German Aerospace Center Research Articles

OCTRA as ultrasonically absorptive thermal protection material for hypersonic transition suppression

Previous investigations in the High Enthalpy Shock Tunnel Göttingen (HEG) of the German Aerospace Center (DLR) show that carbon fiber reinforced carbon ceramic (C/C) surfaces can be utilized to damp hypersonic boundary layer instabilities resulting in a delay of boundary layer transition onset. Numerical stability analyses confirmed these experimental results. However, C/C has some disadvantages, especially the limited oxidation resistance and its low mechanical strength, which could be critical during hypersonic flights. Thus, an ultrasonically absorptive fiber reinforced ceramic material based on a silicon carbide (C/C-SiC) was developed in the past years to fulfill this need. The present paper addresses the numerical rebuilding of the C/C-SiC absorber properties using impedance boundary conditions together with linear stability analysis. The focus of this paper is on the numerical comparison of the original C/C material and the improved C/C-SiC material, referred to as OCTRA in the literature. The influence on the second modes and the transition itself is investigated. The numerical results are compared with HEG wind tunnel tests. The wind tunnel model tested in HEG is a 7^circ half-angle blunted cone with an overall model length of about 1.1 ,textrm{m} and a nose tip radius of 2.5 mm. These experiments were performed at Mach 7.5 and at different freestream unit Reynolds numbers.

Disconnected Cardiac Autonomic Nerves in Genetic Ganglionic Acetylcholine Receptor Alpha-3 Subunit Deficiency.

HomeHypertensionAhead of PrintDisconnected Cardiac Autonomic Nerves in Genetic Ganglionic Acetylcholine Receptor Alpha-3 Subunit Deficiency No AccessResearch ArticleRequest AccessAboutView PDFSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toNo AccessResearch ArticleRequest AccessDisconnected Cardiac Autonomic Nerves in Genetic Ganglionic Acetylcholine Receptor Alpha-3 Subunit Deficiency Karsten Heusser, Florian Erger, Ulrich Ebner, Barbara Namer, Graeme Eisenhofer, Carl-Albrecht Haensch, Henning Weis, Matthias Schmidt, Alexander Drzezga, Jens Tank, Christian Netzer and Jens Jordan Karsten HeusserKarsten Heusser https://orcid.org/0000-0002-2571-5585 Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany (K.H., H.W., J.T., J.J.). *K. Heusser and F. Erger contributed equally. Search for more papers by this author , Florian ErgerFlorian Erger https://orcid.org/0000-0002-2768-1702 Institute of Human Genetics, Medical Faculty, University of Cologne, Germany (F.E., C.N.). *K. Heusser and F. Erger contributed equally. Search for more papers by this author , Ulrich EbnerUlrich Ebner https://orcid.org/0009-0002-4648-8497 Internal Medicine Practice, Regensburg, Germany (U.E.). Search for more papers by this author , Barbara NamerBarbara Namer https://orcid.org/0000-0001-7500-2842 Institute of Physiology and Pathophysiology, Friedrich Alexander University Erlangen-Nuremberg, Germany (B.N.). Research Group Neuroscience, Interdisciplinary Centre for Clinical Research within the Faculty of Medicine at the RWTH Aachen University, Germany (B.N.). Department for Physiology, Faculty of Medicine at the RWTH Aachen University, Germany (B.N.). Search for more papers by this author , Graeme EisenhoferGraeme Eisenhofer Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus, Medical Faculty, Technical University Dresden, Germany. (G.E.) University Hospital Carl Gustav Carus, Medical Faculty Carl Gustav Carus and Department of Medicine III, University Hospital Carl Gustav Carus, Medical Faculty, Technical University Dresden, Germany. (G.E.) Search for more papers by this author , Carl-Albrecht HaenschCarl-Albrecht Haensch https://orcid.org/0000-0001-6479-0265 Kliniken Maria Hilf Mönchengladbach, Autonomic Laboratory, Department of Neurology, Faculty of Health, University of Witten/Herdecke, Mönchengladbach, Germany (C.-A.H.). Search for more papers by this author , Henning WeisHenning Weis https://orcid.org/0000-0001-8638-3281 Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany (K.H., H.W., J.T., J.J.). Department of Nuclear Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Germany (H.W., M.S., A.D.). Search for more papers by this author , Matthias SchmidtMatthias Schmidt https://orcid.org/0000-0002-7519-8897 Department of Nuclear Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Germany (H.W., M.S., A.D.). Search for more papers by this author , Alexander DrzezgaAlexander Drzezga Department of Nuclear Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Germany (H.W., M.S., A.D.). Search for more papers by this author , Jens TankJens Tank https://orcid.org/0000-0002-5672-1187 Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany (K.H., H.W., J.T., J.J.). Search for more papers by this author , Christian NetzerChristian Netzer Institute of Human Genetics, Medical Faculty, University of Cologne, Germany (F.E., C.N.). †C. Netzer and J. Jordan contributed equally. Search for more papers by this author and Jens JordanJens Jordan Correspondence to: Jens Jordan, Institute for Aerospace Medicine, Linder Hoehe, 51147 Cologne, Germany. Email E-mail Address: [email protected] https://orcid.org/0000-0003-4518-0706 Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany (K.H., H.W., J.T., J.J.). †C. Netzer and J. Jordan contributed equally. Search for more papers by this author Originally published10 May 2023https://doi.org/10.1161/HYPERTENSIONAHA.123.21172Hypertension. 2023;0Footnotes*K. Heusser and F. Erger contributed equally.†C. Netzer and J. Jordan contributed equally.For Sources of Funding and Disclosures, see page XXX.Correspondence to: Jens Jordan, Institute for Aerospace Medicine, Linder Hoehe, 51147 Cologne, Germany. Email jens.[email protected]de Previous Back to top Next FiguresReferencesRelatedDetails Advertisement Article InformationMetrics © 2023 American Heart Association, Inc.https://doi.org/10.1161/HYPERTENSIONAHA.123.21172PMID: 37161764 Originally publishedMay 10, 2023 KeywordsCHRNA3autonomic failureganglionic acetylcholine receptorsympathetic nervous systemPDF download Advertisement SubjectsAutonomic Nervous SystemGeneticsMechanismsNuclear Cardiology and PETPathophysiology

