Smart RCS thrusters

[Tyko]

Add ability at higher levels for RCS/Vernier thrusters to adjust power levels automatically to account for CoM. This could be handled in two ways:

1. Require higher tech thrusters
2. Require Pilot level 4 or more advanced Probe Cores

I kind of like option 2 because currently Pilot benefits max out at level 3. This might be a way to add another tier of Pilot skills and also to add another tier of Probe Cores.

[Rocket In My Pocket]

Use Caps Lock to turn "soft" RCS mode on, this will help somewhat in alleviating any control issues.

That said, proper RCS placement in the first place is the most important way to prevent any problems. (All RCS units should be centered around the COM or equidistant to it.)

If you aren't against modding, this may be what you are looking for:

 

Edited July 17, 2016 by Rocket In My Pocket

[Tyko]

Rocket...I understand how to use and place RCS thrusters...that's not my point.

You don't have to spend all day moving your thrusters forwards and backwards along a long ship...you can right click and adjust thrust limiters on your RCS. You can even adjust thrust limits on ships in flight, so as you burn through your gas you can tune your thrusters to account for the empty tanks. It's a pain because you have to click on each one and there's no CoM viewer on a ship outside of VAB but you can do it.

When I realized I could do that, I started to think about how, at high technology levels, it could make sense for your thrusters to be able to thrust limit automatically based on CoM. It would also add a way to tier up pilots / probe cores

(thanks for the mod reference, I'll check it out...)

Edited July 17, 2016 by tjt

[Rocket In My Pocket]

3 minutes ago, tjt said:

Rocket...I understand how to use and place RCS thrusters...that's not my point.

You don't have to spend all day moving your thrusters forwards and backwards along a long ship...you can right click and adjust thrust limiters on your RCS. You can even adjust thrust limits on ships in flight, so as you burn through your gas you can tune your thrusters to account for the empty tanks. It's a pain because you have to click on each one and there's no CoM viewer on a ship outside of VAB but you can do it.

When I realized I could do that, I started to think about how, at high technology levels, it could make sense for your thrusters to be able to thrust limit automatically based on CoM. It would also add a way to tier up pilots / probe cores

(thanks for the mod reference, I'll check it out...)

Apologies, I didn't mean to imply that you couldn't...it's just always prudent to start with the most basic advice. Even the most experienced players can not be aware of a simple function. Something I've been guilty of myself on more than one occasion, Lol.

I think your idea sounds good, but I wouldn't hold my breath waiting for SQUAD to implement it.

That mod is probably the closest thing we'll get.

[EnderKid2]

Even better than TCA: RCS Build Aid. It shows the torque created by thrusters, so you can balance them perfectly, as well as showing engine alignment and torque, thrust to weight ratio, and dry and wet COM indicators.

[klesh]

my mistake.

 

Edited July 17, 2016 by klesh

[Tyko]

thanks guys...please note that I put this in "suggestions", not "Gameplay questions"...I'm quite versed in how to use RCS build aid to balance a ship and I'm not seeking advice on how to do it.

Back on topic...it STILL would be interesting to offer higher tech / higher pilot level ability for thrusters to actively balance their thrust based on changes to CoM - whether this is because you've consumed fuel or because it's a base / large ship and you've added parts. 

I'd welcome others who'd like to discuss whether this would add something to the game - especially late/end game when you're building complex vessels and moving parts around. I have an orbital tug for doing ship assembly and it sure would be interesting if a high tech version could latch onto a part and adjust it's thruster output (within spec limits) to account for the load.

[pincushionman]

Did everybody miss the part of the discussion where @Rocket In My Pocket said they already do this in fine control mode?

[Tyko]

6 hours ago, pincushionman said:

Did everybody miss the part of the discussion where @Rocket In My Pocket said they already do this in fine control mode?

How do they fix it with Fine Control Mode??? If your CoM changes, I don't think FCM accounts for that.

[Rocket In My Pocket]

I can't say for sure whether it accounts for a change in COM, nor can I find any documentation that covers it.

Perhaps a Dev or Moderator could jump in here and provide us with a solid answer.

EDIT: After some forum searching I've found several references to the fact that RCS "fine control mode" does provide some balancing but not enough to correct a ship that isn't pretty close to being balanced in the first place.

Edited July 18, 2016 by Rocket In My Pocket

[Stoney3K]

On 17-7-2016 at 5:45 PM, Rocket In My Pocket said:

That said, proper RCS placement in the first place is the most important way to prevent any problems. (All RCS units should be centered around the COM or equidistant to it.)

I can give you a very specific use case where that will never work: You have a tug that is used for moving stuff around in orbit, and you want to manipulate or dock an otherwise inert payload, which will always be lopsided with respect to the RCS thrusters on the tug.

