They're housed in the HUGE orange external tank. The answer is found in the different molecular structures of the fuel types. Next time you're at a fireworks show start waxing lyrical about the chemistry of fireworks . Chemistry accounts for the differences in the beautiful and always pleasing colors you see. Well, chemists are molecular carpenters.
Atoms are to a chemist like nails are to a carpenter.
Furthermore, the different types of joints that join two or more pieces of wood are like the bonds which hold atoms together. Some are stronger than others. Take the superconductor molecular structure to the right.