Real-Time Simulation of Ground Vehicles on Deformable Terrain

Abstract Sophisticated modeling and simulation, based on rigid and flexible multibody dynamics, are nowadays a standard procedure in the design and analysis of vehicle systems and are widely adopted for on-road driving. Off-road driving for both terrestrial wheeled and tracked vehicles, as well as wheeled and legged robots and rovers for extra-terrestrial exploration pose additional modeling and simulation challenges, a primary one being that of the vehicle–terrain interaction, modeling of deformable terrain, and terramechanics in general. Techniques for modeling deformable terrain span an entire range varying in complexity, representation accuracy, and ensuing computational effort. While formulations such as fully resolved granular dynamics, continuum representation of granular material, or finite element can provide a high level of accuracy, they do so at a significant cost, even when the implementation leverages parallel computing and/or hardware accelerators. Real-time or faster than real-time terramechanics is a highly desired capability (in applications such as training of autonomous vehicles and robotic systems) or critical capability (in applications such as human-in-the-loop or hardware-in-the-loop). We present a real-time capable deformable soil implementation, extended from the soil contact model (SCM) developed at the German Aerospace Center which in turn can be viewed as a generalization of the Bekker-Wong and Janosi-Hanamoto semi-empirical models for soil interaction with arbitrary three-dimensional shapes and arbitrary contact patches. This SCM implementation is available, alongside more computationally intensive deformable soil representations, in the open-source multiphysics package Chrono. We describe the overall implementation and the features of the Chrono SCM model, the efficient underlying data structures, the current multicore parallelization aspects, and its scalability properties for concurrent simulation of multiple vehicles on deformable terrain.

