Using action groups to control an engine like it's an RCS

[shimmy00]

Hi.

This is something I've wondered about for a bit, and that's that I'm not sure how or even if one can use the action groups in the way I'd like to. I have a craft where that there are proper engines facing forward and back that I'd like to use in an "RCS"-like fashion in order to dock it with another. I noticed that there is an action group for "Translate F/B" and you can put there the Thrust Limiter on an engine, and I thought this would work. So I did. I set the action to be set (not gradually increase) the throttle to 100%. However, it seems that it doesn't actually work that way in the game. Once the craft has been lofted and the engines engaged, they burn continuously because apparently before you hit the forward/back controls they start out at 50%. Hitting the F/B makes them go to 100% as I'd expect, but the idle state is not 0% as would be needed, but 50%.

Can what I'm trying to do even be done? If so, how? If not, what would one use that action group for?

[EnderKid2]

You can't do this in stock, I think, but Throttle Controlled Avionics supports using engines as RCS

[splashboom]

Have you checked the Vernor control thruster? It uses Lf+Ox, and it is activated with the RCS controls - no need for action groups. Since it has only one direction you need to place them so you can cover all directions you need. In all, seems a lot like what you are describing - without the bother of creating groups ..

 

[18Watt]

16 hours ago, shimmy00 said:

Once the craft has been lofted and the engines engaged, they burn continuously because apparently before you hit the forward/back controls they start out at 50%. Hitting the F/B makes them go to 100% as I'd expect, but the idle state is not 0% as would be needed, but 50%.

I see what you mean.  I do not believe this is the intended behavior of this feature, I think it is a bug.  Unfortunately, development of KSP has stopped, so I doubt it will get fixed.

The engines do go to idle if you hold the opposite translate control, but that is no help.  Again, I think this is a bug.

[TheFlyingKerman]

I just have two sets of engine, one facing forward and one backward. I set the RCS hotkey to toggle (disable) main engine and toggle (enable) the forward set, and another hotkey to toggle both sets, and use the throttle to control the burn. IME as long as the docking port is aligned and both crafts are free to rotate to face each other, that is enough to dock.