With non-terrestrial networks (NTN) moving towards increased integration with terrestrial networks for 5G, developments in the NTN field are set to progress beyond both the geostationary orbit (GEO) satellite services of old, and the recently emerged class of low-earth orbit (LEO) satellite constellations.
HAPS (High Altitude Platform Systems or High Altitude Pseudo Satellites) may one day fill the gap between Low Earth Orbit (LEO) satellites starting above 400 km, and terrestrial networks.
Wireless Watch recently took a look at HAPS showings at MWC Barcelona 2023, which was very much focused on the future of mobile networks, featuring BT partner Stratospheric Platforms (SPL), and Airbus division Aalto HAPS, in a recent piece here. For more coverage of MWC, see here and here. Today’s issue features SPL and Aalto’s HAPS competitors and partners Sceye and Softbank Corporation’s HAPSMobile.
While far from certain of success and widespread adoption, HAPS operators bring a compelling proposition and have hovered on the fringes of the telecommunications mainstream for the past decade. So far, success has eluded the space, with multiple high-profile projects floundering in the face of technical and market challenges.
HAPS operators seek to address non-terrestrial consumer broadband needs in underserved regions, filling a niche traditional satellite constellations have not been able to fill in the past. GEO satellites benefit from great coverage, requiring only few platforms to reach the majority of the world’s population from 36,000km above the Earth’s surface. They have always suffered from high latency though, and could only establish themselves for point-to-multipoint broadcast, and only two way connectivity where all other alternatives are unavailable.
LEO, the other newcomer, promised to overcome these limitations. The closer distance imposes a latency floor of around 20-40ms, well within a range acceptable for almost all current consumer applications, while also retaining some of the coverage benefits inherent with high altitude systems.
An increasing number of satellite operators and governments have positioned themselves for LEO constellations. Some providers, such as SpaceX with its StarLink constellation, have even begun to offer commercial services and put LEO broadband connectivity on the map as a viable alternative to ground-based communications networks. Notably, StarLink’s adventures as the secure communications system of choice for Ukraine in its war against the Russian Federation have alerted the market to the potency of this technology.
HAPS, on the other hand, are aircraft operating in the earth’s stratosphere, whose base ranges from as low as 30,000 feet above the poles to 70.000 feet over the tropics (9-21km) above sea level, which is usually also above terrestrial weather. Typically, they are designed to keep their payload airborne and operational essentially indefinitely, which is what earns them their pseudo satellite designation. They trade some coverage for an even lower latency floor of around 5-15 ms.
HAPS have been in the conversation for a long time, with Wireless Watch reporting on early developments as far back as 2015. Work focused on early-stage proof of concept (PoC) trials, notably Facebook’s Project Aquila solar-powered HAPS and Google’s Project Loon stratospheric balloon venture. Both these projects were eventually wound down, Aquila in 2018, and Loon in 2021.
Today’s first HAPS company, HAPSMobile is closely linked to Google’s Loon. HAPSMobile’s owner, Japanese operator Softbank, cooperated with a number of partners in the HAPS space, going as far as to invest in Google’s failed venture in 2019. Loon’s wind-down proved a bitter setback, and left Softbank and HAPSMobile with little more than a heap of patents, “valuable experiences”, and a $125m hole in their wallet.
In hindsight, their most impactful cooperation is the co-founding of HAPS Alliance, the most important industry association representing interests of the HAPS community. Alongside HAPSMobile and Loon, other founding members include Airbus, satellite platform operator Intelsat, infrastructure vendors Ericsson and Nokia, along with telcos Bharti Airtel, China Telecom, Deutsche Telekom, and Telefonica.
Since then, notable additions include Capgemini, Tonomus NEOM, Sceye and Aerovironment, alongside the host of smaller HAPS companies vying with each other for future market share and/or favorable acquisition terms.
A subsidiary of Japanese operator Softbank Corporation, HAPSMobile was founded with the intent to develop a platform capable of providing robust mobile connectivity, even in the absence of adequate ground-based infrastrucute. Especially disaster relief weighed heavily on developers minds in the aftermath of the 2011 Tohoku earthquake and tsunami.
Other use cases include connectivity and broadband provisison in regions where extensive ground-based coverage is difficult (and expensive) or expensive to provide. Examples here also include emerging markets and use cases such as Low Power WAN IoT networks for precision agriculture and remote monitoring.
A particular quirk of HAPS platforms relates to the challenge of powering the communications payload. Relying on solar cells, early HAPS platforms are not viable for long-term flight in higher latitudes, where the reduced sunlight does not provide sufficient energy. Viable regions are currently concentrated in a reasonably narrow band around the equator.
