Post date: Oct 23, 2013 3:29:44 PM
NASA has plans to launch a lightweight, highly efficient solar sail in 2015 to explore as far as three million kilometres into deep space. The lightweight sail, propelled by the sun's rays, will also be tested as an early warning system for potentially damaging solar flares headed for Earth.
IN SPACE (NASA) - Solar flares, as recorded by NASA's orbiting Solar Dynamics Observatory, are spectacular to watch but can be extremely destructive to satellites and electrical systems on Earth when accompanied by a coronal mass ejection (CME) of electromagnetic particles.
Scientists hope the NASA-led, $US27 million Sunjammer Mission, scheduled for launch in January, 2015, will provide a much needed early warning system for CMEs, to help engineers on Earth prepare for possible damage.
The project is centred around what will be the world's largest and lightest solar sail, which at 13,000 square feet, is designed to unfold like a giant piece of origami in space. The material looks like a very thin sheet of foil that mimics the movement of a cloth sail blowing in the wind; it's also 10 times lighter than any sail ever flown, weighing in at 70 pounds.
NASA's lead contractor and industry manufacturer L'Garde, Inc., has been working on the latest rendition of the solar sail for the past decade.
The sail area is made of DuPont's Kapton aramid material, a type of pliable plastic resin able to withstand extreme temperatures and coated with a reflective film. It's roughly five microns thick, which is roughly 10-12 times thinner than a human hair.
The venture is based on the premise of spaceflight powered not by rocket fuel or chemical propellants but by streams of photons, or light particles, pushing against a sail in the vacuum of space.
"A solar sail is basically like a giant sailboat in space that instead of using wind to propel it, it actually uses sun pressure, photonic sunlight basically," said Stephen Eisele, vice president of marketing and entertainment at Space Services Incorporated, L'Garde's affiliate. "What this mission will do is a few things, it will demonstrate the capability of solar sails to maneuver and navigate in the solar system and secondly, this mission will head towards the sun and actually provide an early warning system against potentially devastating solar flares."
Some space enthusiasts see solar sailing as a first step in light-powered propulsion technology that may prove the most feasible mode of travel to distant stars.
Nathan Barnes, L'Garde's president, says the sail will serve as a model.
"The solar sail works on the principle of solar radiation pressure," Barnes said. "We're not changing solar energy into electricity and then using it in any way. What we're actually doing is collecting photons and allowing them to strike the surface and then bounce off the surface. The solar energy, the photons from the sun, is actually propelling the sail. Photons don't actually have any mass, but they have some momentum. Every time they strike a surface, and are reflected off of that surface, they create a small amount of impulse on that surface and will allow us to propel that sail off into space."
The project is named after a 1964 science fiction short story of the same name by Arthur C. Clarke, in which sails are pushed by the "wind" from the sun. Although the concept seems like the stuff from science fiction, the Sunjammer mission has already proven otherwise, passing a design test conducted at L'Garde's facilities in Tustin, CA that opened up a quarter of the sail on September 30.
The sail consists of four triangular blades that combine into one large square, with smaller sails at each corner to help the vessel maneuver. Once the Sunjammer mission reaches its orbit in the Sun-Earth system at Lagrangian point L1, the sail will take 45 minutes to unfurl like a giant soft box and continue its orbit for what scientists estimate to be for a year.
"We'll be dropped off in the vicinity of L1," Barnes said. "This is a unique mathematical point that exists between the Earth and the sun where the Earth's gravity is balanced by the sun's gravity is balanced by the centrifugal force of the orbit that the satellite is in. So we'll be dropped off in roughly that vicinity and then we'll do a nice big loop de loop circle and we'll come around back to the sub-L1 point that we want to fly to, which is roughly 3 million kilometers out."
As to the threat of meteorites piercing the sail's flexible and penetrable material?
"The beauty of our solar sail is that it's fairly impervious to these micrometeorites," Barnes said. "If a meteorite passes through the sail, it will simply leave a small micrometeorite shaped hole in the sail and the sail will keep on functioning just as it was before with just a small amount of thrust degradation because there's a little hole there instead."
And Eisele says a successful mission could revolutionise future space travel.
"As long as you have sunlight present the sail will be able to maneuver and change orbits, go to different planets, celestial bodies, perhaps even explore other asteroids, all because you don't have to bring propellant or gas along with you," Eislele said. "Because of that, it also makes the spacecraft incredibly more economical, you save in a lot of costs, you can expand the mission life."
Barnes and Eisele say if everything goes according to plan next year, the technology will have future-term applications in establishing permanent solar weather stations for monitoring magnetic storms on the sun that can wreak havoc on Earth-bound communication networks and electrical grids. It could also be used to help capture orbiting space debris or hover above earth as a moveable, propellantless communicatioins satellite.