Important weather and communication satellites travel in geostationary orbit (GEO), but there is an increasing risk of collisions with nonfunctioning satellites and other space debris. The GRASP-Sat system would keep GEO clear, safely pushing the junk into graveyard orbit (GO). Photo courtesy of Nick Leung

Awards

Proposal to Push Space Junk to “Graveyard Orbit” Earns BU Duo First Prize in National Contest

Novel ways to declutter the skies aim of SmallSat Alliance’s Collegiate Space Competition

A thousand miles and more above our heads, satellites form a critical modern infrastructure, aiding global communication, navigation, and weather forecasting. But once a satellite is decommissioned or dies, it doesn’t disappear. It stays up there, an orbiting hunk of junk, joining cast-off rocket parts and other space debris. If current trends continue—nearly 12,000 working satellites already encircle Earth, with up to 60,000 more expected in just the next six years—that could eventually mean a lot of litter clogging the orbital skyways. Collisions could result, taking out the operational satellites before their time and disrupting communications on the home planet. Even more frightening, space debris can and does crash to Earth—most recently in Saskatchewan, Canada.

This past academic year, a pair of Boston University seniors—now graduates—devised a potential solution. Mechanical engineering majors in the College of Engineering Anisa Chowdhury (ENG’24) and Nick Leung (ENG’24) took up the challenge issued by the SmallSat Alliance in its second annual Collegiate Space Competition: In six months, research and write a detailed proposal for a realistic way to declutter the skies. The technology would need to be feasible technically as well as financially and politically. 

Winners were announced late last month: Leung and Chowdhury took first prize, splitting $2,000.

The two call their proposed technology GRASP-Sat, short for Geostationary Orbit Rendezvous and Space Debris Pusher Satellite Swarm. Most of the conversation about space debris today focuses on objects in low earth orbit (LEO), 1,200 hundred miles up, but Leung and Chowdhury set their sights higher—21,000 miles higher. That’s geostationary orbit (GEO), where a satellite is positioned to travel ever in sync with the same spot on Earth. “It’s where some of the most vital weather satellites are located,” Leung says. It’s also a uniquely challenging tier of the heavens in which to clear debris, simply because it is so distant.

The concept developed by the BU team is a system of modular nanosatellites, also known as cubesats, measuring 20 centimeters wide by 30 centimeters long and 20 centimeters deep. An “agent” (one of the tiny satellites) would set a course for a specified piece of space junk. As the agent nears the region of its target trash, it uses an onboard light detection and ranging (LIDAR) system to precisely track the debris—“to the centimeter,” Leung and Chowdhury write. Once it has guided itself to a careful rendezvous with the dead satellite, the agent uses its solar-powered ion thrusters to gently push on the junk, gradually propelling it a safe 200 miles away, beyond the heavily trafficked GEO belt and into the unused outer belt known as graveyard orbit (GO).

“We think the judges really appreciated our unique focus on an area of space not currently being tackled,” says Leung. “The judges noted that the relatively inexpensive and simple approach of our integrated system was admirable, considering the costs to launch a [larger] satellite into this area.”

Another advantage to GRASP-Sat is that it cuts down on fuel waste: currently, satellites have to burn a portion of their fuel to move themselves to the GO before shutting down. “You might lose a couple of years of use because of that,” SmallSat Alliance chairman Charles Beames says. In contrast, Leung and Chowdhury’s system “allows the satellite to use all the fuel on board” for its main mission, he says, adding: “It’s a very clever idea.”

The students received advice and feedback from postdoctoral researcher Emil Atz (ENG’22) of the BU Center for Space Physics. Hua Wang, a College of Engineering associate professor of mechanical engineering and systems engineering, checked their math. And Leung drew upon his experience working with Brian Walsh (GRS’11), an ENG associate professor of mechanical engineering and electrical and computer engineering, on space instrumentation.

“We would love to fully implement GRASP-Sat past the systems proposal, but would first have to secure significant funding,” Leung says. “Further research and development would need to be completed.”

For now, Chowdhury is conducting research at Bangladesh’s Dhaka University on the properties and effects of metafluid in a vacuum environment (with potential space applications), while Leung is interning at Pratt & Whitney, working on aviation systems analysis.

Beames, who as an investor has heard hundreds of space technology pitches, believes Leung and Chowdhury “absolutely” have a future in the industry in general—and likely could succeed with GRASP-Sat in particular. “Not only would it work, but frankly, it’s kind of necessary, to extract more value out of these geostationary satellites,” he says. “I hope they make a go of it.”