Mark, Sorry for the confusion on your question. I place my ematch on top of the pile of BP. I'll give some history, then I'll state what I think is really happening (albeit non-scientific terms) I'm the guy that came up with the surgical tubing charges, Up to that point getting consistent deployment at high altitudes was iffy. The guys that seem to go well, at recovering from high altitudes seemed to a lot of BP. High altitudes (back 20) ago seemed to be flights of 20K or better. Yes, some colleges, Mark Clark, Frank and others had some really high flights. I did my L3 about 18 (?) years ago and went to 19,696 which at that time was a pretty high L3 cert flight. By the way I'm fortunate in that Black Rock is my "home field" For the longest time I just used charges in the tips of fingers from Latex gloves. I can't really recall what happened to make me look into a different confinement methods. I'm guessing the loss of a rocket or two! So my buddy Steve and I made up and 6" PVC vacuum chamber. I was testing things that I had seen on some of the college high altitudes shots. They were a lot like those big fire cracker things 80M (misspelled on purpose) As a professional Firefighter, I did not feel good about making or putting those sorts of things in my rockets. We did test some of them. They tended to scatter the BP all over the place along with all the parts of the charge "holder" too. We even tested an Estes B engine at a simulated 70K altitude. It lit fairly quickly but had way to much fire inside and outside the test chamber. Yep it ended up outside the test chamber on one test! I managed to extinguish the fire (yep we caught stuff not involved in the testing o fire. I guess now would be a good time for ...Kids, if you've read to this point please do not be like me! Don't play with fire!...So, at this point all of our test sucked. We had always heard that the reason for BP not working was that there was no 'air' for the BP to burn. Or it was to cold for the heat to transfer etc. I got to thinking. BP has it's own "air" and it's not 'up in the cold long enough to matter. It had to be a container issue. I used to race control line airplanes and we used to use surgical tubing for fuel bladders. We would use a syringe to fill the bladder with fuel and it was like the motors were on crack..sorry kids, just say no to drugs...So, I made up some BP charges using latex tubing. They worked really well. At the time I figured we had found a way to burn 100% of the BP at high altitudes. The highest altitude that I know of where the latex tubing charges were used was the 104K
Over the years I would hear of a project or two where the latex charges did not work. Jim Jarvis had written up a paper on some of the tests he had done on BP at high altitudes. Jim found that they were not consuming 100% of the BP and that the % at times, was really not good at all. Jim came up with his copper pipe containment system that is pretty slick. So, a year or so ago I made up one of his systems and did some ground testing. In Jim write up
https://www.rocketryfiles.com/files/Technicalarticles/Jim_Jarvis_Highaltitude_deployment_2013.pdf Around page 9 Jim makes a statement that his confinement system is VERY ENERGETIC. After my first ground test, which luckily was not in a rocket but out on the ground, there was no way one of my crappy rockets could withstand that! I put the stuff aside while I figured out what was going on and why.
The following was, and still is what I think is going on when we use BP for ejection charges. BP has it's own "air". Our (at least my rockets) rockets don't spend enough time in the cold to have much of an affect on the BP converting into gas. The issue has to do with confinement and length of time that the BP is confined. I'm not using the word confined as in sealed. I'm using confined as in keeping the BP in close proximity to itself, each grain close to another. I'll talk about guns for a bit now. I know that guns with longer barrels shoot better then those with short barrels because the gun powder has more of a chance to be used up. So, a long skinny tube is better then short fat tubes for more complete consumption of the BP. Less will be scattered and not burned? Now where to put the match. Placing it at the bottom of the pile will start the process and start the burning pile towards the end of the barrel. Maybe some will not be actually burning by the time it reaches the end of the barrel? Now take that same pile of BP and put the match on top of the pile? The top catches fire and that gas heads for the exit while the piles is consumed it all has to pass the fire to escape out the open end of the tube? So why vinyl tube and dog barf. That's my attempt to make this type of ejection charge system not so violent but still use the "gun barrel" confinement method. I feel that the vinyl tube will expand some during the burn. The dog barf at the plugged end (hot glue plug) should help cushion the shock that way. The dog barf at the open end mainly holds the ematch and BP in place. The electrical tape just keeps things from spilling out. I found that it does not need to actually seal the air inside the tube.
Also, this type of devise actually directs the gasses in a useful direction..and not just filling the body tube with gas.
Always ground test...
If I had to pick a number where to start thinking about high altitude issues it would be 23K MSL.
That's my story and I'm sticking to it...
Sorry for the gramer and spelling issues!
Tony
