Wallows like a drunken cow.

[Vanamonde]

I'm having a hell of a time adjusting to the 3-man rockets. This is the upper stages of my best one, but once in Kerbin orbit with the gimballed engine shut down, it can develop fast and uncontrollable rotations. Do I need more basic-SAS? Some players are reporting that ASAS causes wobbles rather than controls them, so should I remove that? Turning the RCS on helps, but the rotations are so strong that it can run through a whole fuel tank without bringing the ship under control.

The odd thing is that it blasts off and reaches orbit okay, lands on Mun well enough, and returns to Kerbin pretty well. The only time I experince this problem is between Kerbin orbit and Mun orbit.

[Capt'n Skunky]

Are you building that in the VAB or the SPH?

Cheers!

Capt'n Skunky

KSP Community Manager

[Vanamonde]

It's the VAB. I just turned it on its side so the light would be better for a screenshot.

[Randox]

I'm looking at it and wondering how you get it to spin in the first place. With a single SAS and the command pods own SAS, that thing should barely turn at all, and I find things to be quite stable in orbit. Something that would certainly help would be moving the SAS from it's current spot, and assuming your asscent rocket is not toally maxed out on its lifting capacity, stick one on top of each of your little side tanks (or even better, stick them on the bottom closer to the engine, assuming there is room for them there on your rocket). The further out from the center line of your rocket the units are located, the more leverage they have, because they are further from the center of gravity. You can also put them at the ends of your rocket since this is also moving them away from the center of gravity, hence the ideal position being the bottom of those tanks (so that you are low down, and out far). The same rule applies to RCS thrusters. Now, if you followed my previous point, most of your SAS power is located in the back end of your rocket, so your RCS will be most useful up at the nose helping out the command pods SAS if you get maxed out, or need to work quickly. You can stick it under the chute, on top of your command pod. Run a couple struts from the command pod to the RCS tank (you can't run them to the chute unfortunately, or at least I've never been able to make that work) and your golden as long as you ditch the lander before the chute fully opens. You can stick the ASAS unit under the RCS tank as well if you want, so that you don't have this little tiny waist in your rocket (which might be what is giving you problems to begin with). The struts will keep those pieces from seperating when the chute opens, and the extra weight isn't enough to cause any issues.

Edited August 7, 2012 by Randox

[pebble_garden]

I think I see an SAS and an ASAS. Maybe they don't play well together.

Also, I see lots of asymmetries in struts, etc. Those might pile up and produce unintended imbalances.

Or it could just be KSP being fickle.

Edited August 7, 2012 by pebble_garden

[Vanamonde]

As I understand how the components work, I installed the ASAS to control gimballed engines (for attitude) and fins (for roll) on ascent from launch, but it exerts no torque itself, so I also installed an SAS to keep the ship oriented in space. The capsule's own SAS effect is trivial for a ship of this size, I believe, so I don't take it into consideration. It's true that the ship is extremely slow to respond to steering at theses stages, which I also consider trivial because you don't need to make any rapid manuevers until you're close to Mun's surface anyway, and I've discarded the orbiter stage by then anyway. Although I've got linear RCS on the orbital-transfer stage, I really don't like to use RCS for anything except landing fine-tuning because the tanks run out so quickly. The struts may look a little sloppy, but are all placed on 2X symmetry, and so should balance.

It never occurred to me that SAS might be more or less effective depending on where it's located on the ship, though that makes sense now that you point it out. I can play with that. If that's the case, then I guess the middle, where I have it, is just about the worst spot for exerting control.

I really dislike the idea of putting anything on top of the capsule. I tried it after seeing other players do that, but found that chutes were more likely to break loose if attached elsewhere, and the improper balance prevented the capsule from facing its heat shield the right way on re-entry. I know that doesn't matter now, but it feels like cheating to exploit things that I know are not included in the game yet but will be eventually.

So thanks for the suggestions. I think I will try multiple SAS on spots such as the side tanks, and moving the ASAS down a stage so that it's discarded altogether by this point. I believe SAS and ASAS compliment rather than conflict with each other, but maybe it's just as well not to have both working at

once.

Well, that seemed to help a little but not solve the problem. But I couldn't really tell, because in the middle of my test flight the game locked up on me for the fifth time today. This is just loads of fun. How are other players handling these larger rockets? Are SAS and RCS just not scaled to handle these larger ships? Mine are controllable under strong thrust, but not when coasting or under light thrust.

