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Toward A Real-Time Capable and Reconfigurable Middleware for Scalable and heterogeneous Distributed System
No full textThe German Aerospace Center (DLR, Deutsches Zentrum für Luft- und Raumfahrt), Germany’s national research institution for aeronautics, Space, energy, transportation, and security,
is mandated by the federal government to implement the national Space program and advance
technological research and knowledge transfer. Within this framework, this thesis proposes
a data-centric middleware architecture that can enable a Satellite-as-a-Service (SaaS) model,
meeting stringent requirements for safety, real-time performance, predictability, reliability, scalability, and modularity.
Current onboard computing platforms, such as Scalable Onboard Computing for Space Avionics (ScOSA), follow message-centric paradigms with centralized coordination. These architectures impose rigid reconfiguration procedures, suspend operations across healthy nodes during
topology changes, and limit extensibility. In response, this work proposes a Data Distribution
Service-based (DDS), data-centric middleware that ensures strict binary-level service isolation,
peer-to-peer data exchange, and dynamic reconfiguration. The design enables unaffected nodes
to continue running during topology changes, improving system availability and resilience.
A prototype using OpenDDS demonstrates feasibility on flight-representative hardware, achieving low latency in varied operational scenarios and maintaining higher availability during reconfiguration events, with only a modest increase in reconfiguration time. The use of structured
DDS data models and Quality of Service policies facilitates seamless integration of new services
or subservices, accelerating feature deployment.
Nonetheless, the study identifies limitations in OpenDDS for Space-grade applications, including reliance on dynamic memory allocation, non-deterministic behavior, and inefficiencies
incompatible with safety standards such as MISRA C++ and JSF ++. Addressing these shortcomings will require a deterministic, static-memory DDS profile designed for safety-critical and
resource-constrained missions.
Overall, the results confirm that a safe, predictable, and reconfigurable data-centric middleware is technically viable and offers clear advantages over message-centric approaches. Realizing its operational potential will depend on optimizing data handling, refining communication
strategies, strengthening cybersecurity, and developing a Space-qualified DDS implementation—
paving the way for data-centric SaaS middleware as a baseline for future scalable, multi-tenant
satellite systems.
This thesis contributes an architectural prototype that demonstrates how data-centric middleware can sustain availability during reconfiguration, reduce integration effort for new services,
and provide a pathway toward certifiable space-qualified implementations. These contributions
can be applied directly to future satellite missions adopting multi-tenant payload models, where
predictable service continuity and flexible adaptation are paramount
The Interior Design of Research Demonstrators for Modular and Urban Last Mile Applications
No full textModularity is the smartest way to fit our vehicles to various specific needs optimizing on the
materials, energy demand and user comfort. Therefore, we want to introduce human
centered design approaches on our modular vehicle concepts: The Urban Modular Vehicle
(UMV) and the U-Shift. The concept of the UMV vehicle family combines various derivatives
for different use-cases. The UMV vehicle family consists of driver-controlled vehicles and
automated movers for transporting people and goods. Another strategy for an electric,
modular and automated concept is the U-Shift. It consists of the U-shaped Driveboard and
different capsules as a loading unit. The Driveboard includes everything what is needed for
(automated) driving like electrical drivetrain, steering, lifting system and automation system
with sensors. With the lifting system, the Driveboard can lower itself, move into position, and
the load the capsule via a rail system
Analytical Treatise on Endo-Atmospheric Fuel-Optimal Rocket Landings
Get PDFWhile there is a strong current interest in and an increasing body of latest numerical work on fuel-optimal powered descent inside an atmosphere, little recent analytical understanding of the problem has been reported. This paper analyzes the endo-atmospheric fuel-optimal rocket landing problem in three-dimensional motion. The necessary conditions for the problem, that account for both propulsive and aerodynamic forces,are derived. They include the full set of costate equations, and the optimality conditions of the body attitude in terms of the angle of attack and sideslip angle. In contrast to a long-standing assumption of coordinated flight in the literature, it is shown that in general coordinated flight is not optimal, if sideslip modulation is allowed. Special cases, such as small-angle and in-plane motion, are analyzed and harmonized with the previous results that are well known in the literature. The analytical conditions derived in this paper can also serve as independent verification for numerical solutions obtained by direct methods in optimal control, or can be exploited for trajectory-design purposes
Impact of Hydrogen in Aviation
Get PDFAviation accounts for about 4% of the total anthropogenic effective radiative forcing (ERF), resulting from aircraft operations since the 1940s. Thereby more than half of the aviation induced ERF is very likely caused by non-CO2 effects, such as contrails and NOx emissions. One measure to potentially reduce both CO2 and non-CO2 effects from aviation is the use of green hydrogen. Different applications of hydrogen such as direct burn or the use of hydrogen in fuel cells for electric propulsion are developed by the aviation industry, with the promise to decarbonize aviation. Still, the impact of the non-CO2 effects on climate from these propulsion systems is unquantified as direct measurements were missing until recently and model capabilities need to be enhanced. DLR in collaboration with industry and academic partners investigates the effects of hydrogen on the formation of contrails and NOx emissions and their effect on climate in internally and industry funded projects as well as using funding by German and European funding sources. These research activities are flanked by emission and contrail measurements from new lean burn technologies which provide a reference of current technologies for the low-soot regime. As the industry is transitioning to the use of hydrogen, projects on the impact of hydrogen leakages and their effect on climate forcing agents have also been launched
Modified carbon aerogels as Fe-N-C catalysts
No full textCarbon aerogels have a great potential to be used in applications like adsorption, catalysis, supercapacitors, fuel cells or batteries based on their unique properties such as well-controlled pore size distribution, high porosity, large specific surface area, high electrical conductivity and low envelope density.[1] They have a three-dimensional, open porous structure and are produced via carbonization of organic aerogels based on e.g. resorcinol-formaldehyde polymers.
