And how Indemnis found a way to do it.
Drones are not immune to the whole “What goes up must come down” thing, and their descent is not always planned. If a drone falls out of the sky, the plummeting load can weigh up to a dozen pounds and be accompanied by four spinning rotors ready to rip into, or lop off, anything that gets in their way. Amber McDonald, CEO and one of the founders of the company Indemnis, first saw this problem when working in the film industry, so she, and her team, set out to fix it.
Since drones have four rotors, if one of them fails the imbalance sends the machine into a high rpm tumble. If the drone just popped out a parachute like the paratrooper toys you used to throw out the window as a kid, it would almost immediately be sucked into one of the still spinning rotors, providing no protection at all, and adding a tangled mess of rope and fabric to the crash site.
The team at Indemnis looked into other solutions, but the parachute seemed too good to pass up. If they could make it work, it’d be cheap to make, and effective. They just had to figure out a way to keep it away from the drone’s rotors. So, they decided to use a parachute, but have it release outside the draw of the rotors, “By using an inflatable tube that becomes rigid, and stuffing the parachute inside, we could extend from the airframe and then launch the parachute,” says McDonald. While the parachute would be attached to the drone, it could be far enough from its moving parts to avoid failure: “It protects the parachutes lines and keeps the attachment point of the parachute outside of the roll radius.”
While the concept makes sense, turning it into a reality was a far greater challenge. In order to escape the roll radius, the tube would have to extend exceptionally fast. And no material on the market was capable of being inflated fast enough without ripping itself to shreds, so they made one.
The material that caught their eye was Dyneema, a fiber 15 times stronger than steel. The only issue? The military had spent years and piles of money trying to figure out how to attach the fabric to itself, something you need if you’re trying to make a tube, and they failed. “We just tried a multitude of different variations. A lot of trial and error about a year and a half of throwing the entire book at it and being very frustrated,” says McDonald.
But when they stumbled upon radio-frequency welding, it worked. They could attach the material to itself and the bond was stronger than the material alone. They patented the process, and applied it to their idea. The tube could inflate at 30 psi in 30 milliseconds with a launch velocity of 90 mph, and it’d stay strong. Almost as stiff as the hard plastic of the drone itself. It’d work. So they started building their system, Nexus.
They added onboard software to tell when the drone is entering a fatal roll and automatically launch the parachute, but they also gave control to the drone operator to launch the parachute if they saw the drone headed for trouble, like a building, electrical line, or tree.
Indemnis is currently working to get their Nexus system into more applications, and working with the government to get waivers to allow Nexus-equipped drones to fly where most drones aren’t allowed, like over groups of people, greatly increasing the usefulness of a drone.
After that, Indemnis has far greater plans for the material-science enigma they cracked. “It's a lightweight, high-strength material that we can make inflatable. That's never been done. There are a lot of uses for it,” says McDonald. We'll just have to wait and see what they might be.