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Interview with

Dr. Kai-Daniel Büchter

Technology Radar

Interdependencies of technologies, operations and network effects are increasingly important in aerospace.
Dr. Kai-Daniel Büchter

Dr. Kai-Daniel Büchter has been employed at Bauhaus Luftfahrt since April 2011. The 36-year-old physicist is a member of the research area “Technology Radar” and responsible for topics in the fields of photonics, sensors as well as information and communications technologies (ICT).

What is your current research focus, Dr. Büchter?

I am interested in identifying technologically feasible and relevant concepts within the scope of future potential analyses. One of the topics I have been working on is aeronautical ad-hoc communication networking (AAHN) – here, free-space optical communication links offer high bitrates without the requirement for radio spectrum for internet access as well as new perspectives by the high-speed mesh-networking aspect between aircraft itself. In order to investigate such networks, a number of students and I have built up an integrated model-based environment for worldwide AAHN-simulations within the dynamic air traffic network. Within the recently completed, third-party funded project TERA (“Thermoelectric Energy Recuperation for Aviation”, funded by the Federal Ministry for Economic Affairs and Energy under the national aviation research programme “LuFo”), I was involved as project manager in a research consortium looking into a completely different technology: Here, thermoelectric waste heat harvesting in aircraft engines was investigated, with the goal of increasing overall aircraft efficiency by relieving the conventional generators. The technology can in principle also be used to help meet increasing electricity demands of new aircraft generations.

What is the relevance of your work for the future of aviation?

Digitalisation and the trend towards increasing electrification in different mobility sectors are good examples for technology developments, which did not evolve from traditional aeronautical research disciplines. However, such developments need to be identified and benchmarked with regard to innovation potentials in a specific aeronautical context. Currently, I am for example involved in projects looking into health monitoring of aircraft systems and structures, with the prospects of improving maintenance efficiency with regard to scheduling and material utilisation as well as improving fuel efficiency and fleet availability. Improvement potentials arise from increasingly available information concerning usage statistics as well as the state of aircraft systems, components and component assemblies. Novel methods in handling and processing of large amounts of data as well as growing computing capacities and data transmission capabilities are already in high demand today due to increasing amounts of sensor data and other information sources.

Which methods and tools are you using?

The claim of future technology analyses is to provide qualitative and quantitative initial assessments with regard to the potential benefits of novel concepts. Therefore, in order to evaluate new technologies or innovative technologies in a new context, useful performance figures or metrics must first be defined to benchmark these with existing or competing approaches. The methods for evaluation are typically implemented in the form of mathematical models in numerical computing environments. The scope of such evaluations can be limited, for example if a single technology is evaluated based on analytical descriptions of performance. Modelling of telecommunication links is more complex – here, system design parameters as well as propagation effects in the atmosphere need to be considered within the model descriptions. The simulation of “airborne networks” has reached a comparably high complexity, as air traffic movements, infrastructure, network topology, data traffic and clouds are included in the modelling environment.

What are the results of your work?

The “airborne network” simulations show the significant impact of the fleet considered on network performance. Short-haul aircraft often fly in areas with dense air traffic, wherefore the simulated communication network exhibits a very high availability in this case. In the case of long-haul aircraft, the situation is more difficult, and the consideration of isolated airlines is usually not sufficient, as airlines do not send all their aircraft on similar routes, of course. One of the upshots is that business models are required which support the cooperation of different airlines with regard to airborne networking – for example, regulatory measures may be taken; inter alia, mandated by supranational organisations such as ICAO, but also third-party service providers of communication infrastructure and technology could drive the implementation. Economic reward systems for airlines might also be possible as a measure to push the concept. Another conclusion is that an intelligent integration of high-speed satellite communication can substantially increase availability and throughput of the network. As a further example of research results, within the TERA project, the impact of waste heat harvesting using thermoelectrical generators was quantified with regard to the overall mission fuel requirement of a reference aircraft. At the considered place of installation, the fuel savings potential proved to be lower than initially expected, because local thermal conditions and heat transport across the boundary layers have a limiting impact on achievable heat fluxes through the modules. Building on this insight and on the methods developed for the investigations, recommended steps and measures for technology development were derived and provided in the form of a research and development roadmap as part of the project report.

In what way does Bauhaus Luftfahrt provide the best environment for your research?

Bauhaus Luftfahrt provides the opportunity to work on current research topics within an interdisciplinary environment. The contact to our industry partners is valuable as well as instructive towards developing a good grasp on practical challenges in the aeronautical industry – especially for people with a more academic background, where research questions are typically more isolated from broader considerations. The aeronautical context was always appealing to me. I have always been interested in aerospace topics, and I completed private pilot’s training during my time as a doctorate candidate at the university. Therefore, Bauhaus Luftfahrt gave me an attractive opportunity to combine my academic education as a physicist with my private interests in aeronautics.

What were your stations before you joined Bauhaus Luftfahrt?

Before working for Bauhaus Luftfahrt, I studied physics at Paderborn University and graduated in integrated optics, i.e. optics in waveguides and integrated devices. One area of my research was free-space optical laser communication, which I investigated in a lab environment as a visiting researcher at Stanford University. The findings concerning laser communications play an important role in the concept of aeronautical communication networks.