Flight is not easy on the edge of space. But small “microflectors” could rise in the Earth’s atmosphere powered only by sunlight, the experiments suggest.
At altitudes between about 50 and 80 kilometers above the Earth's surface, in what is known as the mesosphere, the atmosphere is so thin that planes and balloons cannot remain high. But mechanical engineer Mohsen Azadi and colleagues at the University of Pennsylvania have been engaged in a technique that uses light to levitate objects. The researchers cut 6mm diameter transparent Mylar disks and coated the undersides with carbon nanotubes. When heated by light, the small plane floated inside a vacuum chamber with a pressure that mimicked the mesosphere, researchers reported Feb. 12 in Science Advances.
Carbon nanotubes are critical for microflectors to achieve takeoff. Nanotubes absorb light and heat the steering wheel. Air molecules gain energy when they collide with the heated aviator, bouncing off at higher speeds. The molecules gain more strength by hitting the carbon nanotubes at the bottom of the spacecraft. This is thanks to the corners of the material: the air molecules collide several times with the nanotubes, heating up even more and gaining more energy than those reaching the top. That extra energy translates into faster molecules. As a result, air molecules bounce off the bottom of the microflate faster than the top, generating elevation.
Microflectors could work with sunlight or lasers and someday could carry small instruments to measure the conditions of the relatively unexplored mesosphere, the researchers suggest.
The light helps take off small planes made of carbon-coated Myotubes coated with Mylar. These “microflectors” could one day be used to explore the height of the Earth’s atmosphere.