The SRBs use solid fuel instead of liquid or gas. This is because solid fuel burns more quickly. It also gives off more energy per kilogram than liquid fuel. The fuel used in the SRBs is powdered ammonia. It is combined with an oxidizer and a binder to hold it all together. If you were to touch the solid fuel, you would find that it feels much like a pencil eraser.

The good thing about solid fuel is that it packs a lot of power. The drawback is that once it starts burning, it keeps burning until it has all disappeared. It canÕt be turned off or controlled. The SRB has been specially designed to deal with this problem.