psikeyhackr - 29 November 2011 03:34 PM

It’s a joke dude.

Thanks. Thought it might be a conspiracy. 

In engineering, very often, the choice comes down to a balance between some counter-balancing factors.  Whether solar powered or nuclear, it was a choice.  There was no “can’t” about either option.  Solar power that was planned for a few months, has out-performed the plan by leaps and bounds, a complete success for solar power.  That it lasted dozens of times longer than the plan gives you much more bang for your solar powered buck!  But far-be-it-from-me to characterize over-engineering as anything but a chance for lowering costs and save space in the next mission.  That frees up space and money for more equipment, and lowering the appeal for nuclear power further.  Choosing nuclear will save space and weight is reduced, and so nuclear makes more room for experiments than solar, and that is what NASA has chosen.  But more is just about greed really, every single centimeter that the pioneering rovers move has been a new discovery, NASA is contaminating the virgin planet with isotopes in their containment vessle, contamination for the sake of greed.  Its their choice.    I don’t like it.  It shows an attitude that instead of tip-toeing on precious land, they are taking a heavy handed measures like colonists of the past, changing the land rather than just exploring it.  It is the start of a avalanche.

Despite my disagreement, I’m still enthusiastic about the new rover, I hope it lands in good shape.  It’ll be an exciting trip. 

Hey good news, the Odyssey rover reached the Endeavour crater on Mars, a great success after a three year long journey.  Solar power do good work. 

“In the past, small “plutonium cells” (very small 238Pu-powered RTGs) were used in implanted heart pacemakers to ensure a very long “battery life.”

Wow, can anyone confirm that wikipedia RTG article, confirm that it has been implanted as heart pacemakers?  That’s so small, so the RTG really is a simple device.

Jump I think its unfair to characterize this as greed or to call the designers of this mission “heavy handed colonists”. these missions have been well thought out with every effort made to minimize biological or nuclear contamination of Mars. The small rovers that we have already sent to Mars have just about reached the limit of what solar power can feasibly do. You are correct that there are always trade offs in engineering but there are also limits. There is only so much that a small rover with limited resources can do. If we want to learn more we need more powerful tools and those tools will require nuclear power systems. Eventually humans will be sent to Mars and when thy go they will have no choice but to bring nuclear power sources. It will be impossible to send large enough solar arrays and the energy they deliver will not be dependable enough when lives depend on the constant availability of power. As I mentioned earlier this is not the first time we have landed RTG’s on Mars. The viking landers each carried one when they landed in the 70’s.

We have used them before, we’re using them on the current mission, and we will most certainly use the again if we ever want to send humans to Mars. Nuclear is a necessary risk for long range space travel but I think the engineers have done a pretty good job of making this as safe as possible. The risk to any life if it exists on Mars is extremely remote.

I agree Macgyver. Not only can more instrumentation be carried and powered, but an RTG allows operation during the Martian winter. Also, we tend to forget the massive amounts of radiation Mars gets naturally because it has no substantial magnetic field to protect it from solar wind.

macgyver - 29 November 2011 07:50 PM

these missions have been well thought out with every effort made to minimize biological or nuclear contamination of Mars.

macgyver, I’m an engineer, I understand technology well.  I know you don’t think NASA had a viable alternative to nuclear.  But can’t we at least, agree on the basic facts?  The Spirit and Odyssey rovers both completed their three month missions successfully, and the Odyssey is still exploring Mars, and they did it with solar power.

jump_in_the_pit - 30 November 2011 11:46 AM

macgyver - 29 November 2011 07:50 PM

these missions have been well thought out with every effort made to minimize biological or nuclear contamination of Mars.

macgyver, I’m an engineer, I understand technology well.  I know you don’t think NASA had a viable alternative to nuclear.  But can’t we at least, agree on the basic facts?  The Spirit and Odyssey rovers both completed their three month missions successfully, and the Odyssey is still exploring Mars, and they did it with solar power.

I certainly agree with you that those were very successful missions, but I’ve also followed them pretty closely and I remember a lot of the concerns from controllers as the solar panels got covered with dust and power levels dropped and how they cheered at the sheer luck when a dust devil scowered some of it off. I also remember the preparation they had to go through to winterize the rovers by propping them at just the right angle and then powering down everything but the heaters in the hopes that they might survive another winter with the small amount of power they had to work with. At least part of the reason Spirit is no longer working is because when it got stuck in the sand it couldn’t be positioned properly for the winter and by the time summer rolled around it had frozen and couldn’t be recovered.  These are all things that Curiosities controllers won’t have to worry about.

i have to defer to your engineering expertise but i think we both have to defer to the experts at NASA when it comes to the decisions made for these systems. It seems to me that at some point you need bigger and better tools if you want to make any progress in exploration. I understand your concerns but I think if you look at the bigger picture and keep it in perspective the risks of contamination and the overall impact of such a small amount of contamination is acceptably low compared to the potential benefit.

macgyver - 01 December 2011 03:03 PM

I certainly agree with you that those were very successful missions,

I’m relieved to hear it. 

