Can sunlight be used for propulsion? The Planetary Society’s long-held wish to raise a satellite’s orbit around the Earth using sunlight could come true this summer with the confirmation that its LightSail 2 spacecraft will launch atop a SpaceX rocket on June 22, 2019.
What is LightSail 2?
It’s a tiny CubeSat no larger than a loaf of bread, and weighing just 5kg. Inside is a ‘solar sail’, which will try to raise its orbit of Earth using only the momentum of solar photons for propulsion. It if does that successfully it could later be used as a way for CubeSats to ‘solar sail’ without the need for fuel. The Mylar solar sail will measure 32 square meters, and will be pointed at the Sun for half of each orbit to receive enough thrust to raise LightSail 2’s orbit by a measurable amount.
Why do we need ‘solar sails?’
We’re not talking high-speed space travel here, but slow, inexpensive journeys. It’s thought that solar sails could one day be used to run ‘interplanetary shuttles’ between planets close to Earth. A close analogy might be yachts or canal boats, which are slow but useful for delivering a steady stream of raw materials.
What was LightSail 1?
2015’s almost identical LightSail 1 had several technical issues, but tested the spacecraft’s sail deployment system before falling back to Earth after about 10 days. A LightSail 3 is also being planned.
Have there been any other solar sails?
Yes. The first was the Japan Aerospace Exploration Agency (JAXA) IKAROS 2010 (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), which hitched a ride to Venus on the AKATSUKI spacecraft before successfully unfurling and being slowly propelled for a three-year journey to the Sun.
Whose idea was ‘solar sails?’
“Forty years ago, my professor Carl Sagan shared his dream of using solar sail spacecraft to explore the cosmos,” said Bill Nye, CEO of The Planetary Society. He went on to honor the three astronomers who founded The Planetary Society. “Carl Sagan, and his colleagues Bruce Murray and Louis Friedman, created our organization to empower people everywhere to advance space science and exploration. We are go for launch!”
What’s the mission timeline?
After launch on June 22, LightSail 2 will ride to space enclosed within Prox-1, a Georgia Tech-designed spacecraft originally built to demonstrate close-encounter operations with other spacecraft. Prox-1 will deploy LightSail 2 seven days after launch, after which its four dual-sided solar panels will open. A day later, four metallic booms will unfurl its four triangular Mylar sails and be on its way to an orbit 720 km above Earth. At that point, the acceleration from sunlight overcomes atmospheric drag so it will be possible to measure how much thrust LightSail 2 receives.
Will I be able to see LightSail 2?
Apparently so. The Planetary Society reports that LightSail 2 may be visible in the night sky for about a year to those positioned within 42 degrees of the equator. That includes the U.S. as far north as Chicago and New York, though only far southern Europe will get a glimpse.
What else will the SpaceX Falcon 9 launch?
LightSail 2 is just one of many satellites going into space on June 22. Taking-off from Launch Complex 39A at NASA’s Kennedy Space Center in Florida, the Falcon 9 will carry another 23 spacecraft to three different orbits as part of the Department of Defense’s Space Test Program-2 (STP-2) mission. On test will be a new atomic clock to improve how spacecraft navigate as well as a small satellite to test the performance of non-toxic spacecraft fuel.
Are there plans to use solar sails in the future?
According to The Planetary Society, results from the LightSail 2 mission are already helping to inform future solar sail projects including NASA’s Near-Earth Asteroid Scout (NEA Scout), a mission to send a low-cost CubeSat solar sail spacecraft on a slow two-year journey to a near-Earth asteroid (NEA) called 1991VG. It’s planned to launch on the first uncrewed flight test of the Space Launch System (SLS) and Orion Crewed Spacecraft to the moon.