Lv-n

[Mighty1]

I just had a brainstorm. The LV-N is basically a nuke reactor with fuel used for cooling. Would it be realistic that a LV-N produces electric charges at a constant rate. Something like an RTG embedded in the engine. RTGs use heat from the decay of heavy elements, LV-N do not shut down their reactor when they are not burning so some rest heat should remain for it to produce electricity by the Seebeck effect.

http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator

I'm no nuclear engine designer, but this suggestion looks like a logical thing the engine would do, or is it?

[lajoswinkler]

Yes, that would simplify a lot of things. I was just thinking about this today because I don't want to haul two nuclear things. It's a good idea, but I doubt we'll see it soon in KSP.

It does exist as a real design.

[Mighty1]

I am interested if it is realistic. Can someone confirm or deny this. If it is I am putting the power generation module of the RTG.Cfg in the LV-N right away

[TheSaint]

Well, technically all an RTG consists of is a lump of radionuclides (usually Pu238) and a bunch of thermocouples that use the heat generated by the radioactive decay of the radionuclides to generate an electrical voltage. So, technically, any source of waste heat (shutdown nuclear reactors/engines, expended nuclear fuel assemblies, Bob Kerman...) could be used to generate electric charge.

However, there are some engineering hurdles. Thermocouples need a certain amount of temperature differential to create a voltage. So you would have to let the temperature of your heat source increase to a certain level before you could start getting useful voltage out of it. Depending on what your heat source is and how you are cooling it, this may or may not be a problem. Another problem would be creating a thermocouple that you could place in the core of your nuclear engine that would be able to withstand the normal operating temperature/pressure/radiation conditions present in the core when the engine is operating as an engine. I suppose you could design a cooling system that could remove the heat from the engine and move it to the thermocouple when the engine is shutdown, but now the cost/mass/complexity of your nuclear engine just went up, and you now have to start deciding if it is cost effective vs just installing another power source.

The design you cited, Lajo, uses a closed-cycle gas turbine to convert the heat from the reactor into electricity. It would certainly work, but it would add a ton of mass to the system, not to mention a large amount of radiator surface area. Again, it would definitely work, but it is a cost/mass tradeoff with pluses and minuses rather than a slam-dunk/no-brainer sort of deal.

And, just as a matter of clarity: Yes, you would have to shut a LV-N down if you weren't running fuel through it. In a nuclear rocket engine, the fuel is the coolant, and if you run a nuclear reactor without coolant VERY BAD THINGS happen. However, even when a reactor is shut down, it is still generating heat due to the radioactive decay of fission products. (Google "decay heat".) This would be the heat that we would be talking about exploiting to generate electric power. (Technically when you shut down an LV-N you would still need to be venting fuel through it to remove decay heat for at least a day or two after shutdown, maybe up to a week depending on how long it was running.)

[Mighty1]

Ahhhh, just great. So if want to modify my LV-N i have to add a lot of mass to be realistic. Then i will use stock RTGs... or clip them in the engine :"muahahaha"

[lajoswinkler]

Yes, that fission product heat (few percent in the first hour or so) which makes LV-N glow like mad for a long time is what we'd like to exploit. We're having a lively discussion right now at the Steam KSP Forum group about it. One guy is trying to code a plugin.

[Pixel of Life]

Alright, I think the basic stuff is working pretty well now. I may or may not have simplified things quite a lot - it's using KSP's stock thermal model, so electricity production is directly proportional to the sum of radiation, convection and conduction flux and is clamped between zero and infinity (meaning the engine can only produce electricity when energy is flowing out of the engine). The engine produces about 7.25 Ec/s when it's near the temperature limit of 2500 degrees. Power output then gradually decreases towards zero as the engine cools after shutdown.

I've also implemented Lajos' nuclear fuel idea. I created a new resource called UraniumDioxide - the engine contains 50 units of this and can not be refueled after all the fuel has been used up. Assuming I did the math correctly, 50 units of UraniumDioxide should last for about an hour at maximum power. The ratio is 0.00815 units of UraniumDioxide per 0.9 units of LiquidFuel. The ModuleManager config also removes the stock LV-N's alternator module and internal power storage. I'll also need to figure out a way to add it to all fission powered nuclear thermal rockets when the plugin is installed, not just the LV-N.

I don't really know how to proceed from here. Any ideas?

Edited May 12, 2015 by CaptainKorhonen

[lajoswinkler]

That is great news and a something for Squad to think about.

Simplified and elegant solution which makes the engine have low or perhaps even zero electrical generation when the radiative transmission is enormous (close to Kerbol, perhaps even near Moho; we need to test this), which is the time to use solar panels. Far away from Kerbol, it's nuclear time.

Have you implemented NuclearWaste, with relation UraniumDioxide + NuclearWaste = 1, or you just used massless UraniumDioxide which diminishes in quantity?

The idea should be expanded, too. If the engine is supplied with radiators (Interstellar has great ones), it could be turned on to fission without thrusting. It could produce electricity and safely dispose off the heat. You don't want to thrust aimlessly far away form home just to get some juice.

Edited May 12, 2015 by lajoswinkler

[rtxoff]

I don't really know how to proceed from here. Any ideas?

How about opening a new thread in the mod development sub forum and releasing the work you did so far? I am sure there will be enough suggestions once people see that you are making a new mod there.

[Pixel of Life]

How about opening a new thread in the mod development sub forum and releasing the work you did so far? I am sure there will be enough suggestions once people see that you are making a new mod there.

Thread is open. http://forum.kerbalspaceprogram.com/threads/120969-WIP-Plugin-1-0-2-RealisticNuke-%28More%29-Realistic-Nuclear-Rocket-Engines.