Cooling for nuclear batteries

[Loren Pechtel]

Rather than haul a bazillion batteries to maintain power at night this time I'm going to build a nuclear version.  How much cooling am I going to need

[SSgt Baloo]

Subscribing to this thread, as I am interested in the answer.

Edited March 29, 2016 by SSgt Baloo

[wibou7]

What do you mean by "nuclear batteries"? Do you mean RTG?

And about the cooling needed... it depends on where you want to go. A single RTG around kerbin probably won't need anything but may cause issues around Moho, obviously.

[Streetwind]

But then again, at Moho you would just use solar power.

[Loren Pechtel]

1 hour ago, wibou7 said:

What do you mean by "nuclear batteries"? Do you mean RTG?

And about the cooling needed... it depends on where you want to go. A single RTG around kerbin probably won't need anything but may cause issues around Moho, obviously.

Right now I'm going to Mun, but I plan to send other copies around the solar system--it's a science hopper that can mine it's own fuel.  Mining operations need a lot of RTGs, not just one.

And while you would certainly use solar around Moho the whole reason I'm using the RTGs is to avoid the enormous battery stack needed to last through the night on the surface.  Why can't we have vessels that shut down the mining operations during the hours of darkness???

[Zhetaan]

1 hour ago, Streetwind said:

But then again, at Moho you would just use solar power.

Not if you're landed.  Night lasts quite a long time on a Moho base.  On the other hand, Ore + Fuel Cells + ISRU converters would take care of that.  On the gripping hand, with the amount of heat generated, the ISRU option might even be harder on Moho during the day, thus requiring solar panels and operator attention to cycle everything, not to mention the truly hellacious amount of fuel needed to move that much heavy hardware to Moho in the first place.  So, provided that you're landing a base, RTGs may easily make the most sense in terms of total power efficiency with respect to weight hauled, time management, and thermal considerations.

 

To attempt to answer the question, I have never needed additional cooling for RTGs.  If I correctly recall it, I think the fact that RTGs have built-in radiator fins was at least partially accounted for when assigning heat values; whatever the case, RTGs don't transfer their core heat directly to active radiators in the same way that, for example, ISRU converters or drills do.  The ideal core temperature is 350 K and the shutdown temperature is 10000 K, but if the part or the outside environment is hotter than the core, heat won't transfer into it, so that 10000 K may as well be infinity.  The core-to-part heat transfer rate (the heat that can leak into the rest of the vessel) is .01 % (one tenth that of ISRU--which also runs a lot hotter than RTGs do), so I'm going to call it and say that you don't need radiators except insofar as you need radiators for the other passive parts on the craft.  The RTG case is relatively light at only 1200 K maximum temperature, so if you are taking a lot of them somewhere hot, you may wish to provide a radiator or two to keep them from blowing up due to imposed heat from other sources.

I will warn you, however, that the configuration values for RTGs are commented using old references, so it is possible that these numbers will get a balance pass with the next version.  Be on your guard.

Edited March 24, 2016 by Zhetaan

[Starhawk]

17 minutes ago, Loren Pechtel said:

Right now I'm going to Mun, but I plan to send other copies around the solar system--it's a science hopper that can mine it's own fuel.  Mining operations need a lot of RTGs, not just one.

And while you would certainly use solar around Moho the whole reason I'm using the RTGs is to avoid the enormous battery stack needed to last through the night on the surface.  Why can't we have vessels that shut down the mining operations during the hours of darkness???

I would not recommend running drills or refineries on RTG's.  If solar won't work for you (for instance, if you're going to Jool or if you want to run at night) then I would go with fuel cells.

I can't even imagine how many RTG's you'd need to run even the small, inefficient ISRU equipment let alone the standard sized stuff.

Happy landings!

[wibou7]

14 minutes ago, Loren Pechtel said:

Right now I'm going to Mun, but I plan to send other copies around the solar system--it's a science hopper that can mine it's own fuel.  Mining operations need a lot of RTGs, not just one.

And while you would certainly use solar around Moho the whole reason I'm using the RTGs is to avoid the enormous battery stack needed to last through the night on the surface.  Why can't we have vessels that shut down the mining operations during the hours of darkness???

To support a mining operation on RTG alone does not seem feasible to me.

To support mining operation solely on RTG, you will need a lot of them... ONE Gigantor XL =  ~32 RTG.

