Disable RCS for rotation? / Enable RCS for translations only?

[Riph]

I use RCS for translation only. My ships always have enough reaction wheel torque to make my maneuvers without expending monoprop.

What this means is that I'm constantly hitting R before my translations, then rushing to hit R again before SAS blows all my monoprop on a maneuver that the reaction wheels could have handled no problem. This is an even bigger problem when I need to rotate and translate at the same time, since I seem to have no choice but to hit R, enable RCS, and watch SAS spend all my monoprop. (Can address this by turning off SAS, but that's its own pile of problems.)

In a perfect world, I'd be able to use IJKL keys to do my RCS translations at any time, and only need to hit the R key when I wanted RCS to assist with my rotation.

Is there a setting somewhere that can make this happen?

Edited July 29, 2014 by Riph
Edit: Setting Answered

[Drew Kerman]

I do the same thing. Would def be nice to only translate with RCS, when needed

[Reactordrone]

You could just use the linear stick anywhere RCS thrusters. Make sure there are none that could rotate the ship so just place them left, right and up down with a few for forward and backwards. If they're directly on the CG they won't even fire up for pitch and yaw changes.

[Cerberus738]

You could just use the linear stick anywhere RCS thrusters. Make sure there are none that could rotate the ship so just place them left, right and up down with a few for forward and backwards. If they're directly on the CG they won't even fire up for pitch and yaw changes.

This!! I discovered this by accident. I recommend getting RCS Build Aid. It shows you if you will have any rotation while using your RCS translation keys. With only 1 port on each side and perfectly centered on the COM your ports should never fire for a rotation maneuver. Course on big ships 1 port on each side makes for some very slow docking.

[Lysius]

Being able to use JKLI with the RCS ports without enabling RCS for SAS (or rotation in general) should really be implemented.

As there is no way to get translation from the translation controls without RCS enabled, it should always work for those and the RCS enabling/disabling should just work for rotation.

[NKL]

If you put RCS perfectlylike with RCS build aid ( as suggested ), even with sas on, you wont be consuming RCS for rotation if you didn't push the rotation button.

I mean that if the translation if perfectly centered they won't be any "side-effect/ noise" rotation to add.

--> RCS Build Aid. this will be a life changing for ya

[Red Iron Crown]

If you have MechJeb there's a function in RCS Balancer that lets you disable RCS for attitude and only use it for translation. I've tried the "place linear ports pointing through the center of mass" trick, it works well for fore and aft thrusters but not so much on the side ones if the CoM changes as fuel is burned. It also ties up the centerline with RCS ports, where you might otherwise want an engine or docking port.

[Geschosskopf]

If you have MechJeb there's a function in RCS Balancer that lets you disable RCS for attitude and only use it for translation. I've tried the "place linear ports pointing through the center of mass" trick, it works well for fore and aft thrusters but not so much on the side ones if the CoM changes as fuel is burned. It also ties up the centerline with RCS ports, where you might otherwise want an engine or docking port.

The thing is, you have to design the ship itself for smooth translation from the get-go, by carefully juggling its parts so that the CoM doesn't move much if at all as fuel burns. And RCS Build Aid helps a lot here, too. RCS BA shows 2 CoM markers, the normal big yellow ball for full tanks and a smaller red ball for 1/2-empty tanks. Turn RCS BA on early in the build process, while you're still arranging the main pods, tanks, and engines, and arrange these parts so that the red ball is inside the yellow ball either completely (ideal) or with only a small part sticking out. Now your CoM won't move much if at all as you burn fuel. Then put your RCS thrusters on and use RCS BA to make sure they don't induce translation. Voila!

Also note that the stock game has a built-in RCS balancer. This comes on when you hit CAPS LOCK for fine controls. This isn't perfect but it's quite good, capable of handling a CoM change where about 1/2 the red ball is sticking out the yellow ball. Beyond that, you might need MJ.

NOTE: This same trick of using RCS BA early in the build really helps with spaceplanes, too, where you don't want the CoM to move relative to the CoL.

[Red Iron Crown]

Also note that the stock game has a built-in RCS balancer. This comes on when you hit CAPS LOCK for fine controls. This isn't perfect but it's quite good, capable of handling a CoM change where about 1/2 the red ball is sticking out the yellow ball.

I didn't know that, thanks for the tip. I'll have to test it a bit.

Usually I just disable RCS attitude control in MJ and turn on SAS, seems to keep reasonably well pointed even if thruster alignment isn't perfect.

