I have tested hexamine with the alkali metal nitrates KNO3, NaNO3, LiNO3 and RbNO3 today. The combustion behavior of all these alkali metal nitrates is very similar. My theory is, that there is an endothermic reaction between hexamine and the alkali metal nitrate (caused by the heat of ignition flame), which converts the alkali metal nitrate into another salt before it could act as an oxidizer for the hexamine.
That's why experimental rocketry is so interesting. It leads you sometimes to unexpected results :) Let us see now, how we can use this knowledge.
