The fuel can be made from a number of substances:
(http://science.nasa.gov/science-news/science-at-nasa/2003/28jan_envirorocket/): Pros: Cheap, readily available, easy to form
Disadvanages: Melts easily so could be problematic to ignite. Can melt and be spewed out the nozzle unburnt:http://myweb.tiscali.co.uk/aspirespace/wax%20hybrids.htm
Pros: Can buy set yourself urethane rubber.
Cons: Could be difficult to handle, potentially toxic when burnt.
Cheap, easy to cast into desired shape.
May melt or clog nozzle
Should be stored in freezer bags to avoid absorbing moisture.
Sorbitol and dextrose are preferred.
: Pros: Available and easy to shape to the required size. Easy to light, as burns on its own
Cons: Could fall apart when burnt
==== High density polyethylene: ==== Pros: Easy to machine (likely to be best to buy a rod, and machine to size( Fairly cheap and available. Clean burning, and popular in the hybrid rocket community.
Increase the specific impulse and burn rate. Generally powdered metals such as iron or aluminium. Carbon black could be used.