Lifesaving drones designed with CAD software

During a visit to Tanzania, the concept of flying drones packed with medical supplies to previously inaccessible countries was born. A researcher at Ifakara Health Institute showed Keenan Wryobek, who later co-founded Zipline International Inc., his collection of thousands of cases in which doctors around the Tanzanian countryside didn’t have what they needed to treat a patient.

Wryobek learned that medical supplies are nowhere near as accessible to doctors in Tanzania as they are in the U.S., and that the lack of adequate blood supplies has resulted in patient deaths. He found that even something as seemingly simple as topical antibiotics to treat cuts were not readily available.

Wyrobek was especially struck by the story of a Tanzanian adolescent who had a minor cut on his arm that became infected after a few days because he couldn’t receive the necessary antibiotic in time. Instead of being treated immediately and then forgetting about it as the wound healed, the infection became so bad that a part of youth’s arm had to be amputated.

“A doctor can save the life of a mother who is bleeding after childbirth with a unit of blood relatively easily,” says Wryobek, who is Head of Product and Engineering at Zipline. “But if you don’t have that unit of blood, it’s deadly.”

“In my career I’ve gotten to work on some very important projects that we never figured out how to scale. I’ve also worked on lots of projects that really didn’t matter, but they sold like crazy. I wanted to find something that mattered and that we could scale,” he says.

In 2016, the company developed and produced reliable drones with great range and precision and launched a drone medical-supply delivery system that operates in Rwanda, a landlocked East African country.

“Our first-generation aircraft and logistics system allowed us to create the first and only drone delivery service in the world, which is helping to save lives in Rwanda every day,” Zipline CEO Keller Rinaudo says. Since launching the service in Rwanda, Zipline has made over 7,000 deliveries of over 13,000 units of blood, including thousands of emergency deliveries.

Traveling at over 100 kilometers per hour (over 62 miles per hour), products arrive faster than in any other mode of transport, with no pilot required. The aircraft’s range is 80 km service radius while it can carry up to 1.75 kilos of cargo. In under 30 minutes, the special-ordered medical products are delivered gently by parachute to a designated area the size of a few parking spaces.

“It’s our job to make a plane that works in all weather conditions and can cover the required distance, while also accounting for any unforeseen problems,” Wryobek says.

Digitalization is a key component of Zipline’s drone design process. During its early years, the company used a cost-effective computer-aided design (CAD) package but soon realized its limitations when it came to practical applications. The engineers needed a solution with additional functionalities that could automate certain tasks and allow them to interact with their CAD database. The engineers also wanted add-on modules as part of the new solution.

“I really pushed hard to move the company to NX”, recalls Scott Parker, Mechanical Engineer at Zipline. “Something that you want to do with an aircraft like this is check that your part fits with the rest of the plane. In the previous CAD package, that would be a multi-hour ordeal. With NX, you just load it up. Everything is fast, and you don’t make mistakes.”

As the team of three engineers became a team of nine, “We needed to have multiple people working on the vehicle at the same time,” says Paul Perry, Mechanical Engineer at Zipline.

“The plane brings together many disciplines: electrical engineering, mechanical engineering, manufacturing engineering, and of course aero engineering,” Wryobek adds. “NX is a powerful tool that brings all these disciplines together.”

The CAD software also allows Zipline to determine the location of critical areas where high-grade aerospace materials are needed versus other areas where they can use a plastic or foam to achieve the same structural integrity and mechanical functionality at a lower cost and mass.

With the amount of medical supplies Zipline’s drones have to carry, testing for weight is critical. Each kilogram saved increases the range of the aircraft by five percent. Using NX Journal enables Zipline to create a custom, bottom-up Bill of Materials that gives a detailed mass buildup, which helps the firm optimize the aircraft. The ability to quickly perform a thickness or stress analysis to cut weight allows Zipline to save on excessive iteration and testing time and to hit their weight targets.

“The majority of the optimization we do on this plane focuses on two things: structural and thermal,” Perry says. “Clearly, mass is the most important single variable we typically optimize, so doing structural optimization allows us to reduce mass while still maintaining our stiffness and strength goals.”

Several simulations are run before the drone is manufactured. During these test flights in the virtual world, Zipline can, for example, simulate the heat characteristics of the battery during the flight or the thermal performance of the drone in the climate of Rwanda, which differs significantly from the conditions in the Bay Area.

Zipline’s drones are designed from the ground up for manufacturability. “We make it easier to assemble,” says Sam Chaknova, Manufacturing Engineer at Zipline. “We also need them to be super-maintainable. That’s going to allow us to maintain it in the field and keep these vehicles running and saving lives.”

And his colleague Jeremy Schwartz, Roboticist at Zipline, adds: “Here in California, we’re performing a test so that when a plane takes off in Rwanda, it’s delivering blood to somebody who needs blood. It’s saving somebody’s life, and just thinking about that is an incredible thing.”

March 2019