How do you attach SRBs to the side of a rocket with multiple decouplers?

[delta wee]

I'm trying to attach some SRBs to the side of my rocket as the first stage. When the SRBs expend their fuel I want to then jettison them and start the next stage. I can't figure out how to attach the SRBs to the side of the rocket with multiple decouplers. Right now I'm putting multiple decouplers on the side and then attaching the SRB, but it only attaches to one of the decouplers. I never had this problem before so maybe something changed in KSP 1.2. Here is a picture of how I'm attaching the decouplers to the main rocket.

 

[HebaruSan]

You can only attach it to one, and it's always been that way. If you need it to be more sturdy, a strut at one end will hold it in place nicely.

[delta wee]

39 minutes ago, HebaruSan said:

You can only attach it to one, and it's always been that way. If you need it to be more sturdy, a strut at one end will hold it in place nicely.

Thanks. I guess they changed the collision box of the decoupler, because before 1.2 using multiple decouplers made the SRBs attach better to the rocket, probably because the other decouplers were slightly clipping the SRB.

[HebaruSan]

2 minutes ago, delta wee said:

Thanks. I guess they changed the collision box of the decoupler, because before 1.2 using multiple decouplers made the SRBs attach better to the rocket, probably because the other decouplers were slightly clipping the SRB.

Hmm. So the booster didn't flex as much because there were decouplers in the way blocking it? I could maybe buy that.

Possibly related, supposedly they're working on the hit box for the Kickback so you'll be able to see the end points of struts that are attached to it in the next version. I suppose you could probably use auto-struts instead in the current version.

[GoSlash27]

Delta Wee,

 KSP doesn't allow for a part to be a daughter of more than one parent. It's like a tree; a single twig does not grow from two limbs.

 As @HebaruSan points out, you can use struts to secure it.

Best,
-Slashy

[AeroGav]

55 minutes ago, GoSlash27 said:

 

 As @HebaruSan points out, you can use struts to secure it.

Best,
-Slashy

Struts will give you the rigidity you wanted with multiple decouplers.  If the ejection force from a single decoupler is not enough, then mount some separatrons at the top of the booster and set the staging up so they fire with the decoupler.   If you push the top end away from the core , aero forces should grab the body of the booster and do the rest, leaving you a beautiful Korolev's Cross 

...and if not,  a very entertaining explosion so it's win/win

[delta wee]

Struts aren't working for me. Even though I use the Heavy struts the SRBs break away from the rocket as soon as they ignite. Here is a picture of my rocket to see how I'm using the struts:

 

[Palaceviking]

Just now, delta wee said:

Struts aren't working for me. Even though I use the Heavy struts the SRBs break away from the rocket as soon as they ignite. Here is a picture of my rocket to see how I'm using the struts:

 

Wow, i thought I was a cheapskate,  I'm impressed, are you sure that lil' engine will be alright on its own after the srbs go?

Anyway, yes that's a lotta struts, probably a bit overkill but hey, as for the explosification I think you need to space your boosters away from your main stack(see-translate tool), and rotate your Sepatrons so they fire out from the stack (see-rotate tool).

And just spotted your staging, fire your "main"(cheap) engine first and give a second for the stresses to settle before firing your srbs and launch clamps at the same time. 

✌ 

[delta wee]

6 minutes ago, Palaceviking said:

Wow, i thought I was a cheapskate,  I'm impressed, are you sure that lil' engine will be alright on its own after the srbs go?

Anyway, yes that's a lotta struts, probably a bit overkill but hey, as for the explosification I think you need to space your boosters away from your main stack(see-translate tool), and rotate your Sepatrons so they fire out from the stack (see-rotate tool).

And just spotted your staging, fire your "main"(cheap) engine first and give a second for the stresses to settle before firing your srbs and launch clamps at the same time. 

✌ 

How can I space the boosters further away from the main stack if the decouplers are so thin?

[bewing]

44 minutes ago, delta wee said:

How can I space the boosters further away from the main stack if the decouplers are so thin?

The visual aspect is mostly irrelevant (except for aesthetic appeal), after anything is attached to anything else. You attach it, click the move tool, move it out a ways, and it still works.

 

[Harry Rhodan]

1 hour ago, delta wee said:

Struts aren't working for me. Even though I use the Heavy struts the SRBs break away from the rocket as soon as they ignite.

That shouldn't happen. Are those (presumably KW Rocketry) struts breaking because they misinterpret the launch clamps as a decoupling event? Have you tried the normal non-mod struts? Or the new auto struts and rigid attachements options (that you have to enable in the main menu if you didn't already)?

[AeroGav]

1 hour ago, delta wee said:

Struts aren't working for me. Even though I use the Heavy struts the SRBs break away from the rocket as soon as they ignite. Here is a picture of my rocket to see how I'm using the struts:

 

That cannot be  -   I used one strut per kickback on my spaceshuttle replica-ish (no external tank, four srbs around the orbiter instead).

Struts are draggy too so you don't want that many.

Either the craft file is bugged or there's a little mistake in the staging.  Remember,  as soon as you fire the redial decouplers that hold the boosters on, the struts that reinforce that connection all disappear.   You haven't put the kickbacks on the same stage as their decouplers have you?  Missiles away ! (we've all done that one..)

[delta wee]

6 hours ago, Harry Rhodan said:

That shouldn't happen. Are those (presumably KW Rocketry) struts breaking because they misinterpret the launch clamps as a decoupling event? Have you tried the normal non-mod struts? Or the new auto struts and rigid attachements options (that you have to enable in the main menu if you didn't already)?

Where can I find the "auto struts and rigid attachements options" in the main menu settings?

[Superfluous J]

3 minutes ago, delta wee said:

Where can I find the "auto struts and rigid attachements options" in the main menu settings?

Space Center, Esc, Settings, Gameplay section, Advanced Tweakables. Then each part on your ship should get those two buttons.

[delta wee]

I turned Rigid Attachment on for the struts, and it seemed to make things slightly better because the SRBs don't just fly off anymore, but the struts still stretch like rubber bands and the SRBs point towards the center of the rocket at an angle.

[AeroGav]

must be a mod..  those aren't the stock struts then? (which hold perfectly fine on a 1 strut per kickback basis)

[delta wee]

The strut I was using was called "EAS-4 Strut Connector Heavy".

I was able to get the SRBs to remain stable by turning on autostruts. The rocket still sometimes explodes right after getting on the launchpad because the SRBs bounce into the main rocket when the physics turn on, but retrying the launch several times usually results in getting a rocket that doesn't instantly explode.

[Harry Rhodan]

3 hours ago, delta wee said:

The strut I was using was called "EAS-4 Strut Connector Heavy".

Again: try using the vanilla struts. Not Heavy, not Medium, just the pure EAS-4 Strut Connector. And if that's stable you should probably go to the KW Rocketry Thread and tell them that their struts are broken.

You could also take a look at the SpaceY mod. It's basically fills the same niche as KW but has some larger radial decouplers with built-in Sepratrons.

[Carl]

Or just use auto struts. Those hold SRB's fine with no other struts on it. Can you share your craft file?

[Sharpy]

SRBs - autostrut: Heaviest Part.

Nose cones on SRBs: autostrut: Root Part.

That should take care of torque problem. If it doesn't - you have too strong boosters. Reduce their thrust through Thrust Limiter (rightclick boosters, drag the thrust limiter down). If you're getting too low TWR - add boosters, with thrust limiter set. This will distribute the load better.

[Carl]

Even kickbacks at full burn aren't remotely close to enough to give auto strut an issue.