The Future of Mobile

Stratospheric Platforms receives investment to develop its cellular network delivered by unmanned aircraft

David Murphy

UK-based Stratospheric Platforms (SPL) has received investment from PT Profesional Telekomunikasi Indonesia (Protelindo), the largest telecommunication infrastructure company in Indonesia. The funds will be used to continue development work on SPL’s plans to provide high bandwidth telecoms network coverage from the stratosphere, using hydrogen-powered High Altitude Platforms (HAPS) situated on unmanned aircraft. This strategic partnership and investment will enable SPL to explore with Protelindo development of a market-leading and innovative HAPS solution to address Indonesia’s challenging topography, to deliver a world-class telecoms network.

Indonesia is the largest country in Southeast Asia, comprising over 17,000 islands and 1.9m square kilometres of land area. Its complex topography, including mountainous landscapes and high seas, presents challenges for telecommunications coverage. Once developed, SPL's HAP unmanned aircraft will have the ability to provide direct coverage to users over 15,000 square kilometres, with connection speeds of up to 200 Mbps. 

SPL said its solution offers seamless integration with terrestrial networks and tower operators, full 5G compatibility, and unparalleled connectivity across all climates, conditions, and terrains. It is a cost-efficient solution that avoids large capital expenditure requirements and provides a revolutionary, agile, and green infrastructure with "last mile connectivity" applications anytime, anywhere.

I spoke with SPL CEO Richard Deakin to find out more about this fascinating project. He told me that the unmanned aircraft will have the wingspan of a Dreamliner (56m). They will fly under normal air traffic control and then on to the stratosphere, at 60,000 feet, way above commercial air traffic, flying in a figure of 8 pattern, powered by liquid hydrogen, which exhausts nothing more toxic than water vapour, and maintaining a constant beam shape.

“We need to use hydrogen because the antenna needs a lot of power, 22 kilowatts, so solar isn’t an option,” Deakin told me. “To cover Indonesia, we would need around 200 aircraft. By way of comparison, for the UK, we would need around 24. It’s a very flexible system. One aircraft sitting above London could deliver an M25-shaped beam, for example.

"But Indonesia would be a great use case. The country is long and thin, with a very challenging topography, lots of mountains and jungles, so the cost of terrestrial coverage is very high, and it takes a long time to establish the infrastructure. Just one of our aircraft replaces 450 terrestrial towers. The system is also very energy efficient, because the signal doesn’t have to get through trees and other ground clutter. It uses 75 per cent less energy than a terrestrial base station.”

All very clever, but what happens when the plane needs to refuel? “This happens once a week,” says Deakin. “At that point, another aircraft comes up to take its place. It’s a seamless handover, a bit like a relay race.”

While the latest investment is from Indonesia, Deakin says it’s impossible to say where the first deployment will be.

“We did a 4G demo in Germany in 2020, a 5G demo in Saudi Arabia last year, and we have a number of discussions going on with customers and investors, so it’s hard to say who is going to be first,” he says. "Our Series A round raised £70m. We’re currently on our Series B, looking for £130m, which will get the prototype flying, and some of the other development and certification work done. With that, the aircraft should be flying towards end of 2024, and operating commercially in 2026.

“We’ve done a lot of work developing and derisking the key elements of the technology, working with our engine makers to develop an engine to burn hydrogen in the stratosphere. One of the biggest challenges was working out how to store liquid hydrogen at minus 253 degrees centigrade for a week with no refrigeration, but we cracked that, and the work goes on.”

This is not the first attempt to deliver comms coverage from the air, of course. Alphabet abandoned its Loon project, using  giant balloons to deliver internet coverage to remote areas, in 2021. This one is equally technically challenging, but, if SPL can get the funding it needs, seems to have been extremely well thought-through.