Balancing Spaceplane RCS

[dlrk]

Hi,

I'm having some trouble balancing RCS on my spaceplanes. Using RCS Build Aid, I can usually get one axis balanced (ex. starboard/port), but this unbalances the other axes. So, I get torque to under 1 on the port/starboard axis, but it winds up being 40 on the fore/aft axis.

Any advice on how to do this properly?

[Rhomphaia]

Use the linear RCS ports instead of the thruster blocks. that way you only have to worry about one axis at a time when you place them.

You can also use single ports to balance out a thruster block setup.  adjusting the thrust limiter on the ports can also help balance them out if you cant balance with placement alone.

Edited May 1, 2020 by Rhomphaia

[Vanamonde]

Given the shapes needed for the craft to fly in an atmosphere, complicated by the shifting COM as you consume fuel, I think this is always going to be an awkward task. I think the best you can do is get a moderately good balance and use gentle burns. 

[dlrk]

11 hours ago, Rhomphaia said:

Use the linear RCS ports instead of the thruster blocks. that way you only have to worry about one axis at a time when you place them.

You can also use single ports to balance out a thruster block setup.  adjusting the thrust limiter on the ports can also help balance them out if you cant balance with placement alone.

I tried this, but once I balance out one axis with linear parts, the other axes become unbalanced.

[Rhomphaia]

Do you have any pics, or a craft file, Its hard to see where you could be going wrong otherwise.

 

You can use the move and rotate widgets to fine tune after you place the ports, RCSBuildaid updates the torque as you do. I would suggest rotating the ports first to ensure they are only firing along the axis you want, then use the move widget to fine tune there position

[dlrk]

I'll post a pic when I'm back at my desktop, thanks. I've been using the move and rotate widgets extensively, but as soon as I get one axis balanced, the other ones go way out of balance. Is it possible that RCS Build Aid is inaccurately showing that all port are firing? I'm not clear on how adding a linear port that is only pointed in one axis destablizes others.

Edited May 1, 2020 by dlrk

[dlrk]

Sorry to re-bump this, but what seems to be happening is that all RCS thrusters are assumed to always be used by RCS Build Aid, even where the craft translates better in the chosen direction without that thruster being used

[Rhomphaia]

7 hours ago, dlrk said:

Sorry to re-bump this, but what seems to be happening is that all RCS thrusters are assumed to always be used by RCS Build Aid, even where the craft translates better in the chosen direction without that thruster being used

RCS build aid does account for actuation toggles, so if you don't want a particular thruster to be used for a particular translation turn the toggle for it off in the VAB

[Snark]

On 5/1/2020 at 2:35 AM, dlrk said:

I'm having some trouble balancing RCS on my spaceplanes.

Apologies if you already know about all this, but I haven't seen anyone mention this in the thread, yet.

Are you turning on "fine control" mode while docking?  (Caps lock, by default)

Because as long as your RCS placement isn't hopelessly bad, turning on fine control mode will basically make your problems go away because it automagically does all the math for you to do variable thrust on your different thrusters to auto-balance it for you.

Detailed explanation here.

If you're already doing this and need further help with placement, then never mind.    Just wanted to check that you're doing it, because if you haven't, then it's possible that something as simple as "just hit caps lock when you're about to dock" could solve all your problems with one keypress.

[dlrk]

@Snark I'm aware, but thank you for posting that nonetheless. Definitely someone is going to come across this post and have that be the answer.

@Rhomphaia Yep, I see that. But it doesn't automatically assume fine control or MJ balancer (or whatever) will automatically turn off a thruster that is doing more harm than good?