Alphabet and SoftBank’s solar-powered drone provides first LTE connection

Airborne cell towers have a number of advantages over their terrestrial brethren. They can cover a greater geographic area and be moved to where they’re needed. But while the concept is years old, the technology is still under development.

Today, though, Google’s parent company Alphabet and Japanese tech giant SoftBank announced a minor milestone in their efforts to make flying cell towers a reality, running a stable LTE connection from a solar-powered drone 62,000 feet high in the stratosphere. It was a good enough connection to support an international video call, with participants from Japan and America, including Vint Cerf, one of the “fathers of the internet.”

The test is part of a partnership between Alphabet’s Loon and SoftBank’s HAPSMobile that was first announced in April 2019. Loon, which is best known for its balloon-based cell towers, provides the communications payload, while HAPSMobile builds the aircraft.

In this case, that is the Sunglider: an enormous autonomous solar-powered drone designed to stay aloft for months at a time. This huge craft looks like a single massive wing, some 78 meters (255 feet) across. It’s powered by 10 propellers with a top speed of 110 km/h (68 mph). While that’s pretty slow for an aircraft, the Sunglider (previously called the HAWK30) is designed for endurance rather than speed. It will linger high in the stratosphere above commercial flights, recharging its batteries from the sun and autonomously adjusting to the changing winds.

The successful LTE test is a world’s first for a fixed-wing autonomous aircraft, says HAPSMobile. “The payload performed as planned in the demanding conditions of the stratosphere where wind speeds reached greater than 58 knots (approximately 30 meters per second) and temperatures were as low as -73 degrees Celsius,” said the company.

Once an LTE connection was established, it was used to support a videoconference. Participants called in on regular smartphones, including Loon CEO Alastair Westgarth; Jun Murai, HAPSMobile’s external director and “the father of the internet in Japan”; and Cerf, who is VP and chief internet evangelist at Google. HAPSMobile claims the call was “high-definition” and “low-latency,” though it did not provide details of connection speeds.

In a press statement, HAPSMobile CEO and president Junichi Miyakawa said the test flight took the company one step closer to realizing its goal of creating green aircraft that can provide high-speed internet anywhere in the world.

“Watching this test flight, I was reminded of Castle in the Sky, the anime directed by Hayao Miyazaki in 1986, and how the airship in the story filled me with aspiration,” said Miyakawa. “We once again moved one step closer to our goal of building a base station that floats in the sky solely on solar energy.”