i still think the dye idea would work well,
Me too . But this will be for the next version, let's keep it simple for a first try.
There is just no way an LED will help track the projectile in flight and I worry if smoke would even be visible after 2000m.
Me too . I really thing smoke would just dissipate too quickly. It might give a good clue for the precise direction, and maybe an idea of the impact point for a short while, tracking it with some strong binoculars.
I've open the alarm, I was hoping that the internal would be a narrow circuit board with everything attached to it, but no luck. The piezo are 20mm diameter which would need a minimum diameter 1" (25mm) to accommodate them. And the resonance chamber is part of the plastic casing. That plus the fact the piezo might not survive the Gs as previously stated, I don't think it worth the try for now.
I have redesigned the missile to keep it around 20mm diameter, and simplified a bit the machining operations. Things will be kept together by a threaded rod (brass or steel), with a large nut/spacer in the middle to be able to make 2 adjustable chambers. The front for some weight, the back for whatever you like I'll drill small holes around at an angle for possible oxygen intake/exhaust so the drag should be minimum.
Unless someone share some better idea, I hope this weekend I'll make some metal chips