How difficult is that to do, in terms of automation? I suppose anything's possible within reason.

What about a different approach, like a special 'plug' that you use only in sustainer applications? Think about those Estes igniter retainers (molded plastic), but using that coating material instead? That way, the manufacturing equipment wouldn't have to be changed, and the plug would be no different than what everyone is already used to. Could something like that be made with enough resilience to work without breaking up more times than not?

Hhhmmmmmm.........how thick is cannon fuse?

Even old Jetex fuse is probably larger than 0.06", so you'd probably have to get it specially made, but that is the tack i'd use.

Wait... I have some Jetex fuse somewhere, and I have a few Apogee motors somewhere.

I'll report back later.

Actually, you're not far off. The old Apogee motors used a piece of wire, maybe 1" long, dipped in pyrogen, as staging aids. I've never used one, but have the motors and staging ignitors at the house waiting for me to finish one of those long, long-neglected projects

I like Carl's idea better, tho. My take was that, while the staging ignitor provided a conduit for getting the sustainer lit, it also blocked the nozzle at the same time. In my mind, I always wondered if that wasn't sorta robbin' Peter to pay Paul.

Painting a thin coat of pyrogen in the nozzle makes way more sense to me. But it needs to have a low flash point. Some of the pyrogen I've worked with is optimized for its burning properties more than its ignition properties, probably because APCP is so hard to light. But in this case, with BP being relatively easy to light if you can just get the heat/flame/hot particles on it, the key is have a pyrogen that flashes quickly. (IMO)

Doug

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I never saw the staging ignitors.

could the doped upperstage motors be successfully used as single stage with no safety concerns?

I have an Apogee B2 that I could never start. tried five different ignitors (solar, bare solar, shaved thermalite, shaved sure shot, old MRC), then flashpan, then scraped the nozzle and tried again. I'm thinking there is still a good bit of clay in there, so eventually I'll use a jeweler's drill bit and get a little further each time. I'm thinking Tim must've been sleepy and added another bit of clay powder while loading it.

More excuses ... ah, reasons!... to use the A2...
 

Here's another design for the A2, using a pair of -5's...

Tuzen...

(Addendum: Use a 48" x 3/16" rod. It requires 42" of that length...)