Tethers Unlimited says early results of deorbit hardware test promising

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WASHINGTON — The first of four small satellites currently flying with Tethers Unlimited’s  experimental deorbit module on board began its slow descent last fall and is coming down according to plan, spacecraft hardware company Tethers Unlimited said Jan. 21.

Observations from the U.S. military’s Space Surveillance Network show the Prox-1 satellite deorbiting more than 24 times faster than before deploying the tape. Credit: Tethers Unlimited.

Prox-1, a 71-kilogram cubesat that launched into a low Earth orbit in June on a SpaceX Falcon Heavy rocket, successfully deployed a 70-meter length of conductive tape in September that is creating enough drag to deorbit the satellite much sooner than simply abandoning the satellite.

“[I]nstead of remaining in orbit for hundreds or thousands of years, the Prox-1 satellite will fall out of orbit and burn up in the upper atmosphere in under ten years,” Tethers Unlimited CEO Rob Hoyt said in a news release. 

Hoyt said observations from the U.S. military’s Space Surveillance Network showed the Prox-1 satellite deorbiting more than 24 times faster than before deploying the tape. 

Prox-1, built by the Georgia Institute of Technology with funding from the U.S. Air Force Research Laboratory’s University Nanosatellite Program, is in a 717-kilometer low Earth orbit, Hoyt told SpaceNews by email. Prox-1, which Georgia Tech owns and operates, is one of 24 small satellites that launched on Falcon Heavy last year as part of the U.S. Defense Department’s Space Test Program-2 mission.

Hoyt said another satellite from the Falcon Heavy launch, NPSat-1, also has a Terminator Tape module onboard that is set to deploy toward the end of 2020. 

Tethers Unlimited also has Terminator Tape on two Aerospace Corp. cubesats currently in orbit, he said, and is waiting for their operator’s mission to conclude before releasing the tapes. 

Terminator Tape works by interacting with the space environment to create drag, accelerating the time it takes for the satellite to fall out of orbit and  reenter the atmosphere. 

“For a typical nanosat/microsat, the Nanosat Terminator Tape should meet the 25-year [de-orbit] requirement up to about 850 kilometers,” Hoyt said. He estimated Terminator Tape can work for cubesats in orbits as high as 1,100-kilometers. 

Hoyt said Terminator Tape can be made longer and wider for larger satellites. 

Hoyt said Tethers Unlimited could potentially attach Terminator Tape modules to defunct satellites using the LEO Knight servicer it is developing. That servicer, which is specifically focused on low Earth orbit, is still three to four years from completion, Hoyt said. 

LEO Knight should be capable of attaching Terminator Tape to abandoned spacecraft such as Iridium’s defunct satellites, Hoyt said, but Tethers Unlimited would need to be paid more than $10,000 per satellite — the price Iridium CEO Matt Desch floated in December as a conversation starter. 

Hoyt said the price for deorbiting satellites using LEO Knight and Terminator Tape would need to be “somewhere between one to two orders of magnitude higher” to make the business case close. 

Iridium has 30 dead first-generation satellites still in orbit, many of them near the altitude of the Prox-1 satellite. 

Hoyt said Terminator Tape and its timer cost the company about $500,000 to develop using a combination of internal funding and U.S. government research grants. The modules weigh less than a kilogram, according to the company. 

Tethers Unlimited has another Terminator Tape demonstration mission launching on a Rocket Lab Electron later this year, Hoyt said. That mission, called DragRacer, consists of two identical satellites in identical orbits. Only one of the DragRacer satellites will unfurl Terminator Tape, allowing Tethers Unlimited to measure exactly how much faster the deorbit system causes a spacecraft to reenter. 

Boeing subsidiary Millennium Space Systems is building the DragRacer spacecraft. TriSept Corp. arranged the launch. Millennium Space Systems is funding the DragRacer mission, with Tethers Unlimited contributing, Boeing spokeswoman Cheryl Sampson told SpaceNews Jan. 23. Hoyt declined to specify how much funding Tethers Unlimited is providing for the mission.