There are two ways to alleviate it: Have a "twin" tug which sandwiches the payload in between, this is a good solution when you don't need to dock the payload on its own, or add a massive amount of reaction wheel torque to counteract the offset RCS thrusters.

But more to the topic, having engines that have a "TCA" feature and thus automatically limit to maintain thrust through the center of mass would be a great feature to have on the later tier engines. It's the primary mode of course attitude control on real spacecraft.

Edited July 18, 2016 by Stoney3K

[Van Disaster]

Just now, Stoney3K said:

I can give you a very specific use case where that will never work: You have a tug that is used for moving stuff around in orbit, and you want to manipulate or dock an otherwise inert payload, which will always be lopsided with respect to the RCS thrusters on the tug.

There are two ways to alleviate it: Have a "twin" tug which sandwiches the payload in between, this is a good solution when you don't need to dock the payload on its own, or add a massive amount of reaction wheel torque to counteract the offset RCS thrusters.

Or put RCS thrusters ( only ) on your movable items, which means you can translate sensibly...

[Rocket In My Pocket]

1 minute ago, Stoney3K said:

I can give you a very specific use case where that will never work: You have a tug that is used for moving stuff around in orbit, and you want to manipulate or dock an otherwise inert payload, which will always be lopsided with respect to the RCS thrusters on the tug.

There are two ways to alleviate it: Have a "twin" tug which sandwiches the payload in between, this is a good solution when you don't need to dock the payload on its own, or add a massive amount of reaction wheel torque to counteract the offset RCS thrusters.

Do I have to start including a disclaimer?

WARNING: Generic advice does not cover edge cases, use at your own discretion, caution is advised, this poster claims no responsibility for broken ships or dead Kerbals.

[Tyko]

Stoney3K is right though and I don't think orbital tugs are that much of an edge case. Orbital assembly is really common mid-late game and a great alternative to kerbalizing huge lifters with 100 SRBs to throw entire space stations into orbit.

[Rocket In My Pocket]

5 minutes ago, tjt said:

Stoney3K is right though and I don't think orbital tugs are that much of an edge case. Orbital assembly is really common mid-late game and a great alternative to kerbalizing huge lifters with 100 SRBs to throw entire space stations into orbit.

I mean...I'm just assuming if you've played long enough to be assembling things in orbit (mid-late game as you said), You should know that "rule of thumb" type RCS advice isn't going to apply.

Obviously if you are going to stick a huge dead payload with no RCS on the end of a craft, there isn't any way to make the RCS equidistant from the COM, and you are going to have to come up with a solution.

However, as @Van Disaster said, there really isn't any reason to not add a few RCS blocks to your cargo so that once it's being towed, it can assist in moving itself...and once again; you'd want it equidistant from the COM ideally. (Also, as far away from the COM as possible, to improve torque.)

[Wjolcz]

Aren't the thrust tweakables a thing though?

Edited July 18, 2016 by Veeltch

[Tyko]

48 minutes ago, Rocket In My Pocket said:

However, as @Van Disaster said, there really isn't any reason to not add a few RCS blocks to your cargo so that once it's being towed, it can assist in moving itself...and once again; you'd want it equidistant from the COM ideally. (Also, as far away from the COM as possible, to improve torque.)

Yes, but it's not going to be balanced because the entire compound craft will be a one-off rather than something created and balanced in the VAB - that's EXACTLY why smart RCS balancing would be amazing. You have RCS on your load and you have RCS on your tug. The two mate up and smart RCS would calculate the new CoM and adjust all the thruster outputs on the combined load to rotate around the CoM.

Again, this isn't supposed to replace good planning/craft design, but it would be a higher level capability that your best pilots or best probe cores would enable. Just like you have to learn to plot courses and fly them manually, but level 3 pilots and better probe cores offer course and target tracking.

[kBob]

It's certainly disappointing when you get a three star pilot and realize they have nothing more to gain from experience.  This seems reasonable and gives them another tier.  (I'd also like to see them maybe just become better pilots without so much jittering on the SAS controls and maybe smarter too like offering autopilot to the next way point, but that's for a different thread.)

[Snark]

On 7/17/2016 at 8:29 AM, tjt said:

Add ability at higher levels for RCS/Vernier thrusters to adjust power levels automatically to account for CoM.

The game already has this feature.

On 7/18/2016 at 6:31 AM, pincushionman said:

Did everybody miss the part of the discussion where @Rocket In My Pocket said they already do this in fine control mode?

^ This.  Just turn on "fine control mode" and the game does exactly, precisely what you want it to do.

16 hours ago, Rocket In My Pocket said:

I can't say for sure whether it accounts for a change in COM, nor can I find any documentation that covers it.

