SRBs fall off!

[Delusional Poet]

So I have noticed that when I get a bit too aggressive with my SRBs, sometimes some will randomly fall off on the launchpad, or shortly after launch.  It’s not a coupler thing specifically, as some of the ones that fall off are directly attached to another booster that doesn’t fall.  Structual supports actually seem to make things worse (more SRBs fall off)

This seems to happen as my TO weight approaches 900t give or take.  
 

Any ideas?

Running vanilla and my launch pad is fully upgraded.

[Cavscout74]

Are you using auto struts?  They are usually a big help. 

[darthgently]

2 hours ago, Delusional Poet said:

So I have noticed that when I get a bit too aggressive with my SRBs, sometimes some will randomly fall off on the launchpad, or shortly after launch.  It’s not a coupler thing specifically, as some of the ones that fall off are directly attached to another booster that doesn’t fall.  Structual supports actually seem to make things worse (more SRBs fall off)

This seems to happen as my TO weight approaches 900t give or take.  
 

Any ideas?

Running vanilla and my launch pad is fully upgraded.

At some point the mass of the craft on the pad can really stress the parts on the ground or attached to launch clamps.  If no launch clamps, make sure all engine bells at the bottom are even so the load distributes evenly across them.  Any difference will be amplified as the craft loads and is "dropped"into the pad.

Consider that with side SRBs the weight of the center core, and all above it, is carried by the SRBs if it is raised above them.  This is true whether the SRBs are clamped or on the ground.  You can have separate clamps on the center core also in addition to the side boosters resting on the ground or in their own clamps.

As mentioned above, manual struts can help, but don't over do it. They increase part count in the physics engine (do they count for career VAB limits? Can't remember).  Not sure how autostruts affect all that but they seem to help stability more than they hurt performance

Finally the World Stabilizer mod can help for that initial loading chaos 

 

[Delusional Poet]

1 hour ago, Cavscout74 said:

Are you using auto struts?  They are usually a big help. 

I have on the outermost SRBs.  Then they don’t fall but they do disconnect and don’t fire.

[18Watt]

On 1/18/2023 at 3:05 PM, Cavscout74 said:

Are you using auto struts?  They are usually a big help. 

I would add that in addition to auto-strutting the boosters themselves, I also autostrut the decouplers too.  

I also usually select 'Rigid Attachment' for both the boosters and decouplers.  I am not 100% sure, but you may need to enable advanced tweakables to see the rigid attachment option for parts.

[king of nowhere]

and if autostruts don't work, use normal struts - in addition to autostruts, not as alternatives. and the clamps, use more of them and spread them more evenly on the rocket. put some on the central core too.

it's all a matter of mass. if you make a big heavy rocket, there is more weight pressing on the joints, and too much will break them. reinforcing them with struts, as well as spreading the weight, can fix the issue.

i launched rockets as heavy as 60 thousand tons, but at this point lag caused by part number was the main killer - they took upward to 10 minutes to load on the launchpad, which made testing them by trial and error a real bother - and they had more launch clamps and struts than any other part. somebody launched a million tons rocket, but it was basically thousands of smaller rockets joined laterally and burning independently, so it doesn't really count here.

[jimmymcgoochie]

Do parts fall off?	Yes	Add MOAR STRUTS
	No	Good to go.

Repeat until parts stop falling off.

[Delusional Poet]

14 hours ago, jimmymcgoochie said:

Do parts fall off?	Yes	Add MOAR STRUTS
	No	Good to go.

Repeat until parts stop falling off.

Moar clamps worked even better.