[Riph]

If you have MechJeb there's a function in RCS Balancer that lets you disable RCS for attitude and only use it for translation.

I'm intruiged by this. It seems to suggest that you could write a mod (or just gut mechjeb) in order to get this feature by itself. I'm really not interested in the rest of mechjeb's features.

I've tried the "place linear ports pointing through the center of mass" trick, it works well for fore and aft thrusters but not so much on the side ones if the CoM changes as fuel is burned. It also ties up the centerline with RCS ports, where you might otherwise want an engine or docking port.

This. This this this. My craft carry a lot of fuel in them, and to engineer every one of them to have a static center of mass would be time consuming, and result in horrifying ovoid abominations and not the long, sleek rockets I'm trying specifically to build.

[Renegrade]

Also note that the stock game has a built-in RCS balancer. This comes on when you hit CAPS LOCK for fine controls. This isn't perfect but it's quite good, capable of handling a CoM change where about 1/2 the red ball is sticking out the yellow ball. Beyond that, you might need MJ.

You sure there's any actual engine behind that? I've noticed that without caps lock, there is a degree of balancing, it's just flawed. Gentle taps tends to reduce the amount of wastage.. are you sure that's not what you're seeing with caps lock?

I'm intruiged by this. It seems to suggest that you could write a mod (or just gut mechjeb) in order to get this feature by itself. I'm really not interested in the rest of mechjeb's features.

I'd love to see the RCS features extracted from MechJeb and rolled into their own separate mod. I'm also not interested in the other features, but I sure would like better RCS capabilities.

[RoboRay]

MechJeb has a modular design. You can install it, then disable any modules you're not interested in (I usually "kill" a few that I will never use myself).

[Geschosskopf]

You sure there's any actual engine behind that? I've noticed that without caps lock, there is a degree of balancing, it's just flawed. Gentle taps tends to reduce the amount of wastage.. are you sure that's not what you're seeing with caps lock?

Yup, there's always a little balancing for rotation at least even without caps lock. But it really kicks in when you use caps lock. Make some test rigs with built-in imbalances, HyperEdit them up, and give it a try with translation.

EDIT: This was introduced back in 0.21 IIRC.

[Renegrade]

MechJeb has a modular design. You can install it, then disable any modules you're not interested in (I usually "kill" a few that I will never use myself).

Hmm, maybe I'll give that a shot, I've always been kinda opposed to the autopiloty bits, if they can be kinda perma-killed then maybe it's RCS fun time

Yup, there's always a little balancing for rotation at least even without caps lock. But it really kicks in when you use caps lock. Make some test rigs with built-in imbalances, HyperEdit them up, and give it a try with translation.

I'll do some testing there. I play a lot of BTSM, which means RCS all the way, and anything I can do to make it more efficient is good. Still, I'd like to see the stock RCS overhauled to be better. At least though our gimballing engines can do rotation if there's more than one

[Red Iron Crown]

At least though our gimballing engines can do rotation if there's more than one

Roll authority via engine gimballing was added to stock in 0.24, with the RAPIER and KS-25x4 having roll authority even with only one engine due to multiple nozzles.

If you do end up trying MechJeb for the RCS balancer module, you might want to look at SmartASS, too. Better SAS behavior with more options that should be stock, IMO.

[Riph]

So it looks like my answer is "No, but kinda if you're willing to mod it." I'm going to mark this thread as 'Answered' and put a note in the Suggestions forum about being able to translate all the time, not just when you push R for RCS enable.

[Red Iron Crown]

So it looks like my answer is "No, but kinda if you're willing to mod it." I'm going to mark this thread as 'Answered' and put a note in the Suggestions forum about being able to translate all the time, not just when you push R for RCS enable.

I actually posted this as a suggestion a while back, maybe bump the thread to show your support if you'd rather not start a new one. Thread is here.

