Their symbols estimated that a 6-centimeter plate could carry 10 milligrams of cargo in the mesosphere under natural sunlight. Ten milligrams may not seem like much; rainfall measures five times. But engineering advances have shrunk silicon chips into much smaller dust-sized sensors. These “smart dust” systems can collect power source, radio communications, and a data collection device in cubes just millimeters across. “Researchers can do a lot when you give them a cubic millimeter of silicon,” says Bargatin. “And a cubic millimeter of silicon measures two milligrams. ”
In their empty room test, they found that when the intensity of the light shone up beyond the power of sunlight, that extra energy carried the fly higher. But after about 30 seconds, the disc began to curl up from a photophoretic force, eventually falling apart. Ultrathin Mylar is very mobile on its own, says Bargatin. The shag of carbon nanotubes makes the Mylar disk harder, but the force of high-speed molecular collisions makes the fly. The team’s model can predict what disk sizes, air pressure, and light intensity are causing this, and Bargatin says work to develop a lightweight frame is ongoing.
Bargatin envies researchers one day releasing sensor-rich levitators in the mesosphere and allowing them to move, like weather balloons or floating ocean sensors. “Another way is to develop smart labels that can control where they go,” he said. The same flattening that stabilizes the levitators can be used to guide them. And, he says, blocking the sensor from the levitator like a parachute hanging from a canopy would help keep the system upright when there is wind.
However, Marsh is not convinced that such a device could withstand mesospheric conditions. “Any instrument must work in the extreme conditions of the mesosphere, where the average winds can exceed 100 mph,” he writes. Winds in the upper mesosphere can be particularly erratic, temperatures can drop to 140 below zero, and space weather radiates through the mesosphere and can damage communications systems.
Paul Newman, chief scientist of Earth Sciences at NASA’s Goddard Space Flight Center, agrees that accounting for mesospheric winds will be a major technical challenge, but it can only help to enjoy the potential applications. “I think this is a great idea,” he said. One opportunity would be to study water mist in the mesosphere, where polar clouds form so high that the sun still illuminates them at night. The secret clouds are not just beautiful, Newman says; their potential connection to more greenhouse gases means they could be more common – but researchers can’t monitor the water content and temperature of the mesosphere as well as they should leo. Mesospheric clouds are “another sign of climate change. And we need information to show that, ”Newman says. “That’s why they can be very attractive to get data on atmospheric composition. ”
Newman says the tininess and levitation potential of the plates could be of interest for Mars exploration. Martian atmospheric air pressure is similar to the Earth’s mesosphere, so light, autonomous levitators may be able to collect temperature or convection measurements. “You can go just once a day, and go up and then come back down and land on your little Martian landlord,” he thinks. “We do not have that information on Mars. That would be just wonderful. ”(NASA plans to test a small helicopter called Ingenuity as part of the Perseverance rover mission soon, but that craft will be much larger and is still at the test flight stage; not ready for science missions yet.)
Bargatin says they are currently investigating applications for Mars, and that the team also hopes to make their microflyers operate at sea level on Earth. But no matter what the past practice, Azadi will always remember seeing Mylar’s creation for the first time, just according to his theoretical prediction. “After that,” he says, “I called my girlfriend and I said, ‘I think I’ll graduate soon. ‘”
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