Small Satellite

Competition

It was a local CanSat competition which held by Space Agency of the Republic of Azerbaijan - Azercosmos. The task was to build small can shaped satellite which afterwards would be thrown from 200±20 meters height with the help of rocket.

Rules

The satellite must be cylindric shaped with the dimensions of: 90mm diameter, 300mm height and with the weight of 500mg±10. Satellite must send telemetry with the help of XBee RF module from the beginning till the end and should record a video after ejection from rocket. Also, when it ejects from the rocket, satellite should sense it and start video recording.

Telemetry: <Team ID>, <Working Time>, <Telemetry Packet Number>, <Battery Voltage>, <Height>, <Speed>, <Longitude>, <Latitude>, <Ejection Time from Rocket>, <Duration of Video Recording>

When satellite touches the ground, it should stabilize itself with the help of legs in the first 1 minute and continue recording while ensuring 50/50 ratio of ground and sky in the video. The main challenge in designing was stabilization and keeping 50/50 ration in the video record. For the overweight problems, we decided to make the ration challenge with the software by twisting video.

Our Mission

Before putting our satellite into rocket, from ground station command sent to take reference point for measuring height and velocity and start sending telemetry.

3D Design

I designed whole body in a way that, it would be easy to work on and add part onto it while also easily accessible afterwards. 3 parts are, main body, electronics house and parachute house.

The holes in the main body are added after printing with the help of soldering iron for reducing weight. Hole in the middle (black arrow) is used to store the battery tight and safe while flight and landing. Rectangular shapes below (green arrow) is used to put the legs for stabilization later. Hole near the middle (blue circle) is used to pull through cables from main body to electronics part. The 2 holes which are parallel each other both sides are used to connect main body to electronics part with nuts and bolts.

Parachute house added onto electronics part with the help of hot glue after measuring parachute dimensions. Parachute had 4 strings which are connected to the electronics house where I added 4 hook (red arrow) for it. You can find link on proper folding technique for parachute here.

Before I created different body for parachute housing but later for the weight problems I recreated it with just cardboard and syringe.

Electronics

I split the work flow into 2 parts, independent part, where all the telemetry/data would be gathered and sent to the ground station and dependent part where only video recording would happen.

For the independent part, I used Arduino Mega 2560 (we had this one on hand) for communication and data gathering. For communication we used 2 XBee S2C RF module with on built antenna on it directed upwards on both sides (satellite and ground station). We programmed them with their program called XCTU for Point2Point connection. You can find instruction video link here.

For the video recording, we just used separate microcontroller ESP32 AI Thinker module. With the help of on build SD card slot and camera it was easy to use and code it. We connected its communication pins (RX, TX) to Arduino communication pins (TX, RX).

In order to detect the moment of ejection from rocket, we used LDR sensor. Inside of the rocket is dark, but ejection time through the sunlight it sense light and confirms its ejection and sends ESP32 command to start video recording.

Stabilization

For legs, I just glued sticks to the end of the motors, which I also glued to the satellite. With the help of altitude, satellite detects landing and stabilizes itself with the legs.

Coding and Testing

When we got our sensors, first we individually tested them. After all testing we assembled all of them together. The Gyroscope should be placed on the flat surface of satellite (blue arrow) and GPS antenna should be open to sky (black arrow). you can place other components as you want. Also, you first need to code RTC module for the current time in order to get real time during the flight.

Before the flight day, we tested our parachute with the 500ml bottle throwing out of 4th floor.

Flight day

In flight day everything went successful except the atmospheric sensor and stabilization. Since there some problems occurred the atmospheric sensor, we couldn't measure height and velocity of satellite and which also affected stabilization of satellite (it knows from the height that when to hit ground).

You can find the flight video in the link below:

Winner

Even though we didn't manage to successfully complete all tasks, we still won the 1st place in the competition! (other teams also had some problems)