Multi-scale modeling of a wind turbine wake in complex terrain

Comparing numerical simulations of wind turbine wakes in neutral atmospheric boundary layer (ABL) flow over complex terrains with full-scale experiments is not always straightforward. Pure neutral ABL conditions are rarely found in the atmosphere as the characteristics of the ABL change during the diurnal cycle. This study presents some insights into how a single wind turbine (WT) and its wake behave under near-neutral ABL conditions in complex terrain. The Perdigão Valley in Portugal was chosen as the test case as it is an excellent case study of three-dimensional flow in complex terrain to validate numerical simulations of WT wake with experimental data due to the availability of extensively deployed remote sensing equipment (e.g., German Aerospace Center (DLR) and Technical University of Denmark (DTU) multi-Doppler lidars). The Weather Research and Forecasting (WRF) [1] model is utilized in large-eddy simulation (LES) mode in order to simulate the period of interest with a multi-scale modeling approach. Five nested domains, with the finest domain having a spatial resolution of 5 m, are used to dynamically downscale mesoscale flow features to microscale. A generalized actuator line (GAL) WT parameterization is used to model the wind turbine-flow interaction. WRF-LES-GAL (hereinafter referred to as WLG) results compare quite well with the experimental data obtained from lidars and meteorological mast, with minor biases between the simulated and observed data. Due to insufficient buoyancy generation from the WRF-LES model, the simulated track wake was found to have lower vertical deflection compared to the lidar data; hence, no recirculation zone is observed in the valley. Overall, the WLG model is able to reproduce the wake characteristics observed on the first ridge top into the valley, as well as the power and thrust generation, and can be used for further analysis of other stability conditions.

Live Trials of Dynamic Geo-Fencing for the Tactical Avoidance of Hazard Areas

The project City-ATM, launched by the German Aerospace Center DLR in 2018, aims to integrate new airspace users like unmanned aerial vehicles into uncontrolled airspace. An air traffic management and traffic flow control concept were developed. The phase 1 demonstration in 2019 showed a bridge inspection featuring, amongst other elements, the flight of several drones in a limited area, beyond visual line of sight operation, strategic flight planning considering strategic geo-fences and tactical conflict detection. To enrich the base concept from phase 1 with more U-Space services, the concept has been extended for phase 2 by dynamic geo-fencing for the tactical avoidance of danger spots. This paper describes how dynamic geo-fences can be modeled around a hazard area, how the dynamic opening and closure of these fences can be distributed to relevant systems, and how the fences are considered by on-ground and already in air vehicles. The complete concept has been implemented and tested at the National Experimental Test Center in Cochstedt. Finally, the execution of successful flight trials is described.

Determination of Bayesian Cramér–Rao Bounds for Estimating Uncertainties in the Bio-Optical Properties of the Water Column, the Seabed Depth and Composition in a Coastal Environment

The monitoring of coastal areas using remote sensing techniques is an important issue to determine the bio-optical properties of the water column and the seabed composition. New hyperspectral satellite sensors (e.g., PRISMA, DESIS or EnMap) are developed to periodically observe ecosystems. The uncertainties in the retrieved geophysical products remain a key issue to release reliable data useful for the end-users. In this study, an analytical approach based on Information theory is proposed to investigate the Cramér–Rao lower Bounds (CRB) for the uncertainties in the ocean color parameters. Practically, during the inversion process, an a priori knowledge on the estimated parameters is used since their range of variation is supposed to be known. Here, a Bayesian approach is attempted to handle such a priori knowledge. A Bayesian CRB (BCRB) is derived using the Lee et al. semianalytical radiative transfer model dedicated to shallow waters. Both environmental noise and bio-optical parameters are supposed to be random vectors that follow a Gaussian distibution. The calculation of CRB and BCRB is carried out for two hyperspectral images acquired above the French mediterranean coast. The images were obtained from the recently launched hyperspectral sensors, namely the DESIS sensor (DLR Earth Sensing Imaging Spectrometer, German Aerospace Center), and PRISMA (Precursore IpperSpettrale della Mission Applicativa—ASI, Italian Space Adjency) sensor. The comparison between the usual CRB approach, the proposed BCRB approach and experimental errors obtained for the retrieved bathymetry shows the better ability of the BCRB to determine minimum error bounds.

Impaired Physical Performance in X-linked Hypophosphatemia Is not Caused by Depleted Muscular Phosphate Stores.

