Technic Panel Rocket
This LEGO Technic Panel rocket flies ~400 feet high on Estes D12-3 engines. For the Shock Cord, use a Lego bb298c82 elastic cord from the Lego Technic Bungee Blaster/Bungee Chopper sets, or get some from your local fabric store. The Estes engine fits nicely inside the lower body (four yellow 11954 Technic Panels) with two wraps of masking tape. Be sure to use flameproof wadding above the engine so that your parachute or streamer does not melt in the ejection charge.