HAPSMobile flew their Sunglider, a solar powered high-altitude platform station (sometimes called pseudo-satellite) airplane, on its fifth test flight to an altitude of 62,500 feet, where its communication payload was able to provide an LTE connection to the ground. HAPSMobile is a joint venture between SoftBank Corp., a Japanese holding corporation with experience in telecommunications, and Aerovironment Inc., an unmanned aircraft systems manufacturer based in Simi Valley, California.
The test flight, having started at Spaceport America in New Mexico, lasted 20 hours and 16 minutes, of which 5 hours and 38 minutes were spent flying in the stratosphere, a first for the aircraft. The Sunglider reached an altitude of 62,500 feet (19km), facing temperatures down to -73 degrees Celcius and winds up to 30 meters per second. The airplane has a wingspan of 78 meters and cruises at 110kmh. Its motor is powered by lithium ion battery which is charged using a solar array which covers the entirety of the upper wing surface. This should give it an endurance of “several months”. The Sunglider flies fully autonomously.
The communications payload was provided by Loon, a company of Alphabet, also known for Google. It delivered LTE connectivity to the ground during roughly 15 hours of the flight. Loon and AeroVironment employees were able to make a videocall to HAPSMobile team members in Tokyo. Sunglider makes use of LTE Band 28 on the 700MHz spectrum, so regular smartphones can be used. Using one aircraft, HAPSMobile will be able to deliver service to an area with a diameter of 200km.
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. We once again moved one step closer to our goal of building a base station that floats in the sky solely on solar energy. Even though the temperature fell below 73 degrees Celsius, our work on endurance tests bore fruit and resulted in a successful test flight. On the day of the test, Sunglider faced aerial currents of roughly 30 meters per second, so I was relieved when it hit the runway after clearing all test items. In this test flight, we also successfully conducted communications with smartphones on the ground and obtained data for fully automated piloting. While there is still much room for improvement, we will continue to work toward realizing our dream.
– Junichi Miyakawa, Representative Director & CTO of SoftBank Corp., President & CEO of HAPSMobile