How I Built a Rocket with a Flight Computer
A few months ago, I came across a video of first stage landing from the Falcon Heavy rocket…
and I thought, THIS IS INSANE!
Full reusable rockets have never existed before much less reusable rockets that have autonomous landings such as SpaceX’s Falcon 9 and Falcon Heavy.
The Space Shuttle Program was supposed to be entirely reusable except… after one launch, the external fuel tanks were basically hollow pieces of metal and were rarely reused. The space shuttle had to undergo so much renovation that the cost was almost as high as building a new shuttle. That is to say, SpaceX’s Falcon 9 and Falcon Heavy are revolutionary!
This gave me an idea…let’s build a flight computer.
A Look into Rocket Flight Computers (Falcon 9/Falcon Heavy)
Flight computers onboard the Falcon 9/Falcon Heavy are extensive and incredibly complex for a model rocket but let’s break down some key ideas.
All rockets will include processors that allow the space segment (rocket) to communicate with the ground segment (mission control). They will also use sensors and cameras to run their coordinates and ensure both the coordinates from the space segment and ground segment match. Another component of the flight computer is to control the thrust-vector mount, or the orientation of the rocket engine to change its direction.
Let’s take a closer took into how SpaceX does this. Their rockets include Global Positioning System (GPS) receivers to verify coordinates and ensure the rocket in the right space at the right time, inertial measurement units (angular velocity, orientation), specific controllers to control propulsion, valve flow, pressurization, separation and payload interfaces, S-band transmitter (allows data to reach ground controls) and a C-band transponder for range safety tracking. SpaceX rockets also have an autonomous flight termination system to limit vehicle damage during a malfunction. This system terminates the flight if coordinates are looking off or if mission rules are violated.
The Inertial Measurement Unit often contains:
- Gyroscope (measures angular velocity and orientation, important to know when going into orbit because angle and orientation is a large factor)
- Accelerometer (measure acceleration, going to different levels of orbit requires a different velocity, therefore, knowing the acceleration is important)
- Temperature (allows engineers to know if parts/heat shield are staying together. If it is manned-mission, it is important to maintain temperature for their survival)
- Barometer (pressure and height sensor, tells engineers where the rocket is in terms of height)
Flight Computer for Model Rocket
There are some great examples of rocketeers who have built extensive versions of the Falcon 9/ Falcon Heavy rockets. One of which is BPS Space
The flight computer I built is not as extensive as that of the Falcon 9 or Falcon Heavy but includes a few key elements:
- Communication with the ground segment via Bluetooth chip
- Gyroscope
- Accelerometer
- Temperature
Choosing a Flight Computer
There are a wide range of affordable processors one can use for model rockets. Here are a few:
- Raspberry pi (3 b+, zero w, 4)
- Beaglebone
- Arduino (nano, uno, 8266)
- Teensy 3.2
- Nucleo
I chose the raspberry pi zero w because it has wireless wifi, a bluetooth chip, enough processing power and it was affordable. (~$12 CAD)
Raspberry Pi (RP) Headless Setup (Mac)
- After getting the raspberry pi, one will need a microSD card to download the software and be able to enter data into it.
- Follow this video
Soldering
Some boards come with GPIO (General Purpose Input/Output) pins already soldered and sometimes if you buy a raspberry pi in a kit, GPIO pins are pre-soldered. If you only buy the raspberry pi, however, you are also going to need GPIO pins which you need to solder on the board.
Materials:
- Solder iron (melts metal onto the pins to form a connection)
- Solder wire ( the metal that needs to be melted)
- Solder wick (to clean up mistakes) — thought I didn’t need this but boy was I wrong😅
Soldering is a pretty simple concept, just be careful as the solder iron can reach temperatures up to 400 degrees celsius.
In addition to soldering, you need jumper cables to attach the raspberry pi to the gyroscope. Here is the schematic of how to attach the two:
Depending on which GPIO pins you purchased, you need different jumper cables. There are female-to-female, male-to-male and female-to-male.
MPU6050 — Sensor
I purchased this sensor module on Amazon. It contains a gyroscope, accelerometer and temperature sensor in one.
Follow this video for further instructions: https://www.youtube.com/watch?v=JTFa5l7zAA4
