The Earth exerts a gravitational force on all objects. A rocket must have a force greater than gravity to lift off. This force, acceleration, can be measured with a micro: bit in 3 different directions or as a combined force of all three. A rocket made from a two-liter soda bottle is made as a test vehicle to measure changes in acceleration as it lifts off and falls back to the earth.
This project will explore 2 different methods of data collection. The first uses a single micro:bit with MakeCode to record the data over a serial connection. The second uses the radio on the micro:bit in the nose cone to transmit the acceleration values back to another micro:bit connected to the computer to collect and record data using MakeCode.
1) For data collection we need to use the radio and MakeCode.
2) Program the micro:bits.
3) Insert micro:bit into the rocket
4) Launch the rocket
5) Report on the findings and observations in the experiments.
1) 2 micro:bits with batteries connected
2) A 2 liter bottle rocket with nosecone
3) A 2 liter pop bottle rocket launcher
4) A longer USB micro:bit cable
5) Spreadsheet for data analysis
After the rocket will fins will be build, we need to put the micro:bit inside the protective sealed wrapping, in order to prevent it from water. Then we need to place the micro:bit inside the nose cone.
Option 1: MakeCode and a USB connection
MakeCode allows data to be directly read from the micro:bit when it is attached using USB cable. Data can be sent from the micro:bit to the browser using a serial data connection. The data collected over the serial connection can be graphed and the data can be downloaded. The data can be downloaded as a data.csv file. This allows the collection of data in real time. This file can be opened in a spreadsheet for further analysis. Many different kinds of experiments can be performed using this data logging technique.
Option 2: Remote collecting unit sending to receiving unit over radio
Two micro:bits can be used to collect and record data using the radio commands. One micro:bit can be setup remotely and the other micro:bit can be used to observe the data. The first micro:bit can send the data it observes to the second micro:bit for the observer to record. Setup 2 micro:bits so they can communicate over the radio they need to be on the same radio group.
Use 2 micro:bits to collect the data on one and send it to another that is connected to MakeCode using a USB cable the experiment to collect and record data remotely. This allows the collection of acceleration data at a distance.
1) Sample Graphed data in MakeCode:
2) Download the data collected and observed using the purple download button. Sample data from the downloaded data.csv file:
3) Try graphing the data in different ways in the spreadsheet.
Using the Micro:bit on our rocket
In the graph above it shows the graph that was taken from the data collected from the rocket accelerating into the air. Along the “x” axis shows time and along the “y” it shows acceleration. We found that this method of measuring the acceleration would be perfect for our target market because it is easy to code but can be made more challenging by choosing which coding language to use. It also gives immediate and clear results as can be seen in the graph above so students can gather data about their rocket to improve it. This might mean that the rocket is not as aerodynamic as it could be, this could be down to the shape of the nose cone or even the shape of the fins can affect it. Another reason the rocket might not accelerate as well as they want could be that the rocket is not stable, so the centre of gravity would be closer to the nose cone than the centre of pressure. This unstable flight therefore causes turbulence to be formed behind the rocket in the separation region, the more turbulence the higher the Reynolds number meaning the more the flight path of the rocket will be affected. This is why if the rocket is stable, as the centre of pressure is close to the nose cone with the centre of gravity behind it. This will create a more laminar flow, lower Reynolds number, resulting in a faster and longer flight. However, as the graph above shows there is a flaw in using the Micro:bit to measure the acceleration because the accelerometer has a limit of measuring up to 8g which is why the straight lines have occurred. Despite this issue though, we would recommend our target market to use these to learn to code and also learn more about the aerodynamics of their rocket.