Polymer electrolyte membrane fuel cells are a very promising technique for converting hydrogen into electrical energy. But until now, one major problem for large-scale application are the high platinum catalyst costs. A suitable alternative to the critical raw materials are iron-nitrogen (Fe-Nx) complexes embedded in a porous, carbonaceous structure.
For the application as a catalyst, the carbon matrix has to be modified in order to incorporate the active Fe-Nx sites into the carbon structure. Therefore, the carbon is treated with different synthesis steps to introduce nitrogen and iron into the carbon structure.[2] Prior nitrogen doping of the carbon aerogel, oxygen doping was identified as a crucial step. To introduce nitrogen and iron, the oxidized carbon aerogel is mixed with nitrogen and iron precursors and thermally treated to obtain Fe-N-C materials.
The presentation will focus on our recent studies showing different synthesis techniques and the results of physicochemical and electrochemical characterization of the doped carbon aerogels using physisorption measurements, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, electrical conductivity measurements and rotating ring-disk electrode measurements.[3]
[1] Pekala, R. W. and C. T. Alviso (1992). Carbon Aerogels and Xerogels. MRS Online Proceedings Library.
[2] Müller-Hülstede, J., et al., Journal of Power Sources 2022, doi: 10.1016/j.jpowsour.2022.231529
[3] Zierdt, T., et al., ChemSusChem 2024, doi: 10.1002/cssc.20240184
Velocity dependent comparison of tonal propeller noise prediction methods against flyover measurements of small propeller aircraft
No full textThis study presents and applies a noise prediction toolchain for propeller aircraft, specifically designed for the preliminary design environment. The work compares two aerodynamic modeling approaches for propeller load
prediction: a simple BEMT method and a full 3D aerodynamic model. Additionally, it evaluates tonal noise predictions from Hanson’s and Farassat’s models against flyover noise measurements of a Do 228 aircraft
under various operating conditions. The comprehensive analysis assesses model performance across different velocity regimes to refine PANAM’s capabilities for accurately predicting propeller noise characteristics of small
aircraft, thereby advancing acoustic assessment methodologies in preliminary aircraft design.
Key findings reveal that maximum sound pressure levels increase with both airspeed and rotational speed. Flight speed significantly influences the radial position of the thrust peak, shifting it outward from approximately
65 % to 85 % of the blade radius as speed increases. However, this outward shift does not significantly affect tonal noise emission. While both noise models successfully predict the velocity trend, simulations consistently underpredict noise levels by 3 dB to 5 dB compared to experimental data
Supporting Virtual Aircraft Certification via Provenance
Get PDFExhaustive physical testing ensures the airworthiness of an airplane and is time-consuming and costly. With the latest advancements in computational models and computing power, testing parts virtually becomes feasible. Ensuring the reliability and trustworthiness of such virtual verification processes is a critical point. We collect and assess the obligations and requirements stated by the certification authorities Federal Aviation Administration (FAA) and European Union Aviation Safety Agency (EASA) and from the contributors towards virtual certification. Then, we discuss the possible applications and benefits of using provenance data, which is the documentation of the origins and history of data. By recording detailed metadata, it can support traceability and thus reliability. We propose two provenance models, the first one captures only the workflow between the contributors and their tools. The second one shows the steps of each tool in detail so that the data flow is traceable. These models can be connected by the inputs and outputs of each tool. In the end, the certification authority can use the workflow provenance graph to request the simulation and tool provenance graphs of each contributor. The certifiers have detailed insights into the computational analyses, while the contributors do not reveal their business secrets to each other. Integration of provenance can support regulatory compliance by fulfilling many of the stated obligations and is therefore a promising approach
TerraSAR-X und TanDEM-X: Missionsüberblick und -status
No full textSummary of the TerraSAR-X and TanDEM-X mission and its current status
Experimentelle Untersuchung des makroskopischen Verhaltens von nachhaltigen Faserverbundwerkstoffen im Versagensfall
Get PDFSeit einigen Jahren nimmt das Interesse an natürlichen Alternativen zu Glas- und Kohlenstofffaser zur Verstärkung von Kunststoffen zu. Dies spiegelt sich in einzelnen Industrieprodukten, sowie einer Vielzahl aktueller wissenschaftlicher Veröffentlichungen wieder. Das Interesse ist getrieben vom Konstruktionsprinzip des Leichtbaus und den ökologischen Vorteilen, aber auch stoß- und schalldämpfenden Eigenschaften, welche natürliche Rohstoffe gegenüber den konventionellen Fasern aufweisen. Die unterschiedlichsten natürlichen Fasern werden zur Verstärkung von Kunststoffen verwendet, einige davon sind Flachs, Kenaf, Kokosfaser, Hanf, Jute und Sisal. Sie bestechen im Allgemeinen durch einen sehr geringen Energieaufwand in der Herstellung, geringen bis negativen CO2-Ausstoß, allgemeine Verfügbarkeit; teilweise als Abfallprodukt anderer industriezweige, geringe Dichte bei guten Festigkeitswerten und eine unkomplizierten Verwertung oder die Möglichkeit zum Recycling. Herausforderungen bei der Verwendung von Naturfasern sind zufriedenstellende und konsistente mechanische Eigenschaften bei einem
von wechselnden Umweltbedingungen abhängigen Werkstoff zu erreichen, sowie weiterführende Fragen der Feuchtigkeitsaufnahme, des Brandschutzes und der Konservierung gegen biologische Zersetzung.
In dieser Arbeit werden nachhaltige Materiallösung experimentell untersucht und ihre mechanischen Eigenschaften unter Biege-, Zug- und Impactlasten charakterisiert