That brings us to this build. My son told me at the time that he learned we were going to get a printer for our house that he wanted to print and launch a rocket. This coming from a 6 year old, I was intrigued and asked him to draw up some plans for it. I told him to draw things such as what the fins should look like, what kind of nose cone styling, and how many fins it would have. With drawing in hand we set out to design it in Tinkercad.
I should mention that he received some rockets for his 6th birthday, but beyond that we are not rocketeers and certainly not rocket scientists. However we are not ones to be deterred with such minor details, so we forged on.
Step 1: Designing Our Rocket
Here are some pictures of the design in Tinkercad; including one picture with all the parts shown in a complete rocket. That is the nice thing about CAD programs in that you can fit all the parts together and make sure that everything is scaled and fitting properly before sending it to the printer.
We used Tinkercad for this and all of our designs, but there are a number of programs at your disposal for designing 3D projects. Many of them have free versions. Tinkercad just happens to be the one that I am most familiar with.
Precautionary note: Whether you build a rocket similar to ours or one of your own design please exercise caution. The power of these rockets needs to be respected. Any rocket should to be well built, properly balanced, launched in a safe manner and in a safe location.
Step 2: Printing and Gluing
We decided that our rocket should have a red, white and blue color pattern. It needed to be printed in pieces and glued together as our build volume is not high enough to print the body tube in one piece. We made the parachute out of a gallon size zip lock bag which we cut into a 10 inch circle and attached 8 strings equally around the perimeter. The strings are attached to the parachute with both 5 minute epoxy and scotch tape. We then attached it to the inside of top tube with kite string and 5 minute epoxy. The nose cone got a kite string tether and was glued inside the top tube as well.
I am sure that the rocket engine we are using fits tight enough into the tube so as not to dislodge, but I decided to lock the engine to the bottom tube with a paper clip to ensure that it does not come out at the time that the flight ends and the parachute gets blasted out the top. We used a design for the engine lock found on another Instructable and bent a paper clip and glued it to the body.
Note: You might also have noticed that the fins seen in the picture of them printing were thicker than desired so we printed some thinner ones for use on the rocket.
Step 3: Balancing and Final Prep for Launch
We learned from a friend, who loved rockets as a child, that the balance point of the rocket should be near or slightly leading the volume (center of Pressure) of the rocket. Since we will be launching this in a public park we attempted to get this as close as we could to “balanced”.
For the Center of Pressure we assume that because a model rocket is fairly symmetrical that we can simply draw a two dimensional drawing of the rocket. We then traced that drawing onto poster-board and hung the cut out from a string to determine the balance point. The balance point of this cardboard cutout is representative of the center of pressure on our rocket. We were told how to do this by our friend, but you too can look up what NASA has to say about it here: http://exploration.grc.nasa.gov/education/rocket/r...
It was easy to determine Center of Gravity for our rocket. We simply used a string to find the point on the rocket that it balances out. (Another way of thinking of Center of Gravity is "balance point".) We of course did this with the engine in place and the parachute and wadding loaded as if ready to launch.
Unfortunately our CG was way behind our CP which is not a good thing. So we printed another collar to add weight right below the cone. We also drilled out the cone and added some lead from fishing sinkers that were cut into pieces and then glued into the center of the nose cone.
Our friend told us that the further apart CG (center of Gravity) and CP (center of Pressure) are the better the flight. With CG always ahead of CP. These numbers do have to be within reason though. We know that if the CG and CP end up in the same location or reversed, DUCK. Remember we are making our maiden launch in a public area so we do not wish to error if we can help it.
The last photo shows our CP vs CG after above adjustments. Our adjustments where successful and we feel much more comfortable about the success of the launch.
Step 4: Launching the Rocket
I did capture a poor video of the maiden launch. It is not a good video in that I was too focused on the launch and the flight path so I completely forgot to follow the rockets path with the camera. My Daughter's video of the flight mirrored mine. My now cut video is at the bottom of the introduction section and my Daughter's uncut video is found below in this Step.
For the record it flew very straight and well. We did however learn more after retrieving the rocket. It did fly almost straight up and fell nearly straight down. In fact the rocket landed less than 20 feet from the launch pad. The good thing is that the rocket is definitely reusable with a new nose cone and a few minor repairs.
What we learned: Apparently we did not use enough wadding to protect our parachute. Either that or our strings were too flammable to survive the ejection blast. We did lose our nose cone completely and the parachute also separated from the rocket and landed near the rocket body after suffering some burns.
Changes for next time: The next rocket we build will have better strings, a longer body, and we will use more wadding to protect it. I also plan to attach the parachute to the nose cone and add a longer and stouter tether to the nose cone so that it has more time to absorb the shock from ejection.
Step 5: In Conclusion
We found this to be a very fun project and it shows that with a little imagination and science you can do anything you want with your 3D printer. What a fun and amazing pastime 3D printing is. We hope to share more adventures in the future.
Thank you for reading about our project. We always welcome any and all comments and questions.
Step 6: Update: Version II
We made the changes to the rocket that we suggested above and launched Version II with success.
Changes that we made compared to version I:
We changed the shock cord for the nose cone from a string to a rubber band and gave it longer length. The rubber band that we used is commonly referred to as a file rubber band, and can be found at office supply stores.
We attached the parachute to the nose cone instead of attaching it to the top tube as we did in Version I.
We added another segment to the body tube. So Version II is three segments long versus two segments in Version I. With this change in length Version II did not require additional weight to the nose cone like Version I did in order to balance CP and CG.
Both versions flew straight, but the parachute deployed and worked properly on Version II.