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Integration of FPM results into design environment PANDORA and application on helicopter floatation studies
No full textAfter an emergency landing on water, the evacuation can be strongly impacted by the sea conditions. Heavy and irregular seas can cause helicopters to become very unstable or to capsize. Therefore, the analysis of the buoyancy of rotorcraft cannot be limited to calm or regular sea conditions. Investigations must incorporate realistic scenarios like those found in the North Sea, which can be described using the JONSWAP spectrum. This work contributes with the integration of Python-based routines into the structural tool PANDORA to generate FE models capable to reproduce realistic sea conditions in meshless numerical simulations using the Finite Pointset Method (FPM)
Automated Ground Segment Operations with EnMAP - Challenges and Experiences from the first Years in Orbit
No full textThe low Earth orbit satellite EnMAP (Environmental Mapping and Analysis Program) was launched in 2022 and is operated by the German Space Operations Center (GSOC) as part of the German Aerospace Center (DLR). The goal of the mission is to monitor and characterize the Earth’s environment by using a hyperspectral camera system. During the planning and implementation of the EnMAP ground segment, a high degree of automation was targeted to reduce the effort of manual and repetitive activities as much as possible. This allows the operations team to focus on non- nominal operational activities as well as the support of other missions. Additionally, it reduces the impact of unforeseen challenges, such as the COVID-19 pandemic and its restrictions, where only a reduced number of personnel is available. While numerous tools for the automation of spacecraft operations exist with a large diversity of programming languages and graphical interfaces, the baseline for the EnMAP ground segment was the usage of the Test and Operations Procedure Environment interface (TOPE), which is part of the SCOS-2000 monitoring and control system. By utilizing already available software, the level of complexity a new tool adds to the system, along with the effort of maintaining and monitoring it, can be kept minimal. This approach, which was originally developed for the TerraSAR- X/TanDEM-X missions, has proven to be reliable for supporting satellites on an active mission as well as satellites in the end-of-life phase, where ideally no manual interaction is required anymore. With the experience gained from these missions, a further step towards the goal of a fully automated operational concept was taken. This includes not only pure satellite commanding activities but also other aspects of ground activities, such as satellite monitoring, controlling data processing, distributing data and information between user groups and managing additional mission specific tools. It also shifts the main task of the spacecraft command operator from manual commanding and execution of support tasks, such as the preparation of operational products, to monitoring the automation system and supporting contingencies as well as recovery activities in case needed. Due to the multi-mission concept of GSOC, where only one command operator is supporting multiple missions and satellites outside of regular office hours, the usability and possibility of manual intervention play an important role in the development of automated processes. This paper will provide an overview of the different stages of automation during the preparation and first years of EnMAP in orbit. This includes the implementation based on the information provided by the interface specifications of the satellite and other parts of the ground segment, as well as the adaptation due to experiences acquired after the launch and the identification of discrepancies. In addition, the effort in operating and maintaining the automation system will be discussed and the achieved performance, together with the ability to recover from non-nominal states, will be evaluated. Finally, the resulting limitations of this automation approach are discussed, and several lessons learned are presented, which will serve as input for the automation system design of upcoming missions operated by GSOC
Materialuntersuchungen an additiv gefertigten Proben aus Ti-6Al-4V: Einflüsse der Pulverwiederverwendung
No full textDas Ziel dieser Arbeit war es, einerseits die Auswirkungen der internen Parameter (Hatchabstand, Laserleistung und Lasergeschwindigkeit) sowie der externen Parameter (Schichtdicke und Gasstromgeschwindigkeit) bei der additiven Fertigung
von Ti-6Al-4V-Proben auf deren Materialeigenschaften zu betrachten. Ein weiterer Schwerpunkt bildete die Betrachtung der Pulveralterung bei der Wiederverwendung des gewählten Ti-6Al-4V-Pulvers und dessen Einfluss auf die Proben. Dafür wurden insgesamt zehn Baujobs in sieben Zyklen gebaut. Der erste Baujob eines jeden Zyklus wurde mit denselben Parametern und Baubedingungen (δ = 30 μm; vG =
12 m*s-1) hergestellt. Wenn mehrere Baujobs pro Zyklus gefertigt werden konnten, wurden externe sowie interne Parameter variiert, damit deren Einflüsse ebenfalls untersucht werden konnten. Zum einen wurden Untersuchungen zur Pulveralterung durchgeführt, welche die Analyse des Sauerstoff- und Stickstoffgehaltes in Pulver- und Vollkörperproben, Dichtemessungen sowie die Untersuchung der
mechanischen Eigenschaften im Kerbschlagbiegeversuch umfassen. Ausgewählte Pulver- und Würfelproben wurden unter dem Rasterelektronenmikroskop untersucht. Zum anderen wurden diese Untersuchungen auch herangezogen, um die Auswirkungen der externen Parameter auf die Bauteileigenschaften zu ermitteln.
Eine Alterung des Pulvers im Verlauf der Baudurchgänge ließ sich durch Sauerstoff- und Stickstoffmessungen nicht direkt nachweisen. Allerdings wurden steigende Stickstoff- und Sauerstoffwerte in den Festkörperproben beobachtet. Des Weiteren trägt eine niedrigere Gasstromgeschwindigkeit von 6 m*s-1 im Vergleich zu
12 m*s-1 im Bauraum zu höheren Porositätswerten sowie schlechtere Oberflächenbeschaffenheiten der Proben bei. Auch die höhere Schichtdicke von 60 μm führt zu diesen unerwünschten Eigenschaften. Vor allem führt dabei eine Kombination dieser Baubedingungen zu einem starken Abfall der Probenqualität hinsichtlich ihrer Porosität.
