Germany’s HAP-alpha solar aircraft nears first flight with 88-foot wingspan, 12-mile goal

Germany s bid to build one of the world s most advanced uncrewed solar aircraft has just taken a major leap forward, after the German Aerospace Center (DLR) revealed that HAP-alpha has successfully completed a full suite of ground tests. The sleek, ultra-light, high-performance aircraft, built for long-duration flights at extreme altitudes, weighs a total of 304 lbs (138 kilograms) even with its 88-foot (27-meter) wingspan.

Its sensor systems, including a high-resolution camera system and a radar system with synthetic aperture, each weighing no more than 11 lbs (5 kilograms), can be used for a wide range of Earth-observation tasks. Now, DLR announced that the high-altitude platform has successfully wrapped up full system tests at its National Experimental Test Center for Unmanned Aircraft Systems in Cochstedt, clearing the way for its much-anticipated first flight in 2026.

Solar aircraft milestone Mounted on a specialized launch trolley and connected to a tow vehicle, the UAV (unmanned aerial vehicle) completed all major ground tests by autumn 2025 in its fully assembled form for the first time. Once rolled onto the test center s runway, the engineers checked that all systems were functioning correctly and collected additional data on its handling.

HAP-alpha on the launch trolley.Credit: DLR HAP-alpha is designed for long-duration flights at very high altitudes, carrying scientific payloads for Earth observation, DLR said. Its solar cells must generate enough electrical power to continuously supply its propulsion and onboard systems with energy. According to DLR representatives, the aircraft flies at very low speeds to minimize power consumption. This is made possible by its large yet ultra-light wing.

It also passed a static vibration test in spring 2025, confirming its structural stability. Set for next year s launch The DLR experts prepared all procedures in advance and practiced them in detail before putting the system through flight-like conditions.

The ground tests were used to verify that all systems operated correctly during these trials. The certifiable UAV s flexible airframe was exposed to vibrations similar to those experienced during takeoff or in flight. Its high-precision sensors recorded every movement. During the trials, the high-altitude aircraft powered itself using only its onboard systems.

It responded only to commands transmitted through the same radio link used in real flight scenarios. To avoid damaging the delicate airframe during the test, the wings and tail were supported to prevent them from flexing under aerodynamic forces. Meanwhile, a patented mechanism holds the aircraft in place and releases it once it reaches the right angle of attack.

The lightweight platform then lifts off automatically and later touches down gently on skids with the engine switched off. The setup for the upcoming flight trials will stay mostly the same. HAP-alpha will again take off from a specialized trailer. Once the aircraft has been sufficiently tested and the ground crew s procedures have been properly established, expansion stages of HAP-alpha will successively fly at altitudes of up to 20 kilometers [12 miles], DLR concluded in a statement.