New SAS Logic

[Tank Buddy]

I have a few questions regarding the new SAS logic in .21:

1. What functions do the SAS and ASAS modules have?

2. What functions do the probe bodies and command pods have in terms of SAS control? (i.e. old ASAS)

I know that using SAS torque requires electricity and it can be turned of and substituted with control surfaces and RCS.

I also know different command modules and SAS modules have different torque forces.

I would appreciate a detailed and/or effective response of my questions. If there is anything important that I should know, please tell me.

Thanks,

Tank Buddy.

Edited November 19, 2013 by Tank Buddy

[zxczxczbfg]

All manned pods now come with SAS built right in, and by default they use capsule torque. The new SAS modules are now "Reaction Wheels", a new control device. Aerodynamic control surfaces provide control using aerodynamic effects, RCS provides directional thrust via small jets, and Reaction Wheels provide additional torque. I think the ASAS modules allow the built-in SAS functions to use control surfaces and RCS rather than just capsule/RW torque. This is just me guessing based on what I've heard, I'm not entirely certain myself.

In short, answers:

1) The SAS module is now a torque-providing Reaction Wheel, the ASAS module is basically the same as it always was, albeit with the new turning-friendly SAS.

2) The command pods now have integrated SAS functions. If you have no ASAS module, it uses cockpit torque and reaction wheels. If you do have one, it uses RCS and control surfaces. IMPORTANT note: Probe cores have no SAS functionality. Learned that the hard way

Edited August 7, 2013 by zxczxczbfg

[Geschosskopf]

SAS now means a computer flight control system that uses the available control mechanisms in the vehicle to try to keep it going straight. It is an active function. It is now an inherent part of cockpits and probe cores.

For the SAS function to actually work, it needs some sort of control mechanism in the vehicle (but of course, you need such a thing to steer it anyway, so this is pretty much a given). Control mechanisms are RCS, thrust-vectoring, aerodynamic control surfaces, or reaction wheel torque.

Besides having the SAS function, all cockpits and most if not all probe cores also contain reaction wheels. So they still have torque like before. The confusing thing in all this is that the old SAS and ASAS parts, which still have the same names and appearances, no longer have the SAS system in them. What they have instead are powerful reaction wheels (more powerful than those in cockpits and probe cores). So, adding these parts adds lots of torque to your vehicle that the SAS function can use to keep the vehicle stable. But they do nothing on their own. Think of them simply as extra control surfaces or RCS thrusters.

[DMagic]

You stopped one sub-forum too soon.

http://forum.kerbalspaceprogram.com/showthread.php/41941-New-SAS-functionality-and-You%21

But in short, all of the probe cores, command pods, and cockpits have the SAS function and provide torque to varying degrees. And all three of the old ASAS/SAS parts in the control parts tab also have the SAS function and provide torque. You can check this in-game or by looking at the part .cfg files. The Inline Reaction Wheel, Inline Advanced Stabilizer, and ASAS Module all provide 20 torque and all have the SAS function. Only the Advanced Avionics Package is different; it only provides the SAS function (and is therefore basically useless; the chair is the only control point that doesn't have SAS).

And yes, both of the above posts are wrong in slightly different ways. Check the tutorial for more detail, but I assure you that the parts have the functions that I described. To be fair though, some of this changed with the 0.21.1 patch, and it will probably change again in the next patch or update.

[Tank Buddy]

Correct me if I'm wrong:

All of the old SAS and ASAS modules, excluding the Avionics Package, now add torque and provide SAS guidance. They are effectively identical.

It is my understanding that all of the command modules (probes, capsules) have torque as well as the new SAS guidence. If this is correct, does that mean that the SAS and ASAS modules sole purpose are to add torque, except for the external chair, in which case it adds SAS functionality. I believe I heard something about the ASAS modules being required to use aerodynamic control surfaces and RCS with the SAS function, as in to maintain heading?

Thanks, I hope you can clarify my confuzlement.

[magnemoe]

That sounds pretty right to me, sas is basically an simple autopilot who keep heading using torque modules, engine gimbal and control surfaces.

You only need one and its included in any of the cores except the chair.