macgyver - 01 December 2011 03:03 PM

... but I’ve also followed them pretty closely

You obviously have, you seem to know some good details.  You’ve obviously been touched by the concerns that the NASA engineers, scientists, and managers have for the rovers.  When an engineer starts with nothing but an empty test bench and creates a device part-by-part, they do get very vested in the device, they want it to succeed and do well, they’ll even get emotionally vested in it.  If you saw their worry written into some of NASA’s articles, that worry is just normal.  They’re exploring a new world with a new device, so of course they worry.  That worry isn’t special and due to the solar power, they’d be worried about nuclear too.  But the difference in what the two technologies makes in the brains of the NASA engineers is that with the solar power now they have proven and learned what the likely risks are when used on Mars, and they’ve learned how to overcome those risks. On the other hand with the nuclear power they wouldn’t have given the dust or the amount of light in the winter much thought, I doubt there are any dust detectors build into the rovers, so they’d know nothing about the dust that accumulates on the rovers. 

That the NASA engineers were worried, is just good engineering.  That the rovers had some challenges in a brand new world is expected.  That they have overcome the challenges and completed the three month mission is a complete success, there’s no undue obstacles that should be blamed on the solar power.  That the Odyssey rover is still exploring, is a great bonus, adding much more value to NASA solor power dollars.   

Its okay to be very enthusiastic and happy with the solar powered rovers, even if you see some article that express worry about the technology succeeding.  There are no problems with solar power, that requires nuclear power nor any other solution.  Really, the rovers succeeded and you can be very happy about it.  macgyver, isn’t it amazing… there are rovers on Mars!  I still don’t really believe it myself. 

macgyver - 01 December 2011 03:03 PM

At least part of the reason Spirit is no longer working is because when it got stuck in the sand it couldn’t be positioned properly for the winter and by the time summer rolled around it had frozen and couldn’t be recovered.  These are all things that Curiosities controllers won’t have to worry about.

Nuclear powered rovers can get stuck in the sand too, that problem has nothing at all to do with the power system, and its nothing that nuclear power will solve.  Having a winter hibernation procedure is just a part of how that particular power system works.  Using the technology correctly isn’t an injury, you wouldn’t use your notebook computer to hammer a nail and still expect it to hold on to your data, would you?  You don’t mind the parallel parking procedure for your car, calling it a failed technology, do you?  Really, the solar power has been a complete 100% success.

Rovers on Mars, aren’t you just amazed as I am.    Little green men, here we come! 

macgyver - 01 December 2011 03:03 PM

i think we both have to defer to the experts at NASA when it comes to the decisions made for these systems.

I’ll defer to the NASA engineering on any topics like Martian geology, Martian atmosphere, and more as they come up.  Really, non-engineers could have made the power decision, maybe a manager made the choice, or maybe an engineer, for the Curiosity robot.  On this forum Traveler is an engineer too, you see he made his choice, I’m just doing the same as him.  I don’t think that a nuclear craft on the surface, is tip-toeing on a planet.

Jump, i never meant to imply that solar was a failed technology. Spirit and Opportunity are amazing successes, but I think you missed my points

1) Solar power is limited to the surface area you have available. If you’re sending a rover the size of Curiosity with the power requirements that is has you would need a huge set of solar panels. You’re an engineer so perhaps you can tell us. How large a set of panels would you need to supply the 125 watts of power that the RTG will supply 24 hours a day to the rover? It seems to me that they would have to be huge. Opportunity’s solar panels apparently provided 140 watts, but for only 4 hours/day and that energy then had to be stored in batteries to be used the rest of the day. That was at its peak before the panels started accumulating dust. Im no engineer but wouldnt you need something close to 6 times as much surface area and six times the battery capacity to store the power. Solar panels that big would make the craft very ungainly and difficult to drive around the planet, not to mention that the rover would be significantly heavier which would require a much heavier launch vehicle and an eaven more complex or heavier landing system. This would have made the entire mission significantly more expensive and perhaps undoable

2) Having to put the craft into hibernation mode for a 1/3 of the year because the solar panels cant generate enough power means a huge loss of science. Sure they’ve accomplished a lot but they could have accomplished a lot more if they didnt have to be parked for 4 months every year.

3) Experience is not an advantage of solar panels. NASA used RTG’s before on Mars. Two Viking landers set down on the surface of Mars in the 70’s and both of them used RTG’s. NASA and other space agencies have sent dozens of RTG’s into space on missions over the past 50 years. Every mission that has gone beyond Mars has had an RTG on board, so they have at least as much experience with this technology as they do with solar. As we already mentioned, dust storms, change of season, and nighttime make solar cells an inconsistent source of power on Mars. Yes, talented engineers can come up with workarounds to get past these difficulties but an undependable power source always results in compromises that an RTG would not require them to make.

