NASA has successfully tested a paraffin-based fuel that could be used in the Space Shuttle's solid rocket boosters (SRBs). The fuel produces an environmentally friendlier exhaust of carbon dioxide and water instead of the usual aluminium oxide and hydrogen chloride-like pollutants.
A liquified oxidiser is gasified before being injected into the combustion chamber containing the solid fuel. Upon ignition, a flame develops over the fuel surface, causing the solid to evaporate, sustaining combustion.
Source: Flight International