Solid Rocket Boosters Detaching for No Apparent Reason.

[riggsy]

My craft launches fine, is very stable, my engines don't even begin to overheat - than about %80 of the way through the fuel of my first stage (7 Rockomax BACC Solid Fuel Boosters), they just slide up through the rest of my ship and everything goes up the creek real fast (explodes). Any ideas why?

Edited November 7, 2013 by Vanamonde

[Vanamonde]

It's hard to tell without pictures of the ship. Can you post some screenshots? (And please mind your language on the forum. )

[Kasuha]

Unless you pressed Space and staged them off while they were still burning, try to press F3 when that happens and check the flight log for structural failures.

[bludy]

did you place them with radial decouplers or just attached to the side of another tank?

add a couple of structures to fix them better..from what you say it seems the ship is too heavy and they go on their own..maybe the rest of the engins is not enough powerful.

[700NitroXpress]

I've had this problem, if the rockets aren't secured to the rest of the ship with duct tape, then they can detach from the radial decouplers. The problem that's happening is that the large solid boosters are providing all of their thrust to themselves and none to the ship. Therefore, the decoupler fails and the rockets come loose. This also happens at high altitude because there is less air resistance keeping the boosters in place. Another problem that might be happening is that, if you have docking clamps attached to the boosters before it launches, then the weight of the craft dropping on the launch pad is causing some structural failures and the boosters are then more likely to come off.

[SRV Ron]

As those boosters burn through their fuel, the forces they place on the decouplers will increase until something breaks. Usually, the failure is caused by twisting.

This example, without braces, would lose boosters halfway up. With braces, it flew flawlessly. But most interestingly, none were needed across the decoupler.

The one bad thing about high powered SRBs is that once they have nearly all of their fuel burned up, the acceleration can be so great that it will crush what is above it unless you use braces. Example;

Once properly braced, this design hit 15G at burnout of the core stage.

It hit Kerban escape;

Edited November 7, 2013 by SRV Ron

[SRV Ron]

I've had this problem, if the rockets aren't secured to the rest of the ship with duct tape, then they can detach from the radial decouplers. The problem that's happening is that the large solid boosters are providing all of their thrust to themselves and none to the ship. Therefore, the decoupler fails and the rockets come loose. This also happens at high altitude because there is less air resistance keeping the boosters in place. Another problem that might be happening is that, if you have docking clamps attached to the boosters before it launches, then the weight of the craft dropping on the launch pad is causing some structural failures and the boosters are then more likely to come off.

Watch the G force meter. You will be surprised at how quickly it can go up as the SRB fuel nears exhaustion. For radically mounted boosters, it is the sheer and twisting forces causing failure. Proper bracing will fix that failure issue. For large powerful boosters under the core stage, compression failure can occur. The stats will tell you what happens. Vertical bracing can protect what is above from high G compression that can occur near the burnout of the booster.

[DrMonte]

Adding heavier decouplers and/or few struts usually solves the problem.

[phunk]

This also happens at high altitude because there is less air resistance keeping the boosters in place.

Also, as the fuel in the boosters burns off, their TWR increases significantly. The amount of stress they are putting on their mount points is greatest right before the run out of fuel.

ETA: I should have read futher before replying, others have already said this.

[riggsy]

http://imgur.com/a/rhyp6

Here's a shot by shot of my problem. Judging by the responses I should just beef up my ship, but I don't have struts or better decouplers yet.

Edited November 8, 2013 by vexx32

[celem]

Yes, that does indeed look like overstress of the boosters. Beefing up may well make the problem worse if you mean adding more thrust.

I think your ship is actually going too fast. (below 14km i use 200m/s as the speedlimit, any faster is counterproductive due to drag)

One of the issues is your altitude, you are still in thick air and being pushed well over terminal velocity by the srbs. Besides being wasteful of thrusting power it stresses the ship like mad. Perhaps seperate those big rockomaxes into seperate stages, take a longer time to make your ascent. Alternately increase the weight of the next stage slightly (i.e. carry more liquid fuel up on those srbs) to reduce the Gs on your first ascent stage. It wont empty and detach quite as high, but the extra fuel you get to the release point should make up for it.

Dare I go against the meme?

Yes... you need less boosters, at least while you are unable to secure them adequately XD

Edited November 8, 2013 by celem

[SRV Ron]

Definitely, compression failure at the core decoupler allowing the booster ring and lower core to telescope into the upper stages and its SRBs. Braces and a stronger decoupler will solve the problem.

[riggsy]

I swapped out the SRBs in favor of some LRBs, much better. I just landed on the Mun for the first time with the new setup.

[magnemoe]

If the rest of the design is stable one strut from the top of the large SBR to the tank its connected too keep it stable.

Also work if you stack the large SRB together two and two like here.