Is there a way to lock RCS thrusters and fuel tanks before launch?

[Gildon]

I'm trying to build a spacecraft capable of going to other planets by launching up multiple engines and docking them together. Each payload has it's own rcs thrusters and rcs fuel separate from the ones on the launch rocket. Every time however, the launch rocket uses the payload's RCS thrusters which disrupts the delicate balance of RCS thrusters on the rocket. Is there any way to lock the fuel and rcs thrusters of a payload before launch so that you dont have to "right click, disable" every time? Thanks.

[Gargamel]

You could Crossfeed the remaining fuel of the booster stage into the payload, then stage it off. You could also bring up a strictly refueling payload to top off all your tanks.

But as to your OQ, I don't know, I couldn't figure it out.

[Cheebsta]

Action group in the VAB should let you do this. 2 blue buttons up top. Click. Click on the thrusters you want to be able to toggle. Add their toggle to a custom group, or use separate groups for on and off if you like that better. Group #'s correspond to number keys.

[Johnno]

RCS fuel gets taken from all RCS tanks equally from anywhere on the ship. Only way to keep payload RCS fuel untouched is right-click and disable (can't be done by action group as far as I'm aware).

For RCS thrusters, action groups should work like Cheebsta mentioned.

[Zephram Kerman]

In addition to the above: I think you can right-click on the RCS fuel tank to disable flow. Also, be aware the action groups on each module carry over after assembly in orbit. So it's prudent to plan ahead for how you want them to work in the long run.

[Cheebsta]

Hmmm, does "Disable Crossfeed" on a docking port work to stop ALL_SHIP fuels crossfeed too?

[Frederf]

It stops crossfeed of flowable resources across that docking port only. Global resources are unaffected.

RCS thruster toggle you can add as an action grouping. RCS fuel you need to click the green play arrow to the red slashed circle every time as it isn't an action groupable feature. Often my RCS fuel is hidden deep in my craft so I can't get to it at launch. However I can transfer prior to separation. Any CoM imbalance that undesired RCS fuel usage produces is unavoidable.

[Starwaster]

get the TAC fuel balancing mod.

http://kerbalspaceprogram.com/tac-fuel-balancer-v1-0/

It gives you good control over where your resources go. It uses a small radial part, very inobtrusive. You can bind it to an action group so you can bring up the menu. In spite of the name it works for ALL resources including O2 / CO2 from the ioncross life support mod. IMO it's one of those 'how did I get along without it' mods that I resisted getting for a long time. It can either balance a given resource so it spreads it evenly or you can choose a tank to suck in all of the resource.

So in your case you would bring up the menu, select the tank(s) on the final stage and click 'In' and any time it is not at capacity it will have more monoprop pumped to it. You would either have that happening continuously during launch / transit or just before staging.

[Cheebsta]

It stops crossfeed of flowable resources across that docking port only. Global resources are unaffected.

I had a feeling that was the case, just never actually tried it. I've been doing the same thing you have with transfer otherwise, it works, but is highly annoying with the speed it goes if you have a couple tanks to empty.

The mentioned mod sounds rather useful though, might have to try that.

[draeath]

TAC uses a part? I get a button to pull it up without having to attach any parts

[Starwaster]

TAC uses a part? I get a button to pull it up without having to attach any parts

Really? That's strange, maybe I need to update or something. I only just downloaded it a few days ago though. Do you mean that a new button appears on the GUI somewhere? If so, I don't even have that; I have to either right click the part and click something OR bind it to an action group. (obviously the better choice)

[SRV Ron]

Actually, I ended up just using one thruster set on the payload stage rather then one on each stage. One set of four is sufficient to maneuver the underpowered rocket into position during flight. It can also be fired laterally for fine course corrections maneuvers. You can, of course, use an action group to disable those other thrusters after you have assembled your rocket in space.

As far as the fuel tanks are concerned, while on the launch pad or in orbit, right click on the payload thruster tank and click on the green arrow on the right. That will disable it from being used. Any tank below that stage will now provide fuel for the payload thrusters. No fuel line is needed for the thrusters regardless of tank location. One tank below the probe stage should be sufficient for orientation maneuvers or you can arrange for the thruster tank on the current stage to be used before you stage. Just don't forget to reactivate the next tank in line after you stage. I have used just thrusters on the probe stage for landing on airless moons and parachutes for those with an atmosphere.

My four stage Vanguard uses a thruster set on its probe stage with its own fuel tank. During flight, that tank is disabled and fuel is drawn from the tank on the fourth stage. Thrusters are only used for maneuvering the three stage assembly after it has reached orbit or escape velocity from a direct straight up launch at dawn. The onion booster gets it up to 40,000+ meters before staging. There is 20% fuel left in the second stage at escape velocity to provide a third of the thrust or more needed to intercept Jool.

RCS thrusters can be locked out with an action group. But, Unless you disable the probe tank, the remaining ones will draw fuel from it first.

Edited July 22, 2013 by SRV Ron