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Solar sail technology was once only theoretical, but it's now being developed to propel spaceships. How did the first solar sails get into space, and why?

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Occasionally, scientists come up with ideas that sound totally Sci-Fi.  Frank Drake decided to look for signals sent by aliens.  Nikola Tesla tried to build a death ray, and in the 1980s in this grand tradition of off-the-wall ideas, an engineer named Vladimir Syromyatnikov proposed that the Soviet Union build a giant space mirror.  The mirror would reflect sunlight back to Earth, which would basically let them turn night into day, if they wanted to.  People could work later, they wouldn't need to turn on lights as much, and they'd have a cool new way to control nature.

The government's response was basically, that sounds fun, let's try it.  Syromyatnikov was already an accomplished engineer.  Before this, he worked on the Vostok program, which sent people to space for the first time, and he designed the docking systems for the Mir Space Station and the ISS, some of which are still in use today, but even though his specialty was docking systems, he was also really interested in solar sail technology.

Solar sails use photons, the particles that make up light a lot like how boat sails use wind.  When sunlight hits a solar sail, those photons bounce off and give the sail some momentum, which you could use to move both the sail and a spacecraft attached to it.  By changing the sail's orientation, you could control that movement.  Solar sails could be super useful, because they take advantage of an energy source that's already freely available in space, so you don't need to be as concerned about fuel consumption.  Plus, they can be pretty lightweight.

In the late 80s, solar sail technology was still very theoretical, and Syromyatnikov wanted to take that theory and put into practice.  He also knew that the Soviet Union wanted to increase worker productivity, especially in agriculture, and he realized that these very different goals could be achieved with the same technology.

By controlling the orientation of a solar sail, you not only control the spacecraft's movement, but also the direction of the reflected light, so he figured if he built a giant solar sail in space, he could use it to reflect sunlight back to Earth.  His proposal called for eventually building an array of giant space mirrors that reflected enough light to extend daylight hours, which is hard to imagine but not impossible.  The sun is pretty bright.  

For whatever reason, the government thought it was a good idea and the Znamya project was born.  Znamya, which means 'banner' in Russian consisted of a set of thin mirrors made of mylar, a thin reflective material that's also used to make those fancy crinkly balloons.  After they were launched, the mirrors would unfold themselves in space and reflect light back to Earth.

If it worked, everybody would be happy.  Syromyatnikov would get to test solar sail technology and the USSR would get its extra long workdays.  (?~2:40), the Soviet Union's space organization and various state-owned companies were all eager to get this project, well, off the ground, but there was a bit of a problem.  While Syromyatnikov and a bunch of other engineers were still working on designing and building their mirror, the Soviet Union ceased to exist.  So that kind of threw a wrench into things, but the Znamya team didn't let a little thing like complete geopolitical upheaval get in their way.

The equipment and engineering expertise needed to complete the project were donated by the companies and organizations that survived the transition, kind of like a big engineering potluck.  Znamya 1 was a successful ground test and Znamya 2 made it to space in 1992 aboard a progress rocket which then docked with the Mir Space Station.  The sail's orientation was fixed, so they couldn't control which way the reflected light beam went, but it was set up so that once it unfolded itself, the light would hit Earth and it totally worked.  

It unfolded itself into a majestic 20 meter wide mylar flower and reflected a beam of light back to Earth that was about as bright as the full moon.  The light was hard to see from Earth because Europe was super cloudy that night, but it was visible from at least one city in France and the Mir cosmonauts watched the beam travel across Europe and into Asia.  

After this success, the Znamya engineers got to work on their next mirror, Znamya 2.5, which was about five meters wider and was built so they could actually control its orientation.  If this mirror worked, they'd be well on their way to lighting up the whole frozen north with an army of space mirrors, plus they could move on to testing how well these mirrors worked as sails.

In 1998, Znamya 2.5 flew aboard a supply rocket to Mir, but this time, it did not go so well.  The unfolding process, which had worked really well for Znamya 2, hit a literal snag when one of Mir's antennas caught and punctured the mirror as it was blooming.  (?~4:36) ground control did everything they could to save it, but the mirror was ripped to shreds.  Once they finally got it untangled, they gave it a satellite's viking funeral and allowed it to burn up in the atmosphere.

After that, the rest of the project was cancelled.  It had become too expensive and people finally realized that making a network of night-defying space mirrors was probably not a great use of the government's money.  So Syromyatnikov went back to designing docking systems, although he remained a major proponent of solar sail development until his death in 2006, and while no one's trying to create a second moon in the sky anymore, engineers are still working on developing solar sail technology so we can use it to propel spaceships.

The Soviet government's goal might have been a fail, but Syromyatnikov's dream of using sails to zoom around the solar system could still come true someday.

Thanks for watching this episode of SciShow Space.  If you'd like to learn more about solar sails and where we are 30 years after Znamya, you can check out one of our earlier episodes where I explain all about it.