…So the agency turned to retroreflectors, tiny glass beads that reflect laser light (in this case, a laser beam) back at its source…In addition to being incredibly maneuverable, dragonflies are exceptionally good gliders compared to other insects, which helps them conserve energy on long flights. The scientist brought in some specimens, and when Adkins pressed him on the issue, “the old fellow plucked the insect from its perch and tossed it into the air”, Adkins wrote. “It made about two circuits and landed nicely on the desk.”
The demonstration convinced Adkins, but the team still needed to figure out how to replicate a dragonfly’s wings, which flap 1,800 times per minute. To pull this off, scientists used a tiny fluidic oscillator, a device with no moving parts that’s completely driven by gas produced by lithium nitrate crystals. When initial tests showed that the prototype couldn’t carry the required 0.2 gm payload, designers added additional thrust by venting exhaust backward, much like jet propulsion. After a quick dragonfly-inspired paint job, the drone was ready for (covert) action, weighing just under a gram. Its glittering ‘eyes’ were the glass retroreflector beads destined to snoop on unsuspecting targets.
…While the CIA now had its robo-bug, it still needed a way to control it. Radio control was out of the question because any extra weight would doom the small insectothopter. So CIA scientists turned to the same lasers used for the retroreflectors. This was a portable laser unit, known as ROME, that produced an invisible infrared beam. The idea was that the laser would heat a bimetallic strip that would then open or close the dragonfly’s exhaust. While effectively throttling the ‘engine’, another laser—acting like a kind of rudder—would then steer the drone to its desired destination. With its gas-pumping engine and laser-based navigation system, the insectothopter could fly for only 60 seconds. But this was more than enough to get the dragonfly—and its payload—to a target some 200 meters away.
…The biggest problem with the insectothopter’s design was that an operator had to keep a laser manually trained on the drone during flight. Easily done in a static wind tunnel, less so in blustery and unpredictable conditions…In theory, the insectothopter could still be flown in less than 7MPH winds, but “the ultimate demonstration of controlled powered flight has not yet been achieved”, Adkins ultimately reported. “Though the flight tests were impressive, control in any kind of crosswind was too difficult.”