sail me to the moon


The Planetary Society is planning to propel a spacecraft using sunlight before the end of next year. Unlike the ill-fated Cosmos 1 solar sail mission of a few years ago, this will be smaller, lighter, and will proceed in three stages.

LightSail 1 will be about the size of a loaf of bread, and that’s before it deploys its sails. The sails are 32 square meters of mylar that will emerge and unfurl on ribs made of exactly the same metal that extends from your average hardware store tape measure. The entire little spaceship weighs 11 pounds. It will take a short trip 500 miles up. Goal: achieve any measurable acceleration from sunlight, and maintain some control of the sail.

LightSail 2 will launch maybe a year later, if all goes well with #1, and will last several days, settling into orbit and then using sunlight to boost itself into a higher orbit. LightSail 3 will go to L1, 900,000 miles out (considerably more distant than the moon) where the Earth’s gravity and Sun’s gravity balance out and it’s easy to stay in one place. LightSail 3 may position a solar storm monitoring station here.

How to sail in space, the short version: Reflected light pressure, caused by photons pushing against the mirror-like sail surface, push the craft and it can be maneuvered by changing the direction of the sail, just like a boat.  Sails can gradually build up some serious speed. A mile-wide sail could cross the entire solar system in five years. According the Planetary Society, this is one known technology that could get a craft up to the speeds needed to leave the solar system and reach another star system in a reasonable time frame (100 years to the nearest stars). It could be helped along by ground-based lasers.

You too can join the Planetary Society and support these efforts. And listen to the highly entertaining Planetary Radio.


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