Mainsail Goes through rocket at end of fuel?

[XOIIO]

Alright so I am having a really annoying problem, every single time. The mainsail is a breeze to get up to the atmosphere, way less frustrating than other rockets, I just used three for this thing, but several times now at the very end of it's fuel, it shoves the tank through my rocket and blows the whole damn thing up.

What the heck is causing this? Does the mainsail get some magical mystery thrust right at the end of the fuel tank from the fumes or something? I thought the max was 1500kn. It runs at that the whole time anyways.

[SRV Ron]

It is compression failure between the reaction wheel and the tapered adapter. It happens due to the increased forces as the fuel tank gets emptied. Get your struts attached to the reaction wheel instead of the base of the adapter. That should resolve the problem.

[Sirine]

Solution: You need to put "strut" on the part that it goes through.

Reason: Too much thrust it bend the structure of your rocket.

Why: Because you get lighter, and the thrust get stronger, but your structure integrity remain the same.

Edited January 16, 2014 by Sirine
Ninja;

[Taki117]

The thrust for the mainsail is constant despite not having any fuel. Basically what's happening is your engine is accelerating an empty tank. This causes your engine to clip through your tank and possibly destroy your rocket.

[XOIIO]

Alright, I'll just whack a load of struts between the decoupler and adapter and the main tank and see how that goes.

[Lunaran]

Try gradually throttling down also. Watch the g meter beside the nav ball, and find how high it goes when your rocket fails. Stay below that.

[XOIIO]

Try gradually throttling down also. Watch the g meter beside the nav ball, and find how high it goes when your rocket fails. Stay below that.

q meter? - Ah, quoting shows that you said g, looks like a q for some reason.

Anyways struts didn't help but gave me a little bit more time to react and throttle down.

Edited January 16, 2014 by XOIIO

[Taki117]

q meter? - Ah, quoting shows that you said g, looks like a q for some reason.

Anyways struts didn't help but gave me a little bit more time to react and throttle down.

You could try Kerbal Joint Reenforcement It will help with that connection in particular.

[Kasuha]

You could try replacing that one mainsail with skipper. If it goes through the rocket, it probably has way too much thrust.

[Guest]

It is compression failure between the reaction wheel and the tapered adapter. It happens due to the increased forces as the fuel tank gets emptied. Get your struts attached to the reaction wheel instead of the base of the adapter. That should resolve the problem.

Those large SAS modules are about the most fragile thing in the game. It might be better to remove it from the stack and mount one or two to the side of the rocket if you need them. If you want them in the stack, strut from below to above it, strutting to it doesn't work that well from what I've seen.

[Max Grant]

Maybe your rocket doesn't need to be a Mainsail, here. You speak as if perhaps you had two other Mainsails attached. I'd replace the center engine with the Skipper. By the time it is the only engine, you're really high up in the atmosphere and do not need the ridiculous TWR of a Mainsail.

[Flixxbeatz]

And this is why I don't always use a Mainsail...

[JumpsterG]

One way to help prevent engines from compressing a light load (and also from spazzing horizontally under a heavy load) is to run a few strut connectors directly to the engine from other parts. If you need somewhere to start the strut from, throw some cube struts just above the engine and connect lines from them to the engine.

You can use this trick to "stitch" other segments of the stack together as well if you find their connections too weak. Throw those cube struts on the big SAS (a known, squishy part), and connect strut lines between the cubes and the segments above and below for sturdier connections.