A US company has demonstrated a neat and inexpensive way to speed up the de-orbiting of satellites at the end of their life.
That involves releasing a 70-metre length of tape – termed a Terminator Tape – which increases atmospheric drag to speed the de-orbiting process.
The company, Tethers Unlimited, said the first of four small satellites currently flying with their experimental de-orbit modules had begun its slow descent last northern autumn fall.
It was de-orbiting at a rate 24 times faster than it was before deploying the tape, according to observations from the US Military Space Surveillance Network.
“Instead 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 10 years,” said Tethers Unlimited chief executive Rob Hoyt.
In practice, any satellite in low-Earth orbit out to around 400-500 kilometres will eventually de-orbit of its own accord because of drag from the atmosphere.
The closer in, the faster that occurs. The further out, the longer that can take, with time to orbital decay measured in decades or more.
With low-Earth orbit increasingly crowded, the reconnaissance is that redundant satellites should de-orbit within 25 years, though many in the industry feel it should be sooner.
For the tether test, Prox-1, a 71-kilogram CubeSat built by the Georgia Institute of Technology with funding from the US Air Force Research Laboratory University Nanosatellite Program, was launched on a SpaceX Falcon Heavy rocket into a low-Earth orbit at an altitude of 717 kilometres in June.
It deployed the 70-metre length of conductive tape in September.
Another satellite from the same launch also has a Terminator Tape module, which is set to deploy towards the end of this year.
Tethers Unlimited also has Terminator Tape on two Aerospace Corp CubeSats and is waiting for their mission to conclude before deploying.
“For a typical nanosat/microsat, the Nanosat Terminator Tape should meet the 25-year requirement up to about 850 kilometres,” Hoyt said.
The company believes this can work for CubeSats in orbits as high as 1,100-kilometres. The tape can be made longer and wider for larger satellites.
As well, Terminator Tapes could potentially be attached to other defunct satellites using the LEO Knight servicer the company is developing but is still three to four years from completion.
This could eventually be a viable business if the price satellite operators are willing to pay right. That would appear to be in excess of US$100,000 per satellite.
Tethers Unlimited has another Terminator Tape demonstration mission to be launched on a Rocket Lab Electron later this year, which will feature two identical satellites in identical orbits, one with the Terminator Tape so that orbital degradation can be measured precisely.
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