X-linked hypophosphatemia (XLH) is a rare genetic disease, characterized by renal phosphate wasting and complex musculoskeletal manifestations including decreased physical performance. To characterize muscular deficits in patients with XLH and investigate phosphate stores in muscles. Case-control study (Muscle fatigability in X-linked Hypophosphatemia [MuXLiH]) with a 1-time assessment at the German Aerospace Center (DLR), Cologne, from May to December 2019, including patients with XLH cared for at the Osteology Department, University of Wuerzburg. Thirteen patients with XLH and 13 age/sex/body weight-matched controls aged 18-65 years were included. The main outcome measure was 31P-magnetic resonance spectroscopy (31P-MRS)-based assessment of phosphate metabolites in the soleus muscle at rest. Further analyses included magnetic resonance imaging-based muscle volume measurement, laboratory testing, isokinetic maximum voluntary contraction (MVC), fatigue testing, and jumping mechanography. By means of 31P-MRS, no significant differences were observed between XLH and controls regarding phosphate metabolites except for a slightly increased phosphocreatine to inorganic phosphate (PCr/Pi) ratio (XLH: 13.44 ± 3.22, control: 11.01 ± 2.62, P = .023). Quadriceps muscle volume was reduced in XLH (XLH: 812.1 ± 309.0 mL, control: 1391.1 ± 306.2 mv, P < .001). No significant differences were observed regarding isokinetic maximum torque (MVC) adjusted to quadriceps muscle volume. Jumping peak power and jump height were significantly reduced in XLH vs controls (both P < .001). The content of phosphoric compounds within the musculature of patients with XLH was not observed to be different from controls. Volume-adjusted muscle strength and fatiguability were not different either. Reduced physical performance in patients with XLH may result from long-term adaptation to reduced physical activity due to skeletal impairment.

Space Diplomacy

Summary After the Cold War and the race in space, space activities increasing became a geopolitical arena of co-operation. This article is based on my personal experience gathered over fifteen years leading European space institutions: in 2007 I became the Chairman of the Executive Board of the German Aerospace Center. In that position I led the German delegation to the European Space Agency (ESA). From 2015 to 2021 I had the honour and pleasure of being the Director General of ESA. During the whole period from 2007 to today I have had various political interactions that developed my current mindset. Even in times of geopolitical difficulties we need some aspects of international interaction; space can play this role.

Unified-Loop Structured H-Infinity Control for Aerodynamic Steering of Reusable Rockets

This paper investigates the use of structured robust techniques for the control design of the aerodynamic descent phase of a reusable rocket. A unified control strategy based on the use of linear-time-invariant structured controllers for both attitude and position is proposed and verified in both frequency and time domains. The architecture of the controller and the observed performance are discussed. Moreover, the nonlinear behavior of the control strategy is analyzed by looking at both the gain-scheduling law in conditions of plant-controller misalignment through the use of misalignment matrices, and simulation results obtained with a high-fidelity, nonlinear six-degree-of-freedom closed-loop model in perturbed conditions. All the results are based on Cooperative Action Leading to Launcher Innovation in Stage Tossback Operations (CALLISTO), a reusable rocket demonstrator jointly developed by German Aerospace Center (DLR), Japan Aerospace Exploration Agency (JAXA), and National Centre for Space Studies (CNES).

Ground Displacements in NY Using Persistent Scatterer Interferometric Synthetic Aperture Radar and Comparison of X- and C-Band Data

In this study, we investigated the quality of Interferometric Synthetic Aperture Radar (InSAR) data to measure surface displacements in upstate New York, an area with dense vegetation, snowy winters, and strong seasonal signals. We used data from the German Space Agency’s TerraSAR-X and TanDEM-X satellites (X-band, 3.1 cm radar wavelength) as well as the European Space Agency’s Sentinel-1 satellite (C-band, 5.6 cm radar wavelength); both datasets covered a ~3-year time period from 2018 to 2021. Using persistent scatterer interferometry (PSI), we were able to observe several deforming features in the region with sub-centimeter/year deformation rates. We also examined a version of the X-band data that we spatially averaged to the same pixel size as the Sentinel-1 imagery in order to separate out the effects of wavelength and pixel size on PSI accuracy and coverage. Overall, the largest number of stable PS points was found in the full-resolution X-band data, which was followed by the C-band data and then by the downsampled X-band data. Our analysis also included a subset of snow-free imagery so that we could assess the effect that snow-covered images had on the distribution and accuracy of PS points and the resulting time series. This analysis revealed that PS populations increased by 50–60% for the snow-free data when compared with analyses using the full datasets. The average deformation rates inferred from the time series generated using only snow-free images were nearly identical to those estimated from the full time series. We assessed the accuracy of the inferred rates through comparisons between the results of different datasets and with limited ground survey data. We found that all of the inferred deformation rates from each of the datasets agreed with in situ measurements in an area of known ground subsidence above an underground salt mine in Lansing, NY. The S1 datasets, however, had higher levels of noise.