Des Weiteren wurde eine Positionsabhängigkeit der Spatterpartikel festgestellt. Proben die ganz rechts auf der Bauplatte stehen, werden kaum bis gar nicht von Spattern betroffen, da der Schutzgasstrom die Partikel schnell genug wegtransportiert. Allerdings landen dennoch Spatterpartikel auf der Bauplatte und auf den Proben, da der Gasstrom diese nicht ausreichend entfernt.
Außerdem zeigen die REM-Untersuchungen sowie die Auswertung der erfassten Pulvermassen, dass die Aufbereitung durch die Siebstation einerseits dazu führt, dass die großen, für LPBF untauglichen Partikel ausreichend entfernt werden. Allerdings wird auch viel Pulver, welches eigentlich noch wiederverwendet werden könnte, herausgesiebt.
Zusätzlich wurde festgestellt, dass die Geometrien der CHARPY-Proben teilweise starke Abweichungen aufweisen. Daher konnten die Kerbschlagbiegeversuche nicht streng normgerecht durchgeführt werden. Allerdings sind die Proben untereinander gut vergleichbar. Und es sind fallende Trends mit der steigenden Pulverwiederverwendung zu erkennen, welche ebenfalls auf eine Pulveralterung hindeuten
Glacial lake mapping using remote sensing Geo-Foundation Model
Get PDFGlacial lakes are vital indicators of climate change, offering insights into glacier dynamics, mass balance, and sea-level rise. However, accurate mapping remains challenging due to the detection of small lakes, shadow interference, and complex terrain conditions. This study introduces the U-ViT model, a novel deep learning framework leveraging the IBM-NASA Prithvi Geo-Foundation Model (GFM) to address these issues. U-ViT employs a U-shaped encoder–decoder architecture featuring enhanced multi-channel data fusion and global-local feature extraction. It integrates an Enhanced Squeeze-Excitation block for flexible fine-tuning across various input dimensions and combines Inverted Bottleneck Blocks to improve local feature representation. The model was trained on two datasets: a Sentinel-1&2 fusion dataset from North Pakistan (NPK) and a Gaofen-3 SAR dataset from West Greenland (WGL). Experimental results highlight the U-ViT model’s effectiveness, achieving an F1 score of 0.894 on the NPK dataset, significantly outperforming traditional CNN-based models with scores below 0.8. It excelled in detecting small lakes, segmenting boundaries precisely, and handling cloud-shadowed features compared to public datasets. Notably, the U-ViT demonstrated robust performance with a 50% reduction in training data, underscoring its potential for efficient learning in data-scarce tasks. However, its performance on the WGL dataset did not surpass that of DeepLabV3+, revealing limitations stemming from differences between pre-training and input data modalities. The code supporting this study is available online. This research sets the stage for advancing large-scale glacial lake mapping through the application of GFMs
Can Airborne Hyperspectral Imaging Detect Hidden Graves?
Get PDFThis paper investigates the use of hyperspectral imaging as a non-invasive method to locate buried remains in open fields. Airborne HySpex data were acquired over two fields containing buried pig carcasses, considered as proxies for human bodies. The objective was to identify local spectral anomalies above the burial sites, indicative of decomposition processes locally enhancing vegetation health. The Red
Edge Inflection Point (REIP) proved to be a particularly sensitive indicator, revealing spectral anomalies aligned with burial sites. A comparison with ground-based spectrometer data, based on absorption integrals in the 660 - 780 nm range, supported this analysis, despite the acquisitions being performed nearly one year apart. This suggests that airborne hyperspectral imaging could provide law enforcement with a scalable, non-invasive tool for locating graves in unsolved cases, complementing traditional ground-based methods
The state of the art in resistance and continuous ultrasonic welding
No full textSeveral techniques are available for joining thermoplastic composites, including resistance welding and ultrasonic welding. While resistance welding uses Joule heating inside an electricallyconductive carbon fibre implant, melting the thermoplastic matrix and forming a strong weld, ultrasonic welding uses highfrequency vibrations to generate heat, melting the polymer and creating a reliable joint. Either way, both methods offer fast, efficient, high-quality welds
Comprehensive Analysis of the Degradation Phenomena of Proton Exchange Membrane Water Electrolyzers with Iridium on Antimony Tin Oxide Anodes
No full textProton exchange membrane water electrolysis (PEMWE) has emerged as one of the most promising technologies for large hydrogen (H2) production from renewable electricity. However, using iridium (Ir) in large quantities is a roadblock in widespread expansion of this technology. One strategy to reduce Ir loading in the anode is the use of an electroceramic support material. This study examines the structural and electrochemical evolution of Ir on antimony tin oxide (Ir/ATO) anodes under extended operation. Initial electrochemical performance demonstrates that low-loaded Ir/ATO (0.2 mgIr cm-2) can achieve a competitive current density of 2.82 A cm-2 at 2 V, comparable to state-of-the-art PEMWE catalysts. However, extended operation leads to a minimal but gradual decline in catalytic activity. Post-mortem analysis reveals changes in porosity and pore distribution, while atomic force microscopy (AFM) studies indicate ionomer degradation in anode catalyst layer (ACL). Transmission electron microscopy (TEM) reveals the dissolution of oxides of Sb and Sn from support material. Furthermore, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) confirmed the oxidation of metallic Ir (Ir0) to IrOxₓ·OHy species before and after operation. Understanding degradation in low-Ir PEMWEs is key to improving long-term stability. These results highlight the need for support stabilization and catalyst structuring to ensure durable performance