Satellite Powered by 48 AA Batteries and a $20 Microprocessor Shows Cheap Way to Reduce Space Waste

SBUDNIC, a bread-sized cube satellite with a drag sail made of Kapton polyimide film designed and built by students at Brown, was launched into space last May on a SpaceX rocket. Credit: Marco Cross

Common sense suggests that space missions can only happen with multi-million dollar budgets, materials built to withstand the unforgiving conditions outside the Earth’s atmosphere, and as a result of work done by highly trained specialists.

But a team of engineering students from Brown University has turned that assumption on its head.

They built a satellite on a tight budget and used off-the-shelf items available at most hardware stores. They even launched the satellite — which is powered by 48 Energizer AA batteries and a $20 microprocessor popular with robotics hobbyists — into space about 10 months ago, where they got a ride on Elon Musk’s SpaceX rocket.

Now, a new analysis of Air Force Space Command data shows that the satellite not only operated successfully, but could have far-reaching effects on efforts to cut down on the growing problem of space debris, which poses a potential danger to all present and future spacecraft.

According to NASA, there are now more than 27,000 pieces of what it calls orbital debris, or space debris, being tracked by the Department of Defense’s Global Space Surveillance Network. Orbital debris ranges from any man-made object in Earth’s orbit that no longer serves a useful function, such as non-functional spacecraft, abandoned launch vehicles, mission-related debris, and fragmentation debris. It also includes defunct satellites that remain in orbit sometimes decades after their mission is completed.

That’s a problem given that most satellites stay in orbit for an average of 25 years or more, said Rick Fleeter, an adjunct associate professor of engineering at Brown. So when his students were given a unique chance to design and build their own satellite to be launched into space, they decided to develop a potential solution.

The students added a 3D-printed drag sail made of Kapton polyimide film to the bread-sized cube satellite they built. When deployed at about 520 kilometers — well above the International Space Station’s orbit — the sail popped up like an umbrella and helps push the satellite back to Earth faster, according to initial data. In fact, the satellite is well below the other small devices that were installed with it. At the beginning of March, for example, the satellite was about 470 kilometers above Earth, while the other objects were still in orbit about 500 kilometers or more.

The graph shows how much lower SBUDNIC’s circuit, represented by the thick blue line, is compared to other units installed with it from late May 2022 to early March 2023. Credit: Brown University

“You can see in the tracking data that we are visibly below everyone else and accelerating away from them,” Fleeter said. “You can see that our satellite is already descending towards re-entry, while the others are still in a nice circular orbit higher up.”

The data suggests the student satellite, called SBUDNIC, will be out of orbit within five years, compared to the estimated 25 to 27 years the students calculated for it without the thruster.

Fleeter and the Brown students believe their initial analysis of the publicly available tracking data serves as evidence that this type of sail could be part of an effort to reduce the amount of space debris in Earth orbit. They hope that similar sails can be added to other units of the same size or scaled up for larger projects in the future.

“The theory and physics of how this works has been pretty well accepted,” Fleeter said. “What this mission showed was more about how you realize that — how you build a mechanism that does that and how you do it so it’s light, small and affordable.”

The project is the result of a collaboration between researchers at Brown’s School of Engineering and the National Research Council of Italy. It is also supported by D-Orbit, AMSAT-Italy, La Sapienza University of Rome and the NASA Rhode Island Space Grant. The name of the satellite is a play on Sputnik, the first satellite to orbit the Earth, and is also an acronym for the project participants.

This is the second small satellite designed and built by Brown students to be sent into orbit in recent years. The previous satellite, EQUiSat, made 14,000 loops around Earth before ending its mission and burning up as it re-entered the atmosphere in late 2020.

However, SBUDNIC is believed to be the first of its kind to be sent into orbit made almost entirely of materials not designed for use in space and at such an astronomically low cost compared to other objects in orbit. The total cost of the student-designed cube satellite was about $10,000.

“The big complex space missions we hear about in the news are amazing and inspiring, but they also send a message that space is only for these kinds of specialized initiatives,” Fleeter said. “Here we are opening that opportunity to more people… We are not breaking down all the barriers, but you have to start somewhere.”

The Kapton polyimide tug attached to the SBUDNIC satellite helps push the satellite back to Earth faster. Credit: Marco Cross

Developed by students at Brown

The satellite was designed and built in a year by a group of about 40 students — about half from Brown’s School of Engineering with others from fields as diverse as economics, international relations and sculpture. It started in the course ENGN 1760: Design of Space Systems, which Fleeter taught in spring 2021.

Italian space company D-Orbit approached with an opening for a satellite on the SpaceX Falcon 9 rocket that would be launched in a year. Fleeter approached his students, who had just listened to their first seminars on space systems design, and gave them the opportunity.

From there the race was on.

The students began by conceptualizing and designing the satellite’s individual subsystems, often in collaboration with industry advisors, who provided feedback and technical guidance on the feasibility of their proposals. Students then put their plans into action, managing the technical aspects of the satellite along with coordinating the administrative parts. The constant prototyping, testing and improvement required was a huge effort on the part of the students in terms of hours and brain power.

“The Brown Design Workshop is very quiet at 4 in the morning, and I’ve been there during that time more times than I can count,” said Marco Cross, who graduated from Brown last year with a master’s degree in biomedical engineering and worked as boss. engineer for SBUDNIC.

Students purchased materials they needed from local stores and online retail websites. They often had to create clever solutions for their materials so that they could survive in space. The approach often meant coming up with test devices that replicated specific environmental conditions in space, like the high vibration of rocket launch, Cross said. For example, the team used reptile heat lamps in a vacuum chamber to test the thermal shield they created to protect the satellite’s electronics from the sun.

To be approved for launch, the satellite had to pass qualification tests and meet strict rules and regulations that SpaceX and NASA follow. “It’s a zero-fault-tolerated environment,” Cross said. “The team never wavered.”

Students working at SBUDNIC did the bulk of their building in the Brown Design Workshop. Credit: Marco Cross

The students were given the green light after a series of vacuum, thermal and vibration tests. A group then traveled to Cape Canaveral, Florida, to deliver the SBUDNIC so it could be inserted into D-Orbit’s larger carrier satellite, which was then put on the SpaceX rocket.

The students said the project helped them think of themselves as creators and innovators, and that the experience ingrained lessons they will use far into the future.

“I went on to use what I learned in this program to intern at Lockheed Martin Space,” said Selia Jindal, a senior at Brown and one of the project leaders. “This project really helped shape how I see the world and has been extremely influential in shaping my undergraduate experience. This feeling is not unique to me. Many team members, like me, came to SBUDNIC with no previous experience in the space industry and left pursuing paths in the field. We have SBUDNIC alumni across industry—from pursuing Ph.D.s to engineering at SpaceX.”

Along with presenting their findings at conferences and submitting their data to a publication, the SBUDNIC team is currently planning a series of presentations at schools throughout Rhode Island. They hope to inspire future innovators and make high school students more aware of the opportunities available to them in space engineering and design.

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