The U.S. Army’s Assured Positioning, Navigation and Timing/Space (APNT/Space) Cross-Functional Team (CFT) has concluded a 64-day stratospheric flight demonstration, utilizing Airbus’s Zephyr 8 ultra-long endurance solar-powered unmanned air system (UAS).
After an unprecedented 64 days in flight, the prototype aircraft‘s flight campaign ended on August 18. The Zephyr 8 UAS encountered events that led to its unexpected termination over the Yuma Proving Ground (YPG) in Arizona.
Launched from YPG on June 15, the solar-powered Zephyr 8 UAS ascended to over 60,000 feet into the stratosphere before executing its flight plan over the southern portion of the United States, into the Gulf of Mexico, and over South America. Once returning to airspace over YPG, the team conducted multiple assessments.
During this flight, Zephyr 8 more than doubled its previous UAS endurance record, just under 26 days. It flew in excess of 30,000 nautical miles (35,000 miles – more than one lap around the Earth. Its 1,500 hours of flight smashed all known uncrewed aircraft endurance records.
In addition to the new endurance record, the flight also marked a number of firsts for Zephyr 8, including its departure from U.S. airspace, flight over water, flight in international airspace, data collection, and direct downlink while outside of U.S. airspace, the longest continuous duration (7 days) utilizing satellite communications, and the demonstration of resilient satellite command and control from three different locations – Huntsville, Alabama; Yuma, Arizona; and Farnborough, U.K.
The flights also successfully demonstrated Zephyr’s energy storage capacity, flight endurance, station-keeping, and agile positioning abilities. In July 2022, Zephyr S spent 26 days airborne, breaking its previous record from 2018.
The Zephyr has a wingspan of 25 meters (82 ft) and weighs less than 165 lb (75 kg). During the day, Zephyr uses its solar cells spread across its wings to recharge high-power lithium-sulfur batteries and drive two propellers. At night, the energy stored in the roughly 24 kg batteries is sufficient to maintain Zephyr in the sky.
The events that led to the termination are under investigation. The Army says no injuries or risks to personnel or other aircraft resulted from this flight-ending incident. Given the amount of data that was generated during the 64-day flight and the time required to analyze it, as well as the need to investigate the termination events, further flight demonstrations have been postponed until 2023.
“Our team is working hard to gather and analyze important data following the unexpected termination of this flight,” said Michael Monteleone, Director of the APNT/Space CFT. “Despite this event, the Army and its partners have gleaned invaluable data and increased knowledge on the endurance, efficiency, and station-keeping abilities of high-altitude UAS platforms. That knowledge will allow us to continue to advance requirements for reliable, modernized stratospheric capabilities to our Soldiers.”