Yeah, I'm now convinced the 18mm motor is the more reliable and flexible. The cost is having to use a BT-60 tube instead of the BT-55 tube I could use with the 13mm boosters. If I used a BT-60 booster tube and a BT-55 sustainer tube, how could I best deal with the launch rod riding on the booster? Do nothing? Use stand offs on the sustainer? Cut a groove in the booster?
My controller is the latest Estes unit that uses 6 C cells. I'll check my inventory for grey tip igniters.
In igniting one motor above from two below, I'm thinking there is a preferred separation distance that would allow the burning particles to mix and fill the center of the space well enough to ensure reliable ignition of the sustainer. Would a difference in nozzle opening size be a factor for the upper stage motor?
Emma Kristal (quite the competitor at NARAM events as a kid and I believe still going strong as an adult) did a great experimental evaluation of black powder staging, effectively proving it is hot gas that ignites the sustainer, not particles.
probably better expressed as infrared photons from hot gas. Makes sense, as the nozzle no matter what size is a blinde ending pocket, not a tube, so no matter how hard you ”blow” a cloud of particles at it, all They will do is compress rather than display the gas in the pocket. Photons however will “shine” right through it.
I haven’t had any problems with lighting B or C sustainers, even with their smaller bores. That said, is still prefer A motors with the larger bores. I go with Ds for 24 mm, simply because I just never buy the 24mm Cs, although I think the bore is the same.
around 53 inches is my max successful in flight gap stage, I’ve succeeded with 72 inches on a test stand but it failed in flight. When you go to long gap staging, the IGNITION really is the easy part, the more challenging part for black powder staging is coming up with a system to safely keep the booster from coming in ballistic. My go to has been a cluster with a small second motor with a short delay that releases a chute about three seconds after staging, but
@Dotini ‘s HSR is a natural. I have done HSR with a ring fin similar to (but not as purty as)
@lakeroadster ‘s design.