Post Mortem on L2 CATO

[n3tjm]

There is no such thing as "was there enough grease to ensure the delay o-ring sealed properly." You only want enough grease on the o-rings to make them shiny. Any more than that you risk contaminating the delay grain and ejection charge, preventing the charge from going off. Only thing the grease does is make squeezing the o-ring between the wall and insulator easier.

With RMS+ Loads, DO NOT grease the rubber washer that in the delay well. Just drop it in the well. I usually lightly grease just the entrance of the delay well in the closure to facilitate inserting the delay assembly. I then usually place the delay assembly on a table and then press the closure down onto the assembly. This allows for a smooth even install, and will guarantee the o-ring wont slip out of place.

For Non RMS+ loads (Hobbyline, and really old HPR Loads) DO NOT GREASE THE DELAY O-RING at all. Just drop it in the well. The BP has direct contact with the o-ring and can absorb the grease, and if it sits on the pad long enough... well... lawn dart.

In my experience, I have learned that DON'T use grease unless you have too. Any Friction Surface needs it. So lightly grease the o-rings that seal the aft and fwd closure. If those bind, bad things can happen. I also learn by experience. NEVER grease liners. Unless you clean the motor while it's still hot, you pretty much gluing the liner into the case, and then you have a huge mess to clean up afterwards anyway.

 

[dontturn]

Just finished doing some real back of the envelope math based on a few pixels and came away with a required pressure differential of about 0.86 atm required, which would exert ~705N on the cone to pop it out in less than 1 frame. This is a lower bound that doesn't take into account friction or the weight of the shock cord.

Ideal gas law would say that inserting a cone with a 4" shoulder into a sealed 30" tube at 1 atm, we'd see pressure rise to 1.154 atm, far short of the 1.86 atm calculated.

 

[rcktnut]

You have one of the best documented anomalies I've ever seen. From what I seen to me looks like the ejection charge went off right after motor started. Nose cones don't "fly off" like that without some help. Your video, pictures and observations all point to that's what happened. Exactly why it happened, will never know for sure. Just be glad it sealed itself up and did not torch your rocket.