Morse Code in the sand of Mars. :)

Mass and Weight are different

[Excelcia]

From the article:

“We have the same wheels on our Scarecrow test rover, which weighs the same on Earth as Curiosity weighs on Mars,” Heverly added. “We have driven Scarecrow about 12 kilometers (7.5 miles) in the Marsyard over rocks and slopes much harsher than we expect for Curiosity. There are some dents and holes in these wheels, but the rover is still performing well.”

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:Mass and Weight are different

[complete loony]

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:Spirit and Opportunity set unrealistic expectat

[hairyfeet]

Really? I think its more a testament to just how well NASA over-engineers and builds everything for the absolute worst case scenario that we get so much extra use out of these things. I mean look at how long Voyager has lasted way the hell out in the cold depths, that's a tough built ship right there.

But this is why I've always supported the robotics space exploration programs, with our current tech "meatbags in spaaace!" really doesn't make much sense. I mean when you figure in what it would take to get a crew of five to mars and back its just insanity, 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 just to carry all the consumables and fuel needed, I don't even want to know how much it would cost for a stay as long as these rovers have had there. At the end of the day we can just get more done with the machine than we can with the man, our tech just isn't good enough right now to make "meatbags in spaace!" viable.