Solar Sails Could Clean Up Space Junk

Future satellites could deploy solar sails to help take down pieces of space junk floating around Earth and a tiny new spacecraft hopes to make it possible.

A British satellite the size of a shoe box is slated to launch next year to test how a solar sail can act as an atmospheric brake and end its mission in a fiery plunge. If successful, the one-year mission could help lead to bigger, better solar sail spacecraft capable of trawling the space around Earth for dangerous space junk, mission planners said.

Just having a cheap, reliable method of ending a spacecraft's life could go a long way toward limiting the size of the space debris cloud surrounding Earth. Even space shuttle missions and the International Space Station must occasionally dodge space junk, which has collectively grown to more than 6,000 tons of debris leftover from 50 years of abandoning spacecraft.

Most satellites rely upon propellant-based maneuvering thrusters that may or may not still function at mission's end ? and that's not even considering the launch expense of carrying all that propellant mass. By contrast, the CubeSail would simply unfurl a 16 square-foot (5 square-meter) sail. Launch of the 6/6-pound (3-kg) sail is set for late 2011.

"Using the sail as a 'propellantless' deorbiting system will allow the extra mass gained to be used for payloads or to extend the lifetime of a satellite further," said Vaios Lappas, an aerospace engineer at the University of Surrey in the UK.

Such a sail would rely upon force of sunlight, and allow scientists to test solar sailing as a space propulsion alternative to other space engines which must carry their own propellant. It also represents a much cheaper and possibly more reliable fallback technology.

Tiny satellite, big mission

CubeSail could piggyback-launch with other missions as a small nanosatellite. It will aim for an altitude of 435 to 497 miles (700 to 800 km) and enter a sun-synchronous orbit so that it can match the motion of the sun across the sky, according to Lappas.

Yet no spacecraft has flown with a solar sail as its main means of propulsion, in part because of launch failures that crippled efforts by the California-based Planetary Society and NASA. Japan successfully deployed solar sails in 2004, but did not try to use them for controlled flight.

That has led the University of Surrey team ? backed by the European aerospace company Astrium ? to try and ensure mission success based on the mantra of simplicity.

"We are keeping our design as simple as possible using well known materials, components and a simple design based on self-deploying booms coiled around a simple roller mechanism," Lappas told SPACE.com.

Taking down space junk

Success might lead to future CubeSail designs that can attach to existing pieces of space junk and take them down, so that space-faring nations can finally begin cleaning up some of the orbital mess.

"Protecting our planet and environment is key for sustainable growth," Lappas said.

At last estimate, there are than 20,000 pieces of space trash in orbit, according to the Space Surveillance Network. But tackling the space littering problem will likely require a nanosatellite to approach a tumbling piece of space junk travelling at high speed, researchers said.

The CubeSail team has already begun figuring out low-cost technologies that could convert small satellites into space debris cleaners, Lappas noted. But for now, satellites with a mass up to 1,100 pounds (500 kg) might soon use the CubeSail design to end themselves more cheaply and efficiently.

"We are working on using carbon-made booms with increased strength and lighter mass for larger sails," Lappas said.

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