Rocket Fuel + Sponge Ti /Microstars, Color?

[LiamPyro]

I’m working on making a variety of flying devices for the 4th, mostly helicopters and 4 oz endburner rockets. My current fuel is milled 75/15/10 made with (usually) airfloat or (sometimes) willow charcoal, plus 5-10% 80 mesh charcoal, FeTi, and/or spherical titanium -30 +100 mesh. My question is two-fold:

1. What are some rough guidelines for adding coarse titanium sponge (-10 +20 mesh) or microstars (ricing star comps through 1mm - 3mm screen?) to rockets or spinners with small nozzles? I know these sorts of effects are common in fountains, but these generally have larger openings. Is a particle size half the size of the nozzle workable? How about larger? The helicopters don’t have much of a convergence leading up to the inside of the nozzle seeing as the hole is drilled perpendicular to the tube, although the clay plug does have a conical shape inside to reduce burn through. Not sure if the large particles would be ejected, burn inside the device, or cause a clog and pop the device.

2. Does anyone have a good formula for colored rocket propellant (no AP/mg)? All devices will be made on a press. I read the Skylighter article on colored rocket fuel, which suggests what basically look like Ruby Red /Emerald Green star compositions plus a few others. Is mixing a color star formula with some proportion of potassium benzoate whistle a viable option for more thrust? I’m looking for something that can be used in an end-burning configuration. I do have a homemade short-core 1lb rocket tool that I may try to use to make some stingers or hot-fuel coreburners.

If anyone has any weird /wacky flying devices they’ve made, please share. I’ve been reading through the Westech Fireworks Manual for inspiration.  Below is a video of the first test of a 3/4” ID x 4” helicopter with AF BP + 10% 80 mesh charcoal fuel. Going to see if these can lift a small payload of stars…
 

 

 

 

[Mumbles]

In terms of size, I don't personally like having anything more than half the nozzle diameter in there.  Preferably closer to 1/3 or smaller.  Convergences tend to help keep the microstars or coarse Ti from accumulating  in the end of the rocket as opposed to getting ejected as desired.  I've never used something as coarse as you're suggesting, but with finer titanium, it is ejected from spinning inserts just fine.  You may want to consider the burn time and fallout zone of using such coarse material.  

Something you may want to consider is that coarse additives will reduce the thrust somewhat.  I would absolutely press at least one increment with straight fuel, if only to prevent titanium from coming in contact with the spindle.  If you're encountering lift issues one potential possibility is to add a few increments of straight fuel to help get it going, and use the material with the tail in the rest of the increments.  It may help with the burn time of the coarse titanium as well.

[LiamPyro]

Thanks for the reply. I’ll probably just stick to the finer titanium for the most part until I get a feel for how the coarse stuff behaves (just bought it, haven’t tried it) and maybe include it in the delay of some 1 pounders with 1/4” nozzle. Maybe microstars too if I have time. I will post results if the effect is interesting.