Here is a video of a two-stage rocket I flew last week. It's an all aluminum rocket flying M motor in the booster and N in the sustainer. Both motors are 100mm in diameter. Booster motor geometry is a 6-point star and the propellant is catalyzed with Ferrocene for fast burn rate. Sustainer motor is a simple core burner with a slow (10 second) burn. Both propellant grains are monolithic and case bonded. Sustainer motor igniter is a wire mesh basket loaded with B/KNO3 ignition pellets. Both sets of fins were canted 0,5° which gave a roll rate of about 300rpm at sustainer burnout. Flight went well until shortly after sustainer burnout, when the telemetry was lost. Exact cause of failure could not be determined, since no sustainer hardware was recovered.