Why are rovers so slow? I assume because so little sunlight reaches them they don't have enough juice to go faster. Why don't they include fuel cells in one of these things? (And contain any exhaust products, of course.) Space probes have fuel cells, why not landers or rovers?
Also...over and over I hear about a probe or rover exceeding it's life expectancy dramatically. Are the engineers that stupid or are they just that conservative or do they just like to sound like their crap is so cool it far surpasses anybody's expectations? Cuz they should've learnt by now...
Registered: Jul 2005
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posted
Space probes are not powered by fuel cells, they use either solar panels or radioisotope thermoelectric generators. Fuel cells are not advanced enough to send on a long-distance space mission, not yet anyway. The chemical reactions can't hold within the extreme heat and cold environments. (And a space probe will always have to deal with both.)
Concerning the time frame of the mission: first, there's a question of budget to pay the engineers and mission controllers who are running the rovers. Second, the designed lifetime was expected to be limited by the accumulation of dust on the solar panels, thus limiting the amount of power the rovers could collect over time. However, it turned out to be a much lower factor than anticipated, because the wind was constantly clearing off the panels.
Finally: Well, why don't YOU design an autonomous robot with, oh, an Erector set or something, launch it in a flaming rocket into the sky to hit a tiny ball that's several million miles away, converging on said tiny ball at a few thousand miles an hour before safely decelerating to a speed where it's NOT smashed into tiny particles when they contact, and then promise that the robot is going to continue working perfectly for three years, through dust storms and freezing cold temperatures without so much as a tune-up or an oil change. Does that sound at all reasonable to you? Or would you rather say that it should last about 90 days and then we'll see how it's going?
There's something to be said for setting reasonably low expectations.
-------------------- “Those people who think they know everything are a great annoyance to those of us who do.” — Isaac Asimov Star Trek Minutiae | Memory Alpha
Registered: Nov 2000
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Daniel Butler
I'm a Singapore where is my boat
Member # 1689
posted
Right, right, that's Apollo and the Space Shuttles that use fuel cells. Mah bad.
I don't recall suggesting that the engineers are stupid or that their rovers suck as you seem to have inferred. What I meant was, as they've sent stuff to Mars before, and lots of stuff through space, you'd think they'd have figured out by now that their operational lifetimes are extremely conservative compared to what actually happens.
Also, you know, I don't think it's quite as bad as sending something built with an erector set out there. I mean, it's not fragile, or it wouldn't work, as you just pointed out.
Registered: Jul 2005
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quote:Originally posted by Daniel Butler: Right, right, that's Apollo and the Space Shuttles that use fuel cells. Mah bad.
I don't recall suggesting that the engineers are stupid or that their rovers suck as you seem to have inferred.
quote:Originally posted by Daniel Butler: Are the engineers that stupid or are they just that conservative or do they just like to sound like their crap is so cool it far surpasses anybody's expectations? Cuz they should've learnt by now...
It's not inference if you use that exact language.
-------------------- "Don't fight forces; use them." --R. Buckminster Fuller
posted
Dont forget that something like one in six Mars missions ends in failure- some of which remain unexplained. They just stop transmitting at some point and that it.
Besides, these lil' rovers perform better than most US made cars.
Registered: Aug 2002
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posted
It's a lot worse than that. Roughly two-thirds of all spacecraft destined for Mars failed before completing their missions, with some failing before they even begin. Mind you, the percentage has been a lot better since 2000 - all but one of nine missions have been successful, and all of those are still operational today.
Registered: Jul 2002
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-------------------- Justice inclines her scales so that wisdom comes at the price of suffering. -Aeschylus, Agamemnon
Registered: Aug 2002
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