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Brad Fitzpatrick

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Mars [Jan. 4th, 2004|01:30 pm]
Brad Fitzpatrick
I'm really fascinated with all the Mars exploration going on. I feel all giddy reading the minute-by-minute news at Spaceflight Now. I was reloading all last night, and I woke up this morning, reloading more. (no RSS feed....)

The "Mission facts" links on the right sidebar are all good reads.

Think about all the areas of knowledge needed to get that rover there: aerospace, math, material sciences, mechanics, software, geology, communications... Must be fun to work at NASA.

Fun tidbits:
Each airbag has double bladders to support impact pressure and, to protect the bladders from sharp rocks, six layers of a special cloth woven from polymer fiber that is five times stronger than steel. The fiber material, Vectran, is used in the strings of archery bows and tennis racquets.
Dealing with temperature:
Batteries and other components that are not designed to survive cold martian nights reside in the warm electronics box. Nighttime temperatures may fall as low as minus 105 C (minus 157 F). The batteries need to be kept above minus 20 C (minus 4 F) for when they are supplying power, and above 0 C (32 F) when being recharged. Heat inside the warm electronics box comes from a combination of electrical heaters, eight radioisotope heater units and heat given off by electronics components.
Slow, reliable computers:
The computer in each Mars Exploration Rover runs with a 32-bit Rad 6000 microprocessor, a radiation-hardened version of the PowerPC chip used in some models of Macintosh computers, operating at a speed of 20 million instructions per second. Onboard memory includes 128 megabytes of random access memory, augmented by 256 megabytes of flash memory and smaller amounts of other non-volatile memory, which allows the system to retain data even without power.
"Gusev is a big hole in the ground, a crater, and it's got this huge dried up river bed flowing into it," Squyres said. "Now if you can come up with an explanation that says there wasn't a lake there, I'd like to hear it. I mean it was water and it flowed into a hole in the ground.

From: jon
2004-01-04 10:16 pm (UTC)


I remember hearing a story about one of the Voyager spacecrafts. Part of its augmented mission brought it around the far (dark) side of Jupiter (I think). It's apparently really cold back there because so little of the sun's radiation reaches that shadowed area, so when it came time for Voyager to retrain one of its radio dishes, the NASA engineers found that the motor assembly no longer wanted to turn. Apparently, the lubrication had frozen. They finally got the assembly to break free by running all of the other motors on the spacecraft until enough peripheral heat was generated to thaw out the frozen lubricant.
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[User Picture]From: brad
2004-01-04 10:18 pm (UTC)

Re: vger

Whoa, that's crazy.
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From: ex_bulatych796
2004-01-04 10:30 pm (UTC)
Could that be lava that flowed into a hole in the ground?
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[User Picture]From: brad
2004-01-04 10:34 pm (UTC)
Don't ask me! :-)
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[User Picture]From: chuck
2004-01-04 10:38 pm (UTC)
if that were true the hole would have already been there. Lava seems to build up the land around it rather than erode it.
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[User Picture]From: krow
2004-01-05 05:32 pm (UTC)
Lava leaves its mark though. If they can get even a slightly good photo of the stratigraphy then they will be able to see immediately that its not a lava tube.

One of the fluids that can leave similar landscape as water is air. They could (though I doubt it) have been created by wind. We need to know a lot more about the history of surface before we can really accurately describe the geomorphic forces that created it.
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[User Picture]From: chuck
2004-01-04 10:36 pm (UTC)
So I have a better computer than the best computer on Mars!!! WOW!

But about working for NASA, all my dad had to say about working there was that he got to ask the astronauts how they could make the space shuttle toilets more comfortable. Not to mention finding a way to keep things from floating and dirtying your butt cheeks.
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[User Picture]From: xunker
2004-01-04 11:21 pm (UTC)


"Slow, reliable computers [...] version of the PowerPC chip"

Compared to other most recent JPL landing (landing, not crash), that's a Cray: The Sojourner was powered by an 2MHz Intel 80c85 with 576kb of RAM and a 12MHz R3000.
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[User Picture]From: brad
2004-01-04 11:22 pm (UTC)

Re: Slow?!?!

It's embarassing that we have all this computing power on our desktops and all people do is look at pr0n and play mp3s.
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[User Picture]From: octal
2004-01-05 12:14 am (UTC)
I think that's the fastest radiation-hardened cpu out there. And quite export-controlled. Heh.
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[User Picture]From: taral
2004-01-05 01:18 am (UTC)
There was a theory that the "river beds" were created by frozen CO2.
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[User Picture]From: daberna
2004-01-05 02:30 am (UTC)

Enter the materials scientist...

...polymer fiber that is five times stronger than steel. The fiber material, Vectran...

Sorry, but i feel abliged to make a comment about your materials (mostly cause i TAed a class all about materials properties and i can't help it anymore)... "Strength" comparisons between polymers and metals are ridiculous.

Acorrding to this, Vectran has a Yield Strength (measure of "strength," point where it starts to deform permanently) of 3 MPa, whereas steel is about 2 orders of magnitude greater. Stiffness is closer, a factor of 2 or 4 greater in steel.

They're probably refering to specific strength (i.e. per unit weight). In that case you might expect polymers to do much better. I'm amazed how fantastical they try and make everything appear though.... Trying to trick all of the non-materials people into thinking polymers are stronger than steels. Kind of irrelevant anyway since not too much steel is going to get sent into space anyway. I guess most people need something common to reference strength to... not everyone is a fuckin' superfly materials scientist, like me ;-)
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[User Picture]From: brad
2004-01-05 02:42 am (UTC)

Re: Enter the materials scientist...

Thanks, superfly!

Whenever I read a computer article from mainstream sources I can hardly follow it, sludging through all the errors and false analogies. I always assumed it was the same for other industries. :-)
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[User Picture]From: daberna
2004-01-05 07:29 am (UTC)

Re: Enter the materials scientist...

True. I always enjoying finding the random things that aren't quite complete/right. Although it seems like it'd be good to educate everyone, it's probably too much trouble. Ignorance is bliss, right? At least in the US.

But remember, whatever they tell you about flying pods (especially as a form of mass transit), believe them. That part is true.
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