High-altitude platforms: why the way to bring the world online hangs in the sky

The airborne technology that could provide internet access to people in the remotest parts of the planet

Zephyr is a high altitude pseudo-satellite, which runs on solar power. Airbus

Internet access is becoming a human right. The World Bank has described it as a basic necessity for economic and human development. And yet, according to Unesco figures, more than half of the world's households are not connected to the internet. In many cases, those households are unable to afford it, but nearly 600 million people around the globe could not access it even if they had the money. There is no infrastructure and no mobile broadband coverage to connect them.

There is, however, a solution to this problem that uses neither cables nor masts, but our skies. A small number of aircraft, equipped with mobile networking equipment, are currently moving around the stratosphere, bringing connectivity to areas beneath them. And the ambitions for this technology are growing. In recent weeks, Deutsche Telekom has partnered with a British company, Stratospheric Platforms, to test a high-altitude aircraft with the aim of delivering blisteringly fast internet connection to urban areas. The vision: 5G internet access for entire nations, all via the stratosphere.

The technology is called HAPs, or high-altitude platforms. They sit above the weather and above air traffic, at a height of around 20 to 25 kilometres, where they remain for days or even weeks at a time. Perhaps the best-known examples are the massive, solar-powered balloons floated by Google as part of its Loon project, founded in 2011. Their capabilities were first demonstrated to the world when Hurricane Maria hit Puerto Rico in September 2017; Google partnered with local telecom companies to ensure that data kept flowing via balloons when traditional networks were disrupted. The experiment was repeated in May 2019, when an earthquake of magnitude 8 hit northern Peru. They saw their first commercial implementation earlier this year, providing 4G access to a 50,000-square-kilometre area of western Kenya.

However, development of HAPs is far from easy. Five years ago, Facebook chief executive Mark Zuckerberg had big ambitions in this area; he launched Project Aquila to test whether solar-powered drones could expand internet access into new parts of the world. But after a number of setbacks – including a crash landing – the venture was abandoned.

"A successful HAPs system has to fuse aerospace, aeronautics, telecommunications and many other fields," says Ogbonnaya Anicho, lecturer at Liverpool Hope University in the UK and researcher of high altitude connectivity. "There have been a lot of struggles with aeronautical design, the elephant in the room being how to keep these gigantic vehicles flying in the stratosphere. During the day you can harness solar power and store it in batteries, which you can feed off at night. But what happens in seasons with less sunlight? Google's commercial targets for Loon depend on the location being 15° north or south of the equator. Outside that zone, they cannot provide the service."

Loon has also had to wrestle with the problem of air currents pushing balloons off course. Google developed clever algorithms to vertically manoeuvre them into airstreams which take them in the right direction. Instances of them crashing received publicity that was, perhaps, disproportionate to the successes being achieved, but it nevertheless provided evidence that their reliability need to be improved.

A competitor, Airbus, has developed a fixed wing HAP called Zephyr whose movements are easier to control, but such craft still have to contend with the problem of staying in the air while performing power-hungry telecom operations.

Richard Deakin, chief executive of Stratospheric Platforms, admires the work being done with solar, but expresses doubts about its ability to deliver connectivity at scale. "[Solar] can enable HAPs to stay flying for a year, but you can't do a great deal with them because the power available for the payload is so small," he says. His company's solution is to power its HAP aircraft with liquid hydrogen, allowing them to remain in the air for nine days at a time before landing, refuelling and taking off again.

“They would each cover an area of 140km in diameter, and serves tens of thousands of users in each of the cells created on the ground,” says Deakin. He says the enormous number of 5G mast installations needed to cover an entire country – estimated by the Institution of Engineering and Technology at 400,000 for an area the size of the UK – presents an enormous practical problem that airborne connectivity could solve. “You would only need around 60 of our unmanned aircraft to cover that area,” he says. It would essentially be like running a small airline.”

Anicho, however, believes that urban connectivity should not be the priority. "Rural areas have a very tough, almost impossible business case," he says. "No matter how humanitarian it is to invest in infrastructure in those parts of the world, it won't be done because there is no business justification for it. HAPs should be providing that option. I don't want to lose focus on the goal, here, which is: can we get everybody online?"

As the ongoing pandemic shapes the way we live and work, the need to get every citizen connected becomes ever stronger. The flexibility of HAPs, in whichever form they take, may help to make that possible – whether it’s bringing mobile banking to remote parts of the world, or giving much-needed extra capacity in urban areas during working hours.

To supply that from a largely unused part of the Earth’s atmosphere is, without doubt, a beautiful example of human ingenuity.