NEW YORK — Solar sails, which use the sun’s energy as a means of propulsion, have long been viewed as potential enabler of low-cost, long-duration missions in deep space, but a group of scientists are now eyeing a new application: orbital cleanup.
A British satellite about 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. Operational spacecraft, including the space shuttle and international space station, occasionally must maneuver to dodge space junk, which has collectively grown to more than 6,000 tons of debris left over from 50 years of space activity.
Most satellites rely upon propellant-based maneuvering thrusters that may or may not still function at mission’s end — and that is not even considering the launch expense of carrying all that propellant mass. By contrast, the CubeSail would simply unfurl a 5-square-meter sail. Launch of the 3-kilogram craft 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 England.
Such a sail would rely upon the force of sunlight, and allow scientists to test solar sailing as a space propulsion alternative to other space engines that must carry their own propellant.
CubeSail could piggyback-launch with other missions as a small nanosatellite. It will aim for an altitude of 700 to 800 kilometers and enter a sun-synchronous orbit so that it can match the motion of the sun across the sky, according to Lappas.
No spacecraft has flown yet 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 a successful mission 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 said.
Success might lead to CubeSail designs that can attach themselves to existing pieces of space junk and take them down, so that space-faring nations can 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 more than 20,000 pieces of space trash larger than a softball in orbit. But tackling the space litter problem will likely require a nanosatellite to approach a tumbling piece of space junk traveling at high speed, researchers said.
The CubeSail team has begun figuring out low-cost technologies that could convert small satellites into space debris cleaners, Lappas noted. But in the nearer term, satellites with a mass up to 500 kilograms could employ the CubeSail design to de-orbit themselves relatively cheaply and efficiently.
“We are working on using carbon-made booms with increased strength and lighter mass for larger sails,” Lappas said.
