SRBs Detaching From Quad Adapter

[VF1SValkyrie]

I have been having a nightmare trying to get my idea to work.

I've connected the SRBs to the quad adapter, but when I try to launch with a ship like this:

The SRBs will randomly detach from the adapter. I have yet to have a launch where the SRBs broke off in the same way. If they broke off in the same way, I could have an idea where the problem is, but like I said, it is completely, totally, and utterly random if/when the SRBs will break off.

The SRBs have struts connecting each other, but I can't figure out a way to connect them to the separator, and they won't connect to the adapter itself. Anything that sticks out far enough to get a strut attached ends up running into something else.

Any and all help would be greatly appreciated.

[SSSPutnik]

You should do the struts in a X pattern between the stacks, not horizontally for a start.

Like so: IXI or two lots in a vertical pattern like so:

IXI

IXI

[cantab]

You could try putting a part projecting from the SRB near the top (I used the fat I beam in a similar case but lighter choices might be possible) and run a strut diagonally upwards from that right to the orange tanks above. And if need be one diagonally downwards to the bottom of the SRB to brace it.

I wonder also if you haven't got some of the SRBs attached to the neighbouring SRB rather than the adapter? That can easily happen.

[Vanamonde]

I suspect you have so much thrust pushing into so much mass that the SRBs are simply tearing loose. You do have them strutted, but it looks like each one is only strutted to other SRBs which are no more firmly attached. I would suggest to you strutting across the stages to distribute the stress on the SRB/adaptor joint, using an arrangement similar to this example.

You can use helper parts like that little cubic strut to avoid the nuisance of hitting the part directly above the SRB.

[Justin Kerbice]

Without jointreinforcement (even with it sometime), when SRB get low on solidfuel, they push so hard that a big weight above them literally crush what's between.

I think SRB are not designed to be use like this, and IRL, they are dropped while they still have some "juice" (perhaps for the same reason ).

You can try by attaching this 4 SRB group to a radial decoupler, it will be a diamond pattern ( -=- ) which might need two decouplers to stay connected maybe.

[SSSPutnik]

4 SRBs that size produce thrust equivalent to just under one mainsail.

[Kasuha]

The emptying SRB is exerting too much force on the adapted above it. Things don't work in KSP much like in real life, the adapter may look massive but for the game it's more like a few wires connecting individual attach points and the wire from the central attach point to the SRB's attach point is under quite an angle so it is getting stressed a lot.

You need to transfer the SRB thrust directly to the payload above it, e.g. by the construction Vanamonde posted.

I also noticed another thing in your image. It looks like you're trying to stick the outer Jumbo tank on a number of radial decouplers at once. That does not work, the tank only sticks to one of them and the rest is just sitting there doing nothing at all (the tank can clip through them). Remove all excess decouplers and install (EAS-4) struts between your tanks instead for increased mechanical strength.

[cantab]

If you have got too much thrust, remember you can set the thrust limiter on solid boosters in the VAB, to get a less forceful and longer burn. Of course there's a limit because you want to have a decent TWR at launch.

[MarvinKitFox]

Lose the fins on the upper body!

Your SRB's are thrusting the blue snot out of those poor quads, the LAST thing they need is a lateral torque of the body above them misaligning stuff.

The extreme thrust of the SRB's is creating a highly stressed junction, and the aero fins on the above stage is injecting random variations to it. That is why they are breaking in differing ways, at differing times.

If you must have fins, put them on the srb, right at the top, or on the oranges, as close to the quad as possible. this will slightly reduce the horror factor.

Also: Multiple radial decouplers on the oranges? NoNoNO! Only *one* of them is linking, the rest are decoration. If your different tanks are linking on different radials, you have an asymmetrical ship!

Also: Your SRBs are not symmetrical! Yes, you have four neatly around each Quad, but the quads are not radially symmetric in their layout. Try this. Built only *one* of your 6 legs for this vehicle. Only once it is complete, then use 6-way reflect to clone the other legs in. This will ensure their rotation is correct, and everything balances.

Also: Your SRBs are not symmetrical! (no this is not deja Vu, they are broken in another way). Your strut stitching is not quite balanced. Normally this is of little concern, but in a close-to-failure setup like yours, having the strut attach to srb#2 at 60 degrees, and on srb#3 at 45 degrees, will cause the srb's in question to torque relative to each other. Just a bit.

My suggestion: Rather than putting 28 SRB in pancake staging under your orange cluster, wrap them around as tight=packed onion ring. I think you will only fit 24 that way, but as each has its own radial link, the result will be more steady. 2 struts between each srb and its left-right neighbor, and a few fins for steering. Not one per srb! You will save in mass, partcount and stability, at the loss of a bit of elegance.