Water Rocket with Raspberry Pi – V1

We have started to learn about rockets. Not only theoretical learning, but also practical. We have build a type of rocket that can theoretically reach (based on current records) close to 1 km altitude. Clearly we will not reach that altitude, that is the record hold by very experienced builders, we are aiming to have tens of meters altitude.

The type of rocket we have build is called Water Rocket.

In short, this technology is based on a plastic bottle (coca cola or others) that can hold well high pressured air. A special nozzle is build to have a small opening that allows water to be pushed out at high speed. Fill the bottle with 1/3 water, with a bicycle pump fill the rest of the bottle with highly pressured air. When you release the water from the bottle through the nozzle, the water that is pushed out of the bottle pushes the bottle with the same force, thus gradually building higher speed.

This is an example how it works:

The parts needed for water rocket:

1. Bottle
2. Nozzle
3. Fins
4. Release mechanism
5. Head of rocket (holding parachute & flight computer)
6. Parachute
7. Flight Computer (hardware and software)

Most of the tutorials were taken from this website: http://www.aircommandrockets.com

We are not describing the entire process and parts in details in this article, the aircommandrockets.com has so great tutorials and we will provide links to tutorials.

The Bottle

Got Coca Cola 2.5 liters.

The Nozzle

Complete tutorials how to make nozzle here: http://www.aircommandrockets.com/construction.htm#Nozzle

The Fins

Created a 3D printed fin holder: https://www.tinkercad.com/things/ciDU5cki01k-perry-wing-holders

And we have cut some fins from a plastic box.

Release Mechanism

We have used gardena hose mechanism and nozzle like in this tutorial: http://www.aircommandrockets.com/construction_4.htm#Launcher

Head of Rocket

The first version (this article) we have built the nose from cut plastic bottle and just 3d printed a small cone.

Tutorial how to create the head: http://www.aircommandrockets.com/construction.htm#Nosecone

3D printed cone: https://www.tinkercad.com/things/3e0UlLhuJyB

Parachute

Made from old umbrella like in this tutorial: http://www.aircommandrockets.com/parachutes.htm

Flight Computer

This is the part we have designed our own Flight Computer using Raspberry Pi.

Flight Computer Hardware Parts

1. Raspberry Pi Zero (with wifi)
2. Li Ion battery (Lithium Ion Cylindrical Battery – 3.7v 2200mAh)
3. Battery charger: PowerBoost 500 Basic – 5V USB Boost @ 500mA from 1.8V+ and Adafruit Mini Lipo w/Mini-B USB Jack – USB LiIon/LiPoly charger – v1
4. Altitude sensor: BMP180 Barometric Pressure/Temperature/Altitude Sensor- 5V 
5. Accelerometer sensor: ADXL345 – Triple-Axis Accelerometer (+-2g/4g/8g/16g) w/ I2C/SPI
6. SG90 servo motor (low power)
7. Raspberry Pi Camera

Flight Computer Software

Full source code can be found here: https://github.com/smarcu/dnd-water-rocket-raspberry

How version 1 looked

Due to some software issues the parachute did not deploy properly and the nosecone was destroyed.

The issues were related to using the altimeter (pressure sensor) to detect the beginning of the descent. After several experiments we have discovered that the pressure sensor is not a good option since the air movement it affects dramatically the measurements.

In the next version we have used accelerometer to detect the max altitude.

Launches

You have to be careful where you launch these rockets. They are heavy (300-400g) and falling from high altitude can be very dangerous.

The launching of V1 failed due to several factors. One mentioned above was software. Another one was low pressure in the bottle was not enough to launch the rocket high enough.

Soon more details in the V2 of the rocket: improved nosecone fully 3D printed.