Aerospace DLR's HAP-Alpha High-Altitude Platform Completes Its First Flight

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On September 2, 2026, the maiden flight of HAP-alpha, an unmanned high-altitude platform, took place at the German Aerospace Center’s National Test Center for Unmanned Aerial Systems.

The first test flight of the High Altitude Platform-alpha (HAP-alpha) developed by the German Aerospace Center (DLR) was conducted to test its airworthiness at low altitudes. The unmanned aircraft completed a safe flight lasting approximately 70 minutes over Cochstedt Airport, reaching altitudes of up to 180 meters (approx. 590 ft) above ground level.

The crew monitored the flight and ensured that all planned processes and procedures were followed. In doing so, they were able to rely on the procedures they had practiced beforehand and on the close communication among team members to handle any situations that arose. In addition, they evaluated various flight maneuvers to test the behaviour of this newly developed aircraft. The tests also aimed to obtain initial validation data for flight dynamic models. Based on this data, researchers can improve the underlying models and further align theory with practice. The results are now being analysed to optimise the flight test program and further refine procedures ahead of the second low-altitude test flight. To collect the necessary data, predefined maneuvers at various speeds and altitudes were flown over the test site.

Choosing the right window is important for a first flight

For weeks, the flight test team had been monitoring the weather forecasts to determine the optimal time window for the maiden flight. Strict limits applied to the first test flight of the HAP-alpha, particularly regarding wind speed, which was not allowed to exceed one meter per second. “The biggest challenge during the maiden flight of such a high-altitude aircraft lies in its susceptibility to even minor turbulence due to its extremely lightweight construction, combined with an enormous wingspan and significant aeroelastic deformation in flight,” explains Dr. Andreas Bierig, acting director of the DLR Institute of Flight Systems. With a wingspan of 27 meters, the platform weighs 138 kilograms.

A total of 25 people were part of the flight test team that got the HAP-alpha airborne for the first time. The interdisciplinary team was coordinated by the Flight Test Director. The flight physicists and structural dynamics engineers monitored the aircraft’s behaviour in flight. Especially during takeoff and landing, the wings must not flutter or, worse, fail structurally. In order to fly at high altitudes later on using the available solar power, the aircraft must fly extremely slowly. The flight speed ranges from 30 km/h (approx. 19 mph) near the ground to about 50 km/h (approx. 31 mph) at high altitudes. The entire flight was monitored by a remote pilot, who was seated in the mission control center several hundred meters away from the runway and controlled the unmanned high-altitude platform using the unmanned aerial vehicle pilot station. A safety pilot was on standby directly on the runway, ready to take over flight control at any time in the event of unexpected incidents.

Objective: Testing at higher altitudes

Designed for altitudes of up to 20 kilometers (approx. 12 miles), HAP-alpha is intended to serve as a flying test platform in the lower stratosphere to test platform technologies and payload systems for Earth observation. These include both the high-resolution MACS-HAP camera system and a synthetic aperture radar, HAPSAR, which are already being co-developed as part of the project. With this high-altitude platform, the DLR also aims to gain comprehensive expertise in the development of high-performance, high-altitude, purely solar-powered platforms.

Once the test campaign is complete, the first flights at higher altitudes over unpopulated or sparsely populated regions—such as over the ocean—are planned. A total of 16 DLR institutes and facilities developed the high-altitude platform and the associated ground systems; the entire team was coordinated by the DLR Institute of Flight Systems Engineering. (se)

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