High altitude ballooning (HAB) is one of the most interesting activities available to technology-minded people. As technology gets cheaper with time, high altitude balloon missions start to be an emerging hobby for teenagers as well as retired engineers and scientists. The main idea behind the HAB projects is quite simple – to launch a balloon filled with helium carrying some useful payload into stratosphere. At some point, mostly well above 20 km, the balloon bursts because of low pressure. The payload, usually consisting of GPS module and some electronics safely returns back to the earth with the help of parachute. The keys to success of such a project are good design, implementation and integration of all critical components. Since HAB projects offer almost unlimited possibilities for research and incorporate interdisciplinary skills, we have decided to start our own HAB project from scratch.
In September 2012 we had a first meeting with students from Solski Center Srecka Kosovela Sezana. Students were divided into two groups. First group – named “Mechanics & physics” – was in charge of the parachute and payload enclosure design. Students of the first group had to perform numerical simulations related to aerodynamics and they were also responsible for the final construction of the system. At the beginning of the project they did a research on a set of super-insulating materials suitable for payload enclosure construction. Once the total weight of the payload was estimated they calculated the required parameters for the latex balloon and dimensions of the parachute. Finally they designed and constructed the enclosure for the payload and sewed the parachute. During design phase of the system special care was taken to ensure compliance with ICAO (International Civil Aviation Organization) guidelines for light unmanned aerial balloons.
Second group of students was named “Systems engineering” group. Their task was to build a suitable flight computer equipped with different types of sensors, positioning system and radio communication device. A lot of efforts were put into development of software applications for data acquisition and in software generation of modulation signal used for APRS (Automatic Packet Reporting System) radio communication. During the first half of the project duration the project members were devoted to the development and construction of an ARM-based embedded flight computer. They also had to learn some Linux and C/C++ software development skills. In the second part of the project duration the student were involved in development of data acquisition and radio communication software. Individuals from both groups took part in project promotion, web site maintenance and photography too. One of the important tasks the students from both groups were also involved in was attraction of sponsors to the project.
The flight computer built is equipped with a diverse set of environmental sensors like temperature, humidity, air pressure, linear and angular acceleration and magnetic field. Simple detector of spectral composition of visual light, UV radiation detector and X-ray radiation detector are also installed in the system. To obtain the exact position of the balloon during the flight a GPS module is used. System also includes a VHF radio module used for transmitting telemetry data from balloon to the earth.
Within a given timeframe (October 2012 – May 2013) we developed a high altitude balloon including all crucial components from scratch. In the following months we plan to conduct a series of additional tests to verify the reliability of the developed components and to fine-tune some of the software parameters. Our official application for balloon launch has also been submitted to the local CAA regulator and we expect its approval within two months.