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Student satellite demonstrates drag sail to de-orbit old hardware

65 AA batteries and $10 Arduino processor power space debris solution

A tiny satellite with a drag chute built by a team of students has been held up as one small possible solution to the thorny issue of space junk caused by defunct hardware cluttering up Earth’s orbit.

SBUDNIC, a “Sputnik-like CubeSat,” was built by students at Brown University, Rhode Island, from low-cost commercial off-the-shelf parts. It has successfully demonstrated the use of a simple drag sail that helps to degrade the satellite’s orbit and push it back into the planet’s atmosphere faster than would otherwise have occurred.

The problem of space debris is a growing one, with US space agency NASA describing low Earth orbit as “an orbital space junk yard” with millions of pieces of debris flying around, from satellites that are no longer working, down to tiny pieces of spacecraft.

The idea behind SBUDNIC was to demonstrate how future satellites could avoid adding to this problem by including a mechanism to help de-orbit them at the end of their life span. The aerodynamic drag device pulls the satellite out of orbit approximately three times faster than comparable satellites, according to Brown University.

The satellite itself is a 3U Cubesat (where 1U is 10 cm x 10 cm x 10 cm, not to be confused with a datacenter rack unit, so 3U is 30 cm x 10 cm x 10 cm). According to details given by the university, it includes a $10 Arduino microprocessor, 65 AA Energizer lithium batteries and a variety of 3D printed parts produced with consumer-grade printers.

Also 3D printed is the drag sail, made from Kapton polyimide film, which apparently has the right combination of properties to withstand extreme temperature and vibration. This was folded flat along the satellite’s frame prior to deployment, using spring-loaded structural masts made of thin aluminum tubing designed to extend out upon triggering of the release mechanism.

The 6kg satellite was launched aboard SpaceX’s Transporter 5 mission last year, and placed into a 550km polar orbit by a D-Orbit ION orbital vehicle, whereupon the sail was supposed to pop open like an umbrella and help to push SBUDNIC back to Earth.

However, it seems like the radio the satellite was equipped with failed to function, as no signal was ever received from the unit. The university is confident that the sail did deploy, however, as SBUDNIC’s observed orbital decay since then is greater than that of the of the other Cubesats deployed at the same time into comparable altitudes and orbits; its altitude is said to be approximately 30km below that of the reference grouping of satellites.

Verification of a kind also comes from the ground-based radar of the US Space Force 18th Space Defense Squadron, which appears to show that SBUDNIC’s cross-sectional area matches that expected of the main chassis with the drag device deployed.

Initial computational predictions suggest that the drag device will decrease the orbital lifetime of SBUDNIC from over 20 years to as few as 6.5 years, depending on fluctuations of atmospheric density.

While this is not a total solution, it does tally somewhat with rules that the US Federal Communications Commission (FCC) was discussing last year for satellite operators, which would require them to ensure their hardware is de-orbited within five years of end of life instead of 25 years.

Last week it was also revealed that Amazon would like the US government to do more about the space junk issue. The megacorp plans to start offering satellite broadband as part of its Project Kuiper scheme in 2024, with the first production satellites likely to launch in the first half of next year.

SBUDNIC’s total program and development budget was $30,000, while other similarly-sized satellites often cost more than a million and a half dollars, according to the university. However, the the satellite itself could be reproduced for less than $7,000, it claimed.

All of SBUDNIC’s design information is available to the public so that other amateur and student groups can emulate and modify its designs, the university said. ®

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