Question about RCS tanks

[Joey]

I have a bunch of radial RCS tanks up top but the giant one at the bottom of the ship I want to use first. Is there a way to automatically deactivate the ones on the top until the lower one runs out or is decoupled?

[leax256]

no, you must manually disable all the top tanks first than reactivate them later. I think though there is a mod that does this though.

[AndrewBCrisp]

Hm. I haven't had any luck attaching fuel tanks of any kind to action groups, so I'd say you'd have to shut them down manually before launch.

That said, the decoupler you have installed will cut off the large RCS tank from the RCS thruster groups I see firing at the top of your rocket. If you're looking to preserve RCS fuel until later, may I suggest redesigning your first stage to rely on fins and perhaps a central liquid fuel engine with thrust-vectoring instead of RCS? That way, you should be able to better control your rocket until it's out of the atmosphere.

[CalculusWarrior]

The mod is called the TAC Fuel Balancer.

However, I have not installed it, so I can't vouch for its utility, and I don't think it has been updated for 0.20 yet either...

[Joey]

Hm. I haven't had any luck attaching fuel tanks of any kind to action groups, so I'd say you'd have to shut them down manually before launch.

That said, the decoupler you have installed will cut off the large RCS tank from the RCS thruster groups I see firing at the top of your rocket. If you're looking to preserve RCS fuel until later, may I suggest redesigning your first stage to rely on fins and perhaps a central liquid fuel engine with thrust-vectoring instead of RCS? That way, you should be able to better control your rocket until it's out of the atmosphere.

Can you describe what "thrust-vectoring" is?

[AndrewBCrisp]

Oh! Sorry...

"Thrust vectoring" is a feature of some liquid fuel engines - basically the nozzle can change direction (slightly), so that engine can change the rocket's direction. Think of it like a rudder

I use the LV-T45 engine as my thrust-vectoring engine of choice... usually in combination with some LV-T30s for raw lifting power. The Poodle, Skipper, and Mainsail also have thrust-vectoring ability, but they're also heavier engines, and the Mainsail is prone to overheating.

[rodion_herrera]

Can you describe what "thrust-vectoring" is?

The ability of an engine to pivot on one axis (i.e. either x, y or z in the case of real-world combat jets) or omnidirectional (from single a reference axis)--the latter case also referred to as "gimballing" in rocket jargon.

[KevinW42]

That said, the decoupler you have installed will cut off the large RCS tank from the RCS thruster groups I see firing at the top of your rocket.

Not true. Monopropellant doesn't act like normal fuel. Monoprop tanks placed anywhere on the ship can feed RCS blocks placed anywhere else on the ship.

[ComradeGoat]

What the others said. There really is seldom any reason to use RCS for ascent, and on a manned ship, for much other than docking. Liquid engines almost always do better than SRBs too, and many of them can steer your rocket for you.