@inproceedings{AdamsLosekammCzupalla2020, author = {Adams, Moritz and Losekamm, Martin J. and Czupalla, Markus}, title = {Development of the Thermal Control System for the RadMap Telescope Experiment on the International Space Station}, series = {International Conference on Environmental Systems}, booktitle = {International Conference on Environmental Systems}, pages = {1 -- 10}, year = {2020}, language = {en} } @misc{ArtmannLinderBayeretal.2017, author = {Artmann, Gerhard and Linder, Peter and Bayer, Robin and Gossmann, Matthias}, title = {Celldrum electrode arrangement for measuring mechanical stress [Patent of invention]}, publisher = {WIPO}, address = {Geneva}, pages = {18 Seiten}, year = {2017}, abstract = {The invention pertains to a CellDrum electrode arrangement for measuring mechanical stress, comprising a mechanical holder (1 ) and a non-conductive membrane (4), whereby the membrane (4) is at least partially fixed at its circumference to the mechanical holder (1), keeping it in place when the membrane (4) may bend due to forces acting on the membrane (4), the mechanical holder (1) and the membrane (4) forming a container, whereby the membrane (1) within the container comprises an cell- membrane compound layer or biological material (3) adhered to the deformable membrane 4 which in response to stimulation by an agent may exert mechanical stress to the membrane (4) such that the membrane bending stage changes whereby the container may be filled with an electrolyte, whereby an electric contact (2) is arranged allowing to contact said electrolyte when filled into to the container, whereby within a predefined geometry to the fixing of the membrane (4) an electrode (7) is arranged, whereby the electrode (7) is electrically insulated with respect to the electric contact (2) as well as said electrolyte, whereby mechanical stress due to an agent may be measured as a change in capacitance.}, language = {en} } @article{AyedKustererFunkeetal.2016, author = {Ayed, Anis Haj and Kusterer, Karsten and Funke, Harald and Keinz, Jan}, title = {CFD Based Improvement of the DLN Hydrogen Micromix Combustion Technology at Increased Energy Densities}, series = {American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS)}, volume = {26}, journal = {American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS)}, number = {3}, publisher = {GSSRR}, issn = {2313-4402}, pages = {290 -- 303}, year = {2016}, abstract = {Combined with the use of renewable energy sources for its production, Hydrogen represents a possible alternative gas turbine fuel within future low emission power generation. Due to the large difference in the physical properties of Hydrogen compared to other fuels such as natural gas, well established gas turbine combustion systems cannot be directly applied for Dry Low NOx (DLN) Hydrogen combustion. Thus, the development of DLN combustion technologies is an essential and challenging task for the future of Hydrogen fuelled gas turbines. The DLN Micromix combustion principle for hydrogen fuel has been developed to significantly reduce NOx-emissions. This combustion principle is based on cross-flow mixing of air and gaseous hydrogen which reacts in multiple miniaturized diffusion-type flames. The major advantages of this combustion principle are the inherent safety against flash-back and the low NOx-emissions due to a very short residence time of reactants in the flame region of the micro-flames. The Micromix Combustion technology has been already proven experimentally and numerically for pure Hydrogen fuel operation at different energy density levels. The aim of the present study is to analyze the influence of different geometry parameter variations on the flame structure and the NOx emission and to identify the most relevant design parameters, aiming to provide a physical understanding of the Micromix flame sensitivity to the burner design and identify further optimization potential of this innovative combustion technology while increasing its energy density and making it mature enough for real gas turbine application. The study reveals great optimization potential of the Micromix Combustion technology with respect to the DLN characteristics and gives insight into the impact of geometry modifications on flame structure and NOx emission. This allows to further increase the energy density of the Micromix burners and to integrate this technology in industrial gas turbines.}, language = {en} } @article{AyedKustererFunkeetal.2017, author = {Ayed, Anis Haj and Kusterer, Karsten and Funke, Harald and Keinz, Jan and Bohn, D.