NeighborJ Posted August 13, 2016 Posted August 13, 2016 (edited) I've been conducting experiments with bp milling media for another topic and one of the results seemed to be extremely reactive. So reactive that I believed I could create the mythical nozzleless endburner. I know this is technically a core burner because it has a 1/4" core but I found it easier to secure the fuse with this short core and am very surprised that it actually flew. Motor specs, 2oz, length 2", 1/4" core hand drilled with 3/32 bit. Bp-75-15-10 with staghorn sumac charcoal ball milled for 20 hrs using nickel media. This motor has no real purpose but to see if it was possible and likely would not carry much more than a firecracker. To prove that this works, I've repeated the test without the core and posted the video. VIDEO0040.mp4 VIDEO0042.mp4 Edited August 13, 2016 by NeighborJ
DavidF Posted August 14, 2016 Posted August 14, 2016 Cool! One thing I have always wondered about rockets is what is the relationship between what it takes to get a rocket going and what it takes to keep it going. If you used your super duper whistle to get it going, I bet your BP would do a good job of keeping it going. The second video really shows how important that little core is, doesn't it?
NeighborJ Posted August 14, 2016 Author Posted August 14, 2016 I believe it burns like a zinc rocket. Meaning it needs a rupture disk to get a spike in pressure which dramatically increases the burn rate. The second video needed a wadd of tissue paper to get that slight rise in pressure. It's the same principal which all nozzleless motors exploit to overcome quickly eroding nozzles. The other trick I used is a recessed grain, the fuel started nearly 1" inside the tube and ended at the top, this helped direct all gases down while maintaining a full bore.
NeighborJ Posted August 15, 2016 Author Posted August 15, 2016 Well David I tried scaling this end burner up and ran into a problem. As I expected the motor would not lift with a 4oz motor and I believe it's because the bp burn rate would need to scale up as well. It simply would not work. If I tried to scale down to 1/4" I believe it will fly rather well. I did try the "super duper whistle" in the 4oz and it fly's well, but when I tried 1/4" whistle on the bottom of a bp fuel grain it lifted and could not maintain forward momentum on bp alone. The ability of the whistle to produce thrust explains why I was never able to get my delay timing right. It never reached apogee even with 3" of delay and my shells would horsetail. They sound ridiculous with that long of a delay.😖 VIDEO0045.mp4
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