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What are the basic differences in burn characteristics of the styles? I know end burning is a long burn.
Rocketjunkie
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STAR used to get high thrust short duration. Must be sized correctly to avoid large slivers of wasted propellant.
FINOCYL is a core burner with fins usually on the nozzle end. The fins increase initial burning area and compensate for the progressive burn of the cylindrical core part of the grain. Usually used for case bonded grains allowing a higher propellant loading in the same size motor.
ROD AND TUBE is a grain where the grain consists of a tube with a very large core and the rod is more propellant. As the tube burns out increasing the burning area, the rod burns in reducing its area. This results in a neutral burn if sized correctly. Lots of mechanical difficulties keeping the rod in the motor. Best solution is an aerospike nozzle.
C-SLOT is a slot along the side of the grain. Aerotech uses this in their long burn motors, K185 vs K550, J90 vs J275.
D GRAIN is what I use for my long burn motors. Cast a solid stick of propellant and slice the side off. Burn starts on the flat of the 'D' and proceeds across to the other side. Using White Lightning speed propellant, I get 7 sec in a 38mm (I85), 10 sec in a 54mm (K160, the CTI K160 is a C-slot), and 17 sec in a 98mm (N800)
END BURNER To get useful thrust from an end burner, you need a fast propellant. The Apogee E6 and F10 were Blue Thunder end burners, The Aerotech I49 and L339 are Warp9 (VERY fast propellant) end burners.
ALL off center core motors require good insulation (liner) as they are exposed during much of the burn.
Thanks RJ! I appreciate the knowledge and can now understand grain geometry when assembling motors.
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