His simulations estimated that a 6-centimeter plate could carry 10 milligrams of charge into the mesosphere under natural sunlight. Ten milligrams may not sound like much; a drop of water weighs five times as much. But advances in engineering have reduced silicon chips to much smaller dust size sensors than that. These “smart pulse” systems can be adapted to a power source, radio communication, and a data collection sensor in cubes just one millimeter in diameter. “Researchers can do a lot when you give them a cubic millimeter of silicon,” Bargatin says. “And a cubic millimeter of silicon weighs a couple of milligrams.”
In the vacuum chamber test, they found that when they increased the intensity of the light beyond the power of sunlight, that extra force of energy carried the steering wheel higher. But after about 30 seconds, the disk began to crawl from the photophoretic force and eventually collapsed. Bargatin, Ultrathin Mylar is very weak on its own. The skin of the carbon nanotubes makes the Mylar disk more rigid, but the force of the high-speed molecular collisions will just close behind the wheel. The team model can predict what disk sizes, air pressures, and light intensities cause, and Bargatin says work is underway to develop a lightweight frame.
Bargatin predicts researchers will one day release sensor-laden levitators into the mesosphere and let them roam, like weather balloons or floating ocean sensors. “Another approach is to develop smart steering wheels that can control where they’re going,” he says. The same inclination that stabilizes the levitators could be used to direct them. And, he adds, suspending the levitator sensor like a parachute hanging from a canopy would help keep the system upright in the wind.
However, Marsh is not convinced that such a device can withstand mesospheric conditions. “Any instrument will have to operate in the extreme conditions of the mesosphere, where average winds can easily exceed 100 mph,” he writes. Winds from the upper mesosphere can be especially sheared, temperatures can drop to 140 below zero, and space climate radiates through the mesosphere and can damage communication systems.
Paul Newman, chief scientist of Earth Sciences at NASA’s Goddard Space Flight Center, agrees that explaining the mesospheric wind will be a major technical challenge, but he can’t help but be pleased with the possible applications. “I actually think it’s a really fun idea,” he says. One possibility would be to explore water vapor in the mesosphere, where polar clouds form so high that the sun still illuminates them at night. Mysterious clouds aren’t just beautiful, Newman says; their possible link to the increase in greenhouse gases means they may become more frequent, but researchers cannot track the water content and temperature of the mesosphere as well as they would like. Mesospheric clouds are “another sign of climate change. And we need information to prove it, “says Newman.” That’s why they could be very interesting for obtaining data on atmospheric composition. “
Newman adds that the fineness and levitation capacity of the plates could also be intriguing to Mars research. The atmospheric pressure of the Martian atmosphere is similar to the Earth’s mesosphere, so perhaps light, autonomous levitators could pick up measurements of temperature or composition. “You can only take off once a day, go up and down again and land on your little Martian scarecrow,” he imagines. “We do not have this information on Mars. That would be great. ” (NASA plans to test a small helicopter called Ingenuity as part of its Perseverance rover mission that will soon land, but this ship will be much larger and still in the test flight phase; it is not yet ready for scientific missions).
Bargatin says they are currently exploring applications for Mars and the team also expects their microflectors to work at sea level on Earth. But regardless of any eventual use, Azadi will always remember seeing Mylar’s creation float for the first time, exactly according to his theoretical predictions. “After that,” he says, “I called my girlfriend and said, ‘I think I’ll graduate soon.'”
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