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How photons could revolutionize space travel

  This image, published by The Planetary Society, depicts the concept of an artist from LightSail 2 above the Earth. Title =
This image, published by The Planetary Society, shows the concept of an artist from LightSail 2 above the earth

In a few days, a SpaceX Falcon Heavy rocket from Florida will launch carrying a satellite the size of a loaf of bread that has nothing but a huge "solar sail" of polyester propulsion.

It has been the dream of scientists for decades, but only recently became reality.

The idea may sound crazy: driving a vehicle without an engine, without fuel and without solar collectors through the vacuum of space, but use the impulse of light energy packets, which are known as photons ̵

1; in this case from our sun.

Launching on Monday, the LightSail 2 spacecraft was developed by the Planetary Society, a US space exploration organization, co-founded in 1980 by legendary astronomer Carl Sagan.

But the idea itself has been around for a long time.

"In the 1600s, Johannes Kepler talked about sailing between the stars." Bill Nye, the director of the Planetary Society, told AFP.

Kepler theorized that sails and ships could be "adapted to the celestial breeze," and "it turns out to be so, it's not just poetry," said Nye, who is known in the US as "Science Guy "is known. after the children's television show, which earned him national fame in the 1990s and now hosts a Netflix broadcast.

And building an awning does not require cutting-edge technology, as you can imagine.

It is essentially a large square of very thin film (less than the width of a human hair) that is also ultralight and reflective.

  The spacecraft LightSail 2 is on its task table after a successful life test at the California Polytechnic St.
The spacecraft LightSail 2 is on the task table after a successful test on May 23, 2016 at the California Polytechnic State University in San Luis Obispo, California

It has an area of ​​32 square meters and is made of Mylar, a polyester brand that has been on the market since the 1950s.

When photons bounce off the sail, they transmit their momentum in the opposite direction to the leaping light.

"The bigger and shinier and smaller the mass of the spacecraft, the greater the thrust," explains Nye.

The thrust generated by these photons is tiny – but also unlimited. "Once you're in orbit, you'll never run out of fuel," he said.

Japan's space agency launched an awning called Ikaros in 2010, but others could not fully test the concept. [19659017] "It's a romantic idea whose time has finally come," Nye said. "We hope that this technology prevails."

Unlimited Energy

Their predecessor was LightSail 1, which was launched in 2015. Sail's test mission.

LightSail 2 cost $ 7 million, a relatively small amount compared to the space mission. It is scheduled to remain in orbit for a year, and represents a more definitive proof of concept.

  Bill Nye, one in the US as
Bill Nye, a popular science communicator known in the US as a "science guy."

"We want to democratize space exploration," enthused Nye, who invited universities and businesses to embrace the technology.

A few days after launching from the Kennedy Space Center in Florida, LightSail 2 will open its hinge Solar modules will then deploy the four triangular parts of their sail, which together form a huge square.

For this demonstration, solar modules will power the satellite's other functions, such as photography and ground communications.

During orbit On Earth, it will gradually gain altitude due to the pressure of solar radiation on the sail.

What will the technology be used for in the near future?

For one, it could facilitate the depth of space exploration. Although it launches much slower than a fuel-powered spacecraft, it accelerates permanently in space and eventually reaches breathtaking speeds.

The other application would be to keep a probe at a stationary point in space, which would require corrections to be made infinite. For example, a telescope that is looking for asteroids near Earth, or a satellite that needs to be fixed in a stationary orbit above the North Pole.

"They would need a tremendous amount of rocket fuel to stay stationary for 10 years, it just is not practical," Nye said.

Photons are unlimited.

As a bonus, the scientist said, "You can see it from the ground." With the naked eye.

LightSail 2 launches next month with the SpaceX Falcon Heavy rocket

© 2019 AFP

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Sailing between the stars: how photons could revolutionize space travel (2019, 20 June)
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