In the summer of 2014, we found a Thingiverse design for a 3D-printable model rocket. Immediately interested, we downloaded and printed a set of parts for two rockets: one with a rounded nosecone and straight fins, and another with a more conical nose and curved fins to impart a bit of spin. After a series of delays and false starts, we were able to launch with an acceptable level of success this fall. Here’s how it worked.
Printing the rocket bodies was just the first part. Over the next few months, needed parts and accessories were slowly acquired, as various other projects took priority. Assemblies were tested, and a couple of parts reprinted.
We found and built a printable launch pad, outfitted with a brass rod to keep the rocket from going sideways during the initial launch. To protect the plastic from the heat of the size D engines, we covered it with thin aluminum.
This would later prove a poor choice.
We decided to build a launch key ourselves. A naked circuit was created and proven to work. However, we never got around to putting the circuit into a box that would constitute the actual launch key.
By early October of this year, we decided the launch key would never get built by us, so we ordered one online. It arrived, and we loaded the rocket up with protective wadding, shock cords and parachutes.
On Monday, October 19 we drove down to the Davidson College golf course and set up the launcher in a sand trap.
Our first launch was…mostly successful. The straight-finned rocket went up, but heeled over sharply to the northwest, and came down in several pieces a few hundred feet away. The rocket separated properly, but the shock cord wasn’t attached securely enough, resulting in a small debris field of parts. The ejection charge also caused significant damage to the two center tubes, delaminating the plastic shells and distorting the shock cord anchors. However, the terminal velocity of the rocket body was so low that it did not get damaged any further by the fall.
Also, we found that the heat of the engine blast was enough to melt a hole in the pad’s aluminum shield. Steel next time.
The second launch, using a base module with curved fins to impart a spin to the flying projectile, was a big step up. The rocket went straight up, ejected the chute, and came down just a few yards away (in pieces again, for the same reason). Again, there was also internal burn damage to the center tubes, but otherwise the parts survived nicely. See for yourself!
We’ll reprint the damaged components, add a steel cover to the launch pad, find a way to better secure the shock cord, and have another go. Also, we may try adding LEDs to allow a nighttime launch. Why not make your own and try for yourself?