What's Inside the Mars Rovers 458
Captain Zion writes "Space.com has a story about the hardware and software of Mars Rovers Spirit and Opportunity. Basically, they're radiation-shielded, 20MHz PowerPC machines wirh 128Mb RAM and 256Mb of flash memory, running VxWorks. I wonder if I could make a nice firewall with one of these for my home network..."
Wait a second... (Score:5, Insightful)
Re:What's the bus speed on that thing? (Score:5, Insightful)
Does a 20mhz processor really need 128mb of ram? I mean, with a bus speed that low, you can probably put the data to flash ROM just as fast. What are the chances of you using all 128mb of ram?
I imagine they can use all the storage they can, since there's no hard drive. So, the RAM acts as a cache for everything that is transmitted (which is a lot, actually). The Flash is used for more permanant software, like OS, commands, other files, ect. I'm amazed they can do it all with as little as they have.
Re:What's the bus speed on that thing? (Score:3, Insightful)
Redundency Check? (Score:3, Insightful)
Your Average plane have a triple backup system, I spoke to some engineer and he said preflight checks are usally just making sure two of the systems are still working
you'd think they could at least send up some more hardware with these little critters. The extra weight would pan out, when things go bad...case in point see what they are dealing with now :)
Re:Wait a second... (Score:5, Insightful)
Modern superscalar (pipelined) processors have a lot more MIPS than megahertz.
Ouch (Score:3, Insightful)
The bold emphasis is mine but that is a big Ouch for Microsoft.
RAD6000 microprocessors are radiation-hardened versions of the PowerPC chips that powered Macintosh computers in the early 1990s
Shouldn't Apple be using this in their commercials somehow to further boost their reliability. I am sure the PR market can put it in a way that non-geeks watching tv can relate, right?
Re:Redundency Check? (Score:4, Insightful)
Ofcourse NASA did implement a measure of redundancy by sending two rovers instead of just one.
Re:Self-warming (Score:3, Insightful)
I don't know, but I'd guess that for rovers of this size and weight, it might be easier to use solar panels than to figure out how to dump all of the waste heat that an RTG would produce. These devices are highly inefficient in terms of converting thermal energy to electrical energy, so they are probably spewing kilowatts of thermal energy at all times, and there's no way to shut them off.
That would pose two immediate problems: with the el-cheapo balloon-based reentry system used, how do you keep the rover from frying when it's wrapped up in its airbag cocoon? The only way would seem to be a heat sink, but that would add significant weight to the spacecraft.
The second problem would be how to radiate all of that heat during operation. The outer planet probes have spindly rods that hold the RTG a few meters away from the main body. A rover couldn't do this and maintain balance, so you would need some kind of closely attached radiator with liquid cooling and/or heat shielding to protect the main unit from the intense heat. Once again, this could end up being heavier than simple solar panels.
Re:But The Question is.. (Score:3, Insightful)
Re:What's the bus speed on that thing? (Score:4, Insightful)
Re:But The Question is.. (Score:3, Insightful)
Re:What's the bus speed on that thing? (Score:4, Insightful)
Re:Radiation hardness (Score:4, Insightful)
Re:RAD6000s seem closest to PPC601s (Score:3, Insightful)
I doubt it, because it probably had little to do with performance. I read an article a while back (tried to Google it now, couldn't find it) that said NASA is generally about ten years behind consumer PC's in terms of the CPU speeds they send into space. These things have to go through so much testing for reliability, etc. that it often takes that long to certify a CPU for space flight. When they do find a CPU they can certify, they'll often continue using it for years. They won't just stick the latest PPC chip in a vehicle, assuming it's the same as the last one, only faster. That's the quickest way I can think of to disaster.
Not much CPU power is really needed for space flight, though, and there's not really much point in taking along more than you need. We went to the moon using slide rules. We can make it to Mars on 20mhz chips - and I'll bet the only reason we even need that much power is for the scientific experiments on the surface. Speed is not really the primary concern on space missions.
Re:But The Question is.. (Score:1, Insightful)
The fact that NASA put a probe on Mars using a 60's style OS architecture is an amazing tribute to the programmers who worked on it.
- No implicit memory protection (protection domains - ha!)
- Goofy GUI-based development environment
- the list just goes on and on...
- Questionable real-time performance (it works great if you shut down all services)
Overall, I am surprised that NASA continues to use this outdated software. There are far better alternatives in the embedded real-time OS domain that would easily run in the same environment.
And before everyone starts talking about Linux, forget it, it is too big and fat and impossible to rate for high reliability missions like this one. By the time you trimmed it down to size, you would be better writing your own OS.
As a company, Wind River is dying, their market share is down, and people are starting to wake up to the fact that you need good programmers to write software, not goofy GUIs and outdated kernels.
Ask anyone who programs embedded systems who has used VxWorks and you will always get the same response - "Man I hate that OS, and management wants us to use their tools, but they are useless".
Amazing things can be done with a watchdog timer...Anyone who uses Wind River for anything remotely serious knows that.
I just hope NASA picks something else when they send people to Mars, or else here will be the conversations:
Astronaut: "Base, I have to hold my breath for a bit while my suit computer reboots, it must have crashed when I exhaled too much...damned OS crashed again!"
Base: "Roger that, maybe you should reload your suit software? or perhaps breath slower?"
Astronaut: "mmmmfffffff!"
Wind River is like the Microsoft of the embedded world, except a choice still remains.
Same problem three times (Score:3, Insightful)
Re:Radiation hardness (Score:3, Insightful)
A) Would never have been chosen as the OS of choice
B) Will never BE chosen to replace VxWorks
Why? It's a great company, but it's based in Ottawa (that's Canada for you Yankees), and NA$A Bucks do not flow over the border.