Edited August 7, 2012 by Vanamonde

[bsalis]

My guess is that it could be the Space Kraken taking a liking to your ship.

The Kraken likes big ships with slight imbalances, even at 2000 m/s.

[BillWiskins]

I can vouch for outlying SAS. My (admittedly smaller) design (http://i.imgur.com/Q7Wsr.jpg) has them on the side-mounted tanks. Still turns fairly slowly, but as you say, in orbit that's not a problem. It is stable, though.

[Vanamonde]

BillWiskins, I and at least one other player have had problems with cantilevered engines simply falling off of upper stage side-tanks like the ones in your pic. It seems to be happening while coasting, possibly associated with going into or out of warp. We both encountered it with the little 20-thrust engines. Are those the 135 thrust engines on your sponsons, and have you noticed any weird behavior with them?

Question: SAS stops rotations when activated, but does it help you rotate when not activated but applying steering commands? In other words, will adding more of them help my ship turn faster?

[pebble_garden]

Vanamonde, can you post that .craft file? I'd like to test out the problem, see if I can find a solution.

Neat looking ship, by the way.

[Vanamonde]

I wish I could post the .craft, but that doesn't seem to be working through this site currently. I know you can do it through file-sharing sites, but I'm already learning the other workaround for stuff that isn't working right now, and fumbling my way through imgur. In fact, I can't seem to remember where the attachment thingy has gone since the forum upgrade. Is it still not up and running?

Neat looking ship, by the way.

Thanks, but it's actually kind of a clunky kluge. What I do is try to cobble together something that works, and then go back and optimize it. So far, I'm still at phase #1 of that process in .16. I was thinking it would be easy to carry my experience and knowledge over from 15.2, but for some reason I'm having as much trouble the second time as I did the first time. I haven't even tried to get to Minmus yet.

By the way, the reason my ship has such a forest of struts on it is that I'm finding it EXTREMELY hard to remove struts that have been attached to the larger tanks. There just doesn't seem to be any clickable spot you can grab to remove them. So whenever I alter the design, half the old struts can't be removed, and I just add more.

Edited August 7, 2012 by Vanamonde

[sal_vager]

The new forums ability to handle attachments is a bit strange in my opinion, it may be best to host your craft on Mediafire or use pastebin, rather than try to upload the file here, the same goes with images, it is better to upload to a site like Imgur and post the link, instead of the pic directly.

There will be some harsh limits imposed on members alloted files here, the server just hasn't the space.

[Vanamonde]

Alright, I'm trying mediafire. Does this work?: http://www./?r8a19eh6ru9baa3 That should be the .craft for the ship in the pics, though I modified it slightly since I made the screenshot. Let me know if the download doesn't work, and if you can, what I did wrong.

[sal_vager]

I downloaded your rocket just fine

[pebble_garden]

I'll give the rocket a try when I get home from work tonight.

[Vanamonde]

I downloaded your rocket just fine

Thanks. Good to know. By the way, that .craft file is my eff'ed up rocket that the engines fall off of, not my eff'ed up rocket that won't fly straight. I'm still tinkering with the S.S. Drunken Cow.

[BlazingAngel665]

Since 0.16 the Kraken has gotten stedily more aggresive to the point that ships in LKO are being fed upon regularly (I made one complicated enough to get attacked on the launch pad, but that was the point of that ship) I can't hardly launch any stations anymore with out my ship spinning out of control into deep space.

[Vanamonde]

Altitude plays a part in the kraken thing? That actually fits. As I noted before, it's actually easier for my ships to land on Mun than to stay steady in Kerbin orbit. So what constitutes a "low" orbit for the purposes of kraken evasion?

Meanwhile, I just tested another variation of a 3-man that also failed miserably, but I watched it more closely. There was a wavering reading of about 1/4th G while I was in freefall with the engine shut off, where there should have been no forces at all. That force is measured by the capsule in the nose and might read if the ship was rotating (like the capsule being swung around on a string), but it was there before the ship started rotating, and seems to be a cause rather than a result of rotation. When I turned control off and let the ship wallow around, it didn't simply spin, either. It would yaw 30 degrees, than yaw back the other way 20 degrees, then pitch 140 degrees, for example. What the hell are these transient forces rolling my ship around? And why don't I hear other players complaining about them?

[E. F. Kranz]

I'd bet you have a parts collision problem, though I don't see one just by looking at the picture.

