Seminar Report on SOLAR SAILSBY Athira raj EEE IIET A solar sail is a spacecraft without an engine - it is pushed along directly by light particles from the Sun, reflecting off giant mirror-like sails. Because it carries no fuel and keeps accelerating over almost unlimited distances, it is the only technology now in existence. Introduction Whereas a conventional rocket is propelled by the thrust produced by its internal engine burn.What is a solar sail? A solar sail. that act like atomic particles. is a spacecraft propelled by sunlight. but with more energy. a solar sail is pushed forward simply by light from the Sun. . This is possible because light is made up of packets of energy known as “photons”. simply put. . typically about the size of a football field. supported by ultra-lightweight structures. The side of the film which faces the sun is coated with a highly reflective material so that the resulting product is a huge mirror. The force generated by the sun shining on this surface is a very gentle force.COMPONENTS OF A SOLAR SAIL Solar sails are composed of large flat smooth sheets of very thin film. SAILING SOLAR . In essence. which is a technology for converting solar light into electrical energy.Solar sailing is a method of converting light energy from the sun into a source of propulsion for spacecraft. a solar sail is a giant mirror that reflects sunlight in order to transfer the momentum from light particles (photons) to the object that is propelling. The phrase "solar sails" is often confused with "solar cells". . While Kepler's idea of a solar wind has been disproven. To take advantage of this force. Johannes Kepler proposed the idea of exploring the galaxy using sails. as much of Europe was still involved in naval exploration of the world. NASA has been experimenting with giant solar sails that could be pushed through the cosmos by light. Through his observation that comet tails were blown around by some kind of solar breeze. he believed sails could capture that wind to propel spacecraft the way winds moved ships on the oceans.THE CONCEPT OF SOLAR SAILS Nearly 400 years ago. scientists have since discovered that sunlight does exert enough force to move objects. just like a ball bouncing of the wall. the light wave pushes on electric charges in the surface of the object.WORKING PRINCIPLE OF SOLAR SAILS How Does Light Push a Solar Sail? 1-Electromagnetism James Clerk Maxwell developed the laws describing electromagnetism and concluded that light is an electromagnetic wave. which in turn push on the rest of the object. If the light is reflected. and again by reflecting back from it. Maxwell predicted that when light hits an object and is absorbed or reflected. the object gets pushed twice as hard. . In this process the photons transmit their momentum to the surface twice-once by the initial impact. A square mirror 1 kilometer on a side would only feel about 9 Newtons or 2 pounds of force. Fortunately.A Very Very Gentle Force Sunlight exerts a very gentle force. space is very empty and clean compared to Earth. so there is plenty of room for a 1 kilometer wide sails to maneuver.2. . and there is no noticeable friction to interfere with your 9 Newtons of thrust. reflective material that is upwards of 100 times thinner than an average sheet of stationery. materials available until the last decade or so were much too heavy to design a practical solar sailing vehicle. . SOLAR SAIL MATERIALS While solar sails have been designed before. The giant sails being tested by NASA today are made of very lightweight. Besides being lightweight. the material must be highly reflective and able to tolerate extreme temperatures. the Planetary Society (a private.Another organization that is developing solar sail technology. supports the Cosmos 1. non-profit group based in Pasadena. which boasts solar sails that are made of aluminum-reinforced Mylar and are approximately one fourth the thickness of a one-ply plastic trash bag. California). . low density. and a good vacuum favor high reflectivity. High deposition rates.ALUMINUM AS SOLAR SAIL MATERIAL The thin metal film. . and a very low vapor pressure. is an aluminum film. near-normal vapor incidence. a reasonable melting point. according to the preferred embodiment of this invention. Aluminum films have high reflectivity. The reflectivity and transmissivity of aluminum film is a function of its thickness. Consequently. any aluminum film thick enough to reflect well in the visible wave lengths should reflect even better in the infrared. The reflectivity of aluminum films varies with the deposition conditions. . where roughly half the sun's power output lies. .Aluminium being manufactured for the Solar Sail. light. not by adding further aluminum. but by adding a reinforcing film of a stronger. more refractory material. may reflect well enough to be of interest by themselves. . The use of a metal as a reinforcing film could reduce the amount of aluminum needed to give good reflectance. such as nickel. Some metals.USAGE OF REFRACTORY MATERIALS Aluminum films of the minimum thickness required for reflectivity may prove too weak to support the stresses imposed upon them during fabrication and operation. or may creep under load at elevated temperatures. A good reinforcing film should be strong. If so. it is possible to strengthen them. and easy to deposit. . the inevitability of manufacturing flaws and micrometeoroid damage makes this a small comfort. adds cost as well. the mesh adds mass to the sail and. transported into space and attached to the film. because it must be fabricated. While even sheets of extremely thin material have adequate strength to support the load expected during fabrication and operation in the absence of stress concentrations.AREA OF CONCERN IN CONSTRUCTION Tears are a critical concern in the use of thin films for solar sails. The most obvious method of limiting tears is to mount the film on a supporting mesh. Patterns of cuts and wrinkles can de-tension areas of film to isolate stress to smaller regions. load-bearing elements. a large manufacturing flow or a grazing micrometeoroid impact is free to initiate a tear--but the tear will cause the failure. not of an entire sheet. but of a small piece of film. convert it from a continuous sheet to a redundant network of small. In such a structure. Each wrinkled region is fabricated with enough extra material to avoid being . perhaps 25 square millimeters in area.REMEDY A more natural approach to tearstopping is to subdivide the film. . Because it carries no fuel and keeps accelerating over almost unlimited distances. It is pushed along directly by light particles from the Sun. where the solar sails can be deployed and the spacecraft sent on its way. reflecting off its giant sails. These spacecraft accelerate gradually. Solar-sail spacecraft need only a conventional launch vehicle to get into Earth orbit. which offer extremely quick acceleration. it is the only technology now in existence that can one day take us to the stars. unlike conventional chemical rockets.ADVANTAGES A solar sail is a spacecraft without a rocket engine. The major advantage of a solar-sail spacecraft is its ability to travel between the planets and to the stars without carrying fuel. .Solar sails will set new speed records for spacecraft and will enable us to travel beyond our solar system. Deploying solar sails is also highly challenging to date. Solar sails have to be physically large. if at all.LIMITATIONS OF SOLAR SAILS Solar sails don't work well. Above that altitude they give very small accelerations that take months to build up to useful speeds. . in low Earth orbit below about 800 km altitude due to erosion or air drag. and payload size is often small. com .com www.REFERENCES www.answers.howstuffworks.wikepedia.org www. 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