Transfering Fuel & Electricity Between Modules

[Zerro]

Greetings,

I am currently in the process of developing a space station and I have a couple of quick questions before I start construction and later find out I forgot something:

With the stock KSP components, is fuel, electricity, and oxygen able to traverse through any parts, modules, or clamp-o-trons, or would I need specific wiring and fuel lines to do so? For example, I have my solars connected to the 'Modular Girder Segment XL'. Will the electricity generated from the solars magically travel through the structures with the use of video game logic or do I need something to aid in power transfers?

Thank you for the assistance.

[astropapi1]

You can transfer any resource by alt+clicking on the two parts as long as they're in the same ship.

If you want to transfer electricity, the solar panels should recharge batteries automatically.

[annallia]

Electricity seems to go through anything, however clamp-o-trons and stack separators/decouplers will keep fuel from transferring automatically. For those you need to do what astropapi1 said.

[metaphor]

You can transfer any resource by alt+clicking on the two parts as long as they're in the same ship.

If you want to transfer electricity, the solar panels should recharge batteries automatically.

Just a minor point, it's alt + right click.

[Thornn]

Just a minor point, it's alt + right click.

Good to know, thanks..I can see this coming in handy.

[Tiron]

Electricty, Monopropellant, and Xenon are all shared automatically throughout a craft without any infrastructure, and when you dock it turns into one giant craft. One of the side effects of this is that it doesn't bother running these resources through the fuel flow logic, and as such when you use one of them, all storage for that resource is drawn upon equally (except any that are empty, obviously).

Liquidfuel and Oxidizer on the other hand, follow a defined flow path. Docking ports are supposed to be able to do fuel crossflow through them (which you can disable on their right click menu), but I've never really tried to use it. In my experience crossflow is a little...erratic at the best of times.

But any resource you really want filled on a particular part you can do transfers as stated earlier, including the three auto-flow ones. Batteries will fill automatically if there's excess power production, so that's usually not a concern.

[Geschosskopf]

Just a word about monopropellant. It's actually a bit more complex than mentioned above, and that has a significant consequence for building space stations.

That consequence comes into play PRIOR to docking. In fact, it happens during the launch of the module. What happens is, if a rocket has multiple RCS tanks, the game will use the fuel from the tank closest to the nose until it's empty, then start on the next one back from the nose, working from nose to tail until all RCS tanks are empty. RCS fuel does NOT burn evenly from all tanks at once but burns in the opposite direction from which LOF is burning, even if there are separators and/or docking ports between the RCS tanks.

This becomes important for docking if your rocket is so long that it requires RCS to make turns during the ascent. You thus have 2 RCS tanks, 1 on the upper stage (module, for docking) and 1 on the ascent stage (for steering during launch). But they burn reverse order. Thus, unless you do something about it during the launch, your RCS fuel will go to zero when you separate from the ascent stage because the small tank in the module was burned out long ago and the big tank on the ascent stage has all the remaning fuel.

There are several things you can do about this.

1. Give the ascent stage enough delta-V to complete getting into orbit before you drop it. Then, once safely in orbit, you can alt-right-click on the 2 RCS tanks and pump all remaining RCS fuel into the module's tank.

2. You can alt-right-click on the 2 RCS on the pad or during ascent and set fuel to flow from the ascent stage tank to the module tank all the way up. This effectively burns the ascent stage tank because the module's tank will remain at 100%. However, doing this means you can't change the view of the rocket during the entire launch because right-clicking to move the camera cancels the fuel pumping.

3. You can get the mod TAC Fuel Balancer to set the module's tank to transfer in. This does the same as alt-right-click but stays active once you close the mod's GUI so you can move the camera no problem and still have a full RCS tank when you get up there.

[Tiron]

Just a word about monopropellant. It's actually a bit more complex than mentioned above, and that has a significant consequence for building space stations.

That consequence comes into play PRIOR to docking. In fact, it happens during the launch of the module. What happens is, if a rocket has multiple RCS tanks, the game will use the fuel from the tank closest to the nose until it's empty, then start on the next one back from the nose, working from nose to tail until all RCS tanks are empty. RCS fuel does NOT burn evenly from all tanks at once but burns in the opposite direction from which LOF is burning, even if there are separators and/or docking ports between the RCS tanks.

This becomes important for docking if your rocket is so long that it requires RCS to make turns during the ascent. You thus have 2 RCS tanks, 1 on the upper stage (module, for docking) and 1 on the ascent stage (for steering during launch). But they burn reverse order. Thus, unless you do something about it during the launch, your RCS fuel will go to zero when you separate from the ascent stage because the small tank in the module was burned out long ago and the big tank on the ascent stage has all the remaning fuel.

There are several things you can do about this.

1. Give the ascent stage enough delta-V to complete getting into orbit before you drop it. Then, once safely in orbit, you can alt-right-click on the 2 RCS tanks and pump all remaining RCS fuel into the module's tank.

2. You can alt-right-click on the 2 RCS on the pad or during ascent and set fuel to flow from the ascent stage tank to the module tank all the way up. This effectively burns the ascent stage tank because the module's tank will remain at 100%. However, doing this means you can't change the view of the rocket during the entire launch because right-clicking to move the camera cancels the fuel pumping.

3. You can get the mod TAC Fuel Balancer to set the module's tank to transfer in. This does the same as alt-right-click but stays active once you close the mod's GUI so you can move the camera no problem and still have a full RCS tank when you get up there.

It used to go outside-in, but they changed it at some point because uh...

I even uninstalled all my mods just to make sure mechjeb wasn't doing something (I doubt the others would've, but I decided to play it safe since I was already copying my installation out). It seems to use them all equally, and I'd seen that behavior as far back as, oh, 0.19 or so on my never completed fueling stations.

[Geschosskopf]

It used to go outside-in, but they changed it at some point because uh..

Hmmm. Well, all I can say is, for me, whether I have any mods on or not, from 0.20 to the present, RCS burns from bow to stern. That's the only behavior I've ever seen it do since I got the game. So I had assumed it was the same for everybody. Wonder why we see different things. I mean, I spent all morning today launching and docking modules into 3 separate interplanetary ships and for every single one of them, I had to intervene to have any RCS fuel in the module tank.

[astropapi1]

Just a minor point, it's alt + right click.

Oops.

Been a long time.

[SnappingTurtle]

I think you can stop resource draw from tanks by using the green arrow buttons that appear when you right click a resource container.

[Tiron]

I think you can stop resource draw from tanks by using the green arrow buttons that appear when you right click a resource container.

Yes, you can, but it won't automatically flip back on, which can be a little problematic if you're in the middle of a burn. Or spinning (The button is attached to the tank's right click menu, which follows the tank!)

And Gess, that's the expected behavior for Liquidfuel and Oxidizer, because the fuel flow algorithm always uses fuel from the 'furthest' connected tank first. I'm almost certain it's never done that for RCS stock, and pretty sure it doesn't now. Just for you I'm going to reinstall right quickly and verify that. I do know it used to go outside-in and then I'm pretty sure it went bottom to top, but I forget. I only recall the 'uses everything equally' bit starting in 0.19.

Edit: On a completely stock, fresh reinstall it still uses RCS from all tanks equally.

The nasty part about that is that it doesn't make allowances for different sized tanks, either, so all your small ones get used up first...

Edit2: Oh, and if it's using fuel from a tank you don't want it to, disabling flow from the tanks you don't want used is the best option. Just make sure you turn it back on when you separate the vehicle it's on or you'll wonder why your RCS doesn't work.

Edited August 4, 2013 by Tiron