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Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

nytimes.com

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Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#191

Post by SmellyGeekBoy »

JohnJamesRambo wrote: post #126
slg wrote: post #23

Opportunity's and Spirit's original missions were planned to last 90 Martian days each. They ended up lasting over 8,000 combined. That is almost as impressive as getting the rovers to Mars in the first place.

I’ve never found it impressive, it’s a horrible padded estimate meant to cover NASA and make them look good. A real estimate needs to be useful and somewhat close to the actual outcome. There’s no way they were this off without it being on purpose. Imagine if your retirement planner or accountant was off by 44X in their number crunches for you. Would you say they were good at estimating?

If my retirement planner predicted that I had 90 days to live and I ended up living for another 15 years I imagine I'd be quite pleased.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#192

Post by emiliobumachar »

classicsnoot wrote: post #92
felipemnoa wrote: post #73

Earlier quoted context omitted.

If I remember correctly the reason they did not expect the mission to last longer than that was because they expected the solar panels to get covered with dust and thus render them useless. I don't think they had banked on martial winds to regularly clean them.

Your recollection is correct. Consider too the dust accumulation predictions for the moon landing. It would appear that we (as humans) are not very good at dust estimates (dustimates?). This is reinforced by the continuing struggle/inability to manufacture dirt. As an avid composter with a ton (lol sorry) of experience, I can make you hummus for days. I can turn 90% of your organic household waste into growth medium,…

Your main point stands, but, for terraforming purposes, a decade is a very short time period.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#193

Post by agildehaus »

mrwnmonm wrote: post #100

Seriously, what is the point of space exploration anyway? and what if we found water on Mars? shouldn't it be a huge amount of water to support life?

We've found water on Mars, but we've also found ancient river and lake beds, deltas, and minerals that can only be found in water on areas of Mars where no water currently exists.

We wouldn't know any of that without having gone there to explore it.

By learning about the mechanisms behind why Mars went from water-rich planet to its current state, we learn more about what could happen us, its closest neighbor.

There also remains the possibility Mars could currently harbor life, or once did and there's evidence of that to uncover. Mars represents our best chance of finding direct evidence of extraterrestrial life.

Please try to have a richer view of this.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#194

Post by dTal »

tzs wrote: post #125
luizfzs wrote: post #82

Earlier quoted context omitted.

I saw a video once saying that SpaceX uses general purpose computers on the rockets instead of specific purpose hardware. If I'm not mistaken, they amount to 6 and have a checking system to assure the output of them is the same.

Those "have N copies and compare them" systems then have the issue that whatever does the comparison is a single point of failure. You could use multiple comparison units and have a second level comparison check them, but then that is your single point of failure, and so on. I've been told, but never actually looked it up, that there is a theorem that proves you always have to have at least one single point of failur…

I don't think it's strictly true that you always have to have a single point of failure. Trivial counterexamples: 6 people carrying a sofa, an ant colony, BitTorrent.

The closest thing I can remember encountering to what you describe is the "Contracrostipunctus" chapter in Douglas Hofstadter's Godel, Escher, Bach, where he writes a dialog featuring record players as an analogy to Godel's Incompleteness Theorem (which only applies to "formal systems" - descriptive mathematical languages). He does go on to explore a real-world example of the principle in the form of viruses - a cell cannot fully defend against DNA modification using only instructions found in its DNA. The same principle applies to cracking copy protection in games - no matter how elaborate the validity checks, there's always a single point of failure in the form of the final decision - "if(checks_pass){run_game()}" - which can be trivially short circuited with a debugger.

I'm not a good enough mathematician to fully understand the limits of Godel's Theorem. But it seems to me that all of the above applications are examples of some sort of well defined formal computational system, and you can't generalize it to "everything has a single point of failure" without some carefully defined rules as to what constitutes the boundaries of system.

http://www.math.yorku.ca/Who/Faculty/Brettler/3500_06/Godels...

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#195

Post by dmurray »

tzs wrote: post #125
luizfzs wrote: post #82

Earlier quoted context omitted.

I saw a video once saying that SpaceX uses general purpose computers on the rockets instead of specific purpose hardware. If I'm not mistaken, they amount to 6 and have a checking system to assure the output of them is the same.

