Should serious (dangerous) chuffs be reported on M.E.S.S,?

[rcktnut]

I've mentioned this elsewhere, but remember that APCP burns more slowly when cold. More chuffs in winter months. They can be minimized. Keep motors in an inside pocket or in a small cooler that was loaded with warm bricks until ready to install them. Get it out to the pad, clip up, and push the button. Not frantically but don't waste time. Small motors will cool down more quickly than larger ones.

I'm thinking that down scaling APCP motors to that size that the propellent has a hard time sustaining pressure, heat or both. The igniters are also filling up most of the core. They must absorb some of the heat.

 

[4regt4]

I'm thinking that down scaling APCP motors to that size that the propellent has a hard time sustaining pressure, heat or both. The igniters are also filling up most of the core. They must absorb some of the heat.

Yes, it seems the bigger the motor, the fewer issues I have.

Hans

 

[Tractionengines]

I'm thinking that down scaling APCP motors to that size that the propellent has a hard time sustaining pressure, heat or both. The igniters are also filling up most of the core. They must absorb some of the heat.

I think "building pressure" may be more of the issue. (Or pressure oscillation waves, maybe) in this image that has been posted a few places on TRF. . . There is quite a bit of room at the core slot. (Not filled up) But there is a large amount of space between propellant grain and nozzle.

Look at how far the igniter needs to go before touching the grain, then need to find and go into the slot. Easy to get it wrong.

[ Not my photo. Wish I could give credit to person who cut motors open and documented internals. Thank you. ]

 

[AeroTech]

Black Max is a perfect propellant for clay nozzles. Little or no erosion. White Lightning can be hard on them depending on the configuration, and Blue Thunder is out of the question.

 

[wsume99]

Look at how far the igniter needs to go before touching the grain, then need to find and go into the slot. Easy to get it wrong.

[ Not my photo. Wish I could give credit to person who cut motors open and documented internals. Thank you. ]
View attachment 627131

You make a good point however most of the complaints I see and the specific issues I have had were with C and D impulse WL motors. I would say it's pretty easy to tell if you have the igniter installed correctly in those motors. A and B impulse it's much more difficult as the picture shows. I've only had one chuff event however it was a bad one. The initial puff lifted the rocket off the rod then it re-ignited once clear of the rod. The rocket abruptly turned 180 and flew directly into the ground. Thankfully it went in a direction away from the crowd.

 

[astronwolf]

I'm thinking that down scaling APCP motors to that size that the propellent has a hard time sustaining pressure, heat or both. The igniters are also filling up most of the core. They must absorb some of the heat.

I tend to blame the propellant. I'm not a fan of White Lightning, or any of the other readily oxidizing propellant formulations. With reloads you can at least attempt to salvage oxidized grains but the SU motors you can't easily do that. Maybe APCP motors ought to have an expiration or a use-by date on them.

But I also tend to agree with @rcktnut in that the combustion instability may just be a function of the size of the motor. I suspect that the choice of propellant has a lot to do with reducing the chuffing - re: anecdotes about the performance of Blue Thunder or White Lightning. Combustion instability may actually be a feature of these very small motors that can't be designed out of the motor while still maintaining affordability and profitability. You get what you get.

Is filing a MESS Report appropriate? I don't know. It may not be.