Month: August 2022

How to Build a DIY Model Rocket Launch Controller

Finished DIY model rocket launch controller with key switch, voltmeter, indicator LEDs and a red covered fire button
DIY Model Rocket Launcher

A DIY 3D Printed Rocket Launcher

After successfully launching a multitude of my 3D printed Bounty Towel rockets, my kids and I decided we needed a more badass rocket launcher than the bland and generic store bought mass manufactured versions. My biggest complaint with the generic store bought models is when you press the switch you get very little feedback on what is happening. This is especially concerning when the rocket doesn’t immediately launch. There is also ample opportunity for improvement in the aesthetics department on these devices.

This project was featured on Hackaday, in their coverage of the Philadelphia Maker Faire.

If we wanted an awesome rocket launcher we were going to have to print, build, wire, and assemble it ourselves!

Model Rocket Launcher Plans

The whole controller is one series loop: battery → inline 5 A fuse → key switch → arm toggle → momentary fire button → igniter clips, and back to the battery. The continuity LED sits across the fire button: with the key on and the system armed, a tiny (~20 mA) current sneaks through the LED and the igniter to prove the circuit is complete. Press the fire button and the full battery current bypasses the LED and lights the igniter. The voltmeter and power LED sit across the battery so you can see pack health at a glance.

Bill of Materials (BOM)

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Model rocket launch controller — DIY 3D printed rocket launcher cover
DIY 3D printed rocket launcher cover

Model rocket launch controller — DIY 3D Printed Rocket Launcher Cover
DIY 3D Printed Rocket Launcher Cover
Model rocket launch controller — DIY 3D Printed Rocket Launcher Cover with electronics mounted
DIY 3D Printed Rocket Launcher Cover with electronics mounted
Model rocket launch controller — Wiring up the DIY model rocket launcher
Wiring up the DIY model rocket launcher

DIY MODEL ROCKET LAUNCHER CONTROLLER WIRING DIAGRAM

Model rocket launch controller wiring diagram (rev B) with inline 5A fuse, key switch, arm toggle, continuity LED and momentary fire button

Updated August 2026 (rev B): the diagram now shows the inline 5 A mini-blade fuse and marks the three LEDs as 12 V panel-indicator modules. Two things the original diagram left implicit, made explicit: the LEDs in the parts list have built-in resistors — do not substitute bare LEDs (a bare LED in the continuity position would send ~10 A through the igniter the moment you turn the key), and the “1 Ω” element on the right is the igniter itself, not a resistor you buy. The continuity check passes a harmless ~20 mA through the igniter whenever the key is on — far below the no-fire current of standard Estes igniters (if you fly more sensitive e-match style igniters, unplug them until you are ready to arm).

Model rocket launch controller — A DIY Model Rocket Launcher
A DIY Model Rocket Launcher
Model rocket launcher in use

DIY Model Rocket Launcher Download Link

https://cults3d.com/en/creations/diy-model-rocket-launcher

3D Printed Rockets

For the second iteration of the bounty towel rocket I made the fins much bigger and I made the nose cone more aerodynamic looking. In an effort to get better flight telemetry we taped two nickels to the inner nose cone in order to get the center of pressure (CP) behind the center of gravity (CG). In our case two nickels was enough for a perfectly straight flight of our 3D printed rocket into the heavens.

Model Rocket Launch
3D Printed Rocket Fins
Comparison of the first and second generation prototypes

3D Printed Model Rockets

3D Printed Model Rocket Prototype 2

For the second iteration of the 3D printed Bounty paper towel rockets I’m now pushing the envelope when it comes to minimum wall thickness of the printed assembly to save weight and material as well as optimizing the print time. I cut down the size of the tapered piece for the nose cone and base that slide into the power towel roll ends. The diameter for the model engine is better but still too much of a tight interference fit for my liking. That will also require some more “dialing in”.

Black: Prototype-1, Red: Prototype-2
Bounty Paper Towel Roll Model Rocket

Next Iteration

The 3D printed rockets are not satisfactorily stable and have a tendency to flip ass over teacup in midair. After further research I have been most recently enlightened that we need to modify the design parameters such that the center of pressure (CP) is behind the center of gravity (CG) for suitable stability. A destabilizing force is created when the CP is above the CG. the next design is going to have much bigger fins and the nose cone will have internal threads to accept a 1/4 UNC bolt (and nuts if needed) to push the model rocket’s CG forward to obtain better stability.

3D Printed “Bounty Towel” Rockets

I always enjoyed building model rockets with my dad and sister as a kid but always found the construction process of cutting, sanding, aligning, and gluing the balsa wood fins to be tedious and take a lot of fun out of the process. Back then the hot glue gun fixed a number of model rocket fabrication shortcomings for me.

Paper Towel Roll Concept

For a good while now every time I see an empty paper towel roll I see a model rocket body. I’ve been mulling a concept in my head for some time now to design and 3D print a model rocket nose cone and model rocket fins that could attach seamlessly to a paper towel roll to serve as the model rocket body. We had some empty bounty paper towels in the house so this weekend we fired up the CAD and the 3D printer and gave it a shot. The final results came out better than I could have expected!

3D printed rocket base
3D printed model rocket nose cone
3D printed model rocket fins and engine mount
3D printed rocket made to fit in a used bounty paper towel roll
Model rocket engine
3D printed model rocket engine mount
3D printed model rocket Prototype-1 and Prototype-2
My son preparing the 3d printed model rocket for launch on our makeshift launch pad.

Verdict

It works! Our only problem was that we only had wimpy “A” rated model rocket engines on hand. Due to the weight of the assembly combined with the underpowered rocket engine the first two 3D. Printer paper towel roll prototypes went less than 100 feet into the air. Other than that everything worked splendidly.

Next Iteration

My goal for the next iteration is to take the design down to the minimum 3d printer wall thickness (the internet is telling me the minimum is about 1.5 to 0.8 mm for the absolute minimum) and see how well the structural integrity of the design holds up. That combined with some “C” rated model engines should add some serious kick to our rocket power of these 3D printed “bounty towel” rockets. This isn’t rocket science (or is it?)

Prusa MMU2S Build

I’ve been wanting to add multi color printing capability to my 3D printing repertoire and pulled the trigger on ordering a Prusa MMU2S. My son has increasingly become more interested in 3d printing and helped me execute the majority of the build. I was grateful for his help. The whole build took us two long (and I mean L-O-N-G) afternoons to complete the build.

Prusa MMU2S build

Prusa Mk3s+ upgrade

The website says you need to upgrade from the MK3S to the MK3S+ before performing the MMU2S upgrade. I didn’t mind the fact the MK3S to MK3S+ was only $49.99.