Cosmos 1 - Physics

Physics

The craft would have been gradually accelerating during each orbit as a result of the radiation pressure of photons colliding with the sails. As photons reflected off the surface of the sails, they would transfer momentum to them. As there would be no air resistance to oppose the velocity of the spacecraft, acceleration would be proportional to the number of photons colliding with it per unit time. Sunlight amounts to a tiny 5×10−4 m/s² acceleration in the vicinity of the Earth. Over one day, the spacecraft's speed would reach 45 m/s (100 mph); in 100 days its speed would be 4,500 m/s (10,000 mph), in 2.74 years 45,000 m/s (100,000 mph).

At that speed, a craft would reach Pluto, a very distant dwarf planet in the solar system, in less than five years, although in practice the acceleration of a sail drops dramatically as the spacecraft gets farther from the Sun. However, in the vicinity of Earth, a solar sail's acceleration is larger than that of some other propulsion techniques; for example, the ion thruster-propelled SMART-1 spacecraft has a maximum acceleration of 2×10−4 m/s², which allowed SMART-1 to achieve lunar orbit in November 2004 after launch in September 2003.