}, title = {CFD based exploration of the dry-low-NOx hydrogen micromix combustion technology at increased energy densities}, series = {Propulsion and Power Research}, volume = {6}, journal = {Propulsion and Power Research}, number = {1}, publisher = {Elsevier}, address = {Amsterdam}, isbn = {2212-540X}, doi = {10.1016/j.jppr.2017.01.005}, pages = {15 -- 24}, year = {2017}, language = {en} } @inproceedings{AyedStrieganKustereretal.2017, author = {Ayed, Anis Haj and Striegan, Constantin J. D. and Kusterer, Karsten and Funke, Harald and Kazari, M. and Horikawa, Atsushi and Okada, Kunio}, title = {Automated design space exploration of the hydrogen fueled "Micromix" combustor technology}, pages = {1 -- 8}, year = {2017}, abstract = {Combined with the use of renewable energy sources for its production, Hydrogen represents a possible alternative gas turbine fuel for future low emission power generation. Due to its different physical properties compared to other fuels such as natural gas, well established gas turbine combustion systems cannot be directly applied for Dry Low NOx (DLN) Hydrogen combustion. This makes the development of new combustion technologies an essential and challenging task for the future of hydrogen fueled gas turbines. The newly developed and successfully tested "DLN Micromix" combustion technology offers a great potential to burn hydrogen in gas turbines at very low NOx emissions. Aiming to further develop an existing burner design in terms of increased energy density, a redesign is required in order to stabilise the flames at higher mass flows and to maintain low emission levels. For this purpose, a systematic design exploration has been carried out with the support of CFD and optimisation tools to identify the interactions of geometrical and design parameters on the combustor performance. Aerodynamic effects as well as flame and emission formation are observed and understood time- and cost-efficiently. Correlations between single geometric values, the pressure drop of the burner and NOx production have been identified as a result. This numeric methodology helps to reduce the effort of manufacturing and testing to few designs for single validation campaigns, in order to confirm the flame stability and NOx emissions in a wider operating condition field.}, language = {en} } @article{BaaderBoxbergChenetal.2023, author = {Baader, Fabian and Boxberg, Marc S. and Chen, Qian and F{\"o}rstner, Roger and Kowalski, Julia and Dachwald, Bernd}, title = {Field-test performance of an ice-melting probe in a terrestrial analogue environment}, series = {Icarus}, journal = {Icarus}, number = {409}, publisher = {Elsevier}, address = {Amsterdam}, doi = {10.1016/j.icarus.2023.115852}, pages = {Artikel 115852}, year = {2023}, abstract = {Melting probes are a proven tool for the exploration of thick ice layers and clean sampling of subglacial water on Earth. Their compact size and ease of operation also make them a key technology for the future exploration of icy moons in our Solar System, most prominently Europa and Enceladus. For both mission planning and hardware engineering, metrics such as efficiency and expected performance in terms of achievable speed, power requirements, and necessary heating power have to be known. Theoretical studies aim at describing thermal losses on the one hand, while laboratory experiments and field tests allow an empirical investigation of the true performance on the other hand. To investigate the practical value of a performance model for the operational performance in extraterrestrial environments, we first contrast measured data from terrestrial field tests on temperate and polythermal glaciers with results from basic heat loss models and a melt trajectory model. For this purpose, we propose conventions for the determination of two different efficiencies that can be applied to both measured data and models. One definition of efficiency is related to the melting head only, while the other definition considers the melting probe as a whole. We also present methods to combine several sources of heat loss for probes with a circular cross-section, and to translate the geometry of probes with a non-circular cross-section to analyse them in the same way. The models were selected in a way that minimizes the need to make assumptions about unknown parameters of the probe or the ice environment. The results indicate that currently used models do not yet reliably reproduce the performance of a probe under realistic conditions. Melting velocities and efficiencies are constantly overestimated by 15 to 50 \% in the models, but qualitatively agree with the field test data. Hence, losses are observed, that are not yet covered and quantified by the available loss models. We find that the deviation increases with decreasing ice temperature. We suspect that this mismatch is mainly due to the too restrictive idealization of the probe model and the fact that the probe was not operated in an efficiency-optimized manner during the field tests. With respect to space mission engineering, we find that performance and efficiency models must be used with caution in unknown ice environments, as various ice parameters have a significant effect on the melting process. Some of these are difficult to estimate from afar.