Connecting the Dots | Avoiding HAPS mishaps

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As low-orbiting broadband constellations become an increasingly dominant force in the satellite industry, stratospheric high-altitude platform stations (HAPS) are closing in on commercializing connectivity from altitudes much closer to Earth.

After being spun out of European aerospace giant Airbus last year, Aalto plans to set up its first permanent base for stratospheric aircraft in Kenya, promising to return the country to the forefront of HAPS commercialization after losing Google’s Loon balloon-based venture three years ago.

Kenya is where Loon first provided commercial connectivity in 2020 with dozens of balloons equipped with payloads mimicking cell towers, only for the plans to burst a year later because it couldn’t create a long-term, sustainable business.

HAPS are often described as pseudo satellites because they also seek to provide connectivity and remote sensing services from up high — around 20 kilometers, below space and above regulated airspace and, critically, still above the weather.

Loon’s early success underlines the demand for connectivity from the stratosphere that can be deployed over persistent coverage gaps or quickly to restore communications following a natural disaster, Aalto CEO Samer Halawi said, but their approach failed to align capability with economics.

Halawi joined Aalto in July 2022 after a long history in the commercial space industry, including chief commercial officer roles at LEO constellation provider OneWeb and geostationary fleet operator Intelsat, and as head of UAE-based regional satellite operator Thuraya.

He puts HAPS in development into two camps: those lighter than air like Loon and heavier platforms such as Aalto’s Zephyr, a fixed-winged drone stretching 25 meters across that is more than two decades in the making.

Loon’s balloons were not as stationary as the Zephyrs Aalto envisions, and Halawi says the venture’s business case fell apart because multiple balloons were ultimately needed to cover a specific area.

Still, Aalto requires reliable access to the stratosphere to get its lightweight glider off the ground, and while this isn’t guaranteed anywhere Halawi says Kenya just so happens to have one of the better climates for deploying HAPS.

The venture also plans to colocate a final assembly line with a Kenyan airport.

It would take 10 days at most for Zephyr to fly from Kenya to a point of service anywhere in the world, according to Halawi. Aalto hopes to have a network of airports, or Aaltoports, to ensure Zephyrs can keep a constant presence over mission areas. Brazil is next on the list.

According to Halawi, Zephyr has spent a record 64 days in the stratosphere during tests, which he says is longer than other heavier-than-air HAPS companies such as U.K.-based BAE Systems and Softbank of Japan are developing.

He says more capable batteries are one of the many elements only recently coming together to make HAPS a commercial reality. Today’s batteries last 90 charge cycles but will extend next year to 200 cycles, putting the limit Zephyr can keep in the air at 200 days.

Ultimately, the aircraft would need to be swapped out with another Zephyr so it can land to replace batteries. This is also part of the advantage over space-based systems, Halawi says, because hardware can be easily upgraded, or a government payload could be quickly added for a responsive mission.

Aircraft and payload flight tests are ongoing but Halawi said Zephyr’s design is nearly finalized and on track to start commercial services around the end of 2025.

Alongside finalizing designs, the company needs to work through regulators for permission to operate commercially.

This first hoop to jump through is at the Civil Aviation Authority in the United Kingdom, where Aalto is based and where it is seeking a “type certificate” that would signify Zephyr’s airworthiness according to its manufacturing design.

However, type certification is just one of many hurdles in the way of creating and regulating a new industry seeking to operate in so far unregulated airspace.

Aalto also sees a growing opportunity in the fledgling direct-to-smartphone market that satellite operators are chasing amid efforts to include non-terrestrial connectivity in standardized terrestrial networking protocols for the first time.

Like Loon, Zephyr could host payloads serving as air-based cell towers.

While initial direct-to-smartphone services provided via Globalstar, Lynk Global, and others in the works are for low-bandwidth applications such as SOS alerts and text messages, Aalto aims to provide a broader range of capabilities from the get-go. “The rule of thumb is you serve 100,000 people with one aircraft,” Halawi said, “and you serve them with full 5G.”

Starlink is developing a direct-to-smartphone business using a LEO constellation currently offering broadband with around 25 milliseconds of latency. According to Halawi, Aalto would be able to provide connectivity with a latency somewhere between five and 10 milliseconds from the stratosphere — if it can become the first HAPS venture to align technology with economics.


This article first appeared in the March 2024 issue of SpaceNews magazine.

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