SoftBank and Sceye prepare stratospheric 5G test over Japan
A U.S. company and Japan’s SoftBank are preparing a stratospheric test flight that would see a large helium-filled airship used as a 5G platform above the Pacific, in what industry players see as another attempt to push mobile connectivity beyond traditional ground networks and satellites.
Sceye, based in New Mexico, is planning to send its roughly 200-foot-long high-altitude platform across the Pacific as early as August. The craft is expected to reach about 18 kilometers above the ocean near Japan, where it will hover in the stratosphere and carry a custom antenna intended to support SoftBank’s 5G services.
The idea is fairly straightforward in concept but still technically difficult in practice. The airship would act like a temporary “tower in the sky”, transmitting mobile data directly to standard smartphones from a position far higher than aircraft, but much lower than satellites in orbit.
Sceye and SoftBank are working within the broader category of HAPS — high-altitude platform stations. These can take the form of airships, balloons or fixed-wing vehicles, and are being developed by several companies, including Airbus-linked projects, as a way to extend broadband coverage to hard-to-reach areas or restore communications after disasters.
Sceye’s system is powered by solar energy and designed to stay aloft for long periods, though keeping a stable position in the stratosphere is one of the more complicated parts of the operation. Winds at that altitude can push the craft off course, meaning onboard systems must constantly correct its position while also managing limited energy storage.
Earlier test flights have been used to prove those basics. One of Sceye’s recent missions kept the platform in the air for 12 days, including a long flight segment toward Brazil, and several extended periods where it remained “parked” above specific locations. The company says those tests were important in showing that the vehicle can operate for durations that make telecom applications realistic, not just experimental.
SoftBank has been active in this field for years, including earlier demonstrations with partners in Rwanda. In one 2023 trial, the company reported successful 5G transmission from a stratospheric platform at around 16.9 km altitude, with a standard smartphone used in the test and connectivity maintained long enough for a video call between Rwanda and Japan.
The upcoming Japan flight is being watched closely because it moves the concept closer to real deployment scenarios, not just controlled tests. If it works as planned, the platform would effectively extend mobile coverage over a wide ocean area, something that normally requires either satellite systems or expensive ground infrastructure.
There’s also a broader industry context here. Companies are still trying to figure out where HAPS fits between terrestrial mobile networks and low-orbit satellite constellations. Stratospheric platforms sit in a kind of middle layer — closer than satellites, cheaper to operate in theory, but also more exposed to weather, regulatory constraints and endurance limits.
For now, Sceye’s airship remains in the testing phase, but the Japan mission is being positioned as one of its most visible trials yet.