Early Ejection Cause

[DeeRoc29]

I flew a new rocket yesterday with my new Stratologger. The chute (single deploy) ejected right after motor burnout. I'm not exactly sure why. Here are the facts:

- The motor was intentionally loaded without an ejection charge
- The only ejection charge was hooked up to the Strato's drogue terminal
- The Strato was used "right out of the box" (i.e. I didn't change any settings)

I'm not exactly sure what caused the early ejection. My only guess is the placement of the vent hole was too close to the nose cone. The rocket also uses a LOC 4" to 3" transition. The altimeter was mounted in the upper 3" section, and the vent hole was drilled 6.5" below the nose cone and 11" above the transition.

Miraculously, the rocket stayed together and returned undamaged.

Thoughts?

[Handeman]

How tight was the nose cone? With the transition, there is more drag on the lower part of rocket, relative to the nose cone then what you get with a straight tube rocket. It could have been drag separation when the motor burned out.

Did you see or hear the ejection charge go off when everything ejected, or did the charge and smoke appear slightly later when the chute stopped it from going up any further?

[stickershock23]

I agree with the transition that is a CLASSIC case of drag separation..

the lower section has more drag than the section above the transition. in this case you have a altimeter and battery in there. plus MAYBE a chute so the top section is also heavier, that means more inertia. so as soon as the motor burnt out the lower section slows down WAY faster than the upper section... and it looks just like the ejection charge went off.

since it suddenly slowed down when that happened, the stratto logger sees a sudden change in pressure, so it too think you have reached apogee, so almost instantly fires your ejection charges..

My suggestion. add schear pins..

[DeeRoc29]

The transition was part of the upper section. In other words, the rocket splits just below the transition. I designed it this way to avoid drag separation, but maybe it's still possible.

I don't remember hearing or seeing the charge going off separately from the early deployment. It may have, but I just didn't see it.

[Stewart]

If you had only 1 vent hole as your description reads, this is most likely the cause, a single vent is more effected by turbulence than multiple holes equaley spaced around the rocket.
Another cause of false triggering is pour'ly sealed avbay ends.