I don't know about your setup, but my mining rig needs 8 Gigantor to run non-stop... So that would mean 256 RTGs. 
I'd consider the number of parts alone to be a no go (my computer won't run anything over 300 parts) but your computer may be faster than mine.

If you are playing career, it also mean a LOT of money (32 RTG is about ~750 000 Kredits, so 256 RTGs is about 6 millions), but again it might not be much concern to you if you are playing science.

Heat generation is not much of a concern for ONE RTG but it may very well b an issue for 256 RTGs...
I'm not quite sure how to calculate the heat generation for RTG but you will probably need to add a few large radiator array to your setup. That mean TONS of extra-weight...

At that point, it seems to me that carrying a dozen of batteries around is still a better idea. Especially if you are only going places where solar panels have good efficiency (i.e. the Mun).
Another approach would be to use fuel cell array; you will need to math it right but that would allow you to operate without solar panel. That would probably be required for places where solar panels are not that great (i.e. Jool and beyond). The part/weight/money requirement would still be lower than RTG.

[Loren Pechtel]

4 minutes ago, wibou7 said:

To support a mining operation on RTG alone does not seem feasible to me.

To support mining operation solely on RTG, you will need a lot of them... ONE Gigantor XL =  ~32 RTG.

I don't know about your setup, but my mining rig needs 8 Gigantor to run non-stop... So that would mean 256 RTGs. 
I'd consider the number of parts alone to be a no go (my computer won't run anything over 300 parts) but your computer may be faster than mine.

If you are playing career, it also mean a LOT of money (32 RTG is about ~750 000 Kredits, so 256 RTGs is about 6 millions), but again it might not be much concern to you if you are playing science.

Heat generation is not much of a concern for ONE RTG but it may very well b an issue for 256 RTGs...
I'm not quite sure how to calculate the heat generation for RTG but you will probably need to add a few large radiator array to your setup. That mean TONS of extra-weight...

At that point, it seems to me that carrying a dozen of batteries around is still a better idea. Especially if you are only going places where solar panels have good efficiency (i.e. the Mun).
Another approach would be to use fuel cell array; you will need to math it right but that would allow you to operate without solar panel. That would probably be required for places where solar panels are not that great (i.e. Jool and beyond). The part/weight/money requirement would still be lower than RTG.

I haven't checked the dark time for Mun, for Minmus I needed something over 30 of the biggest batteries to run through the dark.  My understanding is that a fuel cell array will consume more fuel than is produced, although I haven't checked to see if this might actually be acceptable given that it's only running half the time.

[Snark]

The right way to get through the night with a mining rig isn't to spam batteries; the power requirements are just insane.  Use fuel cells.  As long as you're on a reasonably dense ore deposit and you have a decent-level engineer on board, fuel cells can easily power your mining operation.

You really don't want to try to run a mining operation on RTGs; their power output is just too tiny.  You'd need 20 of them just to keep a single drill running (and that's not accounting for the power needed to refine the ore).

[Loren Pechtel]

16 minutes ago, Snark said:

The right way to get through the night with a mining rig isn't to spam batteries; the power requirements are just insane.  Use fuel cells.  As long as you're on a reasonably dense ore deposit and you have a decent-level engineer on board, fuel cells can easily power your mining operation.

You really don't want to try to run a mining operation on RTGs; their power output is just too tiny.  You'd need 20 of them just to keep a single drill running (and that's not accounting for the power needed to refine the ore).

Since the primary mission is science I don't get a good choice of ore density.  The mining rig is to let me do a whole world without worrying about refueling it.

[Snark]

44 minutes ago, Loren Pechtel said:

Since the primary mission is science I don't get a good choice of ore density.  The mining rig is to let me do a whole world without worrying about refueling it.

Well, sure, but you're going to need an insane number of RTGs to run a drill rig, and those lil' guys are 23,300 funds apiece.  Do you really want to spend nearly half a million funds to get enough RTGs to run one drill?

Basically, two options:

1. Care about ore density, land where the ore is fairly high, run it on fuel cells.  You can have a separate science lander that docks with (and refuels from) the miner in orbit, or some such arrangement.
2. Just give up on mining at night and wait for sunrise.

[Plusck]

It's insane to use RTGs to run a drill. I also consider it a bit daft to use fuel cells, but that's just my opinion.

What you want is plenty of batteries. You will lose a bit of time during the night when you aren't producing, but on virtually any planet or moon that loss is trivial.