4) My point about solar power contributing to the loss of Spirit was not that a nuclear powered rover wouldn’t get caught in the sand. Of course it could, but a nuclear powered rover wouldn’t have frozen to death because it got caught in the sand in an orientation that wouldn’t allow it to survive the winter. Spirit died because it was so dependent on the meager amount of power the solar panels could supply in the winter that being parked just a few degrees out of optimum orientation left it short of power causing it to freeze to death. That wouldn’t happen with an RTG powered rover.

5) Traveler also made a good point that Mars is bombarded with large amounts of gamma rays and solar wind radiation every day due to its lack of a magnetic field. While the type of radiation that would be emitted from the plutonium in the RTG is different, on a planet wide scale its truly a drop in the ocean.

I respect your opinion and its reasonable to see things differently. We may just have to agree to disagree here.

This might all just be a miscommunication.  I do agree that nuclear can power a robot, and I agree it has some attractive features.  I have not said any specific criticisms about nuclear powered space robots.  So I do agree with much of what has been said about nuclear powered robots.

But where I’ve been disagreeing with you macgyver, is where you’ve repeatedly tryed to either dismiss, condemn, fail, or undermine solar power ever since you said it “can’t” be used and in every message since.  When I said that solar power was successful, that was in direct response to the condemnations.  I felt I first had to resurrect the technology, before I promoted it as the tip-toe choice. 

I just think that nuclear should be minimized, therefore when one can opt for another power source, as NASA can do with the rovers, then I think they should.

macgyver - 01 December 2011 08:08 PM

Jump, i never meant to imply that solar was a failed technology.

I believe you.

macgyver - 01 December 2011 08:08 PM

This would have made the entire mission significantly more expensive and perhaps undoable.

2) Having to put the craft into hibernation… means a huge loss of science. Sure they’ve accomplished a lot but they could have accomplished a lot more if they didnt have to be parked for 4 months every year.

3)... an undependable power source always results in compromises that an RTG would not require them to make.

4) Spirit died because it was so dependent on the meager amount of power the solar panels could supply in the winter that being parked just a few degrees out of optimum orientation left it short of power causing it to freeze to death.

I agree that solar power needs more area to provide more power, that this adds mass, more mass for the battery, that Spirit is frozen inhibiting its battery and other components, and to all your technological facts through-out this thread. 

But I don’t agree with your condemnations of solar power, macgyver, I quoted the latest ones above.  Could you stop that please.  Solar power space robots are viable.  You wouldn’t condemn cell phones because they don’t always have reception.  You wounldn’t condemn hard drives because they can have some mechanical failures, nor RAM because it is volitile memory, nor EEPROM/Flash because it is slow.

macgyver - 01 December 2011 08:08 PM

5) Traveler also made a good point that Mars is bombarded with large amounts of gamma rays and solar wind radiation every day due to its lack of a magnetic field. While the type of radiation that would be emitted from the plutonium in the RTG is different, on a planet wide scale its truly a drop in the ocean.

On a planetary scale even California looks small.  That comparison is not valid. 

macgyver - 01 December 2011 08:08 PM

I respect your opinion and its reasonable to see things differently. We may just have to agree to disagree here.

Maybe, but I was just hoping that this might clear up a mis-communication, if and only if that’s what the real problem is here. 

jump_in_the_pit - 01 December 2011 11:21 PM

Maybe, but I was just hoping that this might clear up a mis-communication, if and only if that’s what the real problem is here. 

Yeah, i think we agree on the technology points. I think we just have differing points of view on the risk/benefit equation of sending an RTG to Mars. It doesnt worry me where as you would prefer we take a more kit glove approach to the planet. I dont think we can settle an argument one way or another on that. It really comes down to what your comfortable with.

macgyver - 28 November 2011 06:33 AM

citizenschallenge.pm - 07 October 2011 04:05 PM

traveler - 07 October 2011 06:15 AM

I’m surprised by that as well. While lower density means that wind is about 10 times less forceful on Mars (compared to Earth), a windy day could still damage that rover as it sets down.

well that was a good show stopper. 

but it occurred to me that it’s probably going into orbit first and
the entry sequence will be initiated at the Earth based flight controller’s all-clear.

. . . don’t know, but I figure those folks have considered such problems.

still gonna be heck of a knuckle biter  

I am not 100% certain but I’m pretty sure that curiosity will not be going into orbit prior to landing. No component of the craft remains in orbit so there is no need to establish orbit first. Going into orbit would require carrying a large engine and would consume a lot of fuel especially with a craft this large since the ship has to be slowed down from a speed that is far above orbital velocity to one that can achieve a stable orbit. Both of those things would add weight which would mean you need a larger rocket to launch the craft or you would have to launch a proportionately smaller probe.

{...}

Addendum: I just checked the mission profile. It will definitely not be going into orbit

Well, alrightie, so another thing to chew one’s knuckles over.
Guess, all eyes are going to be on the Mars weather reports during the final few days of the flight.

Thanks for clearing that up.

I’m not going near the nuclear power v solar power debate… besides from what I’ve read this particular mission would be impossible to achieve on solar power… for the same reason an air bag landing won’t work.  It’s too dang big.