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Mars Rover Spirit Down a Wheel
riflemann writes "NASA is reporting that two years into its 90-day mission, Spirit has lost one wheel and is now running on five wheels, dragging the broken wheel. With this reduced mobiity, the rover still needs to make its way to a slope where it can catch enough sun over the Martian winter to keep it operating. 'Even though the rovers are well past their original design life, they still have plenty of capability to conduct outstanding science on Mars.', says project leader Dr. John Callas."
It's more accurate to say that the wheel is free-spinning. It isn't contributing to drive power, but it's not drawing any current, either. It can still steer, so it's not off at some odd angle.
Additionally, there's only been a couple days worth of data -- noone really knows why the motor stalled.
That was in a TNG episode with La Forge.
The computer in each Mars Exploration Rover runs with a 32-bit Rad 6000 microprocessor, a radiation-hardened version of the PowerPC chip. This chip is used in IBM's heavy duty computers and is the same family of chip in the pre-intel Macs, Xbox 360, GameCube and the Cell version will run the PlayStation 3.
The chips are fairly cheap and have lightning fast floating point calculations via alti-vec. They are also very easy to program for.
NASA claimed they would only work for 90 days due to the high iron content of martian soil. In 90 days the solar cells were supposed to be covered with magnetized iron dust and the cells would not get enough sun to charge them. That never happened. Considering the cold, dusty, unsheilded environment they are in it is amazing they have lasted over two years.
It's not that simple. The rovers are full of fairly sophisticated sensor packages, most of which can't handle the extremely low temperatures on the Martian surface. They need the batteries to basically, well, run the heater.
The principle investigator for the missions has written a book, "Roving Mars", that really is worth the read.
Not quite. Martian weather is quite likly to blow away the tracks before anything found them.
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You can get your Martian weather forecast here: http://astro.sci.uop.edu/~harlow/weather/mars.htm
Demented But Determined.
Bingo. Indeed, it's even worse than that: if you can't run the heaters, all of the electronics undergo more extreme thermal cycling. This causes components to contract, flex, break, etc. Several critical components -- e.g., the CPU -- have no redundancy; if one of those goes, the whole rover goes.
This failure is the most dangerous thing to happen to Spirit since the flash anomaly on sol 18, when we effectively lost contact entirely for several days. Frustratingly, we're within sight of a safe haven -- only about a football field away -- but we might not be able to get there. Some people on the team think that if we have to drag a wheel, we can't climb the slopes we need to climb to make it to safety. I would just hate for Spirit to go this way; it would be like dying of thirst within sight of water, and she deserves better. (On the other hand, one thing I've learned is this: never bet against the rovers.)
Agreed! And since Steve's such a great guy, I'll linkify that. :-)
Also looks like it's coming out in paperback soon.
``Life results from the non-random survival of randomly varying replicators.'' -- Richard Dawkins
If memory serves me well (and it often doesn't), Rad 6000 is something like $600000
As for the list of applications you gave, I'm guessing that new designs of these products use mostly brushless motors now, if only for the reason that they last longer and the brushes aren't ground down to dust over time.
My mother doesn't need a Rascal yet. In any event, I doubt these motors are that different from what use use down here on Earth. Sure, they're probably built better, with better materials and such, but the general design and layout is probably very similar.This stuff isn't rocket science. Even things like scooters, Segways and electric cars use similar technology.
I'm guessing that the AC who posted in this thread was right on -- that NASA used brushed motors because they've used them in the past and they worked fine then, so they'll work fine now -- when you're spending billions of dollars on things that can't be repaired in the field, you tend to stick with what's tried and true rather than what's 15% more efficient but not quite so well tested. I suspect that future rovers will have brushless motors, however.Uhm, this gets informative? The Rad6000 chip runs at 20mhz according to wikipedia and 25mhz according to other sources. The chip is based on EARLY power cpu designs (think early/mid 1990s), and most definitely does NOT include any sort of altivec technology.
No radiation hardened space suitable chips are "cheap." Expect to spend tens, if not hundreds of thousands of dollars per CPU.
That's not to say it's not a great chip for what it does, but come on...
That's partially true, but another important aspect of it is that if they had planned on a five-year mission up-front, the budget would have been several times larger - and in fact the project might never have been funded at all. So they decided on a mission length long enough to get some interesting science done, but short enough to look cheap.
After 90 days, they went and asked for additional money. What's NASA going to do, stop running the rovers because they're over budget? Of course not. Unfortunately now they're eating into money that would have gone to other Mars missions. But it's still far more sensible to spend a dollar on the rovers already on Mars than on a future rover that may or may not make it to Mars.