Tag Archives: solar sail

Image taken during the LightSail 2 sail deployment sequence on 23 July 2019. Credit: The Planetary Society.

Spacecraft that sails on sunlight actually works

Image taken during the LightSail 2 sail deployment sequence on 23 July 2019. Credit: The Planetary Society.

Image taken during the LightSail 2 sail deployment sequence on 23 July 2019. Credit: The Planetary Society.

In 1976, Carl Sagan went on the Tonight Show with Johnny Carson where he presented at exciting and extraordinary technology: solar sailing.

Like a ship’s sails harness the wind to move forward, solar sailing allows a spacecraft to move through space using nothing but the pressure of sunlight. More than four decades later, the Planetary Society, a nonprofit organization that promotes the exploration of space through education, has demonstrated the technology’s potential in the real world. They launched a tiny spacecraft that was able to raise its orbit using the power of the sun alone — a world first.

“We’re thrilled to announce mission success for LightSail 2,” said Bruce Betts, LightSail program manager and the Society’s chief scientist, in a statement.

“Our criteria was to demonstrate controlled solar sailing in a CubeSat by changing the spacecraft’s orbit using only the light pressure of the Sun, something that’s never been done before.”

The Lightsail 2 spacecraft that recently reached this milestone took over a decade and $7 million in crowdfunding to develop. For the past month or so, the spacecraft has been in orbit after it was launched with other payloads aboard a SpaceX Falcon Heavy rocket. Last week it opened its sails for the first time. Since then, LightSail 2 has raised its orbit by 1.7 kilometers (slightly over a mile), solely due to the pressure of photons.

Nothing to do with solar panels — more to do with sailing

Credit: The Planetary Society.

Credit: The Planetary Society.

The LightSail is features a very simple design. Essentially, it looks very much like a kite. The sail is made out of thin Mylar and when it’s fully stretched out, it measures 345 square feet.

Interestingly, LightSail is not a novel concept at all. Nearly 400 years ago, when much of the world thought that reaching North America was a monumental achievement, Johannes Kepler proposed the idea of exploring the galaxy using sails. The astronomer thought the tails of the comets he was observing were actually blown away by some kind of solar breeze, so naturally, this sort of idea of using a solar sail came to mind. This is obviously not true since there’s no “real” wind in space, but we do know that sunlight can exert enough pressure to move objects.

Sunlight pressure offered “tiny push no stronger than the weight of a paperclip” each time the spacecraft completed an orbit around Earth, according to the Planetary Society.

That might not sound like much, but the reality is that many scientists believe that this technology might someday help humans become an interstellar species. Because there’s very little to no resistance in space, light sail-powered spacecraft gain more and more momentum as they travel and an increasing number of photons bounces off the sail. As long as photons hit the sail, the spacecraft will endlessly continue to accelerate — at least in theory. So, even though you still need a rocket to lift such a spacecraft in orbit, a solar sail can reach speeds that a chemical spacecraft could never ever attain.

What’s more, when the sunlight isn’t enough, powerful lasers on Earth pointed onto a sail could accelerate a spacecraft even further. According to NASA researchers, a solar sail pushed by lasers could technically reach Mars in only 3 days.

“It’s counter-intuitive, it’s surprising, and to me it’s very romantic,” Bill Nye, famed science communicator and president of The Planetary Society, told reporters during a a press call Wednesday, “to be sailing on sunbeams.”
This was not the first solar sail. That merit belongs to Ikaros, a solar sail prototype that was launched in 2010 by Japan’s space agency. The Planetary Society’s Cosmos 1 was supposed to reach orbit in 2005 but a rocket explosion destroyed the early prototype. There are no drafts drawn out yet for a LightSail 3, but that’s beside the point for now. What interested the Planetary Society and its generous donors was to prove that the technology works, perhaps inspiring other groups to pick up from here. Mission accomplished!

“LightSail 2 proves the power of public support,” said Planetary Society COO Jennifer Vaughn. “This moment could mark a paradigm shift that opens up space exploration to more players. It amazes me that 50,000 people came together to fly a solar sail. Imagine if that number became 500,000 or 5 million. It’s a thrilling concept.”

solar sail

Carl Sagans’ solar sail will be put to the test next week: our shot at interplanetary travel

In 1976, Carl Sagan went on the Tonight Show with Johnny Carson along with a strange contraption, that looked like a tinfoil square. In all likelihood it was probably tin foil, since it was only a model for what Sagan termed as a solar sail – a simple, but effective spacecraft that harnesses the solar winds to generate power, much like a sail uses the wind to move a ship here on Earth. On May 20th, a tiny satellite the size of a loaf of bread will be blasted into Earth’s orbit from an Atlas V rocket that will test Sagan’s design.

solar sail

Image: LightSail

Called LightSail, the project is ran by the Planetary Society, a non-profit organization founded by Sagan himself and now coordinated by Bill Nye. In orbit, LightSail will not only measure solar particles, but also deploy the sail and test the actual mechanism. Hopefully, everything should run smoothly this time, considering a similar attempt was made ten years ago. The first version however never made into orbit since the Russian craft it used to piggyback failed and crashed.

The LightSail is extremely simply designed and looks very much like a kite. The sail is made out of thin Mylar and when stretched out measures 345 square feet.

Nearly 400 years ago, when much of the world thought reaching North America was a pretty solid achievement, Johannes Kepler proposed the idea of exploring the galaxy using sails. The great astronomer thought the tails of the comets he was observing were actually blown away by some kind of solar breeze, so naturally this sort of idea of using a solar sail came to mind. This is obviously false, since there’s no wind in space, but we do know that sunlight can exert enough pressure to move objects.

NASA researchers have found that at 1 astronomical unit (AU), which is the distance from the sun to Earth, equal to 93 million miles (150 million km), sunlight can produce about 1.4 kilowatts (kw) of power. If you take 1.4 kw and divide it by the speed of light, you would find that the force exerted by the sun is about 9 newtons (N)/square mile (i.e., 2 lb/km2 or .78 lb/mi2). In comparison, a space shuttle main engine can produce 1.67 million N of force during liftoff and 2.1 million N of thrust in a vacuum. So… that doesn’t seem like much. However, the solar pressure exerts a continuous acceleration and the longer the sail travels the faster it will become. Eventually, it could reach speeds five times faster than the fastest rockets available today. Because it doesn’t need any fuel, a light powered spacecraft could travel to distant planets and beam back valuable information.

NASA  and JAXA have already successfully tested solar sail technology, but with the  Planetary Society’s latest efforts solar sails might actually come back into interest. If the LightSail demonstrates solar particle powered propulsion is feasible, then maybe NASA and the European Space Agency (ESA) would finally commit serious money for solar sail research and space missions.