The Cosmos 1 spacecraft, seen here in an artist's rendition, will use an exotic fuel to travel through space: sunbeams. Photons from the sun are captured by a large pinwheel structure known as a solar sail.
Cosmos 1 is set to launch June 21--the summer solstice--from a Russian submarine. Sail deployment is scheduled for June 26.
In this photo from 2001, a single piece of the sail dwarfs a gathering of engineers.
The flight electronics are tested in a lab in December 2004. Antennas dot the top, and the flight computer and radios can be found along the bottom disc.
In an earlier suborbital test flight, a Volna rocket bearing the solar sail is lowered into a submarine.