Cesaroni I540 strange ignition sequence

[Michael L]

I launched my LOC IV on a Cesaroni I540 today. Over all it was a good launch. It didn't quite make the 5,010' altitude that Rocksim said it would recovery was 1,500 downwind and easy. At ignition the motor started to come to life, popped, and was off.

Here's the sequence:

Times are from the camera. I can get 10-ish frames per second out of my 1Dx (probably faster than that but I didn't feel like looking it up). Frame 1 (left) has what seems like good ignition. Frame 2, 9ms later it looks like it almost went out. Frame 3, 10ms later and it has come back. Frame 4, 18ms after that, the rocket was on its way. The motor case was melted away from the nozzle to about the middle of the case (5 grain case).

It's a commercial motor so this is more about curiosity about what happened than anything. Performance was fine.

 

[crossfire]

The pop was motor coming up to pressure. The liner be melted that's normal for CTI motors. As long as case has no damage the liner did its job. A lot of the melted liner happens after motor burn.

 

[Michael L]

Yessir, the liner on the last one melted a little too. This one was a lot worse, about 50% of this one was gone. The thing I don't get is why the combustion cut back to almost nothing at the 9ms mark. It lit and came up to what I labeled as T +0, cut way back at T +9ms, lit back to what I have marked as T+0, then came up to full power.

 

[heada]

Just speculation.... The BP is what you saw initially, then it burned out but had started the APCP grain. Then the APCP fully ignites and motor comes up to full pressure.

Normally the BP ignites and starts the APCP and you never see anything between them but maybe the APCP was oxidized some and there was a slight delay.

 

[Michael L]

That makes sense! I tend to ask "why" a lot

Performance wise it was a great motor. It's the largest I that Cesaroni sells (or that I could find). It didn't get to predicted altitude but the rocket had a little arc to it,. Surface winds were higher than they were at altitude. It went down range about 1,500' and then drifted back over and behind us about the same.

4CRA has a huge open area, crisscrossed by dirt roads, to fly in. If it drifted a mile it wouldn't be horrible (as long as it wasn't too far off of the road.

 

[Rocketjunkie]

Chuff. The propellant came up to pressure but spitting out the igniter dropped the pressure enough for the propellant to go out. However, the delay grain was still burning so the propellant re-ignited and the rocket was on the way.

 

[bobbyg23]

Classic chuff. Here is one of mine "chuffing".