Privately funded Cosmos 1, the world's first solar sail spacecraft, was launched on the tip of a converted Russian intercontinental ballistic missile from the Barents Sea on Tuesday at the start of a mission that cost just $4 million.
Its Planetary Society sponsors hope the craft, which will deploy a petal-shaped solar sail to power its planned orbit around Earth, will show that sunlight could power interplanetary space travel.
Mission operations personnel monitoring the spacecraft from the Planetary Society's bungalow in Pasadena cheered as they got word from mission operations in Moscow of the rocket's take off just after 12.45 pm (1945 GMT).
The 100-kg spacecraft was designed to use a "kick motor" to place it about 885km above Earth, where it will orbit for several days before deploying two sets of four triangular-shaped blades.
Mission scientists hope to study images from two onboard cameras pointed at the sails to determine how the ultra-thin Mylar material and inflatable booms behave in space.
The Russian government had to notify a joint US-Russian committee of the launch of a missile capable of carrying nuclear warheads under the terms of the Strategic Arms Reduction Treaty (Start), Planetary Society co-founder Bruce Murray said.
Murray said chances that the fragile craft would fail were "significant".
"It will be a giant leap forward ... if it succeeds," Murray told reporters before the launch. "It will be a not-surprising failure if it doesn't."
The project started as a dream held by Planetary Society founders Carl Sagan, the late science fiction writer, Murray, and Louis Friedman, who proposed sending a solar sail craft to rendezvous with Halley's Comet in the 1970s.
Sagan's widow, Ann Druyan, who provided most of the funding for the mission through her entertainment company, Cosmos Studios, said she was thinking of her husband as the mission unfolded on Tuesday.
Friedman, the society's executive director, and others believed the impact from a constant stream of photons bouncing off a huge sail would be enough to impel a craft through frictionless space at an ever-increasing speed.
With sunlight as its only fuel, a solar sail craft could open the farthest reaches of the solar system to space travel, backers of the mission said.