3D Rocket Engine Contest

DIY Rockets has just released contest to design a 3D printable rocket engine.  There does not seem to be much guidance as far as what fuels and oxydizers to use.  But the goal is to make launch of nanosat payloads (10kg) into Low Earth Orbit.  In the future, printing these components in situ on an alien planet would prove useful.  No more, "uh-oh, rocket is broken, can't get back."  Well, not that simple, but it is interesting as 3D printing changes the manufacturability issues of complex shapes.  That frees up design possibilities which would have been throw out in the past for being economically infeasible to produce.