Crowdfunded spacecraft LightSail 2 prepares to go sailing on sunlight

Among the many spacecraft and satellites ascending to space on Monday’s Falcon Heavy launch, the Planetary Society’s LightSail 2 may be the most interesting. If all goes well, a week from launch it will be moving through space — slowly, but surely — on nothing more than the force exerted on it by sunlight.
LightSail 2 doesn’t have solar-powered engines, or use solar energy or heat for some secondary purpose; it will literally be propelled by the physical force of ph