DLR’s HAP-alpha Passes Key Vibration Test for Stratospheric Flight

DLR’s Solar-Powered HAP-alpha: Advancing Toward Stratospheric Flight with Key Vibration Test Success

The German Aerospace Center (DLR) has recently achieved a significant milestone in the development of its High-Altitude Pseudo-Satellite (HAPS) project, HAP-alpha. The successful completion of a ground vibration test (GVT) marks a critical step toward realizing the platform’s planned stratospheric missions. Designed to operate at around 20 kilometers altitude, HAP-alpha is a solar-powered, unmanned Aircraft capable of carrying out Earth observation and communication tasks for extended durations.

As the aerospace industry seeks sustainable and cost-effective alternatives to traditional satellites, HAPS platforms like HAP-alpha offer a compelling solution. These aircraft fill a unique operational niche, bridging the gap between satellites and conventional aerial systems. With its successful structural validation, HAP-alpha is now one step closer to entering the stratosphere and contributing to a new era of atmospheric monitoring and connectivity.

Understanding High-Altitude Pseudo-Satellites (HAPS)

What Are HAPS?

High-Altitude Pseudo-Satellites are unmanned aerial platforms that operate in the stratosphere, typically between 18 and 50 kilometers above sea level. Unlike satellites, HAPS can be recovered, reprogrammed, and redeployed, offering operational flexibility and cost savings. These platforms can remain airborne for weeks or even months, providing persistent coverage over specific geographic areas.

The concept of HAPS emerged in the 1990s, but early efforts were limited by technology constraints in energy storage, lightweight materials, and solar power efficiency. Notable early projects like NASA’s Helios demonstrated the feasibility of stratospheric flight, while more recent platforms such as Airbus’ Zephyr have set endurance records, highlighting the potential of this technology.

HAPS platforms can be configured as fixed-wing aircraft, airships, or balloons, depending on mission requirements. Their ability to loiter over a fixed point makes them ideal for applications that require continuous monitoring or communication relay capabilities.

“HAPS combine satellite-level persistence with the flexibility of aircraft, offering a new paradigm for Earth observation and connectivity.”, ITU Report on HAPS

Key Use Cases for HAPS

HAPS are increasingly being explored for a wide range of applications. In Earth observation, they can provide near-real-time imagery for disaster response, environmental monitoring, and agricultural analysis. Their high-resolution sensors can identify methane leaks, track deforestation, or support wildfire management efforts.

In the communications sector, HAPS can act as airborne cell towers, delivering broadband connectivity to underserved or remote areas. This capability is particularly valuable in regions lacking terrestrial infrastructure or in post-disaster scenarios where ground networks are compromised.

Security and defense agencies are also investing in HAPS for border surveillance, maritime patrol, and reconnaissance missions. With the ability to remain aloft for extended periods, these platforms offer persistent intelligence, surveillance, and reconnaissance (ISR) capabilities without the cost or complexity of satellite deployment.

The HAP-alpha Project: Development and Technical Milestones

Project Overview and Objectives

Launched in 2018, the HAP-alpha project is a collaborative effort involving 16 institutes under the DLR umbrella. With an initial budget of €30 million, the project aims to develop a certifiable, solar-powered platform capable of sustained operations in the stratosphere. The long-term goal is to enable reusable, environmentally friendly aerial systems for civil and governmental use.

HAP-alpha is designed with a modular architecture, allowing it to carry various payloads for different mission profiles. These include optical cameras, synthetic aperture radar (SAR), and environmental sensors. The platform is intended to support both daytime and, eventually, nighttime operations through advanced solar and battery systems.

The development roadmap includes several phases: low-altitude flight tests, mid-altitude trials with enhanced solar arrays, and finally, full stratospheric missions. Each phase is structured to validate specific subsystems and operational capabilities before advancing to the next stage.

Technical Specifications and Innovations

HAP-alpha features a carbon-fiber-reinforced polymer airframe, weighing approximately 138 kilograms. Its 27-meter wingspan and low surface loading of 3.5 kg/m² are optimized for high-altitude efficiency. The aircraft is powered by gallium-arsenide solar cells that drive two electric motors, each capable of 2.5 kW peak output. Excess energy is stored in lithium batteries for overnight flight.

The platform supports a maximum payload of 5 kilograms. Notable instruments include the MACS-HAP optical camera, which offers 15 cm ground resolution, and the HAPSAR radar system, capable of 50 cm resolution with a power draw of 250 watts. These sensors enable detailed Earth observation from the stratosphere.

HAP-alpha’s modular design allows for rapid reconfiguration between missions. This flexibility makes it suitable for a variety of tasks, from scientific research to emergency response, without requiring significant hardware changes.

