Smart RCS thrusters

[Tyko]

1 hour ago, Snark said:

The other thing I like to do is to use a cool feature that they added in 1.1:  you can specifically tell RCS thrusters what to help with, or, more to the point, what not to help with.  I'd been wanting that for ages.

I like to turn off yaw/pitch/roll authority on all of my RCS thrusters.  They're completely disabled for rotation; that way, I use exclusively reaction-wheel torque for rotating my ships.

<SNIP>

Fortunately, that's easily addressed with a snippet of ModuleManager config, which I keep in a "tweaks" folder in GameData:

// Make all RCS thrusters have yaw / pitch / roll disabled by default.
@PART[*]:HAS[@MODULE[ModuleRCS]]
{
	@MODULE[ModuleRCS]
	{
		%enableYaw = false
		%enablePitch = false
		%enableRoll = false
	}
}

There.  Couple of minutes with a text editor, and I'm done, forever.  All my RCS thrusters now have rotation authority disabled on them, by default. 

This rocks! I also learned to turn off yaw/pitch/roll and rely on reaction wheels. and, yes, I too have spent too much time turning off each thruster manually after I'd launched 

This thread, by the way, has turned into my favorite kind of feature request -

1. Good dialog
2. find out there's a hidden capability already in the game
3. Discover (again) how cool this game is.

[Snark]

26 minutes ago, Somtaaw said:

I should totally do this myself, I absolutely HATE burning up mono for rotation, when I specifically put reaction wheels for that purpose. Now how do I do this myself LOL.

1. Pick a place somewhere in GameData.  Can be anywhere-- in the GameData folder itself, or in a subfolder.  Personally, I like to make my own personal subfolder and put all my personal tweaks there, but do whatever works for you.
2. In that place, create a new text file.  Can call it anything you want, as long as it ends with the ".cfg" extension.  (In my case I called it "NoRCSRotation.cfg", just so I can remember what it's for, but the file name is unimportant.)
3. Using a text editor (Notepad or whatever), paste the above text that I gave into that file and save it.

There, you're done.  The changes will take effect the next time you start KSP. 

Note that this only works if you have ModuleManager installed, which you probably already do if you're running any mods at all (lots of mods depend on it, and they usually just bundle it when you install them).  If you don't have it already, you'll need to install it.  You can get it here:

Incidentally, if you like what I just did with the RCS thrusters, you may find this thread useful, posted by Alshain:

...it's basically just a compilation of various ModuleManager tweaks that players may find useful.

[suicidejunkie]

30 minutes ago, Snark said:

Well, yes, if you're going to be using it to tow some big heavy thing that sticks way out on one side and has no RCS on it at all.  But if you've got that, nothing will help you, including thrust limiters.

There is one thing:  Patience.

As long as you have some translational option, a separate attitude control (gyros or a second RCS thruster) and a lot of time, you can get the job done.

[kBob]

Sometimes this game reminds me of Civ V no matter how many thousands of hours you put into it you'll find there is something you over looked.  I don't use the caps lock much because it turns off automatically and I have to try to remember to turn it back on and just get confused about it's current state so usually I just ignore it, but obviously I need to get used to using it more.  Guess we'll need to find something else for four star pilots to do.  Interesting thread and good tip from @Snark.

[Dr.K Kerbal]

Can't you right click on the RCS thruster to change it's power? 

[Snark]

4 hours ago, Dr.K Kerbal said:

Can't you right click on the RCS thruster to change it's power? 

Yes, that's certainly possible.  The OP's concern here was wanting not to have to do that.  It's fiddly and finicky to have to manually fine-tune the strengths of all the thrusters-- there are a lot of them, they have to be adjusted in coordinated fashion, it's tricky to get the numbers right (unless you've got a mod to help you figure it out) and any manual adjustments get thrown out of whack the moment the mass distribution of the ship changes (e.g. if fuel has been burned), which means having to manually adjust them all over again.

The OP was wishing for a feature that would automatically (and continuously) adjust the strengths of all the thrusters, so as to give appropriately balanced thrust without having to be manually fine-tuning everything all the time.

Fortunately, the game actually already has such a feature.    Just turn on fine-control mode and the game does exactly that.  More discussion earlier in this thread-- just go up a few posts and read through.

[Racescort666]

1 hour ago, Snark said:

Fortunately, the game actually already has such a feature.    Just turn on fine-control mode and the game does exactly that.  More discussion earlier in this thread-- just go up a few posts and read through.

Is this new for 1.1.X? I tested the "fine control balances automatically" in 1.0.5 and it does not automatically balance RCS power. I know being able to toggle pitch/roll/yaw is new but I haven't made it to the point where I'd be using RCS in my latest Career game since 1.1 came out.

[Snark]

5 hours ago, Racescort666 said:

Is this new for 1.1.X? I tested the "fine control balances automatically" in 1.0.5 and it does not automatically balance RCS power. I know being able to toggle pitch/roll/yaw is new but I haven't made it to the point where I'd be using RCS in my latest Career game since 1.1 came out.

No, the auto-balance-in-fine-control-mode has been around for a really long time.  Not sure just when it was first introduced, but it's been around for at least a year-- certainly long before 1.1 came out, even before 1.0.5.

