Satellite powered by 48 AA batteries and a $20 microprocessor shows low-cost way to reduce space junk

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

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

But a team of engineering students from Brown University has turned that assumption upside down.

They built a satellite on a shoestring budget using ready-made supplies available at most hardware stores. They even sent the satellite — which is powered by 48 Energizer AA batteries and a $20 microprocessor popular with robot hobbyists — into space about 10 months ago, hitchhiking on Elon Musk’s SpaceX rocket.

Now, a new analysis of data from the Air Force Space Command shows that the satellite not only operated successfully, but could have far-reaching implications for efforts to tackle the growing problem of space debris, which poses a potential threat to all current and future space vehicles.

According to NASA, there are now more than 27,000 pieces of what they call orbital debris or space debris that are 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 pads, mission-related debris, and fragmentation debris. It also includes defunct satellites that sometimes remain in orbit for decades after their mission is complete.

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 presented with the unique opportunity to design and build their own satellite to go into space, they decided to design a possible solution.

The students added a 3D-printed trailing sail made of Kapton polyimide film to the loaf-sized cube satellite they built. When placed about 520 kilometers — well above the orbit of the International Space Station — the sail popped open like an umbrella and helps push the satellite back toward Earth more quickly, according to initial data. In fact, the satellite is well below the other small devices deployed with it. For example, at the beginning of March, the satellite was about 470 kilometers above the Earth, while the other objects were still about 500 kilometers or more in orbit around the Earth.

The graph shows how much lower SBUDNIC’s orbit, represented by the thick blue line, is compared to other devices deployed 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 toward reentry, while the others higher up are still in a nice circular orbit.”

The data suggests that the student satellite, called SBUDNIC, will be out of orbit within five years, while the students calculated an estimated 25 to 27 years for it without the towing device.

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

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

The project is the result of a collaboration between researchers from Brown’s School of Engineering and Italy’s National Research Council. It is also supported by D-Orbit, AMSAT-Italy, La Sapienza-University of Rome and the NASA Rhode Island Space Grant. The satellite’s name is a pun 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 launched into orbit in recent years. The previous satellite, EQUiSat, made 14,000 loops around Earth before ending its mission and burning up when it re-entered the atmosphere in late 2020.

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

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

The Kapton polyimide towing sail, attached to the SBUDNIC satellite, helps push the satellite back to Earth more quickly. Credit: Marco Kruis

Designed by Brown students

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

Italian aerospace company D-Orbit approached with an opening for a satellite on the SpaceX Falcon 9 rocket due to launch in a year. Fleeter turned to his students, who had just listened to their first seminars on space system design, and offered them the opportunity.

From there the race continued.

The students began by conceptualizing and designing the satellite’s individual subsystems, often working with industry consultants who provided feedback and technical advice on the feasibility of their proposals. The students then carry out their plans, managing the technical aspects of the satellite and coordinating administrative matters. The continuous prototyping, testing and improvement that was required took an enormous effort from the students in terms of hours and brain power.

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

Students purchased materials they needed from local stores and online stores. They often had to come up with clever solutions for their materials so that they could survive in space. The approach often meant devising test equipment that replicated specific space environmental conditions, such as the high vibrations of the rocket launch, Cross said. For example, the team used reptilian heating lamps in a vacuum chamber to test the thermal shield they created to protect the satellite’s electronics from the sun.

To be cleared 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 hesitated.”

Students working on SBUDNIC did most of their building work in the Brown Design Workshop. Credit: Marco Kruis

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

Students said the project helped them see themselves as makers and innovators, and that experience embedded lessons in them that they will use well into the future.

“What I learned in this program I then used to intern at Lockheed Martin Space,” said Selia Jindal, a senior at Brown and one of the project leaders. “This project has really helped shape how I see the world and it has been hugely influential in shaping my student experience. This feeling is not unique to me. Many team members, like me, came to SBUDNIC with no previous experience in pursuing the aerospace industry and departed paths in the field. We have SBUDNIC alumni across the industry – from pursuing Ph.Ds to engineering at SpaceX.”

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

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