How to turn RCS on by stage?

[FennexFox]

Well, Simple qustion: I have some Vernier on 1st stage, and some conventional RCS on rest of the stages.

When I turn RCS on, all of them turn on at a time, only to waste monopropellant of my payload.

Can I turn 1st stage vernier only without other stages RCS?

I know that I can disable RCS with action group, but I don`t prefer to.

Edited October 2, 2014 by FennexFox

[Geschosskopf]

Hmmmm.......

Well, in the VAB, you can right-click on the payload's mono tank and disable it that way. Then when you hit R on launch, only the LFO-vernor system will work. Once you stage, you'll have to right-click on the payload tank and turn it back on before its RCS will work, though.

The alternative is to use mono on all stages instead of vernor engines on the lifter. Then put some small mono tanks on the lifter. The way mono works these days (it seems to change every few builds) is it starts draining the lowest tank in the rocket and works its way up to the nose. Thus, you can make it so the lifter is using its own mono supply instead of the payload during the ascent.

This latter method is what I do all the time, and it doesn't take much mono at all on the lifter. Even big 3.75m lifters with multiple RCS thrusters on all stages only need 2-4 of the small round mono tanks during the typical ascent. So I typically put the small lifter mono tanks on the last stage under the payload (typically the transfer stage) and all stages below that have RCS thrusters, and that's sufficient for all maneuvers prior to payload separation. And the payload ends up with all its mono tanks full without having to muck about with action groups or disabling the payload tank.

[psyper]

you should be able to set up a custom action group to toggle the rcs thrusters - go to the launch pad - toggle them off - launch and then when you stage toggle them back on again

[FennexFox]

Hmmmm.......

Well, in the VAB, you can right-click on the payload's mono tank and disable it that way. Then when you hit R on launch, only the LFO-vernor system will work. Once you stage, you'll have to right-click on the payload tank and turn it back on before its RCS will work, though.

The alternative is to use mono on all stages instead of vernor engines on the lifter. Then put some small mono tanks on the lifter. The way mono works these days (it seems to change every few builds) is it starts draining the lowest tank in the rocket and works its way up to the nose. Thus, you can make it so the lifter is using its own mono supply instead of the payload during the ascent.

This latter method is what I do all the time, and it doesn't take much mono at all on the lifter. Even big 3.75m lifters with multiple RCS thrusters on all stages only need 2-4 of the small round mono tanks during the typical ascent. So I typically put the small lifter mono tanks on the last stage under the payload (typically the transfer stage) and all stages below that have RCS thrusters, and that's sufficient for all maneuvers prior to payload separation. And the payload ends up with all its mono tanks full without having to muck about with action groups or disabling the payload tank.

First one seems perfect to me. I didn`t know that I could disable mono tanks. Thanks!

you should be able to set up a custom action group to toggle the rcs thrusters - go to the launch pad - toggle them off - launch and then when you stage toggle them back on again

Well, that didn`t work to me(hard to explain: just a matter of preference.) Thanks anyway!

Edited October 2, 2014 by FennexFox

[Steve-S]

You could load TAC Fuel Balancer mod and set the upper stage tanks to input so that any used from the upper tanks is automatically replaced from the lower tanks.

[dzikakulka]

1. Create action group

2. AGroupOnStage mod