Fatboy

While the formula for Fatboy will not be released at this time, its operating principle can be discussed in great detail. Fatboy makes use of a significant portion of bismuth (III) oxide present in the propellant formula. While a less powerful oxidizer than ammonium perchlorate, it is over 450% denser. This will lead to the effective specific impulse of the rocket motor to take a hit, but since up to 25% more propellant will be present in an equivalent motor volume, the entire system can have up to 10% greater total impulse than an aluminized propellant. This fact leads to Fatboy finding use in space-constrained motor configurations. Additionally, due to the bismuth (III) oxide being a less powerful oxidant, the flame temperature of the propellant will be lower, which means more propellant can be loaded in lieu of insulation.

The development of the Fatboy propellant has been a complete rabbit hole. For the first several years of its development, it refused to combust well in smaller motors (N-class and below), leading to many different variants being tested. Spinoff propellants were also characterized, Cloud 9 being the leading variant, which used less bismuth and lower solids loading to achieve better combustion efficiency.

After around 25 formula variants being considered, we finally struck a chord with the propellant formula, which led to great combustion efficiencies in even L-class motors. Its characteristic blue-tinged flame with a billowing plume of orange smoke began to shine through, and its specific impulse reached a high of 205 seconds in these small configurations.

More testing is in Fatboy’s near future.

View a compilation of test fires here.