[Tank Buddy]

It sound like you need to control your rotation because the RCS thrusters are not aligned with your CoM. Use the RCS Build Aid, makes building ships for RCS translation a breeze. http://www.curse.com/ksp-mods/kerbal/220602-rcs-build-aid

[Riph]

For those who keep saying align your RCS thrusters with your center of mass, please be aware that some ships (like mine) are many segments that were built on kerbin and assembled in orbit. My CoM moves constantly as segments are snapped on and removed as the mission parameters require. I understand your solution works for some ships, but it is not going to work for mine. Thank you for trying to help though

[Geschosskopf]

For those who keep saying align your RCS thrusters with your center of mass, please be aware that some ships (like mine) are many segments that were built on kerbin and assembled in orbit. My CoM moves constantly as segments are snapped on and removed as the mission parameters require. I understand your solution works for some ships, but it is not going to work for mine. Thank you for trying to help though

I do this a lot myself. The 1st thing to consider is whether there is a real need to dock the assembled mass to anything, or whether the only docking will be by individual modules. If several combined modules won't ever be the active ship in a docking, then there's no need to worry about the RCS balance of the assembly. Balance is only needed for translation and translation (at least the side-to-side directions) is only needed for docking. Fore-and-aft translation, should it be needed to fine-tune orbits, is a no-brainer that happens naturally just by putting RCS blocks on with symmetry.

Now, if you DO want to dock a mass of assembled modules together, what you need to do is build each module individually as described above, using RCS Build Aid. First make sure their CoMs won't move, then put on the RCS thrusters so you don't get unwanted rotation. You want this anyway to assemble the whole thing in orbit. And if all the modules are more or less the same size and weight, the assembly will be close enough to balanced that either the stock or MJ RCS balancer will be able to deal with it. This works for ships up to this big:

This ship was made in 3 modules: the lab and 6-way hub, the orange tank, and the engines. Each module was individually balanced and the assembled mass was well enough balanced that I could dock a bunch of similar things together.

However, sometimes modules are different enough in size and/or mass that just balancing each one in isolation won't do it. If that's the case, and you really do need to dock this whole thing to something else, then sometimes there's nothing for it but to save the modules as subassemblies. Then you can stick them all together in the VAB and balance the lot. This can be a bit complicated because each module still needs its own individual balance so you can dock them together, so you can't change any of the modules. But what you can do is add another module that's simply a counterweight for balancing the assembly just long enough for it to dock, then you discard it.

In general, however, it's a lot easier to just dock individual modules to the growing assembly.

[Red Iron Crown]

Balance is only needed for translation and translation (at least the side-to-side directions) is only needed for docking. Fore-and-aft translation, should it be needed to fine-tune orbits, is a no-brainer that happens naturally just by putting RCS blocks on with symmetry.

Maybe it's just where I'm a mediocre pilot, but I use RCS translation for landing all the time. I like to keep my ship alignment vertical on final approach, then use lateral translation to zero out any remaining horizontal motion; I also use it to fine tune my landing speed. In these cases balance is even more important because landing is more time sensitive than docking in most cases. Being able to use the reaction wheels or gimbals to maintain attitude with SAS while using RCS translation is useful in this scenario, too.

[Geschosskopf]

Maybe it's just where I'm a mediocre pilot, but I use RCS translation for landing all the time. I like to keep my ship alignment vertical on final approach, then use lateral translation to zero out any remaining horizontal motion.

I do vertical landings myself but I've never used RCS translation to help there. I've just used torque and occasionally (on my biggest landers) RCS rotation to give me any control authority to push the retrograde marker around with the main engine like with a small lander. And if the planet has an atmosphere, I'll put on some chutes to save a little on fuel even if they're way too small to land the thing by themselves. Then the chutes also kill off horizontal velocity. But maybe I just don't land anything big enough to need RCS translation. I think my biggest lander ever was only about 60 tons.

[Renegrade]

Roll authority via engine gimballing was added to stock in 0.24, with the RAPIER and KS-25x4 having roll authority even with only one engine due to multiple nozzles.

Yeah, I knew about it being added in 0.24; I play a lot of BTSM which involves having no real reaction wheel torque, which means that you have to rely on fins, RCS, and thrust vectoring to stabilize a ship. Normally fins are very good in the deep atmosphere, but once you get high up, a lot of designs have a lot of rotational torque that fins and stock RCS can't really handle. Thrust vectoring prior to 0.24 also couldn't handle that so um, I've become fairly adept at flying a rapidly spinning ship, and am now very happy that it CAN handle that...especially since there's no reason it shouldn't be able to.

I've seen the RAPIER sub-engines twist in what looks like a proper manner, but it's good to know that is actually providing rolling torque too

If you do end up trying MechJeb for the RCS balancer module, you might want to look at SmartASS, too. Better SAS behavior with more options that should be stock, IMO.

Yeah, stock SAS has um, how do I say this nicely? ah, deficiencies ... I'll definitely check that out too, thanks!

[allmhuran]

Would be nice!