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Originally Posted by Rocketflyer
Hello Mike. Thank you for your time and willingness to post and answer questions.
My questions are mainly about motors. Has the overall performace of some of "todays" motors diminished since the motors of the past? It seems that the "C" impulse motors are a little weaker than the bygone days (then again it could be memory loss on my part  ).
Secondly, why have the longer delays for the 13mm motors been discontinued? A 3 sec delay in most little rockets usually results in shredded chutes, etc.
Thank you once again. I really look forward to hearing of your time and experiences at Estes. The knowlege, insights and asides will be priceless to all of us, I'm sure!  |
This is a great question. This sould make for interesting excahnges with the engine guys here.
Many of you may not realize that there has never been two like batches of black powder ever made. That includes the one that may have been made yesterday, and the batch made today on the same equipment, and from materials from the same bags or sacks.
Terry - feel welcome to jump in on this if you think I miss something----
While potassium nitrate stays relatively constant, both the sulfer and charcoal change ever so slightly from lot to lot. The charcoal is the ingredient that has the greatest overall control over the burn rate of a particular batch. Hickory has historically been the preferred source of charcoal, but woods such as pine can in a pinch be uased as well.
Trees as a species morph over time, which side of the hill they were grown on and where they were harvested changes, the ingrediants in the soil changes, and so does the temperature while they were growing. The variables are staggering that affect the tree before the wood is harvested. And do you use the branches or the truck, or both? Then there is the process of heating the wood to produce the charcoal. Getting to repeatable charcoal for black powder is a serious issue.
To get to your essential question - yes, black powder made today is 'slower' than it was ten years ago, and it's getting slower. That changes the burn rate of our motors just as it does everyone else's motors. We do burn rate tests on every single lot of powder we buy to characterize it. We press and burn a lot of motors in this process. We have to know how many clicks to adjust engine manufacturing equipment in order to maintain the NAR impulse standards we have always adhered to.
Does this help?