The original Stanford Systems – http://ssaerospace.com – offered a DIY rocket motor kit that allowed you to build HPR-class rocket motors out of commonly available materials using some thermodynamic wizardry. We are selling this kit again soon.
The kit includes: manual/software, R45 resin, PAPI hardener, 3 casting fixtures, 4 motor casing kits, durham’s water putty, nozzle casting fixture, inert propellant simulant. Unlike the original kit, it uses a composite propellant rather than “candy” (KNO3/Sucrose) propellant. Also it doesn’t ship with actual chemicals but gypsum-based powder that allows you to practice rocket motor construction in complete safety. Of course, the downside is that the motors cannot be immediately used for propelling an AM/EX or HPR rocket.
Price is $79 USD plus S/H (email us for a quote on how much it will cost to ship it to you). We are planning in a few months to offer the same kind of kit for “candy” propellant (KNO3/Sucrose) for $89 USD+ S/H (it includes the special aluminium melting pot to cast the grains).