RCS fuel tank usage priority

[gcewing]

Is there any way to control which RCS fuel tanks get drained first?

I have two stages, with RCS tanks and thrusters on each stage. I want the fuel from the lower tank to get used first, keeping the fuel in the upper tank for later when I've jettisoned the lower stage. But that's not what happens -- fuel gets used from the upper tank from the beginning. Is there anything that can be done about this?

[Tokay Gris]

You can always transfer the fuel from the lower tank right before decoupling.

That said, I am not aware of a way to select beforehand which tank is used...

[capi3101]

You can lock the flow from the upper tank - right click on it some time before you need it; on the pad's optimal if possible. You should see a little green arrowhead (â–º) right next to the fuel status; click on that and it should turn into a red "no" sign. That's all you need to do. When you're ready to actually use the tank, same process but in reverse; you want the green arrowhead to show up instead. Bear in mind that if you switch to another craft for any reason, the tank will be unlocked again.

[Specialist290]

By default, RCS monopropellant is drained evenly across the craft from all available tanks. I believe this is intentional, though admittedly annoying.

If you're willing to use mods, I'd highly recommend that you check out TAC Fuel Balancer. It has options that allow you to specify whether or not you want a tank to stay full at all times whenever possible.

[iDan122]

You can tell certain Rcs tanks to not let fuel get drained from them. Right click the tank/s you want to lock, to the right from the bar indicating how much juice you got, there will be a green arrow, left click it and it will become a red something. Now Rcs won't be drained from that fuel tank.

[Captain Sierra]

By default, RCS monopropellant is drained evenly across the craft from all available tanks. I believe this is intentional, though admittedly annoying.

If you're willing to use mods, I'd highly recommend that you check out TAC Fuel Balancer. It has options that allow you to specify whether or not you want a tank to stay full at all times whenever possible.

I've tried TAC. It decided to hate me.

ANd yeah, I think RCS fuel should drain prioritized like LFO but it should not require fuel lines so the RCS blocks are happy. I think it should drain from the tank closest the thruster drawing it and it should obey decouplers as not crossfeed capable.

[TheHengeProphet]

In .19 and previous (I am unsure about these latest versions), RCS drained from tanks in the order of placement, thus the first tanks were drained first, etcetera. I may have that backwards, but it was along those lines. I haven't tested to see if the current system is the same or has been adjusted.