The old sas and asas modules just add torque and plenty of it, this is very nice on larger ships, just add an bunch of them, note however that the old 1.25 meter asas module is 0.5 ton while the sas module is 0.3 and the 2.5 meter asas is 0.2 ton so its best as they do the same stuff.

[Tank Buddy]

Thanks for clarifying, I'm going on the assumption that the command pods (except for the chair) all have torque and SAS. So this means the SAS and ASAS modules only add torque to those command pods.

[shand]

The simplist way of putting it is: they are exactly the same as before with 2 exceptions: torque requires power, and you can override the SAS without turning it off (try and move in an axis and it will let you, dampening the others - think avionics package)

SAS = Inline Reaction Wheel = Provides torque only.

ASAS = Inline Advanced Stabilizer = provides torque and utilizes other attitude adjustment equipment (aero/RCS/Gimble) as required - in my experience it doesnt seem keen to use RCS, which is GOOD

Important thing to note, that are still true: SAS (Inline Reaction Wheel) does NOT (to my knowledge) make use of aero/RCS/Gimble. If you want that, use ASAS (Inline Advanced Stabilizer)

PS: the torque in command pods is "SAS functionality" and uses reaction wheels and thus power, in the command pod . i dont know, but i assume it allows "SAS" to be used - IE: attitude stabilisation.

^^Most of this is wrong... ah well ^^^^

Edited August 8, 2013 by shand

[Tank Buddy]

Thank you! That clarifies if you are correct. You need the former ASAS modules to use control surfaces and gimbals, but it may not use RCS, which doesn't seem like too much of a bother. That probably explains why those fins weren't working. And the gimbals too! I have been just relying on torque the whole time. That probably explains why my ships struggled to maintain course without my constant input, at least while in atmosphere.

I appreciate your response that finished off my understanding, thanks, and good luck!

Tank Buddy

[DMagic]

Important thing to note, that are still true: SAS (Inline Reaction Wheel) does NOT (to my knowledge) make use of aero/RCS/Gimble. If you want that, use ASAS (Inline Advanced Stabilizer)

PS: the torque in command pods is "SAS functionality" and uses reaction wheels and thus power, in the command pod . i dont know, but i assume it allows "SAS" to be used - IE: attitude stabilisation.

I'm not sure where this idea keeps coming from, but it's wrong. All SAS functionality is the same. Any of the command pod, probe core, inline reaction wheel, inline advanced stabilizer, ASAS module, or avionics package parts can use all control surfaces, gimbals, reaction wheels and RCS.

All parts with SAS have this line in their .cfg file:

name = ModuleSAS

And all parts with torque have these lines in their .cfg file:

name = ModuleReactionWheel

PitchTorque = 15

YawTorque = 15

RollTorque = 15

RESOURCE

{

name = ElectricCharge

rate = 1.2

}

There were some changes in the 0.21.1 update, so things were a bit different before. But with the current update all of the parts I listed above have those two sets of functions in their .cfg files (with the exception of the avionics package, which only has the SAS line).

Again, you can just check the SAS tutorial stickied in the tutorials forum for more detail on all of this.

That probably explains why those fins weren't working. And the gimbals too! I have been just relying on torque the whole time. That probably explains why my ships struggled to maintain course without my constant input, at least while in atmosphere.

If this really is the case then something is wrong. First, check to see if the fins are moving at all, zoom in really close and you should be able to see even small movements. Second, make sure that you are using the right kind of fins; in my experience the Delta-Deluxe winglets are terrible for controlling rockets. You can use the stock Z-map satellite to confirm this. Try launching it as is (it has Delta-Deluxe winglets already) and it should be really hard to control. Now replace those winglets with AV-R8's and it should be much easier (or even just take off the winglets all together).

If the standard SAS really isn't controlling these surfaces then you should try a clean reinstall; delete your KSP folder and reinstall everything (make backups of your save folder if you want to keep it). And if the problem still persists then you probably have a bug somewhere and you should report it.