UltraFLoads: A Simulation Suite and Framework for High-Fidelity Flight Loads

With the progress of high-performance computing, computationally expensive high-fidelity methods can be applied early in the design process of an aircraft. This enables Computational Fluid Dynamics (CFD) for the assesment of flight performance, handling qualities, flight loads due to manoeuver or gusts, and stability such as flutter. Those aeroealstic analyses require coupling of disciplines to adequately address the interplay of flexibility, aerodynamic forces and inertia forces. Previous work at the German Aerospace Center have demonstrated the proof of concept for those multidisciplinary analyses. Now, UltraFLoads is a simulation suite in the FlowSimulator ecosystem to offer standardized, multidisciplinary scenarios. UltraFLoads can be used as a tool, as a library and as a framework. This work describes the architecture, the integration layers, which scenarios are available and which equations are used. Three different applications are presented. The first case involves a steady fluid–structure-coupled simulation with geometrically nonlinear deformation. The second case compares the deformation of a simulated elastic, free-flying aircraft with actual flight test data. The last application demonstrates the flight dynamic capabilities with a bank to bank maneuver.

AI-For-Mobility—A New Research Platform for AI-Based Control Methods

AI-For-Mobility (AFM) is the new research platform to investigate and implement novel control methods based on Artificial Intelligence (AI) within the Department of Vehicle System Dynamics at the German Aerospace Center (DLR). A production hybrid vehicle serves as a base platform. Since AI-based methods are data-driven, the vehicle is equipped with manifold sensors to provide the required data. They measure the vehicle’s state holistically and perceive the surrounding environment, while high performance on-board CPUs and GPUs handle the sensor data. A full by-wire control system enables the vehicle to be used for applications in the field of automated driving. Despite all modifications, it is approved for public road use and meets the driving dynamics properties of a standard road vehicle. This makes it an attractive research and test platform, both for automotive applications and technology demonstrations in other scientific fields (e.g., robotics, aviation, etc.). This paper presents the vehicle’s design and architecture in a detailed manner and shows a promising application potential of AFM in the context of AI-based control methods.

Spectroradiometer Calibration for Radiance Transfer Measurements.

Optical remote sensing and Earth observation instruments rely on precise radiometric calibrations which are generally provided by the broadband emission from large-aperture integrating spheres. The link between the integrating sphere radiance and an SI-traceable radiance standard is made by spectroradiometer measurements. In this work, the calibration efforts of a Spectra Vista Corporation (SVC) HR-1024i spectroradiometer are presented to study how these enable radiance transfer measurements at the Calibration Home Base (CHB) for imaging spectrometers at the Remote Sensing Technology Institute (IMF) of the German Aerospace Center (DLR). The spectral and radiometric response calibrations of an SVC HR-1024i spectroradiometer are reported, as well as the measurements of non-linearity and its sensitivity to temperature changes and polarized light. This achieves radiance transfer measurements with the calibrated spectroradiometer with relative expanded uncertainties between 1% and 3% (k=2) over the wavelength range of 380 nm to 2500 nm, which are limited by the uncertainties of the applied radiance standard.

Vicarious CAL/VAL Approach for Orbital Hyperspectral Sensors Using Multiple Sites

