DARPA honors drone teams for light copters that carry heavy loads

Presently, cargo-carrying helicopters and multirotor drones have at best a 1:1 payload-to-body-weight ratio. However, think how much more efficient they would be if that ratio could be boosted to 4:1 or beyond.

Well, that's exactly what US Department of Defense organization DARPA (Defense Advanced Research Projects Agency) set out to make happen with its recent Lift Challenge.

In a nutshell, the competition invited teams from around the world to develop VTOL (vertical takeoff and landing) drones weighing less than 55 lb (25 kg) while being capable of lifting at least one 110-lb (50-kg) standard barbell plate. That plate had to be carried down a 100-ft (30.5-m)-wide lane at an altitude of 150 ft (45.7 m) for 4 nautical miles (7.4 km), dropped on the ground, then the drone had to continue flying for one more nautical mile (1.9 km) before landing.

The event took place in Ohio at the National Museum of the US Air Force, from August 2nd to 9th. Almost 100 teams took part, from over 30 US states and 25 countries.

The 1st, 2nd and 3rd-place Payload-to-Weight Performance Awards were slated at US$2.5 million, 1.5 million and $1 million respectively, although teams would only receive half that amount if their drone didn't achieve the 4:1 payload-to-weight ratio. As it turned out, the three top-place teams didn't quite manage that ratio, although they did all come close.

The AVIDrone team from Columbia, Maryland came in first, with a helicopter-type drone that achieved a ratio of 3.84:1. They were followed by MTech Operations from Sudbury, Massachusetts, with a hexacopter that pulled off a 3.64:1 ratio. In third place was Xtreme Aerial Concepts from San Jose, California, with another helicopter drone that managed a ratio of 3.45:1.

Three other teams took home $500,000 prizes, in the Subjective category.

One of these groups, the University of Maryland Autonomous Micro Air Vehicle Team, won the Most Revolutionary Aerodynamic Design Award. Their tri-rotor drone takes off and lands vertically like a multi-rotor aircraft, but once airborne transitions to forward flight via smaller propellers mounted horizontally on each of its rotor blades.

The Portal Aircraft Company from Mansfield, Texas, won the Most Revolutionary Powertrain Design Award with a square-framed quadcopter that uses hot or cold turbine exhaust to drive the rotors, replacing driveshafts and mechanical linkages. Reportedly this approach could boost reliability by reducing the number of mechanical components.

Finally, the DefendTex team from Moab, Utah took the Most Promising Technology Award with its ethereal-looking quadcopter. Although the aircraft does have skinny rigid propeller arms, it utilizes string-based supports to reduce its hub structure and overall weight.

This design reportedly makes the drone easy to deploy, while minimizing disk loading on each propeller. And although the aircraft failed to complete a scored run, it did achieve the highest payload-to-weight ratio of the entire competition, at an amazing 9.63:1.

"We chose the [4:1] target because we believed it might be possible, and what we proved this week ... Even though we didn't hit it in an official score, we saw the path at this competition," said Phillip “Donna” Smith, Lift Challenge program manager.

Source: DARPA