Originally posted by: BigJelly
NASA insisted on the SUV version instead of the hybrid model and look what they've done.
[southpark] WE DIDN'T LISTEN. [/south park]
Hey, the Mars Science Lab may be big, but it's also zero-emissions.
Originally posted by: Minjin
The Mars rovers were designed to last 90 days. They have now lasted over three years on a planet averaging 48 million miles away and have provided volumes of data. The only failure so far has been a wheel on Spirit but they have since programmed it to run on five wheels. The rovers are an amazing engineering achievement and don't desire to be belittled.
Actually, there have been multiple problems, all of which have been solved or worked around.
First there was Spirit's flash memory problem - something kept writing data to the disk, and it eventually filled up the memory completely. Spirit rebooted over 50 times to try to clear it, and then went into a safe mode. It was eventually diagnosed, the memory was wiped, and the software problem was fixed.
Spirit's right front wheel had lubrication problems earlier due to always being driven the same direction. There is really only one kind of lubricant that they can use at such low temperatures, and I guess it doesn't distribute itself well. Solution: they drove both the rovers backwards occasionally to keep the lubricant distributed.
It also was on rough terrain, with sizable rocks all over the place, so it put its suspension system to good use.
It also was cleaned regularly by strong winds across the hills it was on, but it has since ventured into a valley that seems to be a prime dust deposition spot. It was heading for a good slope where it would get good sun exposure, but its right front wheel failed almost completely. It can still steer, but it no longer rotates. It is believed that a wire finally failed due to extended exposure to Mars' extreme thermal cycles. Fortunately, the previous problem with the right front wheel meant that the rover team had experience driving on 5 wheels, and they were able to guide it to a closer slope, where it spent several months doing various soil and atmospheric studies, while keeping its solar panels oriented toward the sun thanks to the angle of the ground. This was necessary to give it the minimum amount of power it needed to continue functioning.
Martian winter is past for Spirit, and it's again on the move back toward Home Plate, a large slab of rock that it had to hurry past in order to make it to safer slopes.
Opportunity had a problem early in the mission - a heater switch was stuck on. This would drain the battery at night, so the only solution was to put the rover into a deep sleep mode, shutting off nearly everything. This meant that other heaters would be shut off too; they were to run occasionally at low power to keep the rover's extremities a bit warmer than the surroundings. So Opportunity had to endure much harsher thermal cycling than Spirit. It also had an occasional reboot problem, possibly linked to issues with its miniature thermal emissions spectrometer.
Its "getting stuck on pebbles" problem happened when it drove into a drift of Martian soil that was around 1 foot deep. The stuff appears to have the consistency of flour. The spinning of the wheels to try to get the rover out would have moved it 629 feet were it free. All that was to get it 3 feet out of the drift. They were more careful about sending it on blind drives in the future, and the team also programmed it to stop automatically if it sensed that it was driving into another drift.
Opportunity has now travelled more than 10 kilometers, several times more than its original specs, which were for less than 1km of driving distance. It visited Endurance crater, explored its interior, exited, traveled beyond its landing ellipse, and is now traversing the perimeter of Victoria Crater, which is 750 meters wide (about a half mile) and 70 meters deep.
Both rovers are also smarter than when they launched. Spirit is capable of 5-wheel driving, with automatic corrections to keep them on target, Opportunity can avoid getting stuck in drifts, and both now have autonomous target tracking. Previously, human drivers themselves needed to position the rovers at interesting targets. Now the rovers can be shown a distant target, track it as they approach, and position themselves so that the instrument arm can study it.
Speaking of driving over "pebbles," the rovers' wheels can pull the rover over rocks as large as the wheel's diameter - 10 inches. Try that with your car sometime. Oh, if something screws up, your nearest shop is 48 million miles away. Good luck.
Citation for specifications and various numbers
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