Edited August 8, 2013 by DMagic

[Diche Bach]

You stopped one sub-forum too soon.

http://forum.kerbalspaceprogram.com/showthread.php/41941-New-SAS-functionality-and-You%21

But in short, all of the probe cores, command pods, and cockpits have the SAS function and provide torque to varying degrees. And all three of the old ASAS/SAS parts in the control parts tab also have the SAS function and provide torque. You can check this in-game or by looking at the part .cfg files. The Inline Reaction Wheel, Inline Advanced Stabilizer, and ASAS Module all provide 20 torque and all have the SAS function. Only the Advanced Avionics Package is different; it only provides the SAS function (and is therefore basically useless; the chair is the only control point that doesn't have SAS).

And yes, both of the above posts are wrong in slightly different ways. Check the tutorial for more detail, but I assure you that the parts have the functions that I described. To be fair though, some of this changed with the 0.21.1 patch, and it will probably change again in the next patch or update.

Wow, this thread is really rather confusing. But that thread you link to DMagic is pretty clear.

One thing I've noticed recently (since I installed a bunch of mods) that I'm not sure I was noticing before (I have only ever played 0.21.1): If I have SAS activated, I cannot pitch, roll or yaw my vehicle: it is in effect LOCKED into place.

A lot of my flights are with _only_ the Probodobodyne OKTO2 (which I think offers the least possible torque) and engines with very slight vectoring capacity, but with SAS off these vehicles are fully maneuverable.

I vaguely remember vehicles retaining maneuverability while SAS was on when I was playing with vanilla 0.21.1, though with muted responsiveness compared to SAS off. Am I remembering wrong?

All command pods and probe cores have both SAS functionality and reaction wheels.

Uh, I'm a little confused by this DMagic as I was under the impression that "SAS" functionality _was_ manifest through reaction wheels; or at least that is how it will manifest if there are no aero parts, gimbaling engines or RCS (which I understand the command pod/module will integrate into its guidance of the vehicle when those additional mechanisms are present)?

Let me see if I understand here.

1. There are four methods to control a crafts orientation in KSP: (a) reaction wheels, which function by producing torque (not deflection or thrust); ( control surfaces (e.g., wings or ailerons), which function by deflecting moving air, and thus will not function in vacuum; © gimballing engines, i.e., thrust vectoring, which functions by swiveling an engine to thrust at an angle relative to the vehicles prograde axis. Some engines have this functionality, some do not; (d) Reaction Control System (RCS), which functions by directing thrust using monopropellant.

2. In order for any of these guidance mechanisms to function, they depend on "SAS" "Stability Augmentation System." As of 0.21.1 all command pod parts in the game have SAS.

3. All command pod parts also include "reaction wheels" which afford some degree of torque. As such . . .

4. A vehicle with only a command pod and a non-gimballing main engine (no control surfaces or RCS) will nonetheless have some degree of guidance control, by virtue of the built-in reaction wheels included in all command pod parts.

5. There are additional parts in the game called "Reaction wheels" (e.g., "Inline Reaction Wheel") which add additional torque to that included in every vehicle by virtue of the vehicles command pod/module.

****ADDIT: actually they seem to be referred to as a sub-type of "Dedicated" SAS units in the KSP wiki now, Dedicated Units.

"Reaction wheels" is not strictly correct because this type of part includes the Avionics Package ****

6. It is possible that a very small command pod (e.g., the Probodobodyne OKTO2) will not produce enough torque to control a massive vehicle, but will be more than enough to control a smaller vehicle. For example, I can get a 4 ton rocket into high orbit using nothing but the Probodobodyne OKTO2, but at 8 tons this rocket seems to become uncontrollable.

7. In sum, if the vehicle is not too big, it is possible to control guide a vehicle with nothing but a command pod/module. Larger vehicles may require additional guidance mechanisms to be sufficiently controllable.

ADDIT: The red font point #8 below is incorrect. SAS has no effect on manual inputs when it is toggled off (T key by default).

8. ADDENDUM: In effect "SAS" has been made synonymous with "Command Pod/Module." All command pods and modules now have "SAS," a functionality which, when activated will lock a vehicle into its present orientation, and when not activated will integrate all of the available guidance mechanisms on the craft into player maneuver actions.

