Building your CanSat
Under the supervision of their teacher/mentor, all the teams participating in CanSat will have to carry out technical work on their CanSats, applying the procedures used in the typical lifecycle of a real space project, which are:
- Selection of mission objectives;
- Definition of technical requirements necessary to achieve these objectives;
- Design of hardware and software;
- Reporting;
- Design of ground station/ground telecommunication system;
- Integration and testing of the CanSat before the national launch campaign
Basic Components
The CanSat casing design is a great way to add some artistic flare. However, all the amazing science is happening using the technology inside. Your CanSat design should show the sensors, electronics and communication hardware that you will use. There is a variety of Commercial Off-The-Shelf (COTS) hardware available, therefore, you should design your CanSat with your specific components in mind.
Using a microcontroller tends to be lighter and allow higher time resolution of data collection than a microprocessor. It requires a power source and an input to run. The most common microcontroller used is an Arduino. The microprocessor is an on-board computer, and unlike the microcontroller, only requires a power source to run. The most common and affordable microprocessor is the Raspberry Pi.
Pins on electrical components can be placed into the terminals on the board. Centrally, rows are connected. This means for example, that the two pins of a resistor should be placed in different rows, otherwise it will form a closed circuit with itself. It’s very important to make a sketch of your circuit before connecting and powering the circuit, because you will risk breaking the components. The outer columns of the board are connected in columns, rather than rows. Typically, these are used to provide ground and voltage connections to reduce the complexity of the setup.
When you assemble the final version of your CanSat you will need to use a typical solder breadboard.
Analogue sensors output a voltage which needs to be converted to a digital signal in order for data to be read. The Raspberry Pi requires an Analogue-to-Digital Converter (ADC) whereas the Arduino has one built in. The benefit of the analogue sensor is that it will continuously measure the variable
Single sensor boards use a digital communications protocol which connect to your microcontroller or microprocessor. The communication protocols can use I2C (2 wires) or SPI (3 wires). Make sure that your CanSat design reflects the correct number of wires depending on the protocol you have chosen.
Important considerations when choosing a sensor:
- Sensitivity: what is the minimum change that can be measured by the sensor?
- Response time: how quickly does the sensor respond to a changing environment?
- Linearity: is the response linear (over the range required for measurements)?
- Range: what is the min/max value that can be measured by the sensor?
- Hysteresis: does the sensor have the same output for the same ambient conditions?
There are a few considerations you need to make when deciding how you will power your CanSat:
- What voltage do you need to supply?
- What battery capacity do you need (mAh)?
- How big (physically) can the battery be?
- How heavy can the battery be?
The UBEC is a device used to provide the correct voltage to your board. It is most commonly used for microprocessors such as the Raspberry Pi which requires 5V, therefore you can use a 9V battery, and through the UBEC, are able to power the Raspberry Pi. Microcontrollers
such as the Arduino are able to use the input jack to connect your 9V power supply. It is also possible to use the GPIO pins to connect your power supply.
A power bank, such as a portable mobile phone charger, is also a suitable option. They come in all shapes and sizes, and with varying battery capacity. Some also have ‘smart’ electronics that do not provide power if the power being used by the device is low. Whilst this could be a useful energy saving feature you will have to investigate what the electronics deem to be ‘low’ and if this is suitable for your CanSat.
The information that the CanSat collects must be sent to a ground station. To be able to do this, we need to take a look at the components we can use to communicate and how electronics communicate.
Wireless transceivers are used to relay information between a CanSat and ground station. They work in pairs, in a similar way to how you might have used walkie-talkies when you were younger (or now!). 
Both the CanSat and ground station are fitted with an antenna. The CanSat antenna transmits information and the ground station antenna receives it. In order to avoid disturbance and interference each team in a competition is given their own frequency. Actually, the word transceiver is a composition of two words – transmit and receive, exactly what the transceiver can do.
When it comes to choosing a transceiver perhaps the most important criteria are the operating frequencies, the power required and the physical size of the transceivers. Of course, you have to also consider the cost of the transceivers. Designing a project often involves some degree of compromise. The perfect components for each job are not necessarily compatible, for one reason or another.
