Gap Staging

[TeslaPenguin1]

So, I have this one idea for a rocket I want to build. The only problem is, I want it to be staged, but the motors aren't next to each other. In fact, they will be 18 inches apart. (length of Estes a la carte body tubes) Is it possible to stage them without electronics?

 

[Nytrunner]

This is possible, although some practice is recommended. You'll need a small hole in the airframe just below the sustainer motor so the cold air in the tube will displace and the hot ejection case can freely light the motor.

Conventionally, I've heard of gap staging up to 12", but some have performed it much further than that.

 

[Wallace]

As Nytrunner stated, it works. The vent being critical to ignition before simply blowing the pieces apart. You can even vent it out the rear if you don't want holes where they'll be an eyesore. It works surprisingly well actually, even at longer distances. Since you didn't mention tube diameter I'll add the fact that a smaller diameter internal stuffer tube is your friend when working with larger diameter body tubes.

 

[rharshberger]

As others have mentioned the gap staging is possible, the next trick is recovery of the booster stage as the sustainer being a long aerodynamic object will fly a ballistic path and lawn dart instead of tumble, unless there is a parachute recovery OR the stage is designed in such a way that it does become unstable after stage separation. There is another recent thread on gap staging and rear eject recovery with only one motor in the booster (its a recent LPR Nike-Apache thread iirc) and the OP or a contributor links a Apogee Newsletter about gap staging with rear eject boosters iirc. I have done gap staging with a cluster and a stable booster but never a single motor gap staged stable booster.

 

[TeslaPenguin1]

As Nytrunner stated, it works. The vent being critical to ignition before simply blowing the pieces apart. You can even vent it out the rear if you don't want holes where they'll be an eyesore. It works surprisingly well actually, even at longer distances. Since you didn't mention tube diameter I'll add the fact that a smaller diameter internal stuffer tube is your friend when working with larger diameter body tubes.

I am using an Estes BT-20 body tube.

 

[Wallace]

Safe bet it'll stage just fine. I actually can not remember ever having a staging failure with black powder motors be it 2,3 or gapped. Recovery is a different story...