johnnydeep wrote: ↑Sun Apr 17, 2022 12:58 pm
Yeah, and 60 kg is 132 lb, which is more than I weigh! There's no way in hades that each of the 6 wheels is anywhere near that. And I doubt that even including the drive train and axels would approach that weight.
Hmmm ... That 6% figure, I can't seem to find it anywhere now that I look back, except in the first article that was describing it as a "student science/engineering project". I did find out that the actual wheels on Curiosity have a mass of only about 2.1 kg each, totalling something like 12.6 kg, if we're just talking about the outer "barrel-shaped" aluminum portion. Beyond the outer skin, though, there is the inner structure which is surely much beefier than the wheel surface, then each wheel has its own drive motor. As you're suggesting, perhaps the 6% limit, if it was a real specification, included all of that, and maybe also the rocker-bogie suspension. I have not seen mass measurements for any of the other parts.
It is kind of scary how things can get so quickly harmed and become a huge problem. It's been a long time, but the "mileage on those tires" is only 27km to date. I'd say they really did skimp on the wheels to save as much weight as they possibly could, using super-thin machined aluminum of just 0.75 mm thickness. (And why not? They had Spirit and Opportunity experience to go on.) Then, when some very nasty rocks started tearing them up, it could become the thing that halts a 2.5 billion dollar machine. Given enough time on Mars, something will eventually give! I suppose each engineering team secretly hopes it's somebody else's subsystem?