The principle is simple: the pressure of the beams of light striking the blades causes the gadget to spin. This wouldnt work if the blades were not sealed in a vacuum, for the pressure of the light is not strong enough to turn the blades in the presence of resistant air. This might seem like a perpetual motion machine, were it not for two factors. Eventually the pivot point where the blades rest on the column will wear out. So far, after many years on my window sill, that hasnt happened. What has prevented this device from running forever is that the glass is not totally impermeable. Atom by atom, air has penetrated the glass so it is not a perfect vacuum and it takes more and more intense sunlight to make it turn.
But what if the same principle were applied to a sail on a space ship? Then, like the marvelous prairie schooner of Pecos Bill sailing across the sea of grass of our Great Plains, a space ship would go on in the vacuum of space, accelerating forever.
That was precisely the intention of a new space experiment launched from the Russian nuclear submarine Borisoglebsk. A Volne intercontinental ballistic missile was modified to carry the sailing space vehicle, Cosmos-1 and launched on what was planned to be a 500 mile high orbit. That was a nice peaceful modification for an otherwise lethal ICBM.
According to the website for the California-based Planetary Society, which sponsored the craft, signals were recorded independently at three ground stations, at Petropavlovsk in Kamchatka, Majuro in the Marshall Islands and Panska Ves in the Czech Republic, that Cosmos-1 was expected to pass over.
The society web page describes the Cosmos 1 as having eight triangular sails, each 50 feet long with the spacecrafts body at the center. If the launch was successful, once reaching orbit the space craft would open the ultra-thin sails to be driven by the power of impacting photons from the sun, just like my window sill gadget.
This is seen as a solution for space flight, for such a space ship doesnt need to carry fuel for propulsion. Like my 22-foot-sloop which sails Lake Superior on free wind, the Cosmos-1 would sail through space propelled by the pressure of a kind of solar wind.
Unfortunately, although it was sponsored by Planetary Society enthusiasts from around the world, the Cosmos-1 has gone missing.. Apparently one engine of the Volne missile failed and the Cosmos-1 disappeared.
This doesnt mean that the adventure is over. If you visit their web site youll discover that the Society sells T shirts, Cosmos-1 souvenirs, and posts a great deal of information about space flight going back to the days of Jules Verne and other science fiction imagineers for whom the Cosmos-1 is a present reality.
Now when I look at that little spinning solar windmill on my window sill, I will think of the Cosmos-1 and adventures of future sailors in space.