A team of Lawrence Livermore National Laboratory (LLNL) scientists and engineers pushed the limits of unmanned aerial systems to earn a place at the DARPA Lift Challenge, hosted by the Defense Advanced Research Projects Agency (DARPA).
The LLNL Collaborative Heavy-lift Aerial unManned Propellor Systems (CHAMPS) team ranked among the 132 teams selected from more than 480 applications to tackle one of aviation's most difficult challenges: breaking the heavy-lifting bottleneck.
By combining an ultra-lightweight body with novel battery technology, CHAMPS aimed to develop a drone capable of carrying a payload of over four times its bodyweight.
"The Laboratory offers a unique environment where people with diverse expertise work under the same roof," said Giovanna Bucci, a computational scientist at LLNL. "We could connect to collaborate and optimize the drone and its energy-storage technology as an integrated system."
In a typical drone, the battery delivers high power primarily during takeoff and landing; however, the 110-pound payload required the aircraft to sustain power throughout the entire distance of the five-nautical-mile course.
To meet that demand without exceeding the payload-to-weight ratio, the team used advanced manufacturing techniques to 3D print electrodes with channels that help lithium ions move more quickly through the battery. The design was optimized for the competition's high discharge rate and demonstrated almost six times better capacity retention than a conventional two-dimensional electrode at that rate.
Scaling the novel battery technology from small laboratory test cells to the larger battery packs required for the drone posed an additional challenge. The compressed development timeline required the team to integrate LLNL-developed components with commercially available technology.
"There's an accelerated learning process that comes with the short timeline of a DARPA challenge," said Bucci. "We went in knowing that failure was the most likely scenario, and many teams did drop out, but that's what we really signed up for - the extreme difficulty of the challenge."
The CHAMPS team experienced a burnout of the electronics system that prevented the drone from flying during the competition. Demonstrating the extreme difficulty of the challenge, there were only five drones that successfully completed the course with a total of nine scored runs.
Bucci credited the team's persistence and LLNL leadership for providing the resources and support that made the effort possible. The Laboratory Directed Research and Development Program also funded parts of the initial technology for the project.
"Everyone worked incredibly hard to make this happen," Bucci said. "We are grateful to our leadership for supporting the team and giving us the opportunity to take on a challenge of this scale."
The battery advances spurred by the competition can be further developed in the Laboratory and in collaboration with industry partners to support applications such as electric vehicles and electric aircraft, where battery weight, energy density and range are also critical.