}, language = {en} } @inproceedings{BaaderKellerLehmannetal.2019, author = {Baader, Fabian and Keller, Denis and Lehmann, Raphael and Gerber, Lukas and Reiswich, Martin and Dachwald, Bernd and F{\"o}rstner, Roger}, title = {Operating melting probes for ice penetration under sublimation conditions and in reduced gravity on a sounding rocket}, series = {Proceedings of the 24th ESA Symposium on European Rocket and Balloon Programmes and related Research}, booktitle = {Proceedings of the 24th ESA Symposium on European Rocket and Balloon Programmes and related Research}, issn = {0379-6566}, pages = {8 Seiten}, year = {2019}, language = {en} } @incollection{BallmannBouckeBraun2003, author = {Ballmann, Josef and Boucke, Alexander and Braun, Carsten}, title = {Aeroelastic sensitivity in the transonic regime}, series = {Symposium Transsonicum IV : proceedings of the IUTAM symposium held in G{\"o}ttingen, Germany, 2 - 6 September 2002 / ed. by Helmut Sobieczky. Fluid mechanics and its applications. Vol. 73}, booktitle = {Symposium Transsonicum IV : proceedings of the IUTAM symposium held in G{\"o}ttingen, Germany, 2 - 6 September 2002 / ed. by Helmut Sobieczky. Fluid mechanics and its applications. Vol. 73}, publisher = {Kluwer Academic}, address = {Dordrecht}, isbn = {978-94-010-3998-7}, pages = {225 -- 236}, year = {2003}, language = {en} } @inproceedings{BallmannDafnisBraunetal.2006, author = {Ballmann, Josef and Dafnis, Athanasios and Braun, Carsten and Korsch, Helge and Reimerdes, Hans-G{\"u}nther and Braun, Carsten and Ballmann, Josef}, title = {The HIRENASD project: High Reynolds number aerostructural dynamics experiments in the European Transonic Wind Tunnel (ETW)}, series = {ICAS 2006 proceedings : 25th Congress of the International Council of the Aeronautical Sciences ; Hamburg, Germany, 3 - 8 September, 2006 : 25th International Congress of Aeronautical Sciences}, booktitle = {ICAS 2006 proceedings : 25th Congress of the International Council of the Aeronautical Sciences ; Hamburg, Germany, 3 - 8 September, 2006 : 25th International Congress of Aeronautical Sciences}, publisher = {Optimage}, address = {Edinburgh}, organization = {International Council of the Aeronautical Sciences (ICAS)}, isbn = {0-9533991-7-6}, pages = {Paper No. 2006-5.11.2}, year = {2006}, language = {en} } @inproceedings{BarnatBosse2016, author = {Barnat, Miriam and Bosse, Elke}, title = {The challenge of creating meta-inferences: Combining data representing institutional and individual perspectives on first-year support in higher education}, series = {9th Conference on Social Science Methodology of the International Sociological Association, Leicester, UK}, booktitle = {9th Conference on Social Science Methodology of the International Sociological Association, Leicester, UK}, pages = {1 -- 20}, year = {2016}, language = {en} } @misc{BaumgartnerWunderlichJaunichetal.2012, author = {Baumgartner, Thomas and Wunderlich, Florian and Jaunich, Arthur and Sato, Tomoo and Bundy, Georg and Grießmann, Nadine and Kowalski, Julia and Burghardt, Stefan and Hanebrink, J{\"o}rg}, title = {Lighting the way: Perspectives on the global lighting market}, edition = {2nd ed.}, address = {McKinsey}, pages = {58}, year = {2012}, language = {en} } @phdthesis{Beckmann2019, author = {Beckmann, Nils}, title = {Characterization of the hydrogen-dry-low-Nox-micromix-combustion-principle for hydrogen-methane fuel mixtures}, publisher = {RMIT University}, address = {Melbourne}, pages = {XV, 160 Seiten}, year = {2019}, language = {en} } @book{BenkoePlescher2013, author = {Benk{\"o}, Marietta and Plescher, Engelbert}, title = {Space law: reconsidering the definition/delimitation question and the passage of spacecraft through foreign airspace. (Essential air and space law ; 12)}, publisher = {Eleven International Publishing}, address = {The Hague}, isbn = {9789462360761 ; 9462360766 ; 9789460948176}, pages = {VII, 159 S.