It’s only got rims to begin with, so no flats, but they’re getting degraded, with a “critical” risk to the entire mission. (I thinkthis is a detail.)
It’s mainly backing up now, for interesting reasons due to its autonavigation.
Clearly the engineers worked their asses off to get this right and optimize material strength with lightness and all the known design requirements. Their work is amazing. But Shit has Happened.
Does anyone know who the subcontractor was on those, or any history of that aspect of the project?
Yup. And some component in the rover has to be the first to fail. That doesn’t mean that whichever one it happens to be was poorly or negligently designed or made.
Read the article, it says they have managed to identify the types of terrain that they believe caused the problem and will try and avoid it from now on.
There’s also a quote in there saying they believe the power source (RTG) will fail before the wheels will.
If anything, it’s amazing that it’s starting to fail when it was expected to. Most NASA probes, if they don’t suffer a mission failure immediately, end up with a mission many times longer than planned. Heck, sometimes they have a mission many times longer than planned even with an immediate failure, like Galileo.
I had to look up RTG. I had heard of it before and was vaguely aware of the details. But reading it more carefully – what an awesome and relatively simple piece of technology. To have a substance that glows red hot with its own radioactive heat for many months while providing electrical power of 500 watts… That is pretty cool.
Henry Ford applied that same principle, but in reverse: After the Model T had been on the road for a few years, he sent his engineers out to the scrapyards, to report on which part had failed in every junked Model T. On finding one particular part that was never the cause of the loss of the vehicle, he ordered that part to be made more cheaply, since it was clearly overengineered.
To answer the question of the o.p., the wheel assemblies themselves were fabricated and assembled by the NASA Jet Propulsion Laboratory. The design is the result of extensive analysis and testing; however, it should be understood that while we’ve sent previous rovers (‘Spirit’ and ‘Opportunity’) and landers (‘Viking 1’, ‘Viking 2’, ‘Pathfinder’, ‘Phoenix’) to the surface, the Mars Science Laboratory (‘Curiosity’) is by far the heaviest mobile explorer landed on Mars to date. (The Vikings were comparable in mass but were stationary.) Our experience with the surface conditions on Mars is more extensive than any extraterrestrial body except for Earth’s moon, but that doesn’t mean we know very much at all. Spirit and Opportunity together have travelled less than 50 km; about the same distance an unencumbered adult could traverse on flat land in one day of walking. And the area where Curiosity is traversing is previously unexplored, so the conditions the rover would face were best guestimates, not observations from prior surveys. With all that being said, while the unexpected wear on the forward wheels is somewhat worrisome, it is not a showstopper and can be mitigated (as is already being done) by selecting different paths and operating the vehicle in reverse to spare the front wheels from absorbing all of the damage. Compared to the problems of charged lunar dust (which will pose a substantial problem and potential instrumentation and health hazard for lunar exploration) it is readily mitigated by procedural steps. And of course, we’re now aware of the issue and can build more robust wheels in the future. (Why soft, unprotected aluminum was selected for the surface of the wheels I don’t know, but it should be relatively simple to provide an abrasion-resistant coating and reinforce the structure for greater strength without substantially increasing the mass of the wheels.)
As Chronos notes, the vast majority of robotic planetary exploration missions end up being extended, often by many times the planned mission duration, because of the robustness of the probe and instrumentation. This is because the systems are designed for what are often poorly understood or unknown conditions, and because clever engineers and scientists figure out new ways to extend or retask the systems via instruction set and firmware modifications even though the actual hardware is hundreds of millions of miles away. This is a feature, not an error; for instance, the Voyager 2 probe ended up completing all of the objectives of the “Grand Tour” exploration of the outer planets despite that mission originally being curtailed to just flybys of Jupiter or Saturn, all for the pittance it costs to keep mission operators and a small engineering team working. Given the enormous costs of launching even a single mission, building in inherent robustness and extending the life of a system represents an enormously valuable return on investment in terms of data per unit mission cost.