At Voltitude we believe future HAPS data services will be provided by constellations of platforms of different types and from many different manufacture’s. All providing complimentary functions to provide a safe, reliable and cost effective constellation.

This includes taking a holistic approach to fixed wing and lighter than air – some places it is simply too dark to ever operate fixed wing aircraft and in other locations, winds are never favourable for balloon navigation. In other missions it will be more cost effective to combine high bandwidth back haul data service via balloons enabling a single directed high bandwidth fixed wing platform.

Voltitude are working on a range of technology solutions for key challenges that must be met to unlock the stratosphere. Solutions aim to be compatible with the worlds leading HAPS fixed wing and lighter than air platforms and work across each Size, Weight and Power class

In the small category, fixed wing HAPS typically have a single tail much like conventional aircraft. To carry a larger payload, wing span must be increased to generate more lift, and this is a simple scale up to medium category. However as span increases so does vulnerability to gusts, and past a certain point, additional tails are required to combat the torsional loads generated from such high aspect ratio efficient wings. Otherwise increased structural mass is needed which then fails to close the cyclic energy balance required to operate in the stratosphere on solar power.

Span / Diameter (m)
(at altitude)
All Up Mass (kg)<5050-200200+
Tails / Motors11-22-4
Payload (kg / W)1-4 / 25-504-12 / 50-20012-25 / 150-500
PlatformsUAVOS ApusDuo 15
Swift – SULE
Kraus Hamdani – K1000LE
WindBourne Systems
Prismatic/BAE – PHASA35
Airbus – Zephyr S
Kea Aerospace – Atmos
UAVOS – ApusDuo 28
Zero2Infinity – STARTOS
AeroVironment – Sunglider
Aurora – Odysseus
Airbus – Zephyr T
Raven AeroStar – Thunderhead

Generally more/fewer motors/tails are required depending on the exact design point intended by the manufacturer, in some cases the designers have removed the tails completely where the trade calculations have shown the tall mass saved is worth the platform instability that must be fixed with less efficient reflex aerofoils.

In the case of balloons, it’s a much simpler calculation – scaling the envelope radius and ordering more helium/hydrogen. Balloons therefore should follow fixed wing HAPS in terms of categorisation into to discrete size, weight, and power systems to ensure cross platform modularity and concept of operations.

All current platforms however face the same set of challenges / present limitations.

Key Challenges


  • Regulatory frameworks – must be adapted/re written to factor the inherent safety and physics of fixed wing HAPS, which operationally are closer to balloons than fixed wing aircraft. Fixed wing HAPS need small, medium and large categories – just like balloons. Voltitude are engaging with leading world regulators to simulate and demonstrate the future operational constellation management framework.
  • Empirical stratospheric gust data and industry standards for structural design – typical regulatory gust models do not represent the structural and flight control risks faced by HAPS in the real world or the aeroelastic influences and consequences. Models must be created and validated with real world data – exactly how current models were created (but this is expensive). Voltitude are working on cost effective methods for collection of long term real world data that will provide a solid foundation for HAPS manufactures’ to design against.
  • Operator to asset ratios – HAPS are simply not commercially viable unless they can be operated in a similar approach to satellite constellations. This mean a hands off approach where an operator is in charge of constellations not single vehicles. Voltitude are working on a range of technology innovations and automation that will enable gradual, safe and mature transition to reduced crew requirements.


  • Power Systems – operational HAPS will require improved battery and solar specific energy densities. Voltitude are working with the worlds leading suppliers to bring forward cost effective, stratospheric demonstrations of next generation technologies for adoption by the wider HAPS industry without having to risk expensive platforms.
  • Fixed Wing – Aeroelastic Tools – Designers need tools and qualification criteria to ensure platforms have the required flight envelope for regular and routine operations. Successful HAPS are extremely aeroelastic, and have very low wing loadings. This represents a challenge to a designers with no standard process to follow.
  • Fixed Wing – Flight Envelope Expansion – all current HAPS are vulnerable to tropospheric gusts and weather and have extremely restricted operational limits. Even with these limits HAPS are still lost due to unforecastable turbulence. It is not credible to solely rely on improved weather analytics and forecasting to enable routine HAPS operations. Voltitude are working on technologies that will expand the flight envelop of fixed wing HAPS improving the operational availability of all HAPS
  • Low Bandwith Data Links – Beyond Line of Sight operations require the use of low rate data links to meet the size weight and power limitations imposed on HAPS. Voltitude are working on technology innovations and automation that reduce the need for data link bandwidth.


  • Stratospheric payloads are less mature than stratospheric platforms, but stratospheric platforms are too expensive for payload suppliers to use as test vehicles. Voltitude are working on a range of payloads that will be specifically designed and already qualified for the majority of HAPS platforms. We are also working on innovations to allow qualification of payloads in a cost effective manner so platform manufacturer’s can concentrate on operational demonstrations not payload technology development.

If you would like to find out how our technology can enable your platform, please get in touch