Purdue University engineers have developed a space-debris-clearing drag sail called Spinnaker3 that is designed to speed up the deorbiting of space junk up to 400 miles (645 km) high so it safely burns up in the Earth's atmosphere. The sail will be put to the test next month on a spent rocket booster at an orbit altitude of about 200 miles (322 km).
Under law, US-flagged satellites must be either deorbited or sent into a safe graveyard within 25 years of ceasing operations. The standard way of doing this is for the spacecraft to use its thrusters to put it into the right disposal orbit. The problem is that such thruster systems and the extra fuel needed for the final trajectory change increase the mass of the satellites, increasing costs and reducing their capabilities.
The alternative is to use a system that doesn't require propellants and complex plumbing. One example of this is a drag sail, which spreads out and passively catches the stray molecules of the remarkably tenuous atmosphere in low Earth orbit, causing the craft's orbit to decay until it hits the atmosphere proper.
Such sails have been tested before, but Spinnaker3 ups the game a bit by wielding 3-meter-long (10-ft) booms to unfurl a 194-sq-ft (18-sq-m) shimmering, translucent fluorinated-polyimide plastic sail. This sail is large enough to help deorbit not only a satellite, but also a booster rocket upper stage from an altitude of up to 400 miles.
Spinnaker3 is scheduled to fly in November on a Firefly Aerospace Alpha rocket lifting off from Vandenberg Space Force Base in California. It will be one of seven “Dedicated Research and Education Accelerator Mission” (DREAM) academic and educational payloads organized by Firefly. Once in orbit, the sail will be used to deorbit the upper stage of the Alpha vehicle from about 200 miles up, in 15 days instead of the estimated 25 days when unaided.
The new sail was developed with startup Vestigo Aerospace LLC under a NASA Phase I Small Business Innovation Research award, with the help of 18 students and graduate students along with faculty and staff at Purdue’s Space Flight Projects Laboratory. Purdue completed ground tests earlier this year, while California Polytechnic State University, San Luis Obispo provided avionics and imaging systems, which will send back photos of the sail from space.
"Lots of things could deorbit on their own in about a hundred years, but that doesn’t do us any good," says Arly Black, a Purdue Ph.D. candidate in aeronautics and astronautics, who conducted system testing and performance analysis for Spinnaker3. "We want to hasten that deorbiting with a drag sail. Taking into consideration predicted atmospheric conditions for November, the Firefly Aerospace launch vehicle could deorbit on its own at a low altitude of about 200 miles within 25 days. Using Spinnaker3, the deorbiting process could shorten to 15 days."
The animation below shows the deployment of Spinnaker3.
Source: Purdue University
