Earth observation and global communication – two terms that immediately make you think of satellites. Construction and positioning are expensive, and space junk can end up being left behind. But airplanes or helicopters are not ideal for this task either. Their use is limited in time and place and is heavily dependent on the weather. A team from the German Aerospace Center (DLR) is researching and developing an unmanned and solar-powered stratospheric aircraft for future scientific experiments that combines the advantages of space travel and aviation.
HAPalpha – this is what the DLR scientists call the technology platform they have developed. “HAP stands for ‘High Altitude Platform'”, explains Florian Nikodem vomDLR Institute for Flight System Technology. “These are mostly solar-powered platforms that are permanently stationed in the lower stratosphere at an altitude of around 20 kilometers.” This means that they fly far above civil air traffic and weather conditions. They can be positioned at any location and, depending on their equipment, used for a wide variety of missions, provided that there is sufficient solar energy. In addition, once they have arrived in the lower stratosphere, regardless of weather conditions and without a crew on board, regardless of the duration of the mission. They have that advantage over classic aircraft.
The video is deactivated for data protection reasons so that no undesired data transmission to YouTube takes place. Please click to activate. The video will then start automatically.High Altitude Platform – unmanned and enduring at great heights
High altitude aircraft suitable for the stratosphere, also known as high-altitude unmanned platforms, are attracting increasing interest in research and industry because of their great application potential. The development of a comprehensive system competence for high-altitude aircraft in German …Credit: © DLR. All rights reserved
HAP alpha is expected to climb to an altitude of 20 kilometers with a payload of five kilograms, but it will not be able to be stationed there for any length of time. The platform is robust and modular so that it can be easily adapted and modified. Its wingspan of 27 meters already corresponds to that of a variant suitable for permanent flight. The total weight of the structure is 36 kilograms. “We achieve the low weight for the size through extremely lightweight construction with carbon fiber-reinforced plastics,” explains Nikodem. “The main spar, fuselage and tail boom are made of wrapped CFRP round tubes. These are very light and yet stable.”
17 DLR institutes are working on the first flight
But it is not just the solar-powered, unmanned demonstrator that the team is developing in the project. A ground station, the operational procedures and three payloads carried by the platform are also part of the scientific research. In the mobile ground station, the scientists coordinate the missions and data reception. It is set up in transportable containers and should be able to exchange data with the HAP at a distance of more than 100 kilometers. The three payloads, including the high-resolution camera system MACS-HAP (Modular Aerial Camera System-High Altitude Platform) and the radar system HAPSAR (High Altitude Platform Synthetic Aperture Radar), offer a multitude of future applications. A total of 17 DLR institutes from the fields of aviation, space travel,
In April 2019, the team showed that the system requirements and concept design are suitable to achieve the project goals. The Preliminary Design Review (PDR) followed. With the preliminary design of the platform, the scientists showed that all system requirements are met with an acceptable risk and within the budget and deadline. It thus forms the basis for the further procedure in the detailed planning and shows that the correct design options have been selected, interfaces have been identified and verification methods have been described. The researchers are currently preparing the following Critical Design Review. It is checked whether the detailed design can achieve the project goals. You can then produce and assemble the individual components. After extensive tests, the HAP alpha demonstrator is created.
HAP takes off
HAP alpha is scheduled to take off for the first time at the end of 2022. The first test flights are at a low altitude above the site of the National Test Center for unmanned aerial vehicles in Cochstedtplanned. The altitude there will be a few hundred meters. After successful tests at low altitude, HAP alpha will gradually fly to the target altitude of 20 kilometers in further high-altitude flight campaigns. “Unlike the first test flights in Cochstedt, where the actual test duration will only be a few hours, a high-altitude flight can take up to 24 hours due to the slow flight speed of the HAP, even if the platform is only about two hours at an altitude of 20 kilometers “, explains Nikodem the challenge of future experiments. For this, the team has to train several crews and their changes in shifts.
The various payloads are then used in such high-altitude flights. With each test, the team gains experience and can modify the HAP so that long-term flights are also possible. With sufficient operational reliability of the team and the platform at height, the stratospheric aircraft could be used as a test vehicle for payloads. And new platform-specific technologies, such as the use of the HAP as a node for digital communication as support for a 5G network, will then be possible.