If you're running 1.0.5 and think you're not getting this behavior in fine control mode-- that's weird.  Screenshot of your ship, please?

[Racescort666]

2 hours ago, Snark said:

No, the auto-balance-in-fine-control-mode has been around for a really long time.  Not sure just when it was first introduced, but it's been around for at least a year-- certainly long before 1.1 came out, even before 1.0.5.

If you're running 1.0.5 and think you're not getting this behavior in fine control mode-- that's weird.  Screenshot of your ship, please?

I decided to try it on a fresh install of 1.1.3 and I'm seeing the same behavior of 1.0.5: 

I'm using HyperEdit out of convenience and MJ for the angular velocity readout. This craft turned out to be reasonably well balanced for just throwing it together but with the reaction wheels off and the RCS ports at anything other than perfect, you get rotation. In the first video the rotation is small but it's consistent I'm only using momentary inputs for RCS. Every time I use a translation it adds to the angular velocity. The second video I held the translation control and the craft visibly started to rotate. Again, this was in fine control mode.

As far as I've seen, RCS ports do not auto-balance in fine control mode.

I'm not trying to be a jerk but auto-balancing is not something that I've seen in the game. It's far more likely that whatever minor torque that is experienced is compensated for by the reaction wheels.

[Red Iron Crown]

@Racescort666 There are limits to what it can balance automatically. It looks to me like the forward set of thrusters is too close to the CoM for it to work in this particular case. Basically the positions have to be fairly balanced in the first place, just not perfectly so.

[Racescort666]

8 hours ago, Red Iron Crown said:

@Racescort666 There are limits to what it can balance automatically. It looks to me like the forward set of thrusters is too close to the CoM for it to work in this particular case. Basically the positions have to be fairly balanced in the first place, just not perfectly so.

The forward RCS blocks are further from the CoM than the aft RCS blocks. I decided to install RCS Build Aid to help demonstrate. At 100% thrust on both sets of blocks, RCS Build Aid shows a torque of 0.498 kNm (very manageable by the reaction wheels in the game) and 4 kN of thrust. 

 

By reducing the thrust of the forward RCS Blocks to 71%, the torque has been reduced to 0.005 kNm which you probably wouldn't notice (I have not tested this but past experience of this low of torque has been negligible). 

Hopefully these 2 pictures help demonstrate that the forward RCS blocks are not too close to the CoM but rather too far. By reducing the thrust, the torque due to these thrusters no longer producing a significant torque on the system. This excess torque was causing the vessel to pitch in the direction of translation. 

I haven't seen anything to support the claim of auto-balancing RCS in fine control mode. I feel like this vessel was pretty reasonably balanced from the start and could have easily been balanced by such a system had it existed.

[OHara]

18 hours ago, Racescort666 said:

I haven't seen anything to support the claim of auto-balancing RCS in fine control mode. 

Fine control has an effect, just not exactly the correct effect.  If you use the longest fuel tank, and spread the RCS thrusters to its ends, you get about 8°/s rotation per m/s translation in coarse mode, 1°/s per m/s in fine mode.

In your case, the thrusters are noticeably different heights from the CoM  -- you worked out that one set is 71% as far as the other -- so you want to scale the thrust from the closer RCS down to 71%, but only for sideways translation.  Fine-control mode seems to reduce that sideways thrust, but not by enough.

It acts as if the RCS thrusts are scaled by radial distance to the CoM, which are close to the same for all RCS blocks in your example craft.  We want the thrusts to be scaled by their lever arms to the CoM, which are different for each thrust-direction in a block.   One might hope that the single-jet RCS thrusters would be scaled correctly, but they seem to suffer the same bug.

[Racescort666]

On 7/23/2016 at 1:14 PM, OHara said:

Fine control has an effect, just not exactly the correct effect.  If you use the longest fuel tank, and spread the RCS thrusters to its ends, you get about 8°/s rotation per m/s translation in coarse mode, 1°/s per m/s in fine mode.

In your case, the thrusters are noticeably different heights from the CoM  -- you worked out that one set is 71% as far as the other -- so you want to scale the thrust from the closer RCS down to 71%, but only for sideways translation.  Fine-control mode seems to reduce that sideways thrust, but not by enough.

It acts as if the RCS thrusts are scaled by radial distance to the CoM, which are close to the same for all RCS blocks in your example craft.  We want the thrusts to be scaled by their lever arms to the CoM, which are different for each thrust-direction in a block.   One might hope that the single-jet RCS thrusters would be scaled correctly, but they seem to suffer the same bug.

Yes. Ultimately, fine control does help manage an unbalanced ship because it reduces thrust from RCS. The only thing that it really does is reduce thrust of RCS though. There might be some other things that fine control does to the PID controller, I don't know, I haven't seen any feedback from the devs.

If you get sick of eyeballing it and docking becomes an issue, I recommend using RCS Build Aid if modding is your thing. 

[OHara]

13 hours ago, Racescort666 said:

The only thing that it really does is reduce thrust of RCS though.

Fine control mode reduces the thrust of each RCS block by a different amount, in a way that reduces the unwanted torque quite a lot, for a given amount of linear acceleration.  

For long skinny rockets with RCS blocks spread along its long axis, fine-control mode works great.  For short squat rockets it doesn't get the ratios close enough to correct to be really helpful, but doesn't hurt.