Over the last few weeks, I've posted a number of questions concerning a scratch-built 2.6" rocket, designed for a cluster of three E9-8 BP motors. Over the course of discussions rising from those questions, I've learned that E9 engines may be unreliable to a point of destroying the rocket. Researching E9 failures on the MESS web site, I've learned that E12 BP motors—which were a second (albeit undesirable) choice to the E9—have a greater incidence of failures.
[Note: As far as I can tell, MESS statistics don't provide a baseline for failure stats, only the failures. So we can't say, "X percentage of these motors failed." Only "X number of these motors failed." So MESS stats are not meaningful to me.]
Discussions of the clustered E9 motor led to discussions of the (probable) need to modify Estes igniters with some type of pyrogen to improve reliability of clustered-motor ignition.
Then I asked a question concerning ejection pressure from three E motors, and the possibility of blowing out the lower body tube. That brought to light speculation concerning the ejection baffle, and possible use of one or two (of the three) motors having no ejection charge, which exposed the fact that the E9 is not available with a 0 delay, or plugged. E12s do, but I can't use one or two E9s and one or two E12s (obviously).
That brought me back to the idea of using E12s. And that moved me to seriously consider chucking the idea of using a cluster, and, in fact, BP motors altogether.
So now I'm looking at Aerotech single-use motors, and learning all I can about them. And coming to grips with the fact that it's becoming more expensive to fly this rocket once it's built.
Anyway, I look back over the long haul and I have to chuckle. At the rate I'm going, I'll still be working on this rocket when the cows come home. I guess it's some consolation that I can fly it in OR. And hey! So far it hasn't blown up!
I want to thank all of you who contributed ideas and advice. It's been a valuable learning experience for me.
[Note: As far as I can tell, MESS statistics don't provide a baseline for failure stats, only the failures. So we can't say, "X percentage of these motors failed." Only "X number of these motors failed." So MESS stats are not meaningful to me.]
Discussions of the clustered E9 motor led to discussions of the (probable) need to modify Estes igniters with some type of pyrogen to improve reliability of clustered-motor ignition.
Then I asked a question concerning ejection pressure from three E motors, and the possibility of blowing out the lower body tube. That brought to light speculation concerning the ejection baffle, and possible use of one or two (of the three) motors having no ejection charge, which exposed the fact that the E9 is not available with a 0 delay, or plugged. E12s do, but I can't use one or two E9s and one or two E12s (obviously).
That brought me back to the idea of using E12s. And that moved me to seriously consider chucking the idea of using a cluster, and, in fact, BP motors altogether.
So now I'm looking at Aerotech single-use motors, and learning all I can about them. And coming to grips with the fact that it's becoming more expensive to fly this rocket once it's built.
Anyway, I look back over the long haul and I have to chuckle. At the rate I'm going, I'll still be working on this rocket when the cows come home. I guess it's some consolation that I can fly it in OR. And hey! So far it hasn't blown up!
I want to thank all of you who contributed ideas and advice. It's been a valuable learning experience for me.