If you have an engineer on board, you need huge tanks to contain the product of a single daylight cycle of drlling. If you don't have an engineer, and you're using fuel cells, you're spending a significant amount of your output just to keep going during the night.

And you're unlikely to be using your mining rig all the time, so wouldn't it be better to just store energy for free while doing other things, all the better to be ready to drill and convert when you actually need it?

Also, if you land on a slope on some moons, the game will not register surface contact without babysitting the craft. Again, fuel cells are useless here because you might as well save electricity then babysit and maximise output while you're watching the thing.

[Loren Pechtel]

2 hours ago, Plusck said:

It's insane to use RTGs to run a drill. I also consider it a bit daft to use fuel cells, but that's just my opinion.

What you want is plenty of batteries. You will lose a bit of time during the night when you aren't producing, but on virtually any planet or moon that loss is trivial.

If you have an engineer on board, you need huge tanks to contain the product of a single daylight cycle of drlling. If you don't have an engineer, and you're using fuel cells, you're spending a significant amount of your output just to keep going during the night.

And you're unlikely to be using your mining rig all the time, so wouldn't it be better to just store energy for free while doing other things, all the better to be ready to drill and convert when you actually need it?

Also, if you land on a slope on some moons, the game will not register surface contact without babysitting the craft. Again, fuel cells are useless here because you might as well save electricity then babysit and maximise output while you're watching the thing.

But doesn't the drill stop every night then?  You would have to keep babysitting it.

[Plusck]

8 hours ago, Loren Pechtel said:

But doesn't the drill stop every night then?  You would have to keep babysitting it.

Again, that depends on whether you plan using an engineer or not. If you have an engineer, you'll probably fill your tanks in one daylight cycle, so the only benefit to fuel cells is to make up for a shortage of sunlight way out at Jool or Eeloo. If you don't have an engineer (and you're not mining an asteroid), mining will be pitifully slow anyway and even more so if you use some of the output to power a fuel cell. I'm not sure if it's even worth doing or what percentage ore concentration you need to break even.

Someone wrote recently that when returning to an operating miner, the game makes a calculation of each operating component over six-hour periods to determine levels of ore, converted fuel, electricity etc. If this is true (and I have no reason to doubt it), then:

- if you lose surface contact (and this has happened at a couple of locations on Ike for me) you get nothing for any non-babysat time;

- if the ISRU depletes the electrical charge, the drill will stop and not restart on its own,

- if you don't have space to store 6 hours of ore, the shortfall is simply lost. If you use fuel cells, they'll still concume 6 hours of fuel...

So (and this is purely my own opinion, not a "certainty") I don't see the point in fuel cells just to run at night, with the possible exception of Moho (since if you can't move your mining ship, nighttime lasts for months), since you're always better off babysitting during the daytime anyway then doing something else during the night.

[Loren Pechtel]

5 hours ago, Plusck said:

Again, that depends on whether you plan using an engineer or not. If you have an engineer, you'll probably fill your tanks in one daylight cycle, so the only benefit to fuel cells is to make up for a shortage of sunlight way out at Jool or Eeloo. If you don't have an engineer (and you're not mining an asteroid), mining will be pitifully slow anyway and even more so if you use some of the output to power a fuel cell. I'm not sure if it's even worth doing or what percentage ore concentration you need to break even.

Someone wrote recently that when returning to an operating miner, the game makes a calculation of each operating component over six-hour periods to determine levels of ore, converted fuel, electricity etc. If this is true (and I have no reason to doubt it), then:

- if you lose surface contact (and this has happened at a couple of locations on Ike for me) you get nothing for any non-babysat time;

- if the ISRU depletes the electrical charge, the drill will stop and not restart on its own,

- if you don't have space to store 6 hours of ore, the shortfall is simply lost. If you use fuel cells, they'll still concume 6 hours of fuel...

So (and this is purely my own opinion, not a "certainty") I don't see the point in fuel cells just to run at night, with the possible exception of Moho (since if you can't move your mining ship, nighttime lasts for months), since you're always better off babysitting during the daytime anyway then doing something else during the night.

I'd prefer a lower fueling rate with no babysitting--fly other missions and come back to it periodically.  My version with gobs and gobs of batteries worked on Minmus, the new version has a science lab on board also.

[Snark]

Fuel cells actually work great, in the right situation.  I use 'em all the time, am quite happy with them.

