Most of the 3d printing is related to Cubesat satellites. They are small (10X10X10 cm) picosatellites that are launched as auxiliary cargo on regular big scale launches.
3d printing is used in design / development phase or for printing working satellites support structure.
There is a full scale model of ArduSat on Thingiverse: http://www.thingiverse.com/thing:27300
Naval Graduate School conducted crash tests and released a paper "Direct Manufacturing of CubeSat Using 3-D Digital Printer and Determination of Its Mechanical Properties" for DARPA. Check links for much more details and videos.
Cubesat design specifications:
http://www.cubesat.org/images/developers/cds_rev12.pdf
Thesis on feasibility of 3d printing Cubesat satellites:
http://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1851&context=theses
From the summary of study:
This study has found that a CubeSat can be developed to successfully incorporate the use of 3D printing manufacturing techniques into its design. This technology provides a potential cost savings of thousands of dollars, even for structures that would be simple to machine. Additional cost savings would be seen for very complex structures that would require advanced machining technology such as Electrical Discharge Machining to produce with aluminum. Using a Tyvak Nanosatellite Systems Intrepid system board at a cost of $3195 for the satellite avionics, it is conceivable that all the flight hardware for a CubeSat with a 3D printed structure could be procured for less than $5000. Not only do these materials provide the necessary strength to survive the rigorous testing and launch environments at a lower cost than machined aluminum, but they allow developers to be more creative with their satellites. Without any limitations from machinability, parts can be produced as they are imagined and new levels of optimization and functionality can be achieved. Further, extremely complex shapes, and even working mechanisms can be produced with 3D printing processes that cannot be manufactured with conventional machining. This allows designers create parts that require no post processing or assembly, streamlining the entire production process.
Students of Montana State University plan to launch their amateur radio satellite PrintSat with nano carbon impregnated plastic by using a 3D printer.
Looks like the future of space exploration is 3d printed. :-)
Let me know if there are some other interesting projects in this area.
Let me know if there are some other interesting projects in this area.


