Between Air and Space: The RAF Perspective on HAPS and the Zephyr Programme

1. Setting the Scene

In military aviation, we measure persistence in hours or days. In the space domain, we talk in months or years. Until recently, there was no middle ground. Satellites offered coverage but lacked flexibility; manned aircraft could manoeuvre but needed constant refuelling and crew changes.

The Airbus Zephyr changes that equation. Operating at over 60,000 feet (FL600+) in the stratosphere, it delivers satellite-like persistence combined with the repositioning flexibility of an aircraft. For defence planners, that’s a force multiplier.

2. The Zephyr Concept

The Zephyr is a solar-powered, ultra-lightweight fixed-wing aircraft designed for ultra-long endurance flights. At a glance:

• Endurance: 30–60+ days on station, depending on season and latitude.

• Altitude: ~20–25 km, well above weather and civil air traffic.

• Payloads: EO/IR cameras, synthetic aperture radar (SAR), communications relay, electronic intelligence (ELINT) packages.

• Launch & Recovery: Can be flown from relatively short runways, recovered for maintenance, and redeployed in new theatres.

It is part of the RAF’s drive to extend the reach of air power into the stratosphere—bridging what is increasingly seen as a seamless Air–Space continuum.

3. Operational Advantages

From a mission commander’s perspective, Zephyr offers:

• Persistent Intelligence: The ability to watch a single area of interest for weeks without breaks. No crew fatigue, no tanker support.

• Agility: If the task changes, we can reposition the aircraft hundreds of kilometres in a day without waiting for orbital mechanics.

• Low profile: From the ground, Zephyr is effectively invisible; it’s acoustically silent and has a minimal radar signature.

• Cost efficiency: Fraction of the cost of launching and maintaining a satellite for similar tasks.

In ISR terms, this is like having a satellite you can park exactly where you want it — and move at will.

4. The Challenges

Despite its promise, Zephyr isn’t without its constraints:

• Payload weight limits — today’s endurance comes at the cost of payload mass. As solar and battery tech improve, we can expect more capacity.

• Weather at launch/recovery — while it flies above weather systems, take-off and landing require calm ground conditions.

• Airspace integration — operating above FL600 is largely unregulated, but coordination with national aviation authorities is essential during ascent/descent.

These are engineering and procedural problems — not deal breakers. The technology is maturing fast.

5. Strategic Implications for Defence

For the RAF and UK MoD, HAPS like Zephyr offer three immediate strategic benefits:

1. ISR Redundancy: They supplement satellites, creating a layered approach to surveillance.

2. Communications Resilience: They can relay tactical comms across large operational areas without relying on vulnerable terrestrial networks.

3. Rapid Theatre Setup: In an emerging crisis, a Zephyr can be deployed and on station within days, providing persistent overwatch before larger assets are mobilised.

For NATO and allied operations, the interoperability of such systems could mean shared persistent ISR bubbles over contested or humanitarian zones.

6. Beyond Military Use

While Zephyr has been developed with defence in mind, the technology will bleed into civil applications:

• Disaster relief communications in coordination with UK emergency services.

• Maritime safety monitoring in partnership with the Coastguard.

• Environmental intelligence in climate-sensitive regions.

This is where public–private partnership becomes critical — a shared HAPS fleet could serve multiple sectors with different payload configurations.

7. The “So-What” for Decision Makers

For defence ministers, chiefs of staff, and industry partners, Zephyr signals a paradigm shift:

• It’s not just about replacing satellites; it’s about complementing them.

• It enables persistent presence in airspace where no permanent infrastructure exists.

• It provides a scalable, reusable asset in an era of tightening defence budgets.

The countries that master stratospheric operations will gain both strategic advantage and operational flexibility.

“HAPS bridges the gap between air and space, giving commanders new ways to watch, connect, and respond.”