Those "have N copies and compare them" systems then have the issue that whatever does the comparison is a single point of failure. You could use multiple comparison units and have a second level comparison check them, but then that is your single point of failure, and so on. I've been told, but never actually looked it up, that there is a theorem that proves you always have to have at least one single point of failur…

So long as you can trade off robustness for performance, the fact that there must be a single point of failure is less important. You make the single point of failure more robust. In the example of the control surface, perhaps some ionizing radiation could flip bits in the flight control computers, but it takes a physical collision to damage the control surface.

To argue otherwise is to imply that all designs and all systems are equally robust, which is clearly not true.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#196

Post by magicalhippo »

slg wrote: post #23

Opportunity's and Spirit's original missions were planned to last 90 Martian days each. They ended up lasting over 8,000 combined. That is almost as impressive as getting the rovers to Mars in the first place.

The 90 days was, as mentioned, a lower bound, not an upper bound. They were planned to last at least 90 days.

Framed this way it's not entirely surprising they lasted longer, especially given the fortunate turn of events with the martian wind cleaning the solar panels of dust.

This of course does not in any way diminish the engineering and ingenuity involved with designing and operating the rovers.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#197

Post by Strilanc »

tzs wrote: post #125
luizfzs wrote: post #82

Earlier quoted context omitted.

I saw a video once saying that SpaceX uses general purpose computers on the rockets instead of specific purpose hardware. If I'm not mistaken, they amount to 6 and have a checking system to assure the output of them is the same.

Those "have N copies and compare them" systems then have the issue that whatever does the comparison is a single point of failure. You could use multiple comparison units and have a second level comparison check them, but then that is your single point of failure, and so on. I've been told, but never actually looked it up, that there is a theorem that proves you always have to have at least one single point of failur…

> I've been told, but never actually looked it up, that there is a theorem that proves you always have to have at least one single point of failure.

In what context? There's a theorem that arbitrarily-reliable computation can be done with noisy components, as long as the noise is below some threshold (e.g. picture less than 1 error per 10 operations). [1]

1: von Neumann, J. (1956). "Probabilistic Logics and Synthesis of Reliable Organisms from Unreliable Components", in Automata Studies, eds. C. Shannon and J. McCarthy, Princeton University Press, pp. 43–98 http://www.cyclify.com/wiki/images/a/af/Von_Neumann_Probabil...

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#198

Post by sametmax »

classicsnoot wrote: post #92
felipemnoa wrote: post #73

Earlier quoted context omitted.

If I remember correctly the reason they did not expect the mission to last longer than that was because they expected the solar panels to get covered with dust and thus render them useless. I don't think they had banked on martial winds to regularly clean them.

Your recollection is correct. Consider too the dust accumulation predictions for the moon landing. It would appear that we (as humans) are not very good at dust estimates (dustimates?). This is reinforced by the continuing struggle/inability to manufacture dirt. As an avid composter with a ton (lol sorry) of experience, I can make you hummus for days. I can turn 90% of your organic household waste into growth medium,…

Jumping on the opportunity to have somebody who knows about those things.

I used to have a huge garden, and made a compost by barely dumping anything organic on a big pile. It worksed great: low maintenance, never one problem, plenty of compost produced.

I now live in a flat, and have composter using worms.

I can't make it practical for the love of me.

If I put it inside, I get flies, no matter how much carbonated material I put in it.

So I put it outside, but it dies from either heat, or cold.

Even when I manage to avoid the worm genocide, the process is so slow. It does produce a fantastic liquid fertilizer in mass, but the volum of organic matter consummed is nowhere close to what I need. I eat a lot of vegies and fruits, and in 2 weeks, I have to put most of it in the trash can, waiting for the worms to work on the legacy pile of trash.

Any advice ?

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#199

Post by sidcool »

Timothycquinn wrote: post #81
slowhand09 wrote: post #77

Earlier quoted context omitted.

Earth minute or Martian minute?

Excellent question. I assumed that one mars minute differs from an earth minute but I just learned that they don't. Seconds, minutes and hours are universal. Hours in a day is what varies by planets, moons etc. Funny that I never thought of that before :)

Not if we take gravitational time dilation into account. But for most practical purposes between Earth and Mars, a minute will be the same.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#200

Post by the6threplicant »

perfmode wrote: post #79

How much money would you pay me if I were to travel to Mars, find it, and bring it home?

As one of the PIs said at the NASA briefing. If you can bring Opportunity home I'll prefer if you bring back 180kg of Mars rocks. We already know what the rover is made of. :)
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