}, year = {2013}, language = {en} } @inproceedings{BergmannGraebenerWildetal.2019, author = {Bergmann, Kevin and Gr{\"a}bener, Josefine and Wild, Dominik and Ulfers, H. and Czupalla, Markus}, title = {Study on thermal stabilization of a GEO-stationary telescope baffling system by integral application of phase change material}, series = {International Conference on Environmental Systems}, booktitle = {International Conference on Environmental Systems}, pages = {1 -- 14}, year = {2019}, abstract = {The utilization of phase change material (PCM) for latent heat storage and thermal control of spacecraft has been demonstrated in the past in few missions only. One limiting factor was the fact that all concepts developed so far envisioned the PCM to be applied as an additional capacitor, encapsulated in its own housing, leading to mass, efficiency and accommodation challenges. Recently, the application of PCM within the scan cavity of a GEOS type satellite has been suggested, in order to tackle thermal issues due to direct sun intrusion (Choi, M., 2014). However, the application of PCM in such complex mechanical structures is extremely challenging. A new concept to tackle this issue is currently under development at the FH Aachen University of Applied Sciences. The concept "Infused Thermal Solutions (ITS)" is based on the idea to 3D print metallic structures in their regular functional shape, but double walled with internal lattice support structures, allowing the infusion of a PCM layer directly into the voids and eliminating the need for additional parts and interfaces. Together with OHB System, FH Aachen theoretically studied the application of this technology to the Meteosat Third Generation (MTG) Infra-Red Sounder (IRS) instrument. The study focuses on the scan cavity and entrance baffling assembly (EBA) of the IRS. It consists of thermal analyses, 3D-redesign and bread boarding of a scaled and PCM infused EBA version. In the thermal design of the alternative EBA, PCM was applied directly into the EBA, simulating the worst hot case sun intrusion of the mission. By applying 4kg of PCM (to a 60kg baffle) the EBA temperature excursions during sun intrusion were limited from 140K to 30K, leading to a significant thermo-opto-elastic performance gain. This paper introduces the ITS concept development status.}, language = {en} } @article{BergmannMoehrenBraunetal.2023, author = {Bergmann, Ole and M{\"o}hren, Felix and Braun, Carsten and Janser, Frank}, title = {On the influence of elasticity on swept propeller noise}, series = {AIAA SCITECH 2023 Forum}, journal = {AIAA SCITECH 2023 Forum}, publisher = {AIAA}, doi = {10.2514/6.2023-0210}, year = {2023}, abstract = {High aerodynamic efficiency requires propellers with high aspect ratios, while propeller sweep potentially reduces noise. Propeller sweep and high aspect ratios increase elasticity and coupling of structural mechanics and aerodynamics, affecting the propeller performance and noise. Therefore, this paper analyzes the influence of elasticity on forward-swept, backward-swept, and unswept propellers in hover conditions. A reduced-order blade element momentum approach is coupled with a one-dimensional Timoshenko beam theory and Farassat's formulation 1A. The results of the aeroelastic simulation are used as input for the aeroacoustic calculation. The analysis shows that elasticity influences noise radiation because thickness and loading noise respond differently to deformations. In the case of the backward-swept propeller, the location of the maximum sound pressure level shifts forward by 0.5 °, while in the case of the forward-swept propeller, it shifts backward by 0.5 °. Therefore, aeroacoustic optimization requires the consideration of propeller deformation.}, language = {en} } @article{BindalSharmaJanseretal.2013, author = {Bindal, Gaurav and Sharma, Sparsh and Janser, Frank and Neu, Eugen}, title = {Detailed analysis of variables affecting wing kinematics of bat flight}, series = {SAE International Journal of Aerospace}, volume = {6}, journal = {SAE International Journal of Aerospace}, number = {2}, issn = {1946-3901}, doi = {10.4271/2013-01-9003}, pages = {811 -- 818}, year = {2013}, language = {en} } @article{Blome1994, author = {Blome, Hans-Joachim}, title = {The scale of the universe: a unit of length}, series = {Comments on astrophysics. 17 (1994)}, journal = {Comments on astrophysics. 17 (1994)}, isbn = {0146-2970}, pages = {327 -- 335}, year = {1994}, language = {en} } @article{BlomeChiconeHehletal.2010, author = {Blome, Hans-Joachim and Chicone, Carmen and Hehl, Friedrich W. and Mashhoon, Bahram}, title = {Nonlocal modification of Newtonian gravity}, series = {Physical Review D}, volume = {81}, journal = {Physical Review D}, number = {6}, isbn = {0556-2821}, pages = {065020}, year = {2010}, language = {en} } @article{BlomeChuHoelletal.1988, author = {Blome, Hans-Joachim and Chu, Y. and Hoell, J and Priester, W.