[trekkie_]

the issue is lack of symmetry. you're creating a lot of disproportionate weight on the bottom, both before the decouple and after. also you're just using regular RCS on the back, but the 4 pronged one on the top, which could cause some issues (plus 2 sets on the final stage area rather than one would help alot). I think all of that combined is the source of your problem. rework the design a little and I'm sure it will go away.

first I would try to reduce the spin as much as possible without RCS then activate it to take care of the rest. also, I'm not sure if ASAS works when disconnected or not, I usually put it right below the command module. it's really important to catch a violent spin early on or no amount of RCS will get rid of it.

Edited August 8, 2012 by trekkie_

[BillWiskins]

BillWiskins, I and at least one other player have had problems with cantilevered engines simply falling off of upper stage side-tanks like the ones in your pic. It seems to be happening while coasting, possibly associated with going into or out of warp. We both encountered it with the little 20-thrust engines. Are those the 135 thrust engines on your sponsons, and have you noticed any weird behavior with them?

The engines on that craft are the new, larger landing engines. No issues at all with them. I have also been using a very similar configuration based on the one man command pod (central tanks (in this case RCS), three radial half-size tanks plus landing engines). Image here. Two of the engines are missing there due to a slight landing mishap, but I've never experienced any random detaching or other odd behaviour.

[Vanamonde]

After wrestling with big rockets for several days I went back to my tested and proven 1-man ship. And you know what? It had EXACTLY the same problems. EXACTLY. The difference is, the control systems are scaled to rockets of that size, and you can easily get it back under control or keep it from getting out of control in the first place, so that I never thought of them as problems until now. I'm coming to the belief that the issue is that much like the large decouplers that crush under the new loads, they didn't scale the control systems up in proportion to the size of the larger tanks, engines, and capsules. As supporting evidence, I point out that even my worst 3-man rockets fly straight while gimballed engines are thrusting, and only start going ape**** when I shut those powerful attitude controlling devices down and try to rely on the old, non-scaled SAS and RCS. I'm tempted to just not screw around with the large rockets until the developers give us a full set of components scaled to work with each other.

Either that or rely on BlazingAngel655's suggestion and just keepy continually thrustin until I'm up to 200,000m or something ridiculous like that.

[BillWiskins]

In my opinion (bearing in mind that the first image I linked to represents pretty much the largest craft I use on a regular basis) the fact that the SAS and ASAS can't be used for adjustments as easily as they can on the smaller sized parts adds to the experience. Clearly certain issues are inconvenient and those need to be sorted, like the wallowing that occurs for certain vehicles. But in my mind, the difficulty in rotation and control just equates to one of the challenges of piloting a much heavier object.

I have encountered this with the aforementioned craft - winglets allow it to turn easier when within atmosphere, and when in orbit, if I need to manoeuvre the thing before the bulk of it is staged away, then the gimballed engines on the lowest possible throttle setting give me enough leverage to get it pointed where I want. Maybe I'm just looking on the bright side a bit too much, but I wouldn't let it get in the way of using the full repertoire of parts.

[Vanamonde]

I see your point point BillWiskins, but it's not that just it's more difficult. When I've got RCS firing, an ASAS, the capsule's inherent attitude control, and 3 SAS modules all trying to hold the ship still and the random rotations are not even slowing down, that's a problem. And the rotations are not constant anyway, as if forces are acting on the ship while it's in freefall vacuum, which is not a piloting challenge but a physics flaw. Furthermore, the SAS and ASAS modules need to be reworked anyway because they are too narrow to form stable structural components between the wider tanks and capsules. In short, it might be a challenge to try to fly a 787 with the steering controls of a Cesna, but it's not much fun.

[bsalis]

Apologies to anyone who knows this already, but please remember that it does not matter how large or asymmetric or imbalanced a space craft is. When in space, it should not start moving or rotating unless a force is applied, such as from a control input (eg. pod reaction wheels). More mass just means sluggish but still predictable reactions. Imbalances just mean odd but still predictable reactions (ie. multi-axis response to single axis force eg. twisting).

Any phantom forces that are moving the your ship is work of the Space Kraken. You don't need to be doing 9km/s or more to see her maul your ship. A fix is being worked on for 0.17, which will be needed to make inter-planetary travel practical.

Note that if your getting issues that only happen with (A)SAS turned on, then yeah, it may be the ship design is conflicting with how SAS works.