Differences in black powder propellant between boost, delay, and ejection charges?

[BABAR]

Just curious

what is the actual difference in the propellant composition between the propellant, the delay, and the ejection charges?

if this question violates forum rules, moderators please feel free to delete this.

not looking for formulas, just a qualitative difference.

how does it go from thrust producing propellant to non thrust producing smoke?

is the ejection charge the same stuff as the propulsive powder?

thank in advance!

 

[shockie]

the propellant grain is hydraulically pressed black powder in a typical formulation (meal powder which is super-fine flour like BP) ....the delay train/smoke charge is BP plus a lot more sulfur added to produce the smoke trail; the ejection charge is BP granulate 3F size.... when the propellant charge ends....the engine chamber pressure drops to atmospheric pressure of 14.7 psi..... minimal thrust if any is produced by the delay train/smoke charge burning ....then when the delay train/smoke charge bursts it catches the BP particulate on fire and it burns and produces gas and solid particles

 

[BABAR]

the propellant grain is hydraulically pressed black powder in a typical formulation (meal powder which is super-fine flour like BP) ....the delay train/smoke charge is BP plus a lot more sulfur added to produce the smoke trail; the ejection charge is BP granulate 3F size.... when the propellant charge ends....the engine chamber pressure drops to atmospheric pressure of 14.7 psi..... minimal thrust if any is produced by the delay train/smoke charge....then when the delay train/smoke charge bursts it catches the BP particulate on fire and it burns and produces gas and solid particles

Thanks!

 

[SharkWhisperer]

Thanks!

Shockie gave a pretty good description. The granular ejection isn't "loose" like free or adjustable granules under the plastic endcap of an aerotech, but is pressed down with a thinnish compacted layer of bentonite for the end-cap (for storage/transport), so it sees a little compression/compaction, but still burns fast and purposefully. If you have any older motors with the clay cap starting to fall apart, you'll note that the granular ejection charge still mostly remains intact from the initial compaction.

And unlike the added sulfur for smoke trails in delay comps, I just dumb down my propellent by adding 10-15% sodium bicarbonate as a burn rate inhibitor, or use time fuse through clay if I have enough empty tube left after the propellant is loaded. Other's use fuel rich/oxidizer poor mixes for delays (either high sulfur--Estes, or high charcoal; both work).

You might find this link interesting; old Ned's pretty well known in the fireworking circles, and this is pretty much the way I make my own F/G BP motors, just bigger: https://www.skylighter.com/blogs/how-to-make-fireworks/how-to-make-estes-model-rocket-engines