Ground Vibration Test: A Critical Milestone

In July 2025, HAP-alpha underwent a successful Ground Vibration Test (GVT) at DLR’s National Test Center for Unmanned Aircraft Systems in Cochstedt. The test involved subjecting the aircraft to simulated flight stresses using electromechanical actuators. This procedure is essential for validating the structural integrity and dynamic behavior of the airframe.

Due to the aircraft’s lightweight and flexible structure, engineers had to address unique challenges during the test. Sensors were strategically placed throughout the airframe to measure resonance frequencies and damping characteristics. These data points were used to refine aerodynamic models and ensure safe flight performance.

Julian Sinske from DLR’s Institute of Aeroelasticity noted that the test results “validate our aeroelastic models and de-risk future flight operations.” With this milestone completed, HAP-alpha is now cleared for low-altitude flight trials scheduled for 2026.

“The successful vibration test marks a turning point in HAP-alpha’s journey toward the stratosphere.”, Julian Sinske, DLR

Industry Landscape and Future Outlook

Global HAPS Developments

HAP-alpha enters a competitive and rapidly evolving market. Airbus’ Zephyr platform recently set a 67-day endurance record and is targeting commercial deployment in 2026. Meanwhile, Sceye’s stratospheric airship has demonstrated 24-hour diurnal flights and is being considered for environmental monitoring and broadband delivery.

Governments and private companies alike are investing heavily in HAPS technologies. The U.S. Department of Defense is funding projects for persistent ISR capabilities, while Japan has announced plans for commercial HAPS services within the next two years. These developments underscore the growing strategic importance of high-altitude platforms.

According to market research, the global HAPS industry could reach a valuation of $2.66 billion by 2030. This growth is driven by increasing demand for real-time data, climate monitoring, and resilient communication networks.

Regulatory and Technical Challenges

Despite their promise, HAPS platforms face several challenges. Energy storage remains a limiting factor, particularly for nighttime operations. While solar cells can generate ample power during the day, current battery technologies constrain overnight endurance. HAP-alpha’s early configurations are limited to daytime missions as a result.

Another hurdle is regulatory integration. DLR is working with the Joint Authorities for Rulemaking on Unmanned Systems (JARUS) to develop airspace protocols for stratospheric operations. These efforts aim to ensure that HAPS can safely coexist with other aerial systems and comply with international aviation standards.

Environmental resilience is also a concern. Operating in the stratosphere exposes platforms to extreme temperatures, low pressure, and high radiation levels. Engineers must ensure that all onboard systems can function reliably under these harsh conditions.

Strategic Implications and Sustainability

HAP-alpha’s development aligns with broader trends in sustainable aviation and space technology. Its solar-electric propulsion system produces zero emissions during operation, offering a greener alternative to fuel-based aircraft and satellites. The platform’s reusability further enhances its environmental credentials by reducing waste and operational costs.

Florian Nikodem, project lead for HAP-alpha, emphasized that the platform represents a “sustainable Earth observation solution without contributing to space debris.” As battery and solar technologies continue to improve, the potential for multi-week or even month-long missions becomes increasingly realistic.

Economically, HAPS could disrupt traditional satellite services by offering similar capabilities at a fraction of the cost. This shift could democratize access to high-resolution Earth data and reliable communications, especially in regions where satellite launches remain prohibitively expensive.

Conclusion

The successful ground vibration test of DLR’s HAP-alpha marks a major milestone on the path to operational stratospheric flight. By validating the aircraft’s structural integrity, DLR has cleared a critical hurdle toward launching a new class of persistent, solar-powered aerial platforms. The upcoming low-altitude flight trials in 2026 will further demonstrate the system’s capabilities and readiness for higher-altitude missions.

As the HAPS industry matures, platforms like HAP-alpha could play a vital role in transforming how we observe, communicate, and respond to events on Earth. With their unique combination of endurance, flexibility, and sustainability, these aircraft are poised to complement, and in some cases, replace, existing satellite infrastructure in the years ahead.

FAQ

What is HAP-alpha?
HAP-alpha is a solar-powered, high-altitude pseudo-satellite developed by the German Aerospace Center (DLR) to perform long-duration missions in the stratosphere for Earth observation and communication.

What was the purpose of the ground vibration test?
The Ground Vibration Test validated the structural integrity and dynamic response of the HAP-alpha airframe to ensure it can safely operate in flight conditions.

When will HAP-alpha begin stratospheric operations?
Stratospheric missions are planned for 2027 following phased testing, including low-altitude and mid-altitude trials in 2026.

Sources:
Military Aerospace,
DLR,
Wikipedia,
ITU,
Frontex,
Airbus Zephyr,
Sceye