Solid fuel

@Toinkove thanks

As previously stated: it is simply identified as “solid” fuel (not by any chemical makeup).

@Toinkove Is it HTPB type?

@Toinkove booster

They are not identified as a particular type found in real world rocketry.
…….
There are a couple different types like “amateur” and (forgot what the other is called) as well as a few diffrent grain types like ramp up, ramp down, steady and basic.