# Curiosity's power source ? **URL:** \ **Category:** Factual Questions\ **Created:** [August 13, 2012, 11:05am UTC](https://boards.straightdope.com/t/curiositys-power-source/631362 "2012-08-13T11:05:57Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Chickenwrangler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chickenwrangler/32/91_2.png) [@Chickenwrangler](https://boards.straightdope.com/u/Chickenwrangler)\ **Post date:** [August 13, 2012, 11:05am UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/1 "2012-08-13T11:05:57Z")
Curiosity instead of having solar panels like previous rovers is nuclear powered. What I’d like to know is how is the electricity generated? I’ve always been under the impression that nuclear power stations make electricity by heating water to create steam to drive the generators. But surely they would not take a miniature water driven steam turbine to Mars where the prime directive is to look for traces of water. I’ve done some Googling but can’t find the answer so appeal to the knowledgeable masses here. So how do they generate electricity from the nuclear source? Another point comes to mind. Without solar panels when the power source is finished, in a couple of years, the rover will be dead, unlike the previous couple of guys that kept going long past their operational date and one I believe is still working even now. Is there no back-up plan to get more years out of such an expensive mission? ---
**Author:** ![Airman\_Doors\_USAF](https://avatars.discourse-cdn.com/v4/letter/a/e36b37/32.png) [@Airman\_Doors\_USAF](https://boards.straightdope.com/u/Airman_Doors_USAF)\ **Post date:** [August 13, 2012, 11:13am UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/2 "2012-08-13T11:13:32Z")
I can’t really link to anything thanks to this being an iPad (hence useless), but the answer you’re looking for is that it is using a radioisotope thermoelectric generator (RTG). It works by generating heat and using thermocouples to generate the energy. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [August 13, 2012, 11:13am UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/3 "2012-08-13T11:13:43Z")
Looking at Curiosity’s wikipedia page I’m lead from power source to: > **[Radioisotope thermoelectric generator](https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator)** > > A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This type of generator has no moving parts. Because they don't need solar energy, RTGs are ideal for remote and harsh environments for extended periods of time, and because they have no moving parts, there... ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [August 13, 2012, 11:14am UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/4 "2012-08-13T11:14:56Z")
Not just a couple of years: 14, apparently. [How does the Curiosity Rover Nuclear Battery work?](http://www.about-robots.com/curiosity-rover-nuclear-battery.html) ---
**Author:** ![Chickenwrangler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chickenwrangler/32/91_2.png) [@Chickenwrangler](https://boards.straightdope.com/u/Chickenwrangler)\ **Post date:** [August 13, 2012, 11:41am UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/5 "2012-08-13T11:41:11Z")
Thank for the links. Guess I didn’t use the right search words :smack: 40 year old technology I am waaaaaaaaaaaay behind. :eek: [http://mars.jpl.nasa.gov/msl/mission/rover/energy/](http://mars.jpl.nasa.gov/msl/mission/rover/energy/) This power source gives the mission an operating lifespan on Mars’ surface of at least a full Martian year (687 Earth days) ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [August 13, 2012, 11:53am UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/6 "2012-08-13T11:53:59Z")
That “one martian year” life span is a waaay conservative estimate. Plutonium has a half-life of 88 years; although apparently the real-world power output decays faster than that since the thermocouples don’t last forever either. The Voyager probes have similar RTGs, and they’ve now lasted 35 years, and have many more years of life left (though at considerably reduced power output). ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [August 13, 2012, 12:37pm UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/7 "2012-08-13T12:37:48Z")
The Viking landers similarly used RTGs. They landed on Mars in 1976. Curiosity’s RTGs are a more recent design, bigger, and deliver twice the power, but that is about it. Galileo also used RTGs when it visited Jupiter and so on. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [August 13, 2012, 1:33pm UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/8 "2012-08-13T13:33:47Z")
> [@Airman\_Doors\_USAF](#): > > I can’t really link to anything thanks to this being an iPad (hence useless), but the answer you’re looking for is that it is using a radioisotope thermoelectric generator (RTG). It works by generating heat and using thermocouples to generate the energy. Just copy and past the link. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [August 13, 2012, 1:51pm UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/9 "2012-08-13T13:51:49Z")
One side benifit of these power sources is they constantly generate a large amount of waste heat (my wag is a few thousand watts are available for use). They use this heat to keep parts of the rover at better temps than they would have been normally. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [August 13, 2012, 2:18pm UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/10 "2012-08-13T14:18:38Z")
> [@billfish678](#): > > One side benifit of these power sources is they constantly generate a large amount of waste heat (my wag is a few thousand watts are available for use). They use this heat to keep parts of the rover at better temps than they would have been normally. You’re not far off: “is designed to produce 125 watts of electrical power from about 2000 watts of thermal power at the start of the mission.” (from wikipedia) ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [August 13, 2012, 2:21pm UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/11 "2012-08-13T14:21:20Z")
> [@Francis\_Vaughan](#): > > The Viking landers similarly used RTGs. They landed on Mars in 1976. Curiosity’s RTGs are a more recent design, bigger, and deliver twice the power, but that is about it. Galileo also used RTGs when it visited Jupiter and so on. IIRC one of the Viking landers was shut off accidentally by a stray line of code sent to it, so It may have continued to broadcast for many more years, as it was it lasted very long. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [August 13, 2012, 2:34pm UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/12 "2012-08-13T14:34:40Z")
Every time I see the title of this thread, I can’t help but think: “Cats, of course…” ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 13, 2012, 3:34pm UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/13 "2012-08-13T15:34:47Z")
How long a useful life you can get from an RTG depends on what your power requirements are, and how much margin you were willing to build in. If you’re willing to build your generator to initially supply twice the power you need (or alternately, you’ve got a low-consumption efficiency mode you’re willing to use late in the mission that only needs half the original power), then you can keep running for a full half-life. If you’ve got a whole suite of absolutely essential power-consuming tasks, and you build the generator to just barely be able to meet those, then your useful life will be much shorter. As for why they’re using RTGs instead of solar panels, I’m guessing that it’s due to the square-cube law. One would expect that, since the probe is packed full of instruments that all need power, the power consumption of a probe would be roughly proportional to its volume, but the power you can get from solar panels would scale with the surface area of the probe. So for a large probe, solar wouldn’t be able to keep up. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [August 13, 2012, 3:45pm UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/14 "2012-08-13T15:45:41Z")
> [@Chronos](#): > > . So for a large probe, solar wouldn’t be able to keep up. Good point. As well as the fact those solar panels aren’t going to provide all that useful waste heat. I think some of the other rovers may have had some radioactive materials place here and there to warm parts of them but I doubt it was 4000 thermal watts worth. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [August 13, 2012, 4:44pm UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/15 "2012-08-13T16:44:42Z")
> [@Chronos](#): > > As for why they’re using RTGs instead of solar panels, I’m guessing that it’s due to the square-cube law. Also significant are the ability to operate at night and to not have to respect seasonal variations in solar radiation. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [August 14, 2012, 11:29am UTC](https://boards.straightdope.com/t/curiositys-power-source/631362/16 "2012-08-14T11:29:21Z")
NASA has a big problem in that they are [running out of Plutonium](http://www.newscientist.com/article/mg21528771.400-space-fuel-crisis-nasa-confronts-the-plutonium-pinch.html) Pu[sup]238[/sup]. Without additional production, future missions may have problems supplying non-solar power. Si