To be honest, I think all the effort to explain the current system in terms of how it changed relative to the older system is simply confusing things further. Best to just describe how it works as of 0.21.1 and remove all comparisons to how it used to work.

Edited August 8, 2013 by Diche Bach

[shand]

No probs

Also, using multiple ASAS has no benifit over using a SAS instead of the second one. so i tend to put an ASAS on the "final" stage (so lander, or return module) or any seperate module the will need seperate control. for more torque add SAS - if that makes sense!

I'm not sure where this idea keeps coming from, but it's wrong. All SAS functionality is the same. Any of the command pod, probe core, inline reaction wheel, inline advanced stabilizer, ASAS module, or avionics package parts can use all control surfaces, gimbals, reaction wheels and RCS.

Pretty sure that's incorrect. but i'm not a machine where i can double check it.

Whats the difference between SAS (inline reaction wheel) and ASAS (Inline Advanced Stabilizer) then?

Edited August 8, 2013 by shand

[Crater]

No probs

Pretty sure that's incorrect. but i'm not a machine where i can double check it.

Whats the difference between SAS (inline reaction wheel) and ASAS (Inline Advanced Stabilizer) then?

EDIT:

Short answer: as of v0.21 NOTHING

The long convoluted answers above about asas using every control authority mechanism available, and sas just being a reaction wheel were correct through KSP version 0.20, but are obsolete as of KSP version 0.21.

Now, as stated by DMagic

if your vessel has one or more SAS-computers (which are in pretty much all the pods and probe cores), then it has access to ALL the attitude control systems on the vessel.

The reason that there are still two parts not one, for SAS and ASAS is simply so as not to break all the old .craft files that had the parts on them.

If you look in the config files for all of the stock SAS and ASAS parts, you will find that they have

MODULE

{

name = ModuleReactionWheel

}

and

MODULE

{

name = ModuleSAS

}

meaning that they give control, and have torque. The only differences are in the total torque they deliver. Nothing else. Not any more.

[shand]

*quick download and test later*

Yup thats right, i am sorry - the only difference seems to be mass!

What through me was the in the description it says ASAS (as it was) has an inbuilt flight control computer, while such a sentence is missing from the SAS. thats your source!

But yes, ASAS is the same as SAS but heavier.

ALSO: cockpits seem to have this system built in.

Edited August 8, 2013 by shand

[Crater]

Most likely, the descriptions haven't been updated along with the actual part functions.

And maybe Jeb left his lunchbox in the ASAS unit? could that explain the extra mass?

[shand]

I wonder what direction they will go in? get rid of the advanced entirely? only allow one to use RCS? but perhaps thats for another discussion

[Diche Bach]

Short answer: as of v0.21 NOTHING . . . The only differences are in the total torque they deliver. Nothing else. Not any more.

Well, except for one other thing:

The Dedicated SAS Units are not recognized in the vehicle construction window as being "command modules." So a vehicle with an "ASAS" part will not be able to get to the launch pad if it does not also include a command pod or probe body. These "Dedicated SAS Units" add torque (and possibly precision or speed?) to the crafts built-in SAS functionality, but they do not serve as "command pods" per se.

Once the vehicle is on the Launchpad/runway, it may be that you can transfer "Control From Here" to the dedicated SAS unit (I'm not sure).

[Crater]

Well, except for one other thing:

The Dedicated SAS Units are not recognized in the vehicle construction window as being "command modules." So a vehicle with an "ASAS" part will not be able to get to the launch pad if it does not also include a command pod or probe body. These "Dedicated SAS Units" add torque (and possibly precision or speed?) to the crafts built-in SAS functionality, but they do not serve as "command pods" per se.

Once the vehicle is on the Launchpad/runway, it may be that you can transfer "Control From Here" to the dedicated SAS unit (I'm not sure).

Uhhh, so the difference between SAS and ASAS is that neither of them are probe bodies?

Probes or command pods are a very different beast. This discussion is about SAS/ASAS parts, and how they impact on the new since 0.21 mechanics.

[DMagic]

Wow, this thread is really rather confusing. But that thread you link to DMagic is pretty clear.

