In Christchurch, New Zealand, a small group is testing the boundaries of flight. Kea Aerospace hopes to fly close to 65,000 feet with the Kea ATMOS series, which is powered by lithium-sulfur batteries (Li-S) at night and sunlight during the day.
These incredibly light aircraft are compatible with the High Altitude Platform Station (HAPS) model, which avoids airports and can remain in the air for weeks to months. High-altitude drones are used in the HAPS model to provide imaging and data.
In partnership with Li-S Energy, the company is building solar-powered aircraft for zero-emission aviation, mixing sustainable flights, clean energy, and real technological innovation. Long missions can be held by solar air travel, as already shown by the ATMOS Mk1 and ATMOS Mk2 early models. And in the same high-flying class, projects like PHASA-35 show a bigger trend toward resilient platforms.
How it works: Sunlight by day, Li-S by night
Endurance is the basis. Using lithium-sulfur (Li-S) batteries on board, Kea ATMOS is recharged at night after being powered by solar-harvesting wings during the day. The Li-S Energy cells are not heavy and offer about twice the energy density of many lithium-ion cells without using cobalt. Less battery mass allows for longer flight, and at 55,000–65,000 feet, every gram matters. As a result, landings are planned around maintenance rather than refueling, and missions can take weeks or months to finish.
The aircraft, operating as HAPS, fly above most weather conditions to provide repeated observations and high-resolution imagery for commercial and governmental purposes. It somewhere halfway between satellites and conventional drones because is close enough to obtain clear data, yet it’s high enough for extensive, continuous coverage. It doesn’t need an airport routine either because it takes off, climbs, and circulates silently using clean energy.
Consistent power, steady flight, and emission-free aviation is what solar aviation and Li-S storage promise.
From Mk1 to Mk2: Designing for Endurance
The intention is to expand capability in ATMOS Mk2 following the integration of Li-S in ATMOS Mk1. The stress test is conducted at night if sunlight supports daytime operations. The system keeps the aircraft in the air after dark by completing an energy cycle by replenishing Li-S daily. Energy density advantages can be exchanged for heavier sensors, longer missions, or wider coverage.
This strategy changes between logistics and expectations because it eliminates refueling cycles, reduces ground restrictions, and has long stratospheric arcs that provide accurate data for mapping, environmental monitoring, or communications tests. The platform can operate as a “local satellite,” offering continuous services, without going into orbit.
Other projects like PHASA-35 show the same growth in high-altitude drones, but the partnership between Kea Aerospace and Li-S Energy brings to light a huge insight: performance depends as much on storage as it does on solar capture.
Clearer airspace, easier operations
The consequences are obvious. First, zero-emissions aviation at stratospheric altitudes advances clean energy goals without sacrificing performance. Second, it’s less expensive and complicated to avoid airports. Third, ongoing flight provides constant data instead of snapshots, which is useful for emergency planning, agriculture, maritime oversight, and infrastructure monitoring.
There is also a change in the point of view. An aircraft that can “live” in the sky for months challenges runway and fuel-based habits. Value is defined not only by speed anymore but also by coverage and uninterrupted operation. For months-long missions, high-resolution imagery HAPS roles, emission-free operations, sunlight during the day, and Li-S batteries (Li-S) at night, Li-S batteries (Li-S) were integrated from ATMOS Mk1 into ATMOS Mk2.
The same is true for PHASA-35 and other high-flying systems. Solar aircraft have a good future thanks to increased skytime, fewer airport restrictions, and patiently rewarding services.