On 11 July 2018, a Zephyr S aircraft took off on its maiden flight in Arizona. It flew for 25 days, 23 hours and 57 minutes, marking the longest flight duration ever achieved without re-fuelling. The Zephyr aircraft has also flown in excess of 74 000 feet and repeatedly demonstrated an ability to remain in the stratosphere overnight. These achievements of un-interrupted and persistent flight have proven the readiness of Zephyr as a platform capable of delivering connectivity services from the stratosphere, and are the result of a 15‑year journey.
Zephyr is an ultra-light solar-powered high-altitude platform station (HAPS). Solar energy powers daytime flight as well as re-charging batteries for night-time operations. It has a 25 metre wingspan (one third the width of an Airbus A380) and can launch from a selection of sites strategically positioned across the globe.
“Committed to success for HAPS at the upcoming WRC‑19 in November, Airbus is focused on broadening the previous HAPS allocations.”
Zephyr flies above the weather and regular air traffic, covering distances of over 1000 nautical miles a day — that’s 1852 kilometres! Of particular interest to telecoms operators is Zephyr’s ability to remain persistent over a designated location for long periods of time, delivering connectivity services across a wide area.
Zephyr weighs less than 75 kilograms, the same as two aircraft seats. It is this highly optimized aircraft mass, together with the available power of the Zephyr propulsion system and the high efficiency of the solar cell technology, which permits Zephyr to remain continuously within the stratosphere after launch, day after day, performing station keeping, mission specific manoeuvres and providing sufficient power for connectivity payloads during service delivery.
An optimized power-to-weight ratio ensures that Zephyr can remain above a minimum dawn altitude (the point at which battery capacity is typically at its lowest), which is acceptable for delivery of service.
The Zephyr S aircraft that set the endurance benchmark in Arizona was the first serial production Zephyr aircraft. In July 2018, Airbus opened a dedicated Zephyr production facility in Farnborough (United Kingdom), the world’s first HAPS assembly line. In addition, Airbus has established a permanent operations and evaluation facility in Wyndham, Western Australia. The site has been operational since September 2018 and has been selected due to the largely unrestricted surrounding airspace and reliable weather conditions.
The Zephyr platform provides a unique combination of advantages for the delivery of connectivity services:
• Persistence: Providing controlled coverage over a designated area. The tight stationkeeping capabilities of Zephyr have been well proven in flight trials.
• Low-latency: Zephyr is close enough to ground stations to have little latency and offer real-time services.
• Flexibility: The ability to re-position/re-task the platform after launch. Providing the ability to re-deploy connectivity assets to areas where demand is peaking.
• Scalability: The ability to add/remove aircraft to adjust the combined footprint of a Zephyr constellation.
• Rapid Evolution: Aircraft can be fitted with enhanced payload capabilities and returned to service rapidly with enhanced performance/coverage capabilities as technology advancements become available. The same is true of platform technologies which can extend the life and service intervals for aircraft.
Configured with the corresponding payload Pod, the Zephyr platform is able to provide a range of connectivity applications: public protection disaster relief (PPDR), emergency communications, theatre backhauling, cellular backhauling, 5G connectivity, direct to device communication and direct to home services. In the near-term, Zephyr will provide cellular backhaul services to rural and semi-urban under-served regions, and where temporary capacity is required.
Low-latency performance and the ability to provide lower data rate services across wider areas makes Zephyr well suited to the Internet of Things (IoT)/machine-to-machine (M2M) connectivity applications. In the military and institutional markets, the high availability of service offered by Zephyr makes it ideal for resilient secure networks and radio-relay applications.
As well as supplementing existing connectivity infrastructure in highly-developed regions, Zephyr will be able to connect the unconnected, support the under-connected, and open new regions and segments. Market demand will be driven by lower capital expenditure (CAPEX) investment, short lead-times and operational flexibility, which make the decision to go with HAPS connectivity low risk.
The ability to quickly add a high throughput capability over a desired region of demand makes Zephyr an attractive proposition to telecom operators for key applications such as surge provisioning, expanding network coverage and filling connectivity black spots. As such, the ability of Zephyr to integrate with existing ground infrastructure, and be interoperable within an established eco-system of affordable terminals, will make it a good fit in these segments.
The key geographic areas that will have a high interest in HAPS connectivity are within countries with relatively high populations, high average revenue per user (ARPU), but poor terrestrial infrastructure, particularly within but not limited to equatorial regions. Zephyr is predicted to take a significant share of the HAPS market. The connectivity segment alone is estimated to require thousands of aircraft across the globe.
In recent years, Airbus has been at the forefront of championing spectrum allocation for HAPS. As part of its current campaign, the company has held close dialogue with relevant stakeholders, national and regional administrations, mobile and fixed-service satellite communities, and smaller but significant stakeholders such as the radio astronomy community. Committed to success for HAPS at the upcoming WRC‑19 in November, Airbus is focused on broadening the previous HAPS allocations to serve the backhauling and PPDR segments.
Airbus is working closely with payload providers and operators to refine and demonstrate the required technologies, concept of operations and commercial business models for connectivity. Driven by the knowledge that no single connectivity platform or technology will be sufficient to meet the forecast global and regional demand for connectivity, Airbus is keen to engage with the wider HAPS community and with technology partners to create connectivity solutions which will complement current and planned terrestrial and satellite communication technologies.
*This article is one of a series commissioned for ‘Terrestrial Wireless Communications’ edition of ITU News Magazine. Views expressed do not necessarily reflect those of ITU.