}, title = {On the observational discrimination of Friedmann-Lema{\^i}tre models}, series = {Large Scale Structures of the Universe: Proceedings of the 130th Symposium of the International Astronomical Union, dedicated to the memory of Marc A. Aaronson (1950-1987) held in Balatonfured, Hungary, June 15-20, 1987. Edited by Jean Audouze, Marie-Christine Pelletan and Sandor Szalay.}, journal = {Large Scale Structures of the Universe: Proceedings of the 130th Symposium of the International Astronomical Union, dedicated to the memory of Marc A. Aaronson (1950-1987) held in Balatonfured, Hungary, June 15-20, 1987. Edited by Jean Audouze, Marie-Christine Pelletan and Sandor Szalay.}, publisher = {Kluwer Academic Publishers}, address = {Dordrecht}, isbn = {90-277-2742-2}, pages = {517}, year = {1988}, language = {en} } @article{BlomeKosbow2005, author = {Blome, Hans-Joachim and Kosbow, Michael}, title = {The Pioneer Anomaly in the context of non-Newtonian Gravity}, series = {International Astronautical Congress : final papers : October 17-21, 2005, Fukuoka, Japan}, journal = {International Astronautical Congress : final papers : October 17-21, 2005, Fukuoka, Japan}, publisher = {International Astronautical Federation}, address = {Paris}, pages = {20 -- 20}, year = {2005}, language = {en} } @article{BlomeKosbow2004, author = {Blome, Hans-Joachim and Kosbow, Michael}, title = {Perturbation of a satellite orbit by gravitational waves}, series = {Jahrbuch 2004 der Deutschen Gesellschaft f{\"u}r Luft- und Raumfahrt - Lilienthal-Oberth e.V. (DGLR)}, journal = {Jahrbuch 2004 der Deutschen Gesellschaft f{\"u}r Luft- und Raumfahrt - Lilienthal-Oberth e.V. (DGLR)}, publisher = {DGLR}, address = {Bonn}, isbn = {0070-4083}, pages = {2083 -- 2088}, year = {2004}, language = {en} } @article{BlomeKundt1987, author = {Blome, Hans-Joachim and Kundt, W.}, title = {Hypersonic Jets from Young Stars in Molecular Clouds}, series = {Circumstellar matter : proceedings of the 122nd symposium of the Internat. Astronom. Union held in Heidelberg, FRG, June 23 - 27, 1986 / ed. by I. Appenzeller ...}, journal = {Circumstellar matter : proceedings of the 122nd symposium of the Internat. Astronom. Union held in Heidelberg, FRG, June 23 - 27, 1986 / ed. by I. Appenzeller ...}, publisher = {Reidel}, address = {Dordrecht u.a.}, isbn = {90-277-2511-X}, pages = {73 -- 74}, year = {1987}, language = {en} } @article{BlomeKundt1988, author = {Blome, Hans-Joachim and Kundt, Wolfgang}, title = {Leptonic jets from young stellar objects?}, series = {Astrophysics and Space Science. 148 (1988), H. 2}, journal = {Astrophysics and Space Science. 148 (1988), H. 2}, isbn = {0004-640X}, pages = {343 -- 361}, year = {1988}, language = {en} } @article{BlomeMashhoon1984, author = {Blome, Hans-Joachim and Mashhoon, B.}, title = {Quasi-normal oscillations of a Schwarzschild black hole}, series = {Physics Letters A. 100 (1984), H. 5}, journal = {Physics Letters A. 100 (1984), H. 5}, isbn = {0375-9601}, pages = {231 -- 234}, year = {1984}, language = {en} } @article{BlomePriester1991, author = {Blome, Hans-Joachim and Priester, W.}, title = {Big Bounce in the very early Universe}, series = {Astronomy and Astrophysics. 250 (1991), H. 1}, journal = {Astronomy and Astrophysics. 250 (1991), H. 1}, isbn = {0004-6361}, pages = {43 -- 49}, year = {1991}, language = {en} } @article{BlomePriesterHoell1995, author = {Blome, Hans-Joachim and Priester, W. and Hoell, J.}, title = {New Ways in Cosmology: II. Alternative Models for the Very Early Universe}, series = {Currents in high energy astrophysics : proceedings of the NATO Advanced Study Institute and Ninth Course of the International School of Cosmic Ray Astrophysics on Currents in High Energy Astrophysics, Ettore Majorana Centre, Erice, Sicily, Italy, 7 - 18 M}, journal = {Currents in high energy astrophysics : proceedings of the NATO Advanced Study Institute and Ninth Course of the International School of Cosmic Ray Astrophysics on Currents in High Energy Astrophysics, Ettore Majorana Centre, Erice, Sicily, Italy, 7 - 18 M}, publisher = {Kluwer}, address = {Dordrecht [u.a.]}, isbn = {0-7923-3354-3}, pages = {301 -- 312}, year = {1995}, language = {en} } @article{BlomePriesterHoell1995, author = {Blome, Hans-Joachim and Priester, W. and Hoell, J.}, title = {New Ways in Cosmology: I. Friedmann-Lemaitre Model Derived From the Lyman Alpha Forest in Quasar Spectra}, series = {Currents in high energy astrophysics : proceedings of the NATO Advanced Study Institute and Ninth Course of the International School of Cosmic Ray Astrophysics on Currents in High Energy Astrophysics, Ettore Majorana Centre, Erice, Sicily, Italy, 7 - 18 M}, journal = {Currents in high energy astrophysics : proceedings of the NATO Advanced Study Institute and Ninth Course of the International School of Cosmic Ray Astrophysics on Currents in High Energy Astrophysics, Ettore Majorana Centre, Erice, Sicily, Italy, 7 - 18 M}, publisher = {Kluwer}, address = {Dordrecht [u.a.]