The hyperspectral (HSR) sensors Earth Surface Mineral Dust Source Investigation (EMIT) of the National Aeronautics and Space Administration (NASA) and Environmental Mapping and Analysis Program (EnMAP) of the German Aerospace Center (DLR) were recently launched. These state-of-the-art sensors have joined the already operational HSR sensors DESIS (DLR), PRISMA (Italian Space Agency), and HISUI (developed by the Japanese Ministry of Economy, Trade, and Industry METI and Japan Aerospace Exploration Agency JAXA). The launching of more HSR sensors is being planned for the near future (e.g., SBG of NASA, and CHIME of the European Space Agency), and the challenge of monitoring and maintaining their calibration accuracy is becoming more relevant. We proposed two test sites: Amiaz Plain (AP) and Makhtesh Ramon (MR) for spectral, radiometric, and geometric calibration/validation (CAL/VAL). The sites are situated in the arid environment of southern Israel and are in the same overpass coverage. Both test sites have already demonstrated favorable results in assessing an HSR sensor’s performance and were chosen to participate in the EMIT and EnMAP validation stage. We first evaluated the feasibility of using AP and MR as CAL/VAL test sites with extensive datasets and sensors, such as the multispectral sensor Landsat (Landsat5 TM and Landsat8 OLI), the airborne HSR sensor AisaFENIX 1K, and the spaceborne HSR sensors DESIS and PRISMA. Field measurements were taken over time. The suggested methodology integrates reflectance and radiometric CAL/VAL test sites into one operational protocol. The method can highlight degradation in the spectral domain early on, help maintain quantitative applications, adjust the sensor’s radiometric calibration during its mission lifetime, and minimize uncertainties of calibration parameters. A PRISMA sensor case study demonstrates the complete operational protocol, i.e., performance evaluation, quality assessment, and cross-calibration between HSR sensors. These CAL/VAL sites are ready to serve as operational sites for other HSR sensors.

Ground-Based Experiment for Electric Propulsion Thruster Plume—Magnetic Field Interaction

Electric space propulsion is a technology which is employed on a continuously increasing number of spacecrafts. While the current focus of their application area is on telecommunication satellites and on space exploration missions, several new ideas are now discussed that go even further and apply the thruster plume particle flow for transferring momentum to targets such as space debris objects or even asteroids. In these potential scenarios, the thruster beam impacts on distant objects and subsequently generates changes in their flight path. One aspect which so far has not been systematically investigated is the interaction of the charged particles in the propulsion beam with magnetic fields which are present in space. This interaction may result in a deflection of the particle flow and consequently affect the aiming strategy. In the present article, basic considerations related to the interaction between electric propulsion thruster plumes and magnetic fields are presented. Experiments with respect to these questions were conducted in the high-vacuum plume test facility for electric thrusters (STG-ET) of the German Aerospace Center in Göttingen utilizing a gridded ion thruster, an RIT10/37, and a Helmholtz coil to generate magnetic fields of varying field strength. It was possible to detect a beam deflection on the RIT ion beam caused by a magnetic field with an Earth-like magnetic field strength.

Air Traffic Management as a Vital Part of Urban Air Mobility—A Review of DLR’s Research Work from 1995 to 2022

Urban air mobility is a rapidly growing field of research. While drones or unmanned aerial vehicles have been operated mainly in the private and military sector in the past, an increasing range of opportunities is opening up for commercial applications. A new multitude of passenger-carrying drone or air taxi concepts promises to fulfill the dream of flying above congested urban areas. While early research has been focusing on vehicle development, solutions for urban air traffic management are lagging behind. This paper collects and reviews the main findings of past urban-air-mobility-related research projects at the German Aerospace Center (DLR) to serve as a basis for ongoing research from an air traffic management perspective.

Time-resolved pressure-sensitive paint measurements for cryogenic wind tunnel tests

A first time-resolved pressure-sensitive paint (PSP) test campaign at the European Transonic Wind Tunnel (ETW) was conducted within the research initiative “Unsteady flow and interaction phenomena at High Speed Stall conditions”. One of the objectives of this wind tunnel campaign was to resolve time-series of surface pressure distributions caused by complex 3-D buffet phenomena on a full-span airplane model XRF-1 transport aircraft configuration. At higher angle-of-attack and high Mach number, pressure fluctuations with a frequency of several hundred Hertz are expected to occur on the main wing and the horizontal tail plane (HTP) caused by the buffet effect. To capture the expected buffet phenomena by PSP, the German Aerospace Center developed a time-resolved PSP measurement and data acquisition system as well as a post-processing method for measurements in ETW. The measurements were conducted on the main wing and HTP simultaneously, with a camera frame rate of up to 2 kHz. The transonic buffet phenomena were observed at the flight relevant Reynolds number Re = 12.9 × 106 and Re = 25.0 × 106. The time-varying surface pressure distribution on the model was successfully captured by PSP. The time-series and spectra of both PSP and pressure transducer data match very well.