One thing I've noticed recently (since I installed a bunch of mods) that I'm not sure I was noticing before (I have only ever played 0.21.1): If I have SAS activated, I cannot pitch, roll or yaw my vehicle: it is in effect LOCKED into place.

Yes it is a bit confusing. I think some of the problem is the terminology everyone still uses. The old ASAS function is gone, and if they would change the name of the 2.5m grey ASAS module, all references to it would be gone too. C7's last blog post clarifies this in the first section:

http://forum.kerbalspaceprogram.com/entry.php/740-Updated-Information-on-SAS-in-0-21-1

And to add to the confusion, mod parts can still access the old ASAS function, which I suspect might be happening in your case. If you just add the right line in the .cfg file, you can make your crafts behave in the same way they used to.

Uh, I'm a little confused by this DMagic as I was under the impression that "SAS" functionality _was_ manifest through reaction wheels; or at least that is how it will manifest if there are no aero parts, gimbaling engines or RCS?

Let me see if I understand here.

....

You're right SAS requires some control function to actually do anything. But SAS will use any and every control method available, adding more control surfaces, or gimbaling engines will just add to the amount of control your craft has. The SAS function and the Reaction Wheel function are controlled by two separate lines in the .cfg file, so they are related, but one does not require the other.

The first seven points (there are eight, you have two sixes) you list are all correct and very succinctly summarize the new system. The last point, the addendum, is not totally correct. When turned off SAS doesn't have any effect on manual inputs. You could remove the SAS line from the .cfg file, and your manual inputs would behave just the same, but otherwise you're right.

To be honest, I think all the effort to explain the current system in terms of how it changed relative to the older system is simply confusing things further. Best to just describe how it works as of 0.21.1 and remove all comparisons to how it used to work.

I agree. That is what I tried to do in my tutorial, but it can be tricky to do because so many people still refer to the parts and functions by their old names and by how they used to work.

Whats the difference between SAS (inline reaction wheel) and ASAS (Inline Advanced Stabilizer) then?

The only difference is the mass. The 0.21.1 update was hastily released, so I expect some of these things to be fixed in the next update or patch, but for now that's the only difference.

Edit: Wow, that was a lot of posts between when I started and finished.

Most likely, the descriptions haven't been updated along with the actual part functions.

Most of the in-game description doesn't actually have to be manually changed. Anything thing with the moduleSAS line in the .cfg file will show that in the in-game description, the same for torque values and mass.

Uhhh, so the difference between SAS and ASAS is that neither of them are probe bodies?

Yeah, none of the parts under the Control Parts tab can be used as probe bodies/command points.

And it's best not to rely on the wiki for any of this information. Those parts especially are in need of an update and the current descriptions don't reflect how they work now.

Edited August 8, 2013 by DMagic

[Diche Bach]

Ah glad to hear I got it basically figured out. Thanks for clarifying that SAS has no effect on manual inputs, i.e., that my point #8 was wrong!

. . . And to add to the confusion, mod parts can still access the old ASAS function, which I suspect might be happening in your case. If you just add the right line in the .cfg file, you can make your crafts behave in the same way they used to . . .

So it is -not- normal that my vehicle becomes locked into place and unresponsive to my manual orientation inputs (WASDQE keys) whenever I have SAS turned on (T key)? This is a reflection of how it 'used to work' to work prior to 0.21.1 and it is likely that some of my installed mods are causing it work this way eh?

[DMagic]

So it is -not- normal that my vehicle becomes locked into place and unresponsive to my manual orientation inputs (WASDQE keys) whenever I have SAS turned on (T key)? This is a reflection of how it 'used to work' to work prior to 0.21.1 and it is likely that some of my installed mods are causing it work this way eh?

Yep, you can check for the line "module = AdvSASModule" in the mod part .cfg files if you want. That's what will add the old ASAS function and lock out your controls when active.

[Diche Bach]

Yep, you can check for the line "module = AdvSASModule" in the mod part .cfg files if you want. That's what will add the old ASAS function and lock out your controls when active.

Must be MechJeb 2.09, which overwrites all the stock command pod parts so that they have MechJeb computers included. Now that I understand what is causing it, think I'll just leave it as is. Kinda nice to be able to stop extreme osccilations by simply hitting T