One day, in the not so distant future, the light sails will race through space at the speed of about 20% of light (or 60 000 km/s), not push the fuel, and the pressure of the radiation of powerful lasers on Earth. Moving from these relativistic velocities, the light sails on the lasers could reach the nearest neighboring star (to the Sun) is alpha Centauri, or the nearest potentially habitable planet of Proxima Centauri b, in just 20 years. Both sites are more than four light years from us.
However, the design of the light sails — a complex engineering task that requires the almost impossible: the perfect light sail shall have a width of several meters and be mechanically strong enough to withstand the intense pressure of radiation, however, its thickness should be 100 nm and a weight of few grams.
What is a light sail and what is the complexity of its creation
Other requirements depend on the working mechanisms of these very light sails. According to Maxwell’s equations, light has momentum and can exert pressure on objects. But the light sails not just pushed by the pressure of radiation as an ordinary sail is by the wind force. Instead, the pressure of being born because of the light sail reflects the light. Therefore, the optimal sail should reflect most of the radiation in the laser beam of the near infrared spectrum and at the same time to emit in the middle infrared spectrum for efficient cooling.
In a new study published in Nano Letters, scientists, Covering Ilic, core Vent, and Harry Atwater from the California Institute of technology in Pasadena showed that nanophotonic structure may have the potential to meet stringent requirements of the material from which to make sail, capable of traveling at near-light speeds.
If in the previous constructions were used such materials like superfine aluminum, various polymers, and carbon fiber, nanophotonic structures can manipulate light at the subwavelength scale, and thus solve the problem of the effective repulsion (repel) and distribution of heat (radiation). As an example, scientists have shown a two-layer sandwich of silicon and silicon dioxide, which possess the desired properties. Silicon has a high index of reflection — resulting in efficient movement, but it is bad cools, the silica cools well, but worse reflects.
In the future this concept can be used to minimize the power limitations of the laser and size of the laser array.
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Nanofotonika the light sails can be accelerated to relativistic velocities
Ilya Hel