Hypersonic flow over spherically blunted cone capsules for atmospheric entry. Part 2. Vibrational non-equilibrium effects

Atmospheric entry capsules shaped as spherically blunted, large apex-angle cones are widely used in space missions. In Part 1 of this study (Hornung, Martinez Schramm &amp; Hannemann, J. Fluid Mech., vol. 871, 2019, pp. 1097–1116) we explored flows over the two elements of the capsule shape, the sphere and the sharp cone with detached shock, theoretically and computationally. Using a large number of inviscid, perfect-gas computations, analytical functions of two independent variables, the normal-shock density ratio $\varepsilon$ and a cone-angle parameter $\eta$ (which is a function of $\varepsilon$ and the cone half-angle $\theta$ ) were found for the dimensionless shock wave stand-off distance and the drag coefficient of a sharp cone. An analytical description was found for the shock stand-off distance in the transition from the 90 $^\circ$ cone (flat-faced cylinder) to the sphere. In Part 1, it was speculated that the perfect-gas results have relevance to non-equilibrium situations if the normal-shock density ratio is replaced by the density ratio based on the average density along the stagnation streamline. In Part 2, the investigation is extended to blunted-cone capsule shapes. High-precision force measurements and schlieren image analysis are performed in the High-Enthalpy Shock Tunnel Göttingen (HEG) of the German Aerospace Centre using air as the test gas, at conditions where vibrational non-equilibrium effects are significant. Accordingly, results are compared with viscous numerical predictions using different physico-chemical models. A theoretical model is constructed for the density profile along the stagnation streamline that is determined by the free stream conditions and gives the average density. Comparisons of the experimental and numerical results for the dimensionless shock stand-off distance and the drag coefficient, with the extension of the analytical functions of Part 1 to vibrationally relaxing flow, exhibit very good agreement in all of a range of geometries.

AUTOMATION OF TESTING AND FAULT DETECTION FOR ROCKET ENGINE TEST FACILITIES WITH MACHINE LEARNING

The German Aerospace Center (DLR) Institute of Space Propulsion has unique expertise in operating test facilities for rocket engine testing and development in Europe since 1959. However, essential elements of the test site were designed up to half a century ago. In order to ensure a futureproof and intelligent digital test infrastructure, the potential of test automation, advanced control, and monitoring systems is investigated based on machine learning. Such intelligent control systems are expected to reduce engine development and test preparation times, thereby lowering the associated costs. Additionally, advanced monitoring systems are anticipated to increase the safety and reliability of the test infrastructure. This paper presents the results of two pilot projects: the first project uses reinforcement learning to automatically generate test sequences based on test requirements, while the second project develops a feed-forward forecasting model to predict deviations from expected behavior in the feed-line of a rocket engine test facility.

Dynamic Predictive Quantization for Staggered SAR: Experiments With Real Data

Present and future spaceborne synthetic aperture radar (SAR) missions are designed to acquire an increasingly large amount of onboard data. This is a consequence of the use of large bandwidths, multiple polarizations, and the acquisition of large swath widths at fine spatial resolutions, which result in challenging requirements in terms of onboard memory and downlink capacity. In this scenario, SAR raw data quantization represents an essential aspect, as it affects the volume of data to be stored and transmitted to the ground as well as the quality of the resulting SAR products. Dynamic predictive block-adaptive quantization (DP-BAQ) is a novel technique, recently proposed by the authors, consisting of a low-complexity data compression method, and its application is particularly suitable for staggered SAR systems. DP-BAQ exploits the existing correlation among the azimuth raw data samples by applying linear predictive coding (LPC). This results in a data rate reduction of up to 25% with respect to state-of-the-art SAR quantization methods. In this letter, we test and validate the potential of DP-BAQ on airborne SAR data which emulates the system scenario of Tandem-L, a German Aerospace Center (DLR) mission proposal for a bistatic L-band system. For this purpose, an experimental SAR image has been acquired at the L-band by the airborne DLR flugzeug-SAR (F-SAR) sensor over the Kaufbeuren area, in Southern Germany. In order to simulate the staggered SAR acquisition mode, we implemented a dedicated resampling and filtering of the data. Our analyses confirm the effectiveness of DP-BAQ for efficient data volume reduction, exhibiting a consistent and promising performance when tested on areas characterized by different land cover types and backscatter statistics.