As long as you've got a reasonable engineer present, and you're on a decent ore deposit, then the fuel cells only need a small fraction of the fuel produced-- it's way past the break-even point.  And if the miner has big fuel tanks (which mine always do-- if I'm spending all that mass on drills and an ISRU, then the bigger the tanks are, the better), it takes more than one day cycle to fill the tanks, so mining at night is a timesaver.

It's less of an issue in the inner system.  If I'm mining on Ike, or Gilly, I just wait for sunlight, no problem.  If I'm on Moho, I just land where there's sunshine and it lasts for-frickin'-ever, no problem.

However, in the outer solar system (Jool and beyond) ... solar panels are practically useless, and fuel cells are how I mostly power my drills even during the daytime.  (I spend a lot of my game time out there-- I like to run OPM.)

So a lot of it comes down to, first, where in the solar system do you spend your time, and, second, what sort of designs do you use for your mining rigs.  There's a fairly broad section of the problem space where fuel cells make a lot of sense.

[Loren Pechtel]

19 minutes ago, Snark said:

Fuel cells actually work great, in the right situation.  I use 'em all the time, am quite happy with them.

As long as you've got a reasonable engineer present, and you're on a decent ore deposit, then the fuel cells only need a small fraction of the fuel produced-- it's way past the break-even point.  And if the miner has big fuel tanks (which mine always do-- if I'm spending all that mass on drills and an ISRU, then the bigger the tanks are, the better), it takes more than one day cycle to fill the tanks, so mining at night is a timesaver.

It's less of an issue in the inner system.  If I'm mining on Ike, or Gilly, I just wait for sunlight, no problem.  If I'm on Moho, I just land where there's sunshine and it lasts for-frickin'-ever, no problem.

However, in the outer solar system (Jool and beyond) ... solar panels are practically useless, and fuel cells are how I mostly power my drills even during the daytime.  (I spend a lot of my game time out there-- I like to run OPM.)

So a lot of it comes down to, first, where in the solar system do you spend your time, and, second, what sort of designs do you use for your mining rigs.  There's a fairly broad section of the problem space where fuel cells make a lot of sense.

Interesting point about Moho--I normally will only land in daylight anyway, it looks like I can simply use panels when I get down there.  What counts as a "reasonable" engineer?

[Snark]

24 minutes ago, Loren Pechtel said:

Interesting point about Moho--I normally will only land in daylight anyway, it looks like I can simply use panels when I get down there.  What counts as a "reasonable" engineer?

Not only can you just use panels on Moho-- you can use much fewer of them than you'd need in Kerbin's neighborhood.  Sunlight is bright on Moho. 

I like to aim for at least a level-2 engineer, or level-3 if possible.  However, that's really only crucial if you're running a rig on fuel cells and you care about where you are relative to the break-even point.  If you're running on solar power alone, it's much less critical; having a higher-level engineer just means it mines somewhat faster, is all.  Moho daylight is so long that even with a low-level engineer I expect you'll be able to fill up your tanks before sunset.

Just make sure you bring enough radiators, you'll need more of them to stay cool when you're on Moho.  Be sure to get the folding ones, since they auto-rotate to stay edge-on to the sun (important when solar heating is an issue).  If you don't have enough radiators, your drills and/or ISRU will overheat, slowing them down.

[Loren Pechtel]

3 minutes ago, Snark said:

Not only can you just use panels on Moho-- you can use much fewer of them than you'd need in Kerbin's neighborhood.  Sunlight is bright on Moho. 

I like to aim for at least a level-2 engineer, or level-3 if possible.  However, that's really only crucial if you're running a rig on fuel cells and you care about where you are relative to the break-even point.  If you're running on solar power alone, it's much less critical; having a higher-level engineer just means it mines somewhat faster, is all.  Moho daylight is so long that even with a low-level engineer I expect you'll be able to fill up your tanks before sunset.

Just make sure you bring enough radiators, you'll need more of them to stay cool when you're on Moho.  Be sure to get the folding ones, since they auto-rotate to stay edge-on to the sun (important when solar heating is an issue).  If you don't have enough radiators, your drills and/or ISRU will overheat, slowing them down.

In the long run I intend two missions--one for science and one to establish a fuel supply.  I'm playing this no-kerbal-left-behind and some rescue missions spawn way down there.

[Loren Pechtel]

Followup:

I flew it with a level 2 engineer and fuel cells.  The fuel flow is positive at night.