With a little programming know-how, you can use this project to define your own model rocket, and print it. Depending on your printer and how you print your rocket parts, you can print a complete rocket in under two hours. All you have to do is is snap it together, add an engine, and off you go.

You can find out more information from the rockit wiki. You can also check out the instructables write up here.

Rockit provides a framework to rapidly generate 3D models of workable model rockets. It leverages OpenSCAD to render rocket part specifications to three dimensional models. This allows you the ability to configure and generate individual model rocket parts suitable for manufacturing on a wide range of 3D printing platforms. With carefully configured parameters, you can design, print and fly your rocket in under two hours. Rockit parses JSON rocket configuration files and writes out to a variety of formats including .json, .scad, .stl, .dxg, .png. It ships with a variety of default templates based on different engine sizes, but these will require local tuning for proper operation.

You can find out more information from the rockit wiki. You can also check out the instructables write up here.