DLR has set itself the goal of developing and providing comprehensive expertise for the realization of high-performance, certifiable, high-flying solar aircraft. Under the leadership of the Institute of Flight Systems, DLR is pursuing a holistic approach and is developing not only a platform, but also the necessary ground station, payloads that can be carried on the platform for Earth observation as well as the operational procedures essential for carrying out corresponding missions. To this end, DLR is pooling a wide range of expertise from the fields of aeronautics, space and security with a total of 16 participating institutes. The aim of the project, which was launched in 2018, is to test promising technologies and design concepts and to demonstrate various potential applications.
The platform has a conventional configuration, but with a total weight of 138 kilograms and a span of 27 meters, it has an extremely lightweight design. The sensor systems, including a high-resolution camera system and a radar system with synthetic aperture, will each weigh no more than 5 kilograms. These sensor systems can be used to perform numerous tasks in the field of earth observation. These include, for example, monitoring shipping lanes, reconnaissance in the event of flood disasters and forest fires as well as monitoring ice surfaces. A high performance sensor system like a radar with not more than 5 kg of weight seems almost impossible at first, however, a aircraft that shall be stationed at an altitude of 20 kilometers must achieve surface loads of significantly less than 5 kg/m², which is why even differences of just a few grams are of decisive importance in the planning and design of the aircraft and its systems.
Both the project itself and the industry's efforts to date show that such high-flying solar platforms and their lightweight sensor systems, which can be stationed for weeks and months, must therefore be developed and built at the edge of what is technically feasible. As a result, industry is showing a keen interest in the progress of the project.
The first test flights with the technology demonstrator known as HAP-alpha are planned for 2025, with the first flights initially planned at low altitude at the National Test Center for Unmanned Aircraft Systems in Cochstedt. Along the way, the project will pass through several review gates at which the status of the project and the feasibility of achieving the objectives will be assessed with the involvement of external experts.
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. Extensive demonstration flights with the developed payload systems will then be carried out at high altitudes. In order to realize the high-altitude flights, the team is in talks with suitable flight test facilities around the world that have the necessary wide-ranging ground and air exclusion zones up to high altitudes.
