Example of a public education promotion for the Planetary Society’s launch of LightSail2 on June 24 2019. The mission will prove the feasibility of solar sailing in outer space using CubeSats.
In the 1970s, I bought a book published by the Whole Earth Catalog called “Space Colonies”. I read it over and over. The book was a compilation of articles about ways humanity might leave our planet and start living in outer space. The central theme was a proposal about building orbital space stations where people would live permanently.
Of course, none of that never materialized. The future hasn’t much like what the futurists predicted in a lot of ways. Even so, there were some other articles tucked into that anthology that were a bit off topic. I found one of these oddball pieces fascinating.
The article was about something called “solar sailing”. Nobody I knew had ever heard of the concept at that time. I was amazed to learn that there was something called the “solar wind”. Even more inspiring was that scientists and engineers believed that there was a way to use this solar wind to travel around the solar system.
Large, reflective sheets of material would capture energy from the sun. Then they would use it to propel small vessels to which they would be attached, like tall ships on the ocean. I loved stories like Treasure Island and Mutiny on the Bounty, so the adventure fired my imagination. It turns out that the idea of solar sailing dates back to the age of sail. Kepler first shared the idea with Galileo in 1608. Turns out, those futurists from the 1970s weren’t telling me anything new.
For once, something they predicted has come true. I am one of 50,000 people who belong to the Planetary Society. The society is the word’s largest and most effective non-profit space organization. They have embarked on a crowd funded project called LightSail. The goal is to prove flight by light for 10cm x 10cm x 10cm spacecraft called CubeSats.
We can’t use solar sails to reach escape velocity. Spacecraft will continue to gain most of their momentum when they leave the launch pad. The difference will come after the spacecraft has escaped earth’s gravity. Conventional spacecraft use smaller chemical rockets to steer. These have to carry fuel, which adds weight and runs out in time.
The Planetary Society thinks that there might be a better way. If the solar sail idea that I read about in the 1970s works, it could offer continuous, practically limitless acceleration. If you can accelerate indefinitely, you can reach much greater speeds. The faster you can go, the further away your destination can be.
Solar sails are as simple as wind sails. The light from the sun consists of particles called photons. Although they have no mass, photons are moving, so they have momentum. When the photons hit the surface of a reflective sail, they give it a push. When they bounce off the sail, they give it another push. Both pushes move the spacecraft.
You may be wondering why light never moves objects on earth. Because of earth’s atmosphere, light energy is not as strong as the air resistance. In the vacuum of space, though, it provides enough energy to change the sail’s speed.
I used to be a would-be sailor. I learned that, although I couldn’t sail directly into the wind, I could “tack”, as in maneuver my sail so that my boat could travel at an angle to the wind. I might have to zigzag for a while but I could end up where I wanted to be. A solar sail can do the same thing, so it isn’t restricted to the direction in which the light is traveling.
Solar sailing has already been tried attempted, with varying degrees of success. The Planetary Society has embarked on a new project called LightSail. Though miniature, CubeSats can contain 34 square metres of sail. The sails are ultra thin, measuring a mere 4.5 microns in thickness. The CubeSat is the size of a loaf of bread while he sails are the area of a boxing ring.
The Planetary Society held a trial launch called LightSail1 in 2015. LightSail1 succeeded based on both launch and deployment but it didn’t test solar sailing itself. Probably its most unexpected accomplishment was that it inspired a Kickstarter campaign. That campaign raised over a million dollars for LightSail2, a project to prove that solar sailing itself can work. LightSail2 broke the KickStarter record for the most backers of a space project.
The launch date for LightSail2 is almost here. On June 24, a SpaceX Falcon rocket will lift LightSail 2 into orbit. From there, it will be ejected from Georgia Tech’s Pro-X 1 spacecraft. After a few days, the flight crew will hoist the sails. They will then prove that the sails can steer the CubeSat by up to angles of 90 degrees within its orbit. After about a year, the atmospheric drag will force LightSail2 lower into Earth’s atmosphere where it will burn up.
I know where I will be on June 24. I’ll be putting in some screen time at the Planetary Society’s website planetary.org. They will be livestreamng video of the launch.
You can watch too, as well as learn more about the world’s largest non-profit space organization. Mark June 22 in your calendar and prepare to blast off!