What is the “solar sail” and how does it work?

About 5 thousand years ago in Ancient Egypt, something happened that radically changed the world. According to archaeological discoveries, around this time, the Egyptians invented sails, which began to be used to control the ships by force of wind. It’s hard to believe, but at the moment humanity is once again on the verge of opening, which will affect the whole world. Scientists are trying to use so-called “solar sail” to control space satellites. Left quite a bit of time until the spacecraft can operate without fuel and engines.

At the moment, the majority of artificial satellites are circling our planet, working on the energy of ion engines. These engines are heavy, are quite expensive and are only about three years, so scientists have long been trying to find an alternative. In the distant 1920, the Soviet inventor Friedrich Zander realized that for flying in space you can use a kind of sail used in boats. But as, in his opinion, the sails can result in the movement of space objects? After all, in space there is no wind.

The contents

How to fly satellites?

The fact that in space there is a wonderful alternative to the wind — sunlight, which consists of an unimaginable number of particles, called photons. Each of them can hit a solid surface and create a pressure that can push objects forward. Imagine a billiard ball collides with other balls on the table — or so photons of light and affect the surface of the sail. So why not make that a solid surface has been a huge sail, and a movable object — a tiny satellite?

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Scientists tried many times to bring satellites in motion using solar sails, but they failed. The fact that the particles of the solar light is very small and it is not enough to push great companions forward. Scientists took decades to reduce the satellites to a tiny smartphone. Some of these compact devices are they were launched, which are made in sizes of 10 x 10 x 11 inches. Despite its small size, they have everything you need for Earth observation.

The first working solar sail

The first space satellite employed a solar sail was the Japanese machine IKAROS. Its launch took place on 21 may 2010, when the small sail with a 20-metre diagonal was folded. After reaching orbit, the sail began to open up and completed this process only a week after the start. With this sail in the sunlight, the device could adjust the direction of their motion. But then the camera was in the shadow and fell into “hibernation”, from which the experiment had to be stopped.

IKAROS is the first spacecraft with a working solar sail

Solar sail LightSail 2

But scientists have not given up and testing a solar sail going on right now. If you look at the night sky, there it is possible to see the spacecraft LightSail 2 from the Planetary community. He was launched into the orbit of the planet in June 2019 with the help of the carrier rocket Falcon Heavy. A few weeks later he revealed his solar sail — its area is 32 square meters and that is why people have to see it from the Ground. Just think — the sail has almost the same area that the average apartment!

The apparatus LightSail 2 right now is orbiting the Earth

The sail has an ulterior motive of such a huge size. The fact that driving even a small machine the size of a loaf of bread, the particles of sunlight needed to influence the largest possible area of the sail. Perhaps in the future scientists will be able to build satellites of a smaller size, for example, a matchbox. Then the sails do will be small, and see them from Earth would be impossible.

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By the way, the device LightSail-2 was a prototype called LightSail-1. He was launched into orbit on 20 may 2015 and unfurled the sail on 7 June. After another 7 days it conducted its test flight, which lasted not more than a day. In contrast to the prior art, the apparatus LightSail-2 will fly in Earth’s orbit until at least mid-August.

What is the speed of the solar sail?

You’re probably wondering what kind of speed can be developed with the help of solar sails? Speed and acceleration depends on the size of the sail and the satellite. The apparatus LightSail 2 at this point makes a complete revolution around the planet in 90 minutes. The velocity of the satellite, by the way, is constantly growing — for one month under sunlight, it is accelerating at 549 kilometers per hour. Until the speed of the device is quite small, but over time, if left in working condition, it can reach the speed of the International space station, which is more than 27,000 kilometers per hour.

Unit 2 LightSail must be constantly turned to catch the sun’s rays

As the health of the satellites with solar sails depends on the particles of light, they cannot be used outside the Solar system. Although, in other parts of the Universe surely there are other sources of light, so in the very distant future, solar sails can also be useful.

The advantages of solar sails

Solar sails do work, and very soon, satellites may lose their ion engines. This will significantly reduce their cost because the solar sail is clearly cheaper engines, because in fact it is mirror canvas, stretched around the satellite. Moreover, aerospace companies do not have to spend money on expensive fuel — in “sailing” companions, it simply is not necessary.

The ion engine actually looks more expensive than solar sails, doesn’t it?

Unfortunately, having the opportunity to create cheap satellites, companies can often pull them into orbit. And objects around our planet and so very much, and in the next ten years they will be even more — after all nobody has forgotten that Elon Musk wants to create global Internet Starlink with 12 000 satellites? We, the people, have almost created a working solar sail — now we need to think about how to get rid of space debris.

Wait, maybe from space debris, it is possible to extract some benefit?

Finally, I want to recommend the story British science fiction writer Arthur C. Clarke’s “solar wind”. It tells of the regatta spacecraft, which move with the pressure of the solar wind. In his work the writer spoke about the different types of solar sails (they still exist!) and how to manage them.

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