Their simulations estimated that a 6-centimeter plate could carry 10 milligrams of cargo into the mesosphere under natural sunlight. Ten milligrams may not sound like much; a drop of water weighs five times as much. But engineering advances have reduced silicon chips in sensors with much smaller dust dimensions than that. These “smart dust” systems can be fitted with a power source, radio communications and a data collection sensor in cubes of only one millimeter. “Researchers can do a lot when you give them a cubic millimeter of silicon,” says Bargatin. “And a cubic millimeter of silicon weighs a few milligrams.”
In their vacuum chamber test, they found that when they turned on the light intensity over the sun’s power, that pile of extra energy carried the flyer higher. But after about 30 seconds, the disk began to bend with photophoretic force, eventually collapsing. Ultrathin Mylar is very weak on its own, says Bargatin. The shag of carbon nanotubes makes the Mylar disk more rigid, but the force of high-speed molecular collisions eventually closes the flyer. The team model can predict what disk sizes, air pressures and light intensities are causing this, and Bargatin says work is underway to develop a lightweight frame.
Bargatin intends to one day release sensors-laden levitators into the mesosphere and let them circulate, such as weather balloons or floating ocean sensors. “Another approach is to actually develop smart leaflets that can control where it’s going,” he says. The same tilt that stabilizes the levitators could be used to guide them. And, he adds, suspending the sensor from the levitator like a parachute hanging from a canopy would help keep the system upright when facing the wind.
However, Marsh is not convinced that such a device could withstand mesospheric conditions. “Any instrument will have to operate in extreme conditions of the mesosphere, where average winds can easily exceed 100 mph,” he writes. Winds in the upper mesosphere can be especially shear, temperatures can drop to 140 below zero and space weather radiates through the mesosphere and can damage communications systems.
Paul Newman, an Earth scientist at NASA’s Goddard Space Flight Center, agrees that accounting for the mesospheric wind will be a major technical challenge, but he can’t help but enjoy the possible applications. “Actually, I think that’s a very interesting idea,” he says. One possibility would be the sounding of water vapor in the mesosphere, where polar clouds form so high that the sun still illuminates them at night. Mysterious clouds are not only beautiful, says Newman; their possible connection with the increase in greenhouse gases means that they may become more common – but researchers cannot track water content and mesosphere temperature as they would like. Mesospheric clouds are “another sign of climate change. And we need information to show that, ”says Newman. “Therefore, they could be very interesting to obtain data on the atmospheric composition.”
Newman adds that the tiny plates and levitation capacity could also be interesting for research on Mars. The air pressure in the Martian atmosphere is similar to the Earth’s mesosphere, so perhaps light, autonomous levitators could collect temperature or composition measurements. “You can take off once a day, climb and then turn down and land on your little Martian lander,” he imagines. “We do not have this information on Mars. That would be fantastic. “NASA plans to test a small helicopter called Ingeniousness as part of its upcoming Perseverance rover mission, but that boat will be much larger and still in the test flight stage; it is not yet ready for missions. scientific.)
Bargatin says he is currently exploring applications for Mars and that the team also hopes to make its microfilters work at sea level on Earth. But, regardless of any possible use, Azadi will always remember that he saw Mylar’s creation floating for the first time, exactly according to his theoretical predictions. “After that,” he says, “I called my girlfriend and told her, ‘I think I’ll graduate soon.'”
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