Can you create more connection points between parts of a rocket?

[Sarik Vaster]

I'm having an issue with my rocket breaking apart. I have the top two stages as inline tanks and engines, but my last two stages used for the brunt force of early launch are 6 tanks and engines radially around the core tank. I have only in line decouplers, no radial ones. I noticed that at some times during a launch, if conditions are right, the engines start to flail around and it gets worse as time goes on until it causes the rocket to brake apart. it would appear that the first tank 3rd stage is where the radial attachment is and nowhere else along the whole length of the 3rd and 4th stages.

Is there a way to tighten this down? Some component I haven't unlocked yet or a command in the construction interface I'm not aware of?

If you need any more information or screenshot so the rocket or the problem occurring, I can capture those for you.

Thank you for your assistance,

Sarik

Edited March 5, 2014 by Sarik Vaster

[stevism]

you will be able to do this in 0.24 i think

[Pursuedtank]

Are you using struts? You also say that you have no radial decouplers, so how have you attached the radial tanks to the rocket.

[Vanamonde]

Pictures always make it easier to answer questions like this. Can you post some?

[Sarik Vaster]

I am not using struts. I'm playing in career mode and haven't unlocked them yet. I attacked the 6 tanks directly to the core tank by clicking on the outside of the core tank. I figured that maybe the I needed to use radial decouplers so I put one at the top tank of the stage and the bottom tank of the stage. Doing that I could only get the radial stacks of tanks to attach to one of the couplers not both. I was using the angular snap so I know they were lined up.

[Vertibirdo]

Also you can use the Kerbal Joint Reinforcement mod to make your rockets a bit more rigid.

[Trann]

If you have any girders and struts, you can attach the girders 6x radially around the upper stage. Since struts have a length limit, attach girders to each stage then attach struts between girders and the rocket body and, finally, to the bottom 6 tanks. Double the struts if necessary. You should now have a series of triangles reinforcing the structure of the whole rocket.

Best sketch I can do at the moment...

EDIT: Ah, you don't have struts yet....Never mind

[Sarik Vaster]

Ok here's some pictures of the rocket. In the first the green lines are where the stages separate. The red line is the only point of contact I can see when the sections start to flail. the second picture is the other 5 radial copies removed.

[Red Iron Crown]

You could try locking the gimbals of the engines mounted on your radial tanks, if they have them.

[Capt. Hunt]

you can't attach parts to multiple decouplers, it just doesn't work like that, parts are connected like branches on a tree, they can only be attached to one thing. Your best bet is probably just to build smaller rockets until you unlock struts, you're probably too early in your career to be shooting for the Mun. There is plenty of science to do on and around Kerbin.

[Trann]

Yup, when you have your first contact point radially, the rest of the radial stack is not attached to the core of the rocket; they just hang off the first mount point.

You need struts (or smaller rockets and more local science) 8)

[Claw]

I'm having an issue with my rocket breaking apart. I have the top two stages as inline tanks and engines, but my last two stages used for the brunt force of early launch are 6 tanks and engines radially around the core tank. I have only in line decouplers, no radial ones. I noticed that at some times during a launch, if conditions are right, the engines start to flail around and it gets worse as time goes on until it causes the rocket to brake apart. it would appear that the first tank 3rd stage is where the radial attachment is and nowhere else along the whole length of the 3rd and 4th stages.

Is there a way to tighten this down? Some component I haven't unlocked yet or a command in the construction interface I'm not aware of?

If you need any more information or screenshot so the rocket or the problem occurring, I can capture those for you.

Thank you for your assistance,

Sarik

Yes, they are flailing because of the single connection point (as others have pointed out). It will be worse when you try to maneuver, especially in roll, and especially when the SAS gets involved (especially with all those fins). Lots of especiallys in there...

I am not using struts. I'm playing in career mode and haven't unlocked them yet. I attacked the 6 tanks directly to the core tank by clicking on the outside of the core tank. I figured that maybe the I needed to use radial decouplers so I put one at the top tank of the stage and the bottom tank of the stage. Doing that I could only get the radial stacks of tanks to attach to one of the couplers not both. I was using the angular snap so I know they were lined up.

Struts are the way to go, but you haven't unlocked them yet so I'll get to how to try and get around it. Radial decouplers can be a bit more solid than attaching directly to the mainbody, but in this case you'll still have the same problem. Regardless of if you use a radial decoupler or not, the radial booster will only attach at one point. This is the core of the problem.

Ok here's some pictures of the rocket. In the first the green lines are where the stages separate. The red line is the only point of contact I can see when the sections start to flail. the second picture is the other 5 radial copies removed.

http://i263.photobucket.com/albums/ii152/sarik_vaster/Rockets/rocket1_zps0a05b0ac.png

http://i263.photobucket.com/albums/ii152/sarik_vaster/Rockets/rocket2_zpscbf43e29.png

Thanks for the pictures. Here's what I would recommend. I don't think it's too early to shoot for the Mun, but it might take some tinkering. If it's not working, consider trimming your payload if you need to.

For my recommendations, consider the central fuel stack as the core and the radially attached pieces as the boosters (for simplicity in typing).

1) Split your side boosters between your bottom stage and the next stage up (at your bottom most line). What I mean by that is don't connect your bottom most boosters to decouplers on the boosters up. Leave the core piece connected and disconnect the lower booster portion from the upper. Slide those boosters down and radially attach them to the bottom core section. This should create a separate bottom stack that is connected by only one coupler on the core.

2) Use your active fins more sparingly. Find a good balance between what you actually need, and having too many. Having too many things for the SAS to move around can be stressful on the rocket. Maybe trade some fins out for SAS units (if you have them). You can place two SAS units on your newly available mount points on top of your lower boosters. (Probably don't need symmetry 6 for those. Place them one at a time and opposite each other.) Having them on top (near the connection point) is less bendy than fins at the bottom. If you don't have SAS units, try to see if you can get away with moving some of the fins up a little. Splitting your boosters (as per #1) will help the bending.

3) I somewhat simulated your rocket and it seems like you would get better performance if you cut down your second to bottom stage with 3x symmetry and leave your bottom stage at 6x symmetry. The TWR seemed kinda low with 6x all that length. It does knock the delta V down a bit, but the low TWR would have spent a lot of that dV fighting gravity anyway.

4) Don't be shy about using more FL-T800s in place of stacking two FL-T400s (unless you're going for looks or something else). Fewer parts and fewer joints mean less bendy-ness.

Just my $0.02. Good luck!

Edited March 5, 2014 by Claw

[SRV Ron]

Way too much rocket with no struts for the mission intended. Try probes to get the tech needed for struts and fuel lines before doing the manned landing.

This early career mode ship, no braces, flies stable enough to do a manned Mun and Minmus flyby.

[Sarik Vaster]

Thanks guys. All your advice was very helpful.

[cantab]

Like Trann says, when you put a stack radially onto another, that second stack is only attached at one point, the first point you place.

I find things are more stable if you make that first point down low. That way a given twist at the attachment point moves the engine less. So build your central stack as normal, then add the bottom fuel tank in your lower radial stack, the engine below, and the other tanks above. Make sure the other tanks "snap" onto the radial stack and don't attach directly to the central stack (or the fuel won't flow). Repeat for the upper radial stack, keeping it separate with the only decouplers in the central stack.