One of the most common choices is the APC220. It is capable of communicating over a distance of 1000m and operates between 418MHz and 455MHz. A popular alternative is a LoRa module (like the RFM95). They generally offer an increased range, up to 2000m, but operate at discrete frequencies rather than over a range like the APC220.
Parachutes are a vital part of any CanSat mission. It could be forgiven that they are often overlooked, given that they are often simple pieces of fabric compared to the complex electronics that lies within the CanSat, but that would be a big mistake! Without a well-designed parachute your CanSat might not have time to complete its scientific objectives, or worse yet, it could crash land!
The deployment of the parachute will be relatively violent, so the fabric and fibres you use need to be strong. Take into account that the force that the parachute experiences (and also the payload at which it is attached) can be as high as twice the force acting during the terminal velocity!
The simplest types of parachutes are the flat circular sheet and the spherical parachutes. The problem with these designs is that they fill up with air and tilt to one side to spill out air. Sometimes a spill-hole can help to stabilise a parachute.
Once you’ve decided on a design for your parachute it is vital that you test it. Whilst the equations can give you an idea of what to expect you should always
test your designs in the real world. With successive tests you can refine your parachute design. Investigate the effects of every aspect of your parachute, this should include:
- The material used
- How it is attached to the CanSat
- The area of the parachute
- The way the parachute is folded
How to build a cansat?
Supporting materials such as classroom resources and educational videos can be accessed through the link below.
CanSat Requirements
The CanSat hardware and mission must be designed following these requirements and constraints:
These may differ per national competition. Make sure to check the complete list of requirements with your National Organiser.
All the components of the CanSat must fit inside a standard soft drinks can (115 mm height and 66 mm diameter), with the exception of the parachute. Radio antennas and GPS antennas can be mounted externally on the top or bottom of the can, depending on the design, but not on the on the sides.
Note: The rocket payload area usually has 4.5 cm of space per CanSat available, along the can’s axial dimension (i.e. height), which must accommodate all external elements including: parachute, parachute attachment hardware, and any antennas.
The antennas, transducers and other elements of the CanSat cannot extend beyond the can’s diameter until it has left the launch vehicle.
The mass of the CanSat must be between a minimum of 300 grams and a maximum of 350 grams. CanSats that are lighter must take additional ballast with them to reach the 300 grams minimum mass limit required.
Explosives, detonators, pyrotechnics, and inflammable or dangerous materials are strictly forbidden. All materials used must be safe for the personnel, the equipment, and the environment. In case of doubt by ESA, Material Safety Data Sheets (MSDS) may be requested from the teams.
The CanSat must be powered by a battery and/or solar panels. It must be possible for the systems to remain switched on for four continuous hours.
The battery must be easily accessible in case it has to be replaced/recharged.
The CanSat must have an easily accessible master power switch.
Inclusion of a positioning system for retrieval (beeper, radio beacon, GPS, etc.) is recommended.
The CanSat should have a recovery system, such as a parachute, capable of being reused after launch. It is recommended to use bright coloured fabric, which will facilitate recovery of the CanSat after landing.
The parachute connection must be able to withstand up to 50 N of force. The strength of the parachute must be tested to ensure that the system will operate nominally.
For recovery reasons, a maximum flight time of 120 seconds is recommended. If attempting a directed landing, then a maximum of 170 seconds flight time is recommended.
A descent rate between 8 and 11 m/s is recommended for recovery reasons. However, the CanSat’s descent speed must not be lower than 5 m/s or higher than 12 m/s for safety reasons. Additionally, the airfield or weather conditions might determine additional mandatory restrictions on the velocity.
The CanSat must be able to withstand an acceleration of up to 20 g.
The total budget of the final CanSat model should not exceed 500€. Ground Stations (GS) and any related non-flying item will not be considered in the budget. More information regarding the penalties in case the teams exceed the stated budget can be found in the next section. In the case of sponsorship, all sponsored items should be specified in the budget with the actual corresponding costs on the market.
The assigned frequency must be respected by all teams in the Launch Campaign. The range of allowed frequencies changes depending on the country where the event is hosted and will be communicated in due time. It is recommended that teams pay attention to the design of the CanSat in terms of hardware integration and interconnection, so the radio frequency can be easily modified if necessary.
The CanSat must be flight-ready upon arrival at the launch campaign.
