When staging radial boosters, they blow up my main stage. How to prevent?

[Xuixien]

When pitching, a lot of times if I decouple my radial boosters, the "top" one falls into the main fuel tank and blows up my rocket. I've tried heavier decouplers (more ejection force), ulage motors, separatrons. Nothing seems to prevent it. Anyone got tips? Other than only having 2 radial boosters?

Edited October 7, 2015 by Xuixien

[Padishar]

You could try spinning your rocket as you decouple, I've seen quite a few people use that technique successfully. Or just roll before decoupling to make the boosters horizontal. Either way you'll need to be careful with your steering afterwards.

[Right]

Pointing you're ship surface prograde at the time of separation helps.

Rotate you're ship 90 degrees so that you're top one doesn't fall on the ship too

[zolotiyeruki]

Oh, my, I've had that happen a LOT of times. Here are some things I've found that help:

1) Mount the boosters so that their tails are behind/lower than the tail of the center engine. That way, if they try to go toward the middle after decoupling, your rocket will already be beyond them.

2) If the boosters are SRBs, mount them as low as you can on the decouplers, so that when when you decouple, the top of the SRB moves away from your rocket more than the bottom

3) If the boosters are liquid-fueled with multiple tanks stacked, attach the *top* tank to the decoupler and additional tanks/engines below it, so that the top of the booster is the part that gets pushed away.

4) Right is right--point surface prograde.

5) Get more practice using sepatrons . Stage separation is what they're (intended) for.

Can you post a picture or a craft file for a ship that's having trouble with stage separation?

[Xuixien]

Rotating worked. I'll have to build my radial stages at angles from now on so I don't have to roll my rockets. Thanks guys!!!!!!!! Awesome as always.

- - - Updated - - -

Here's my craft. No file - I use a lot of mods.

I have plenty of time before I get a launch window for Eve, just trying to get a stable platform. I'm sure my service module/probe will work fine once it's on mission.

[Ripper2900]

Another tip: put a small fin towards the bottom of long radial boosters. That helps stability and when separated, will drag the booster slightly away from the center stage due to the offset drag.

I have good xp with that when doing hex- and octo-staged asparagus rockets where spinning won't help.

[FancyMouse]

I thought slanted tanks/adapters are more likely to have this kind of problem? I always thought so and consciously avoid that in my design, but I've never proved that to myself via testing.

[ForScience6686]

Add a sepratron on the nose cone and adjust the angle so it doesn't burn directly into your center stack. Make sure your boosters are at or below center engine.

[Van Disaster]

Is this the old decoupler bug, or just a design issue? I put parachutes on the outside of the upper part of my boosters so they get pulled away, which countered the decoupler bug happily. Seperatrons at a diagonal so they don't set fire to everything else also work.

[Warzouz]

Placement of the decoupler is very important. Don't hesitate to "offset" the booster on the decoupler so the decoupler is higher but near the CoM of the booster (which you'll have to guess).

When the decoupler fires, the booster will go outward and the pushed by the airflow away from your core, not inward (and again pushed by the airflow) to your core.

I never needed any separatrons, but I must confess I use a lot of SSTO rocket to LKO...

[ForScience6686]

Sepratrons are not the best answer, however they are my default so I don't have to worry about this issue. In fact I made a sub assembly with the nose cone to quickly throw it together and never worry about it. Plus it looks great staging them.

[A_name]

I can see you've labeled this as answered but here's another tip for posterity: Don't be supersonic when decoupling your radial boosters. The main force driving them to smash into the central stack is aerodynamic drag. If you keep under 300 m/s until after you've ditched the boosters they'll peel off nice and easy. Then you can throttle up. I know this won't fit with all launch profiles and might even be inefficient depending on particular craft design, but it works.

[Stoney3K]

I can see you've labeled this as answered but here's another tip for posterity: Don't be supersonic when decoupling your radial boosters. The main force driving them to smash into the central stack is aerodynamic drag. If you keep under 300 m/s until after you've ditched the boosters they'll peel off nice and easy. Then you can throttle up. I know this won't fit with all launch profiles and might even be inefficient depending on particular craft design, but it works.

That depends on altitude. Decoupling at Mach 3 above 25km, no problem.

[arise257]

Simple solution: Don't use Separatrons. If you're detaching radial boosters in-atmosphere, just put two small fins on the sides of them near the top. Then angle those fins away from the stack so that they use lift and drag to peel outward and down. You only need to use Separatrons when you have MAJOR clearance issues, such as a wider rocket stack beneath the radial boosters.

- - - Updated - - -

Also -- you can, just like any other booster -- reduce the thrust and fuel load of your Separatrons in the VAB/SPH. I found that 1/4 the fuel and 1/3 the thrust is more than enough to push any boosters away. The decreased thrust and fuel will also prevent them from firing hard or long enough to overheat/blow up other parts.

Edited October 9, 2015 by arise257
Clarity