Over-energetic ejection charge?

I flew my Atomic Avenger at NSL with a CTI 29mm G80 skidmark. I drilled the delay down to 5 seconds. It flew fine, had normal tracking smoke, and deployed a little after apogee. But it separated.

When I found the body, I found that not only had the shock cord mount been ripped away, but also the entire interior of the baffle destroyed, and the bottom of the nose cone that used to be convex is now concave. :y:

I can only conclude that the ejection CATOed

Perhaps this happens now and then, but this is the first time I have every had an issue with a CTI reload.

Have any of you seen anything like this before?

Thanks.

perhaps the 1.3g of BP in the 29mm is just too much?

I know Aerotech gives .7g with their hobbyline 29s, and 1.4 with their HPR. I'm not familiar with this rocket, but it sounds like it was just too much BP.

Nate

A shame to what happened...

The lift-off was great!

This is of interest to me. Anyone reduce the CTI ejection charge or does it cause problems? They say you can easily add more ...

I am not sure that you can reduce the BP charge without a bit of work as you would have to remove the forward paper seal then glue a new one in place and it may not be a certified motor at that point. Just guessing on that one, I am sure someone who knows will pipe in.

One thing I know you can do, which is what I did on my AeroTech Arreuax, is to use a longer shock cord. This will help dissipate the energy so when it gets to the end there will much less forces acting on your bulkheads or shock cord mounting points. You can also look at the materials your using, Kevlar has little stretch, nylon has more and elastic has a lot. But Kevlar is stronger, so you can down size and typically pack more in, plus it is fire resistant.

mpitfield said:

One thing I know you can do, which is what I did on my AeroTech Arreuax, is to use a longer shock cord.

Click to expand...

However, the fact that the bottom of the nose cone was bashed in, and the baffle eviscerated, this was more than a shock cord failure.

Ive seen a few CTI charges added or subracted from in both case the individual just used dog barf and white masking tape just like is done on AT RAS forward closures.

I suspect that the charge was too large for the rocket, a part of the baffle broke loose when the charge went off, and that piece or some other hard piece of the recovery system impacting the bottom of the nose cone is what dented the bottom.

I really can't see the pressure needed to cave in the bottom of the nose cone being more then the force needed to eject it out of the rocket, which is what would have had to occur for pressure alone to cause the nose cone dent. If it is a paper BT, I also expect it would have split before the nose cone bottom would have collapsed. Something hit it.

What does the reload look like? Does the fore end look normal?