Back in 2021, I developed an interest in aerospace, specifically rockets. Not being able to found my own space agency to fuel my passion (haha, get it?), I turned to water rockets! With their ease of development and being relatively safer than developing rocket fuel in one’s bedroom, I used my allowance and persuaded my parents to take me to the hardware store.
The result was a water rocket launcher made using PVC pipes cut and glued together, zip ties to act as the rocket hold-down mechanism and a locking-pliers based release mechanisms. Below is a version I made a year later but they worked the exact same way.
The actual launcher can be seen in the beginning of a video I posted on Instagram showing the progress of my water rockets!
The way it works is quite simple at the core. Ever noticed how when a balloon filled with air is let go with the end open, it goes flying away? Same thing with water rockets! You fill a soda bottle with pressurized air, in my case a bike pump, with some type of mechanism to hold the bottle down while filling it. Then when the rocket is “launched” or “let go”, the pressurized air has no where to escape other than the opening which is conveniently at the bottom. The escaping air propels the bottle the opposite direction which is hopefully up! If the bottle is filled with water (1/3rd of the volume is a good amount), there’s now much more mass being accelerated out the “nozzle”, so it’s pushed the opposite way even harder. Once you add some fins and a nosecone, your rocket is complete 🙂
Once I started testing the limits of my cycle pump and launching my water rockets higher and higher, a new problem emerged… I had no parachute. My rockets were literally glorified lawn darts. This was a problem, not just because my rockets were being destroyed by hitting the ground at terminal velocity, it was a potential threat to my surroundings.
That’s where my previous Arduino experience came in. Looking back at it now, 13 year old me was a bit dumb. My first prototype was REALLY janky. It was basically an Arduino Uno with a button, a 9V battery and a servo glued haphazardly into a 500ml Sprite bottle water rocket. I used to press the button in the rocket while it was set up on the launcher, run to my cycle pump while counting down from thirty in my head, pump air into the rocket like my life depended on it and then launch said rocket once my countdown reached zero. Then it would hopefully deploy the parachute upon apogee, saving the rocket from utter destruction.
As you can probably guess, my janky Arduino setup did eventually end up greeting the dirt at over 60 kmph. It did not survive 🙁
Learning from my prior experiences, I got to building a new water rocket. Using a 1.5L soda bottle this time, I had plenty of room to experiment with the parachute mechanism. My final design was a self-made flight computer sporting an Arduino Nano as the microcontroller with a BMP180 barometric sensor, an OLED display and a break-wire trigger. The barometric sensor read and recorded the highest altitude the rocket reached in-flight. The OLED display allowed me to easily review this info on the go. The trigger consisted of two wires twisted together with a string tied between the twist. This string was also attached to the launcher so that when the rocket launched, the string would end up pulling apart the twisted wires. This would be detected by the Arduino which would start a countdown and trigger a servo, ejecting the parachute out the side of the rocket at apogee! 😀
It worked perfectly on the first try! The string broke apart the wire connection and triggered a countdown which ejected the parachute cleanly at apogee, allowing the rocket to gently float down to the ground, as can be seen in the video posted on my Instagram.
And thus, we reach the end of my “functioning” water rocket journey. On 22nd November 2022, I launched my rocket with my prized flight computer for the last time. Upon launch, the parachute deployed prematurely. The high speed of the rocket led to the parachute inflating rapidly, leading to a sudden jolt in the string attaching it to the rocket and causing it to snap. I’ll never know how high the rocket went as the flight computer was destroyed beyond repair when it hit the ground at terminal velocity. I never got around to remaking such rockets afterwards as I realized how dangerous a parachute failure was as it could have struck someone. I was simply not willing to take such a reckless risk again.
And that’s it! I did experiment with a new water rocket launcher design later on using a 3D printer however it was never actually used to physically launch one as I had started working on radio controlled planes by then. Thanks for taking the time to read my experience of working on water rockets, and I hope it inspires you or someone you know as well.