|
|
Post by beta on Oct 14, 2016 1:22:04 GMT
I noticed a while ago there is an article in the Infolinks about them in game.
Are they a planned feature? Something that didn't make it in or was abandoned?
Would be interesting to see the differences between these and thermocouples and if they are comparable for mass/energy output.
|
|
|
|
Post by captinjoehenry on Oct 14, 2016 1:28:34 GMT
Umm in space they are really not a good idea that was what the article was talking about. They are just far too heavy and big to be practical. And all of the reactors that have been in space have been thermocouples. They are not a planned feature rather an idea that just isn't that good at all for a space craft but it is in common use so it should be mentioned.
|
|
|
|
Post by beta on Oct 14, 2016 2:05:20 GMT
en.wikipedia.org/wiki/Advanced_Stirling_radioisotope_generator"The energy conversion process used by an ASRG is about four times more efficient than in previous radioisotope systems to produce a similar amount of power, and allows it to use about one quarter of the plutonium-238 as other similar generators." en.wikipedia.org/wiki/Safe_Affordable_Fission_Engine"Most known is the SAFE-400 reactor producing 400 kW thermal power, giving 100 kW of electricity using a Brayton cycle gas turbine." en.wikipedia.org/wiki/BES-5"It generated 3 kW of electrical power [4] created by thermoelectric conversion of 100 kW of thermal output. The reactor weighed 385 kg including the radiation shielding." So, yeah, they are actually being looked into and are quite competitive. As an example, the most common nuclear reactor that flew into space was the BES-5 (as far as I know ...), the Russians put them on a bunch of satellites. It used a thermocouple to create 3kWe from 100kWt for 385kg. The SAFE-400 (not flown) produced 100kWe for 400kWt using a turbine. Further example, NASA is looking into a nuclear reactor, a 1kWe/4kWt, that runs off a sterling engine again. permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-14-23402
|
|
|
|
Post by captinjoehenry on Oct 14, 2016 3:27:55 GMT
Ok I will admit that for small scale power systems it is definitely a thing. I do not know for sure but I don't think it is going to scale into the 10s to 100s of MW power range which is from 100 to 1000 times higher power and using a whole load more nuclear material. I might be wrong but the author of the game definitely did his homework for everything and from that blog post it seems like something not going to be in the game.
|
|
|
|
Post by nerd1000 on Oct 14, 2016 3:33:48 GMT
IRL thermocouples are HIDEOUSLY inefficient- you'll see around 5% efficiency from a modern semiconductor based device, the only reason we use them at all is their lack of moving parts means they need no maintenance. So outside what is possible in-game due to our optimistic thermocouple performance, a brayton cycle turbine may be the only option for high powered spacecraft (unless you like using football field sized radiators to dump 95% of your reactor's heat output into space).
|
|
|
|
Post by zuthal on Oct 14, 2016 9:52:44 GMT
One downside of the Brayton cycle is, I think (besides the moving parts, which require maintenance), that the turbogenerator, as it spins up, would act like a reaction wheel, especially for large generators, applying an equal and opposite torque to the ships. This is not an issue for terrestrial or even naval powerplants, as they can easily dump that torque into the environment, but may be a problem for spaceships.
Also, the large spinning mass will act as a gyroscope, impeding any rotation perpendicular to its axis of rotation.
In addition, what cooling cycle should be used? I can in principle see four possible designs:
- Single-loop cooling, with the reactor, turbine and radiator in a common loop. This radioactively contaminates both turbine and radiator.
- Two-loop cooling, with either the reactor and turbine or the turbine and radiator in a common loop. The first of these also has the issue of radioactively contaminating the turbine.
- Three-loop cooling, with reactor, turbine and radiator each in their own loop.
Though, apart from the last, using a Brayton-cycle turbine might limit reactor or radiator performance, since the light gases you would ideally use to run such a turbine will not make the most effective of coolants. A better solution there might be a Rankine-type liquid-vapour turbine, though that will include additional complexity.
|
|
|
|
Post by ross128 on Oct 14, 2016 13:42:50 GMT
You could counter the torque and gyro effects by having two counter-rotating turbines. If the vanes have opposing threads (one is left-handed and the other is right-handed) they could even be in line with each other.
Because they're spinning in opposite directions at the same speed, they should apply equal and opposite torques to the ship. And their gyro effects should also be equal and opposite, or at least I think they would be. Though in certain conditions, their opposing forces may just form a torque centered between them, due to the distance between the rotors...
|
|
|
|
Post by bigbombr on Oct 14, 2016 14:18:14 GMT
You could counter the torque and gyro effects by having two counter-rotating turbines. If the vanes have opposing threads (one is left-handed and the other is right-handed) they could even be in line with each other. Because they're spinning in opposite directions at the same speed, they should apply equal and opposite torques to the ship. And their gyro effects should also be equal and opposite, or at least I think they would be. Though in certain conditions, their opposing forces may just form a torque centered between them, due to the distance between the rotors... So 4 turbines would solve all of this. |
|
