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How the Curiosity Rover's Nuclear Battery Works

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Re: How the Curiosity Rover's Nuclear Battery Works

#41

Post by saraid216 »

brudgers wrote: post #40
grecy wrote: post #10

Many people here in the far north have extensive solar setups and live completely off-grid. Unfortunately in winter, we only get ~4 hours of sunlight, and it's a pain to sweep snow off the panels every day at ~ -30C to -40C We don't get much wind, and rivers are only liquid for ~4-5 months, so wind and hydro are not popular. I've been investigating commercial thermoelectric couplings as a source in the winter. Everyo…

My understanding of the problem is that nuclear sources tend to be nasty stuff and not the sort of thing that one really wants lay people responsible for discarding.

Looking through the Wikipedia page on RTGs, there is a noted risk classified by the US-DOD that Beta-M RTGs could be used as dirty bombs, which is about what I expected. =/ I wonder if this risk extends to other RTGs in the wrong hands? I imagine so, but I honestly don't know.

Re: How the Curiosity Rover's Nuclear Battery Works

#44

Post by peterwwillis »

grecy wrote: post #33
Erifcit wrote: post #15

Earlier quoted context omitted.

This might interest you. http://www.biolitestove.com/campstove/camp-overview/features...

Thanks. I looked into that a while ago (and a similar one), and it looks like any power produced from the TEC is considered a bonus, and is in the range of 1-5W, probably only enough to charge a phone, etc. I'm looking to produce a sustained 150W + to charge deep cycle batteries.

Tech specs show the biolite to have about a 2.5in radius and (approx) 6.5in high fuel compartment, which is about 2.1L (http://www.wolframalpha.com/input/?i=volume+of+a+vertical+cy...). Using its design you can get about 2W continuous power at 5V.

Scaling this up, roughly, you would need about 157.5 liters of fuel space, though probably much less if your fuel was more compact (obv you don't fill up exactly 2L of space in the canister while burning twigs). The realistic output of heat/power based on space is probably much more efficient than something this large, considering they say 46 grams of fuel can boil 1 liter of water, and 46 grams is approx 0.046 liters (based on water density).

Somebody please correct my horrible assumptions, but basically, fill an oil drum up most of the way with wood and build a thermoelectric generator and you should be good to go.

(Also, if you're charging deep-cycle batteries, i'm assuming you're not going camping? Maybe solar would be simpler? http://www.mdpub.com/SolarPanel/index.html) (Edit again: I forgot your original post, no solar)

More edit: Check this page for an adaptable thermoelectric generator: http://www.tegpower.com/

And more edit: https://www.youtube.com/watch?v=bUH1HA3EnZE (i'll stop posting links now!)

Re: How the Curiosity Rover's Nuclear Battery Works

#45

Post by saraid216 »

danweber wrote: post #34
digitalsushi wrote: post #31

Earlier quoted context omitted.

Our line of sight to Mars is independent from Mars seeing the sun.

Not really. If the rover is on the side of Mars facing away from the Sun, it's almost always facing away from the Earth, too, since the Earth is deeper inside the solar system. Facing the Earth and facing the sun are highly correlated. Seeing one xor the other is possible, but unusual.

He's still right in a very technical, strict sense. I'm too lazy to look up numbers and do the math, but I expect there's a window near the Martian sunrise/sunset when the sun isn't visible over the horizon and we have line of sight.

I expect that window is small to the point where no one actually cares. It would be an interesting applied-math problem for a grade-schooler, though.

Re: How the Curiosity Rover's Nuclear Battery Works

#47

Post by ilamont »

Negitivefrags wrote: post #38
ilamont wrote: post #37

What are the safety implications of launching 10 pounds of plutonium-238 on a rocket that could malfunction or explode before gaining escape velocity? The article says the plutonium would not explode, but what about plutonium particles or radiation entering the atmosphere and ocean?

Somehow I stumbled on the exact PDF you want to see: http://www.nasa.gov/pdf/604332main_APP%20MSL%20Launch%20Nucl...

Thanks. The relevant bits:

Like previous generations of this type of electrical- power generator, the MMRTG is built with several layers of protective material designed to contain its plutonium dioxide fuel in a wide range of po- tential accidents, verified through impact testing. Each MMRTG carries eight individually shielded general purpose heat source modules (compared to 18 modules in the previous generation). The thickness of the protective graphite material in the center of the modules and between the shells of each module in the MMRTG has been increased by 20 percent over previous modules.

However, the same report says there is about a 3% chance of an accident with no release, and a .4% chance of an accident "with release".

Re: How the Curiosity Rover's Nuclear Battery Works

#48

Post by banana_bread »

ceejayoz wrote: post #17
shabble wrote: post #7

Earlier quoted context omitted.

For a short while they were used in implantable pacemakers as 'lifetime' power sources[1] The main issue is that they're really rather inefficient. The efficiency of the thermocouple at converting thermal->electrical is only about 5-10%, and combined with the cost of shielding, expense of the radioisotope to begin with, and security/safety considerations, they're really only suitable for niche aerospace/defense appli…

The bigger issue using it in pacemakers is it's actually beneficial to have a battery that needs replacing every 10 years or so - pacemaker tech gets better so fast that a 30 year old device would be crap compared to the current generation.

How much better really, if the current one wasn't working well you would find out real quick.

Re: How the Curiosity Rover's Nuclear Battery Works

#49

Post by aik »

>> The Curiosity Rover Nuclear Battery will supply the system with constant power, allowing it to work as much as needed, all year long for as long as 14 years.

Very cool. Massive improvement over the solar panels that only worked during the day and non-winter times.

Re: How the Curiosity Rover's Nuclear Battery Works

#50

Post by JoeAltmaier »

Shadow6363 wrote: post #35
mpyne wrote: post #24

Earlier quoted context omitted.

It would be easier to lift the rover perhaps, but F=ma, so since the mass of the rover hasn't changed, neither has the acceleration you can develop for a given force applied.

Isn't the friction dependent upon the normal force which on Mars would be less. Therefore, shouldn't the force required to overcome that also be less?

Wheels need friction to develop acceleration. So its a negative not a positive.
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