}, isbn = {0-7923-3354-3}, pages = {291 -- 300}, year = {1995}, language = {en} } @article{BlomePriester1987, author = {Blome, Hans-Joachim and Priester, Wolfgang}, title = {The problem of the primeval explosion: 'Big bang' or 'big bounce'? I}, series = {Sterne und Weltraum. 26 (1987)}, journal = {Sterne und Weltraum. 26 (1987)}, isbn = {0039-1263}, pages = {83 -- 89}, year = {1987}, language = {en} } @article{BlomePriester1985, author = {Blome, Hans-Joachim and Priester, Wolfgang}, title = {Vacuum energy in cosmic dynamics}, series = {Astrophysics and Space Science. 117 (1985), H. 2}, journal = {Astrophysics and Space Science. 117 (1985), H. 2}, isbn = {0004-640X}, pages = {327 -- 335}, year = {1985}, language = {en} } @article{BlomeSeboldtDachwaldetal.2004, author = {Blome, Hans-Joachim and Seboldt, Wolfgang and Dachwald, Bernd and Richter, Lutz}, title = {Proposal for an integrated European Space Exploration Study}, series = {Space Debris and Space Traffic Management Symposium 2004 : proceedings of the International Academy of Astronautics Space Debris and Space Traffic Management Symposium, held in conjunction with the 55th International Astronautical Congress (IAC), October 4 - 8, 2004, Vancouver, British Columbia, Canada / ed. by Joerg Bendisch}, journal = {Space Debris and Space Traffic Management Symposium 2004 : proceedings of the International Academy of Astronautics Space Debris and Space Traffic Management Symposium, held in conjunction with the 55th International Astronautical Congress (IAC), October 4 - 8, 2004, Vancouver, British Columbia, Canada / ed. by Joerg Bendisch}, publisher = {Univelt}, address = {San Diego, Calif.}, isbn = {0-87703-523-7}, pages = {XI, 432 S. : Ill., graph. Darst.}, year = {2004}, language = {en} } @article{BlomeWilson2004, author = {Blome, Hans-Joachim and Wilson, Thomas L.}, title = {The entangled Universe}, series = {Relativistic Astrophysics and Cosmology, Proceedings of the 13th Course of the International School of Cosmic Ray Astrophysics, held in Erice, Italy, 2-14 June 2002 / edited by Maurice M. Shapiro ... [et al.]}, journal = {Relativistic Astrophysics and Cosmology, Proceedings of the 13th Course of the International School of Cosmic Ray Astrophysics, held in Erice, Italy, 2-14 June 2002 / edited by Maurice M. Shapiro ... [et al.]}, publisher = {World Scientific Publishing}, address = {New Jersey, NJ}, isbn = {981-238-727-7}, pages = {23 -- 38}, year = {2004}, language = {en} } @article{BlomeWilson2005, author = {Blome, Hans-Joachim and Wilson, Thomas L.}, title = {The quantum temperature of accelerating cosmological models of an entangled Universe}, series = {Advances in Space Research. 35 (2005), H. 1}, journal = {Advances in Space Research. 35 (2005), H. 1}, isbn = {0273-1177}, pages = {111 -- 115}, year = {2005}, language = {en} } @article{BlomeWilson1996, author = {Blome, Hans-Joachim and Wilson, Thomas L.}, title = {Observational cosmology from the moon. Wilson, Thomas, L.; Blome, Hans-Joachim}, series = {Engineering, construction, and operations in space V : proceedings of the Fifth International Conference on Space '96, Albuquerque, New Mexico, June 1-6, 1996 / sponsored by Aerospace Division of the American Society of Civil Engineers ... [et al.]; edite}, journal = {Engineering, construction, and operations in space V : proceedings of the Fifth International Conference on Space '96, Albuquerque, New Mexico, June 1-6, 1996 / sponsored by Aerospace Division of the American Society of Civil Engineers ... [et al.]; edite}, publisher = {The Society}, address = {New York}, isbn = {0-7844-0177-2}, pages = {864 -- 870}, year = {1996}, language = {en} } @article{BlomeWilson1996, author = {Blome, Hans-Joachim and Wilson, Thomas L.}, title = {Nanotechnology and Orbital Debris}, series = {Engineering, construction, and operations in space V : proceedings of the Fifth International Conference on Space '96, Albuquerque, New Mexico, June 1-6, 1996 / sponsored by Aerospace Division of the American Society of Civil Engineers ... [et al.]; edite}, journal = {Engineering, construction, and operations in space V : proceedings of the Fifth International Conference on Space '96, Albuquerque, New Mexico, June 1-6, 1996 / sponsored by Aerospace Division of the American Society of Civil Engineers ... [et al.]; edite}, publisher = {The Society}, address = {New York}, isbn = {0-7844-0177-2}, pages = {328 -- 333}, year = {1996}, language = {en} } @article{BlomeWilson1996, author = {Blome, Hans-Joachim and Wilson, Thomas L.}, title = {Nonlocal Cosmology}, series = {Bulletin of the American Physical Society. 