HAPSMobile also boasts American defense contractor Aerovironment as a minority owner. Aerovironment and NASA were both involved in early design stages of the Sunglider platform around 2018.
Sunglider’s design philosophy is similar to that pursued by Aalto for Zephyr, and centres around a long-endurance, solar-powered glider platform. In contrast to Aalto’ 25m span Zephyr craft, Sunglider boasts a wingspan of 78m, though both craft should eventually be able to remain airborne essentially indefinitely.
Little else is known about Sunglider’s technical specifications, capabilities and telecommunications payload. Sunglider underwent successful test flights in the stratosphere from 2020 onwards and successfully beamed down LTE signals around the same time.
Beyond these successes, it seems Sunglider is simply not far enough advanced in its technology to make definitive statements in this direction, or else Softbank is playing its cards very close to its chest.
When pressed about roadmaps and current focus at the company, forthcoming answers centre around the many fundamental challenges associated with stratospheric flight. The solar cells and motor propulsion technology, but also challenges related to remaining in as fixed a position as possible to avoid cell handover challenges when providing cellular connectivity, remain the most active areas of development.
In a recent announcement the company notes advances with its battery technology, claiming it offers unparalleled energy at 439 Wh/k per cell, and 300Wh/kg for the battery pack. Another recent announcement relates to the development of a radiowave propagation simulator, vital to assess the strength and reliability of the payload antenna’s connection on the ground.
Targeting 2027 for commercial launch, there is still a lot of work to be done.
For an example of a company more advanced in its plans and maturity, there is US-based material science/ HAPS specialist Sceye. Founded in 2014 by Danish entrepreneur Mikkel Vestergaard Frandsen, who previously had found some success with companies based on materials science patents, Sceye differs from both Aalto and HAPSMobile, but also SPL.
Sceye pursues a lighter-than-air philosophy, meaning its craft will not glide through the stratosphere on wings, but rather float like an airship of centuries past, buoyed by a massive reservoir of helium. At its core, Sceye is built upon materials science patents relating to the hull fabric of its craft.
The hull is Ultra-lightweight, resistant to ozone and UV degradation, and, most importantly, “1500 times more gas tight” when compared to the “nearest (unnamed) alternative”..
While it also boasts impressive battery and solar cell technology which it claims to have improved and adapted for stratospheric flight in-house, Sceye is focused mainly on providing a stratospheric platform on the back of its patented fabric.
The most important practical impact of its differing design compared to SPL, Aalto and HAPSMobile, lies in the payload carrying capabilities and scalability of its craft.
Gliders and fixed-wing craft are severely limited by weight constraint. For example, Zephyr weighs 75kg and can currently carry 5-8kg of payload, though that is set to increase by commercial launch in late 2024. SPL’s stratocraft on the other hand is said to have the weight of a small-sized van.
Sceye is able to fly payloads in the hundreds of kg, with no real limit other than the size of the given aircraft, which the company says can be scaled up or down essentially at will, according to the needs of the customer.
It targets similar use cases to HAPSMobile and most other HAPS companies, mainly broadband and connectivity provision to unserved and underserved communities around the world, though it too is geographically restricted to near-equatorial regions.
As a first step, however, Sceye will target not connectivity contracts, but rather focus on delivering earth observation payloads for monitoring activities , for example of wildfires and greenhouse gas emissions in the Southern US where it is based. It believes decisive cost advantages over aeroplane and satellite monitoring will tide it over while it continues to develop the capabilities and technology needed to perfect what it sees as its greatest challenge, stationary flight.
It targets 2024 for commercial launch of its earth observation business, and later, towards the end of 2024, mobile connectivity, though it will focus on the US for the time being. Sceye points towards an undeveloped regulatory landscape as a particular challenge for international expansion to Europe.
Infrastructure and government programs such as the US $45 billion Broadband Equity, Access, and Deployment (BEAD) Program, a spiritual companion of the $20.4 billion Rural Digital Opportunity Fund (RDOF) are important targets for the company as well, and will sweeten the stay in the US.
It claims it could do this and would be economically viable even without government subsidies. Life without BEAD would be quite challenging indeed, especially given the fact that HAPS companies make most economic sense in the scarcely populated, underserved areas targeted by BEAD, and Sceye would have to compete directly with grant recipients there.
Servicing markets outside of the United States could prove more challenging, especially with the low ARPU of developing countries. Sceye claims it has conducted twelve feasibility studies with tower and telecommunication companies already, and its customer base counts one of the largest telecommunication providers in the world.
It is doubtful how lucrative international markets will prove, especially considering ARPUs tend to drop considerably for equatorial bands away from the US. Sceye claims it has conducted twelve feasibility studies from 2020 to 2021, and has lined up partners willing to work with it upon commercial launch.