NASA have put a 3d printed exhaust port on a rocket engine and test fired it successfully. - http://www.nasa.gov/exploration/systems/sls/j2x/3d_print.html#.UvU0

NASA have put a 3d printed exhaust port on a rocket engine and test fired it successfully. - http://www.nasa.gov/exploration/systems/sls/j2x/3d_print.html#.UvU0hF4fOWM http://www.nasa.gov/exploration/systems/sls/j2x/3d_print.htm... Besides, as long as you know what you are doing it is just another material to select from and you just calculate critical dimensions based on measured properties.