40 (1996)}, journal = {Bulletin of the American Physical Society. 40 (1996)}, isbn = {0003-0503}, pages = {2121 -- 2121}, year = {1996}, language = {en} } @article{BohnFunkeGier1999, author = {Bohn, D. and Funke, Harald and Gier, J.}, title = {Temperature jet development in a cross-over channel}, series = {Third European Conference on Turbomachinery - fluid dynamics and thermodynamics : : 2 - 5 March 1999, Royal National Hotel, London, UK / organized by the Energy Transfer and Thermofluid Mechanics Group of the Institution of Mechanical Engineers (IMechE); with support and sponsorship from European Commission / Vol. B.}, journal = {Third European Conference on Turbomachinery - fluid dynamics and thermodynamics : : 2 - 5 March 1999, Royal National Hotel, London, UK / organized by the Energy Transfer and Thermofluid Mechanics Group of the Institution of Mechanical Engineers (IMechE); with support and sponsorship from European Commission / Vol. B.}, publisher = {Professional Engineering Publ.}, address = {Bury St. Edmunds}, pages = {671 -- 680}, year = {1999}, language = {en} } @article{BohnFunkeGier1999, author = {Bohn, D. and Funke, Harald and Gier, J.}, title = {Numerical and Experimental Investigations on the Flow in a 4-Stage Turbine with Special Focus on the Development of a Radial Temperature Streak}, series = {ASME Turbo Expo 1999, Indianapolis, USA, 1999}, journal = {ASME Turbo Expo 1999, Indianapolis, USA, 1999}, year = {1999}, language = {en} } @article{BohnFunke2003, author = {Bohn, Dieter and Funke, Harald}, title = {Experimental investigations into the nonuniform flow in a 4-stage turbine with special focus on the flow equalization in the first turbine stage}, series = {ASME TURBO EXPO, Proceedings of the ASME Turbo Expo, 2003}, journal = {ASME TURBO EXPO, Proceedings of the ASME Turbo Expo, 2003}, isbn = {0-7918-3689-4}, pages = {281 -- 289}, year = {2003}, language = {en} } @article{BohnFunkeHeueretal.2000, author = {Bohn, Dieter and Funke, Harald and Heuer, Tom and B{\"u}tikofer, J.}, title = {Numerical and experimental investigations of the influence of different swirl-ratios on the temperature streak equalization in a 4-stage turbine}, series = {ASME Turbo Expo 2000 ; Munich, May 8-11 2000}, journal = {ASME Turbo Expo 2000 ; Munich, May 8-11 2000}, address = {Munich}, year = {2000}, language = {en} } @article{BohnFunkeSuerkenetal.2001, author = {Bohn, Dieter and Funke, Harald and S{\"u}rken, Norbert and Kreitmeier, F.}, title = {Numerical and experimental investigations on endwall contouring in a four-stage turbine}, series = {ASME Turbo Expo Land Sea \& Air 2001 : June 4 - 8, 2001, New Orleans, Louisiana / IGTI, International Gas Turbine Institute. American Society of Mechanical Engineers. International Gas Turbine Institute ..}, journal = {ASME Turbo Expo Land Sea \& Air 2001 : June 4 - 8, 2001, New Orleans, Louisiana / IGTI, International Gas Turbine Institute. American Society of Mechanical Engineers. International Gas Turbine Institute ..}, publisher = {ASME}, address = {New York, NY}, isbn = {0-7918-3528-6}, pages = {CD-Rom}, year = {2001}, language = {en} } @article{BohndickBosseJaenschetal.2021, author = {Bohndick, Carla and Bosse, Elke and J{\"a}nsch, Vanessa K. and Barnat, Miriam}, title = {How different diversity factors affect the perception of first-year requirements in higher education}, series = {Frontline Learning Research}, volume = {9}, journal = {Frontline Learning Research}, number = {2}, publisher = {EARLI}, issn = {2295-3159}, doi = {10.14786/flr.v9i2.667}, pages = {78 -- 95}, year = {2021}, abstract = {In the light of growing university entry rates, higher education institutions not only serve larger numbers of students, but also seek to meet first-year students' ever more diverse needs. Yet to inform universities how to support the transition to higher education, research only offers limited insights. Current studies tend to either focus on the individual factors that affect student success or they highlight students' social background and their educational biography in order to examine the achievement of selected, non-traditional groups of students. Both lines of research appear to lack integration and often fail to take organisational diversity into account, such as different types of higher education institutions or degree programmes. For a more comprehensive understanding of student diversity, the present study includes individual, social and organisational factors. To gain insights into their role for the transition to higher education, we examine how the different factors affect the students' perception of the formal and informal requirements of the first year as more or less difficult to cope with. As the perceived requirements result from both the characteristics of the students and the institutional context, they allow to investigate transition at the interface of the micro and the meso level of higher education. Latent profile analyses revealed that there are no profiles with complex patterns of perception of the first-year requirements, but the identified groups rather differ in the overall level of perceived challenges. Moreover, SEM indicates that the differences in the perception largely depend on the individual factors self-efficacy and volition.