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Energy efficiency of Airbus Zephyr S

Published 21 October, 2022

The Airbus Zephyr S:

  • covers around 1490 m/kJ
  • and moves mass at around 111.7 kg*m/J


The Airbus Zephyr S is a lightweight, solar-powered, unmanned plane that first flew in 2018. 1)

Distance per Joule

Zephyr S carries 24 kg of lithium-ion batteries with a 435 Wh/kg specific energy.2) In August 2022, Zephyr S flew 56,000 km over the course of 26 days.3) This gives us 1490 m/kJ.

Mass*distance per Joule

Zephyr S has a mass of 75 kg.4)

We have:

  • Distance per kilojoule: 1490 m/kJ
  • Mass: 75 kg

This gives us 111.7 kg*m/J.


“The first stratospheric UAS of its kind, Zephyr provides a persistent and adaptable solution, unlike other unmanned aircraft. Its persistence enables a capability of flying continuously for months at a time, at around 70,000ft, above weather and conventional air traffic. It is a HAPS: a High Altitude Platform Station, and is the only HAPS to have demonstrated day/night longevity in the stratosphere.” Zephyr. Airbus. (2021, August 3). Retrieved October 21, 2022, from
“In summer 2018 for its maiden flight from Arizona, the Zephyr S remained aloft for 25 days 23 hours 57 minutes, nearly twice as long as the previous record flight of 14 days set by its predecessor.[16] It used Amprius lithium-ion batteries with silicon nanowire anodes for a 435 Wh/kg specific energy up from 300–320 Wh/kg.[17] High-efficiency, lightweight, and flexible inverted metamorphic (IMM) multi-junction epitaxial lift-off (ELO) GaAs solar cell sheets manufactured by MicroLink Devices provided the solar power with specific powers exceeding 1,500 W/kg and areal powers greater than 350 W/m2.[18]” Wikimedia Foundation. (2022, September 27). Airbus Zephyr. Wikipedia. Retrieved October 21, 2022, from
“During this flight, Zephyr 8 more than doubled the previous UAS endurance record, just under 26 days, and flew in excess of 30,000 nautical miles – more than one lap around the Earth. The 1,500 flight hours beat all known unmanned aircraft endurance records, marking significant capability and informing future mission requirements.” APNT/Space CFT concludes high altitude experimentation. (n.d.). Retrieved October 21, 2022, from
“The Airbus Zephyr is the world’s leading solar-electric stratospheric Unmanned Aerial System (UAS), with a wingspan of 25 meters and it weighs less than 75kg.” Wang, B. (2021, October 24). Airbus solar powered aircraft can fly for 18 days and replace 250 cell towers. Retrieved October 21, 2022, from
power_of_evolution/evolution_engineering_comparison/energy_efficiency_of_airbus_zephyr_s.txt · Last modified: 2022/10/21 21:16 by harlanstewart