Conquered not only space, but international science

After the successful launch, the SMOG-P PocketQube satellite, developed by BME, has reached orbit and still operating perfectly. An interview with Viktor Józsa and Róbert Kovács, assistant professors of BME, Faculty of Mechanical Engineering, Department of Energy Engineering, who are lead mechanical engineers of the satellite project.

What was your role in the development of the SMOG-P PocketQube satellite?

Róbert Kovács (RK): The Faculty of Mechanical Engineering joined the project in the fields of structural design, thermal analyses, and other mechanical-vibrational investigations.

Viktor Józsa (VJ): The MaSat-1, the first Hungarian satellite, got to orbit in 2012 and had operated excellently until its return to Earth’s atmosphere in 2015. The most important function of small satellites is the ability to communicate. Thus, mostly electrical engineers, radio amateurs, smaller hobby groups, and university study groups build them. However, reliable operation also requires mechanical engineering knowledge. The 2.7 Kelvin (minus 270 ˚C) background temperature of space is the most important from thermal engineering point of view. Also, the rocket’s vibrations and the acceleration are important since the launching procedure exposes the satellite to the highest load which must be withstood. The role of vibrations and acceleration are highlighted because the majority of rockets are unmanned so they are not limited to 2-3 g. Instead, the payload is exposed to 10 g or even beyond to minimize the launch cost besides the hammer blow-like 100 g acceleration when the first stage is separated. Only then we get to the point to see if the spacecraft is still able to communicate or not.

Mostly electrical engineers designed the MaSat-1 satellite, and they concluded that mechanical engineering knowledge is inevitable for the next project. The PocketQube developer team was established at the beginning of 2014. The project leader of MaSat-1, András Gschwindt asked professor Gábor Stépán, the former dean of our faculty, if he can recommend experienced professors and students in mechanical engineering, especially in thermal engineering. I was a first-year PhD student at that time, and as a young and enthusiastic student, I was asked to solve and support the mechanical engineering-related tasks. Rocket companies ask for numerous data before the launch. For instance, shake and thermo-vacuum test results are requested, which ensures that the payload doesn’t fall apart, harm others or risk the main mission’s success.

The mechanical engineering tasks have been peaked at the beginning of the project when the framework was designed and the thermal calculations performed. These parts were critical input for the electrical engineers to progress with their tasks. In the design phase, mechanical tasks were so urgent that more mechanical engineering students were working on the project than electrical engineers.

RK: Also, education is an emphasized part of the project. Students wrote space exploration-related BSc and MSc theses, and Scientific Conference of Students (TDK) papers and they received credits for their tough work.

How long have you been working on the project?

VJ: We have been working on it for five and a half years, since March 2014. I was the team leader until mid-2016, when I had to focus on writing my PhD thesis. At that time, I have asked Róbert Kovács, my colleague, if he could take the lead. I still supported the project from the background, and after I got my PhD degree, we have shared the team leading role.

The longest process was not engineering-related at all

What kind of challenges did you face during the project?

RK: Regarding thermal issues, the greatest challenge was to ensure the appropriate thermal balance of the satellite. On the other hand, to estimate if the spacecraft would work within the proper temperature range in space, especially the long term operation of the electronic parts.

VJ: The battery requires the most care during design. Ensuring 0˚C temperature inside in the 0 K environment is quite a challenge, even more, in a 5x5x5 centimeter structure – almost 270 °C temperature difference has to be maintained.

It was also a tough part to find a contractor who would deliver the SMOG-P satellite to orbit. It was the longest part of the project, although this is not an engineering problem. Since most commercial satellites weigh a few hundred kilograms, it was extremely difficult to find a place for such a small one. The CubeSat class dominates the small-satellite industry nowadays, but its volume (10x10x10 cm) is eight times larger than that of the SMOG-P. The CubeSat size is so much wide-spread that the whole space industry set up for this size as the smallest payload. Smaller sizes are simply not worth the space companies due to the excessive administration.

Although the 5x5x5 cm PocketQube standard was removed from the internet during the development phase, several groups started working on this satellite class. Here, the CubeSat weight limit of 1,33 kg was loosened, and 250 g per unit was the maximum. Finally, the weight of SMOG-P was 183 g. Nevertheless, we would have been happily beefing up the satellite as it is beneficial for the overall thermal capacity, but we ran out of space.

Becoming space debris is another challenge. Inoperable satellites, but even if a nut when traveling at 8 km/s (28 800 km/h), crashes with any rocket or the International Space Station (ISS), fatal damage may result. The lower sensitivity limit of NORAD (North American Aerospace Defence Command) radar network, the organization monitoring space objects, is around 5 cm. This was the most probable reason for the designation of the current orbit to be on lower orbit than the ISS. Hence, a mission failure will not threaten any important spacecraft. Also, small satellites do not feature thrusters which would allow performing an anti-collision maneuver in need.

What is the mission goal of SMOG-P?

VJ: The main goal of SMOG-P is ensuring that the SMOG-1 would operate flawlessly. Such a small-sized, fully functional satellite like this one has never operated in space before. There were smaller ones, called leaf satellites, which operated only on a solar panel and featured a radio circuit but no battery. Hence, they were unable to operate in Earth’s shadow. This project was supported by radio amateurs, only for receiving their signal, with a designed lifespan of few days on a notably lower orbit than the SMOG-P.

RK: The mission goal of the SMOG-P is testing that our calculations were appropriate to guarantee the success of the SMOG-1’s mission.

The SMOG-P is presently at around a 360 km sun-synchronous orbit and continuously descending. The orbit lifetime also influenced by the space weather; according to current estimations, we can hear SMOG-P’s signal by April 2020.

Good team, outstanding results

What were the scientific results of this project?

RK: We published our thermal analyses in 2018, using various approaches that were read and cited by other satellite developer teams. Now it is internationally known that a Pocket Qube satellite was made at BME.

VJ: Researchers studying the thermal balance of the Alpha Magnetic Spectrometer of the ISS not only cited our studies but have decided to use certain modeling processes based on our paper.

Afterwards, a request has arrived from Springer Centre, UK, that as we could interpret our results clearly and in good quality to the international scientific community, they have asked us to write a book in thermal engineering. The book is already available online and in hardback; also, the National Technical Information Centre and Library at BME (OMIKK) lends it.

I would also like to highlight our team. Even at the beginning of the project, we have gathered a positive, constructive team, so we are glad that we could have worked together.

László Benesóczky

This interview was originally published at the English version of our faculty website.