A private team of space-savvy civilians has hit a major milestone in plans to launch the first spacecraft propelled by sunlight after shipping the small probe to be loaded atop ballistic missile.

The solar sail-propelled Cosmos 1 vehicle, hailed as the world's first solar sail spacecraft, has left its Moscow testing center and now bound to Severomorsk, Russia, where it will be loaded into a modified intercontinental ballistic missile (ICBM) and readied for a June 21 launch, mission planners announced Monday.

Cosmos 1 is set to fly atop a Volna rocket and launch from a Russian submarine submerged beneath the Barents Sea. If all goes well, the spacecraft will unfurl its solar sails in Earth orbit and demonstrate the first, controlled use of solar sail propulsion.

"Reaching this milestone puts us on the doorstep to space," said Louis Friedman, Cosmos 1 project director and executive director of The Planetary Society, a space advocacy group that organized the upcoming space shot. "We are proud of our new spacecraft and hope that Cosmos 1 blazes a new path into the solar system, opening the way to eventual journeys to the stars."

The Cosmos 1 spacecraft consists of a small central hub and eight triangular sail blades, each packed into a container the size of a coffee can. Hollow tubes along the sides of each mylar blade are inflated with nitrogen gas to deploy the sail, the components of which can be rotated to control the spacecraft.

Cosmos 1 was developed for the Planetary Society by the Lavochkin Association and Russia's Space Research Institute.

Mission directors said there is some reasoning behind the flight's launch date, which is scheduled for the summer solstice.

"Launching Cosmos 1 on the summer solstice is a great way to honor our ancestors and to continue the journey to the stars which they began," said Ann Druyan, the flight's program director and head of Ithaca, New York's Cosmos Studios, which provided the bulk of funding for the solar sail mission.

While Cosmos 1 could demonstrate the feasibility of controlled solar sail-based spaceflight, it won't be the first sail deployed in space.

The Japanese Aerospace Exploration Agency (JAXA) launched and deployed two large solar sails in August 2004, the same month that NASA researchers unfurled a 33-foot (10-meter) sail in ground-based vacuum chamber tests. The European Space Agency, German Aerospace Agency and Russia have also performed solar sail tests.

"The solar sail is an important step in [the] development of space technologies," said Konstantin Pichkhadze, of the Lavochkin Association, in a statement.