In Yolo County, California, startup Zipline has begun testing its second-generation drones with dozens of flights each day. The drones are already in use delivering blood to hospitals in Rwanda, but Zipline hopes to expand to other countries and other medical supplies.
Zipline's system flicks a cord up to catch a hook at the back of a passing drone to snatch it out of the air. The cord pays out to decelerate it then winds back in to lower the drone like a caught fish.
Zipline drones are designed to fly at night and in the rain. They integrate with air traffic control systems and are equipped with blinking lights like ordinary aircraft.
After each flight, a Zipline drone's battery and electronics package is placed into a rack for recharging. It takes about five battery packs to operate two drones continuously.
Zipline's test site in Yolo County, California, consists of a storage container, a couple of temporary buildings on a graded gravel patch, and the aluminum struts of the launch and capture systems.
Dual propellers move the drone at speeds up to about 80 mph. If one motor fails, the drone will still fly on a single one, and during cruising only one is used.
The rolling hills around Zipline's test site is surrounded by oak trees filled with acorn woodpeckers and fields filled with western meadowlarks. In summer after winter rains stop, much of the green fades to brown and yellow.
Zipline tries out new software at its Central Valley 's test site, and drones don't always snag the cord that's supposed to stop their flight. If they miss, they buzz around in a circle for another attempt.
