HAP-alpha – the uncrewed high-altitude platform

Visualisation of the final HAP-alpha design
The uncrewed high-altitude platform HAP-alpha completed a flight lasting approximately 70 minutes over Cochstedt Airport on 2 September 2026, reaching altitudes of up to 180 metres above ground. The aim is for the uncrewed aircraft to ascend into the lower stratosphere, to an altitude of approximately 20 kilometres.

The uncrewed high-flying platform HAP (High Altitude Platform)-alpha is a solar-powered aircraft developed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). It was built as a technology demonstrator in a joint project involving 16 DLR institutes and facilities, and completed its first flight test on 2 September 2026. During the inaugural flight, which lasted approximately 70 minutes, the uncrewed platform reached altitudes of up to 180 metres above ground. The aim is for HAP-alpha to ascend into the lower stratosphere, to an altitude of approximately 20 kilometres, serving as an alternative to satellites for Earth observation and communication.

What is HAP-alpha?

Stratospheric high-altitude aircraft – also known as high-altitude platforms (HAPs) – offer a sustainable alternative to satellites for remote sensing and communication tasks. Compared with satellites in Earth orbit, HAPs can be manufactured and launched more cost-effectively. They can also land, undergo maintenance and be reused for other missions.

High-altitude, uncrewed, solar-powered platforms are attracting increasing interest from research and industry due to their wide range of potential applications. Unlike orbiting satellites and crewed aircraft, HAPs can be stationed for extended periods over any given location. Like satellites, they operate autonomously. Their ability to take off and land enables them to be maintained and equipped with different payloads. In addition to conventional applications such as remote sensing or in-situ measurements for Earth observation, HAPs can also, for example, be deployed over crisis areas or serve as hubs for communication networks.

Aims of the HAP-alpha project

The aim of the interdisciplinary HAP-alpha project is to build up comprehensive system-level expertise in high-altitude aircraft at DLR. This expertise is intended to enable DLR to develop, build and operate a certifiable overall system for continuous operation, comprising the platform, payload, ground station and operational procedures.

Advanced lightweight design concepts, the miniaturisation of sensor and avionics systems and further developments in energy storage technologies are intended to make a wide range of applications possible.

Milestones – from ground tests to first flight

  • HAP-alpha took off on its inaugural flight in September 2026.
  • The first flight was preceded in 2025 by important ground tests, during which DLR comprehensively tested the structure and systems of the uncrewed solar-powered aircraft and qualified them for flight operations.
  • Following these ground tests, DLR conducted ground roll tests with HAP-alpha to test the aircraft's taxiing behaviour.

With the first flight completed, findings are now available from all phases of the project – from design and construction through to ground testing and flight operations. This experience will be incorporated into DLR's ongoing research into high-altitude platforms.

The aircraft in figures

 

Wingspan

27 metres

Mass

138 kilograms

Propulsion

Electric, solar-powered

Target altitude

Approximately 20 kilometres

Multimedia

Members of the flight test and ground crews celebrate a successful first flight
The HAP-alpha project team celebrates the successful inaugural flight of the high-altitude platform at the airport in Cochstedt.
Image: 1/10, Credit:
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Video: HAP-alpha on its first ground test outside the hangar
The highlight of the ground tests was the aircraft leaving the hangar for a ground roll test at the airport in Cochstedt. This meant the team could rehearse flight preparation procedures and test aircraft systems under realistic conditions.
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Visualisation of the uncrewed high-altitude platform HAP-alpha
Researchers from 16 DLR institutes and facilities working in aeronautics, space and security contributed their expertise to the development and unique design of the uncrewed high-altitude platform HAP-alpha.
Image: 10/10, Credit:

News about HAP-alpha

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HAP-alpha project – uncrewed high-altitude platform

  • Duration: January 2018 to December 2025
  • Lead institute: DLR Institute of Flight Systems
  • Project type: Programme-oriented Funding of the Helmholtz Association (Helmholtz-Gemeinschaft Deutscher Forschungszentren; HGF)
  • Funding body: DLR Programme Directorate for Aeronautics, Space and Security

Participating DLR institutes and facilities

In­sti­tute of Flight Sys­tems

Responsible for the overall administrative and technical management of the project, as well as for the flight mechanical design, avionics, propulsion, simulation systems, flight control, mission management, integration planning and flight test planning.

German Remote Sensing Data Center (DFD)

Responsible for the communications component of the ground segment, specifically the mobile receiving unit.

Institute of Aeroelasticity

Responsible for the aeroelastic design of HAP-alpha and, together with other institutes involved in this phase, established a design loop for the overall design of the aircraft.

Institute of Aerodynamics and Flow Technology

Responsible for the aerodynamic design of the aircraft and the propellers. Together with other institutes involved in the design, it established a design loop for the overall aircraft design.

Institute of Electrified Aero Engines

Leads administrative work on the propulsion system and contributed to the design of the electric propulsion units.

Institute of Flight Guidance

Responsible for the operator segment of the ground station, where pilots and flight test crew are located. It has also adapted DLR’s UFly guidance software to the needs of HAP-alpha.

Microwaves and Radar Institute

Responsible for developing the synthetic aperture radar (SAR) for HAP-alpha. 'HAPSAR' offers a 50-by-50-centimetre resolution, consumes less than 250 Watts of power and weighs just five kilograms.

Institute of Communications and Navigation

Designed and is responsible for the onboard communication systems of the aircraft.

Remote Sensing Technology Institute

Responsible for developing AI-supported evaluation methods for optical images from the high-resolution camera system (MACS-HAP) and synthetic aperture radar (SAR).

Institute of Atmospheric Physics

Supports the project by collecting and evaluating weather data for the initial selection of potential flight test areas and for flight test campaigns.

Institute of Software Technology

Responsible for developing and maintaining the core software of the flight control computer.

Institute of System Dynamics and Control

Now part of the Institute of Flight Systems.

Institute of Lightweight Systems

Responsible for the design and construction of the aircraft structure made from carbon-fibre-reinforced polymer (CFRP). Participated in the design loop with other institutes involved in the overall aircraft design.

Systemhaus Technik

Supports the development of the aircraft's computer-aided design (CAD) model and has manufactured major structural components. The institute is also responsible for the design and construction of the launch vehicle and the airframe's transport structures.

Institute of Networked Energy Systems

Responsible for the solar generator component of the propulsion system.

Institute of Space Research

The DLR-Institute of Space Research is a world-leading competence center for optical sensor systems and their application in planetary research, Earth observation and security.

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