Perhaps a Dev or Moderator could jump in here and provide us with a solid answer.

It does.  Given the large fraction of a typical ship's mass that consists of consumables (i.e. fuel), the feature would be pretty useless if it didn't.

15 hours ago, tjt said:

Yes, but it's not going to be balanced because the entire compound craft will be a one-off rather than something created and balanced in the VAB - that's EXACTLY why smart RCS balancing would be amazing. You have RCS on your load and you have RCS on your tug. The two mate up and smart RCS would calculate the new CoM and adjust all the thruster outputs on the combined load to rotate around the CoM.

You're absolutely right!  What a great thing that precisely, exactly that feature is already in the game, then, huh? 

[Tyko]

1 hour ago, Snark said:

You're absolutely right!  What a great thing that precisely, exactly that feature is already in the game, then, huh? 

My understanding was that FCM just equally reduced the power of RCS and Reaction Wheels so a push of the button resulted in less torque. I didn't read where it would actually load balance the whole craft. I'll test it tonight.

Thanks!

[Snark]

22 minutes ago, tjt said:

My understanding was that FCM just equally reduced the power of RCS and Reaction Wheels so a push of the button resulted in less torque. I didn't read where it would actually load balance the whole craft. I'll test it tonight.

Thanks!

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.

Take that, and combine it with the fine-control mode that means that RCS thrusters only generate linear thrust that won't rotate the ship, and it gives a perfect separation between translational and rotational control.  When I'm on close approach and preparing to dock, I just turn on RCS and fine-control mode, and the ship does exactly what I want it to with the minimum-possible use of monopropellant.

The main drawback to this approach (for me, at least), is that I appear to be genetically incapable of remembering to disable the yaw/pitch/roll on the thrusters while I'm still in the VAB.  It's possible to do it later, when in flight... except that it's excruciating.  Takes no fewer than six (count 'em!) finicky mouse-clicks on each individual thruster (because in flight, unlike the VAB, the controls tweak just the individual thruster rather than the entire symmetry group at once), which is a royal pain.  Especially since the moment when I discover my oversight is generally when I'm in the final throes of docking and don't have a lot of time or attention to spare to do, typically 48+ mouse clicks on tiny finicky things, half of which are guaranteed to be in deep shadow even if the ship is in daylight.

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. 

[Raptor9]

28 minutes ago, tjt said:

My understanding was that FCM just equally reduced the power of RCS and Reaction Wheels so a push of the button resulted in less torque. I didn't read where it would actually load balance the whole craft. I'll test it tonight.

Thanks!

I've been playing KSP for years and I didn't even know this.  I thought the very same thing.  Ever since the RCS thrust limiter tweakable became available, I've been thrust limiting and tweaking every craft to try and get the balance right.

And yes, I also know about placing RCS thrusters around the CoM, but sometimes it's not possible (like spaceplanes or other asymmetric designs).

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.

Take that, and combine it with the fine-control mode that means that RCS thrusters only generate linear thrust that won't rotate the ship, and it gives a perfect separation between translational and rotational control.  When I'm on close approach and preparing to dock, I just turn on RCS and fine-control mode, and the ship does exactly what I want it to with the minimum-possible use of monopropellant.

The other drawback is that if you change your control axis, such as selecting your docking port as the "Control From Here", the ship won't rotate/translate correctly because the axes have changed orientation.  Makes docking a pain sometimes, but regardless, I'm glad that capability is there.

Now if we can make it so enclosed RCS thrusters don't enable themselves when the fairing is jettisoned.  If I disable the thruster in the VAB, I don't want it to activate until I Action Group it...

 

Edited July 19, 2016 by Raptor9

[THX1138]

If your vessel is a tug, RCS thruster placement will never be exactly where you need it for any random payload. I guess it would be nice to not have to adjust the thruster limiters manually.

[Snark]

Just now, THX1138 said:

If your vessel is a tug, RCS thruster placement will never be exactly where you need it for any random payload. I guess it would be nice to not have to adjust the thruster limiters manually.

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.

Whereas, if you just get in the habit of putting some RCS thrusters on every payload, the fine control mode will take care of that for you by automagically adjusting everything for you.  Problem solved.

I guess what I'm driving at is this:  given the existence of the automagic thruster adjustment provided by fine control mode, which gives you a perfect experience (if you have at least a halfway-reasonable arrangement of thrusters) or the imperfect-but-best-possible experience (if you don't)... I'm having trouble seeing any scenario at all where you would want or need to adjust the thruster limiters manually, including the tug scenario.

Can you explain what you're getting at?

[Somtaaw]

56 minutes ago, Snark said:

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. 

 

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.