RTG failure in hot environments

[lajoswinkler]

As most of us know, I hope, RTGs are just as any other heat engine, working because there's a temperature gradient between the radioisotope lump inside and vacuum of space outside.

I propose the following failure mechanism:

1) Establish a fixed temperature of the RTG's core and decrease its electrical power output in accordance with the heat gradient across its skin. Exponential decrease with a certain equation, corrected to actually reach zero when the temperature of atmosphere is identical to the core temperature of the unit.

2) Core temperature well below Eve's minimal atmospheric temperature (360 K @ sea level) so that RTGs are completely useless on its surface.

This would leave the player with two options for probe landings - fuel cells or solar panels.

(It would be interesting if Eve gets shrouded in clouds one day so that even the panels themselves aren't very useful. This combination would indeed turn every probe into a ticking failure, just like it is in reality.)

Edited July 22, 2015 by lajoswinkler

[Coyote27]

Ooh, I like this suggestion. I mean, I like making Eve more challenging in general, but this would be a nice addition to the heat-dynamics system and possibly lead to extra fun no matter the location. A ship with multiple RTGs in vacuum would probably need some extra radiators to operate efficiently, which is fine.

[lajoswinkler]

RTGs have their own radiators and their heat output is very small compared to reactors and engines, so they are fine. This would only mean they would stop working in certain environments. So far they're the ultimate lifesaver.

This plus decay is what KSP's RTGs need.

[GDJ]

RTG's are great for long term small power solutions, but so far for me it's fuel cells and a few OSCAR fuel tanks. The amount of fuel and oxidizer they use is really tiny for the power you get......

....BUT, for the purpose of this thread, I like the idea of having a definite expiry time on the RTG's. I have had probes out in Kerbal space for at least 5 game years and they still show a 1.0 efficiency. We all know that's BS. In real life, there would be a definite measurable decrease in power output.

[Signo]

That would be cool, but solar panels are already limited on Eve's surface (you can gather something less than 200U of energy with a couple of small OX-STATs with a good exposure for a whole day well above 2000m). They are practically not working at sea level. This would leave just fuel cells as a reliable power source.

[lajoswinkler]

Let's focus on the failure in hot environments; decay already has its mod and it's working perfectly.

Signo, what do you mean solar panels don't work on the sea level? They work for me...

[ChickenNugger429]

I like the concept of the isotope slowly decaying, decreasing power output over time. It would make for a very interesting style of gameplay for those exploring the outer Kerbol system for extended periods of time.

[Whirligig Girl]

Eve with clouds, RTGs with decay and heat-failures. I like it. The only power generation would then be from nuclear reactors from mods (you'd need some real interesting way of cooling down. Maybe the oceans are cooler?), batteries, and fuel cells.

[juanml82]

RTG's are great for long term small power solutions, but so far for me it's fuel cells and a few OSCAR fuel tanks. The amount of fuel and oxidizer they use is really tiny for the power you get......

....BUT, for the purpose of this thread, I like the idea of having a definite expiry time on the RTG's. I have had probes out in Kerbal space for at least 5 game years and they still show a 1.0 efficiency. We all know that's BS. In real life, there would be a definite measurable decrease in power output.

But real life RTGs last decades...

[KrazyKrl]

But real life RTGs last decades...

I can accept the abstraction of unlimited RTG lifespans for gameplay purposes. That 30+ year lifespans of RTGs can be ignored for the sake of gameplay. (Time is nearly a nonissue in KSP, as you might spend a year doing literally nothing but waiting for a planetary alignment. If/when KSP gets Kerbal Alarm Clock, then maybe RTG decay can be a trackable thing.)

As for the RTG thermals; I agree that they should become less efficient the hotter they are. As the RTGs directly tie into the heat system already in KSP.

[GDJ]

But real life RTGs last decades...

Very true, and there is several examples of RTG's in long term use (Pioneer 10 and 11, Viking 1 and 2, Voyager 1 and 2, New Horizons, The rover "Curiosity", Ulysses, Apollo 11 thru 17 used them for experiments) and for long term use, RTG's are great in deep space.

But, the Pioneer probes are dead, the Viking Probes are dead, Voyager 1 and 2 are still running but at a greatly diminished power, New Horizons is fine for now, Curiosity is okay so far, don't know about Ulysses, and Apollo is in the history books. RTG's have a life to them.

As they age, their power starts to diminish, even after one year (a very minuscule amount of drop to say the least).

I would be happy with a 10 gameyear lifespan in KSP. That would be realistic enough for the game.

As for efficiency drop due to their working environment (Eve for example), ABSOLUTELY! That would be just fine with me.

Edited July 23, 2015 by GDJ

[Signo]

Signo, what do you mean solar panels don't work on the sea level? They work for me...

Well, yes they do but they are not a reliable power source there. Without an RTG I am more often standing still than moving.

[lajoswinkler]

Can we please drop the RTG decay discussion? This is not the topic of the thread. Topic is failure to produce power in hot environment. Decay has been suggested numerous times and we even have a great mod that simulates it.

Well, yes they do but they are not a reliable power source there. Without an RTG I am more often standing still than moving.

http://i.imgur.com/KKAJBA6.png

The same would happen on Kerbin if it was sunset. Use your rover when Kerbol is higher, and position the panels differently.

[Signo]

That is the north pole, so this is almost the best exposure you can have.

[lajoswinkler]

Then what did you expect?

[Signo]

I was expecting to power up at least 2 drills with 4 gigantors, but they give me a meagre 4U with 100 exposure.

This is not the way it works at Kerbin poles. And exposure does not work like that anywhere else afaik.

Just to expand a little bit the concept: the energy you can gather using the same OX STAT on Kerbin near a random pole is more or less equal to the amount you could gather on KSC landing strip at dawn. That amount is more or less halved compared to the energy you can gather at noon.

With a comparable exposure (85-95) and as close as possible to sea level (max 75m altitude) the energy gathered is as follows:

Kerbin pole - 0.05/0.08

KSC dawn - 0.05/0.08

KSC noon - 0.18/0.22

Eve north pole - 0.00/0.01

Eve equatorial region dawn - 0.00/0.01

Eve e.r. noon - 0.01/0.03

If you make RTGs to explode down there you should provide an reliable and feasible alternative, it might not be comfortable to bring down there a single seat rover propelled by a random number of gigantors.

I was not particularly happy with the RTG solution myself so I thought to model a kind of ram air turbine to propel the rovers but that is still WIP.

Edited July 24, 2015 by Signo
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