Researchers in the Centre for Climate Adaptation and Environment Research have been awarded £1.9 million from the Advanced Research + Invention Agency (ARIA) to develop a ‘stratospheric sat-nav' to help high-altitude unmanned aircraft ride atmospheric waves and dramatically increase flight endurance.
The project, named ‘STRAT-NAV', forms part of ARIA's Enduring Atmospheric Platforms Programme, which is developing platforms that can remain aloft in the stratosphere for extended periods. The wider programme aims to use these platforms to provide the high-performance communications infrastructure needed to deliver truly global connectivity, support the next generation of AI and digital services, and reduce dependence on satellites.
Operating in the stratosphere between 10- 25 km above the Earth, High-Altitude Pseudo-Satellites (HAPS) are long-endurance aircraft that can provide remote-sensing observations or communications services. Most HAPS are solar-powered ultralight gliders, with limited battery capacity on board. As a result, many face acute power challenges, especially during long winter nights over the UK, when solar energy is lowest.
Soaring on gravity waves in the sky
Also prevalent in the stratosphere are atmospheric gravity waves. These ripples in the atmosphere are created when air is forced upwards by mountains or from deep convection, rising upwards and falling back down under gravity in a wave-like motion.
Like eagles riding thermals, STRAT-NAV will guide HAPS platforms to soar on atmospheric gravity waves, delivering energy savings similar to carrying at least a 20-40% bigger battery, at no additional cost.
Dr Neil Hindley, a research fellow in the Centre for Climate Adaptation and Environment Research and project lead, said: “This project is an exciting opportunity to translate our knowledge of the atmosphere into a practical tool to transform high-altitude aviation and unlock the stratosphere as an operating environment.
“Atmospheric gravity waves have been studied by scientists for decades, but until recently we've lacked the sub-km scale forecasting capability needed to predict them accurately enough to use operationally. If we can help HAPS aircraft navigate and exploit these naturally occurring energy sources, it could fundamentally change what's possible for long-endurance HAPS flights over the UK and beyond.”
Solving the winter power deficit
The UK’s unique position beneath the undulating jet stream, combined with the rugged mountain terrain of Wales and the Pennines and the stratospheric polar vortex that forms each winter, makes it a global hotspot for gravity wave activity. “Exploiting stratospheric gravity waves for HAPS is a uniquely advantageous strategy for the UK due to our geography”, Hindley explained.
“While the available solar energy falls to a minimum during winter, this is when gravity wave activity maximises over the UK - exactly when it is needed.”
This abundance of power in the sky could allow HAPS to operate year-round, realising the vision of an operational HAPS fleet providing services that until now have only been possible from satellite.
Navigating nature's invisible energy highways
While atmospheric gravity waves contain abundant energy, they remain difficult to forecast and exploit. HAPS aircraft need reliable, high-accuracy forecasts and intelligent routing systems to find and use these rising currents safely and efficiently.
STRAT-NAV will use AI-enhanced, ultra-high-resolution, real-time atmospheric modelling, validated by observations, to forecast the gravity wave field around HAPS up to 72 hours in advance. It will then use platform-specific intelligent routing algorithms to maximise gravity wave energy for soaring, while maintaining communications coverage.
The project will move from model development to field testing through observational campaigns in late 2026 and 2027, validating gravity-wave forecasts ahead of flight trials with HAPS industry partners later in the programme.
The ‘gravity wave assist’ capability is designed for use with any HAPS platform, whether they are lightweight fixed-wing aircraft or even rotary platforms, with no modifications or expensive ground infrastructure.
Led by Programme Director Rico Chandra, ARIA's Enduring Atmospheric Platforms programme is backed by £70 million over 3.5 years. 18 funded teams (R&D Creators) are working on technologies to allow aircraft to operate reliably and cost-effectively in the stratosphere, providing the physical backbone for next-generation advanced communications and a path to connectivity for underserved regions.
The STRAT-NAV project begins in September 2026.