A light-powered spacecraft moored for unmanned terrain

It’s a bird, it’s a plane … No, it’s a tiny light levitating aircraft designed to fly in the air “ignoro-sphere.

We’ve been sending both crafts and people into space since the 1960s, however never whether a spaceship was able to sustain flight in a special zone of the Earth’s atmosphere called the mesosphere. Surrounded between the airfield containing planes and the high atmosphere containing satellites, the mesosphere is largely an unoccupied territory in the confined area between Earth and space. So far.

A team of engineers from the University of Pennsylvania has created a small spaceship that they say can levitate in the mesosphere, using only sunlight.

Why it’s important – Built using affordable low-cost materials such as mylar (a plastic used in some balloons), the nearby spacecraft could allow scientists to finally study make the Earth’s mesosphere. Doing this would provide access to vital measurements of carbon dioxide, which scientists need to properly monitor climate change.

The research was published Friday in the journal Advances in science.

Here is the background – The Earth’s atmosphere is made up of four main layers:

  • Troposphere – the highest point, up to 375 miles above Earth and home to observatory centers, such as Hubble (370 miles) and the International Space Station (250 miles).
  • Stratosphere – the ozone layer resides here.
  • Thermosphere – covering the atmosphere, up to 10 miles above the ground, through which planes fly.
  • Mesosphere – child of the central atmosphere, the mesosphere lies between the troposphere and stratosphere, at about 31-53 miles above the ground.

In the video outlining the research below, Igor Bargatin, lead author of the study and associate professor of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania, makes a hilarious comment. on the mesosphere as the “ignoro-sphere.”

And for good reason.

Using only direct sunlight intensity, the researchers were able to build the crafts near this location.Azadi et al., Sci. Adv. 2021; 7: eabe1127

Here’s why: Due to the pressure at this altitude above the Earth – around 10-30 Pascals – this part of the atmosphere causes too much drag on satellites, which can lead to overheating on them, and not building enough for planes.

Rockets, for their part, occasionally pass through the mesosphere on their way out of the Earth’s atmosphere, but they do not last long.

So the research team decided to try to build a craft that could go beyond the needs of planes and satellites by using a more natural fuel source: the Sun.

Using a process called photophoresis, the only way to rely on maintaining power to light sails, the research team decided to design a small spaceship that would be able to hold flights in the Earth’s mesosphere.

“It’s an interesting idea, that you can just light up something and make it navigate and get over gravity,” Bargatin says in the video.

What they did – The researchers designed a disc-like craft, six millimeters in diameter, with a flat mylar top and a scratch base made of carbon nanotubes.

The idea, the researchers explain, is that air molecules at mesosphere-like pressures treat these two surface textures differently. Air molecules kick off the abrasive bottom of the disc with a higher speed than they can on the top side of the disc, creating a net lifting force that balances, or lowers, the disc in mid-air.

Azadi et al., Sci. Adv. 2021; 7: eabe1127

The researchers worked hard to recreate atmospheric pressure and sunlight in their Pennsylvania laboratory, creating an optical light trap that they could shape and adjust to control the movement of the discs. .

Why did they find out – Unlike a previous study by the team, which showed how temperature differences on both sides of the discs were needed for levitation, the new design shows that the same levitating effect is possible with the same temperature on levitation. each side.

Not only were their tiny discs capable of sustaining “levitated flights”, but the researchers show in the study that they can carry large payloads, including many scientific instruments. times the weight of the discs themselves. For trades like those in this study, a payload of up to 10 milligrams could be measured, which the authors write is enough for the discs to carry small dust or a carbon dioxide sensor into the mesosphere.

What Now – While the first results are promising, the researchers write that there is still a lot of work to be done before these small crafts can begin calling the mesosphere home. For one, this study was done in a controlled laboratory setting, so it remains to be seen whether these lightweight spacecraft can perform in the real world.

The researchers also have to try ways to scale their technology, so a craft can hold more than 10 milligrams of cargo at a time. It would also be great to be able to lead and control the craft once they are in this forgetful stage of the atmosphere as well.

Summary: We report light transfer of macroscopic polymer films with nanostructured surface as candidates for near-distance flight. We built centimeter-scale discs made of 0.5-micron-thick commercial mylar film coated with carbon nanotubes on one side. When illuminated by an intensity of light similar to natural sunlight, the polymer disk heats up and interacts with incident gas molecules differently on the upper and lower sides, emitting net recall force. We observed levitation of 6-mm-diameter discs in an empty chamber at pressures between 10 and 30 Pa. Additionally, we controlled the flight of the discs by using a shaped light field that captured the optically levitating discs. Our experimentally tested theoretical model predicts that the lift forces can be many times the weight of the films, allowing payloads of up to 10 milligrams for low-cost microflyers under solar power at altitudes of 50 to 100 km.