}, language = {en} } @incollection{BorggrafeOhndorfDachwaldetal.2012, author = {Borggrafe, Andreas and Ohndorf, Andreas and Dachwald, Bernd and Seboldt, Wolfgang}, title = {Analysis of interplanetary solar sail trajectories with attitude dynamics}, series = {Dynamics and Control of Space Systems 2012}, booktitle = {Dynamics and Control of Space Systems 2012}, publisher = {Univelt Inc}, address = {San Diego}, isbn = {978-0-87703-587-9}, pages = {1553 -- 1569}, year = {2012}, abstract = {We present a new approach to the problem of optimal control of solar sails for low-thrust trajectory optimization. The objective was to find the required control torque magnitudes in order to steer a solar sail in interplanetary space. A new steering strategy, controlling the solar sail with generic torques applied about the spacecraft body axes, is integrated into the existing low-thrust trajectory optimization software InTrance. This software combines artificial neural networks and evolutionary algorithms to find steering strategies close to the global optimum without an initial guess. Furthermore, we implement a three rotational degree-of-freedom rigid-body attitude dynamics model to represent the solar sail in space. Two interplanetary transfers to Mars and Neptune are chosen to represent typical future solar sail mission scenarios. The results found with the new steering strategy are compared to the existing reference trajectories without attitude dynamics. The resulting control torques required to accomplish the missions are investigated, as they pose the primary requirements to a real on-board attitude control system.}, language = {en} } @inproceedings{BorggraefeDachwald2010, author = {Borggr{\"a}fe, Andreas and Dachwald, Bernd}, title = {Mission performance evaluation for solar sails using a refined SRP force model with variable optical coefficients}, series = {2nd International Symposium on Solar Sailing}, booktitle = {2nd International Symposium on Solar Sailing}, pages = {1 -- 6}, year = {2010}, abstract = {Solar sails provide ignificant advantages over other low-thrust propulsion systems because they produce thrust by the momentum exchange from solar radiation pressure (SRP) and thus do not consume any propellant.The force exerted on a very thin sail foil basically depends on the light incidence angle. Several analytical SRP force models that describe the SRP force acting on the sail have been established since the 1970s. All the widely used models use constant optical force coefficients of the reflecting sail material. In 2006,MENGALI et al. proposed a refined SRP force model that takes into account the dependancy of the force coefficients on the light incident angle,the sail's distance from the sun (and thus the sail emperature) and the surface roughness of the sail material [1]. In this paper, the refined SRP force model is compared to the previous ones in order to identify the potential impact of the new model on the predicted capabilities of solar sails in performing low-cost interplanetary space missions. All force models have been implemented within InTrance, a global low-thrust trajectory optimization software utilizing evolutionary neurocontrol [2]. Two interplanetary rendezvous missions, to Mercury and the near-Earth asteroid 1996FG3, are investigated. Two solar sail performances in terms of characteristic acceleration are examined for both scenarios, 0.2 mm/s2 and 0.5 mm/s2, termed "low" and "medium" sail performance. In case of the refined SRP model, three different values of surface roughness are chosen, h = 0 nm, 10 nm and 25 nm. The results show that the refined SRP force model yields shorter transfer times than the standard model.}, language = {en} } @inproceedings{BraunBouckeBallmann2005, author = {Braun, Carsten and Boucke, Alexander and Ballmann, Josef}, title = {Numerical prediction of the wing deformation of a high speed transport aircraft type wind tunnel model by direct aeroelastic simulation}, series = {Conference proceedings : CEAS/AIAA/DGLR International Forum on Aeroelasticity and Structural Dynamics IFASD 2005 : M{\"u}nchen, June 28 - July 1, 2005. DGLR-Bericht. 2005,04}, booktitle = {Conference proceedings : CEAS/AIAA/DGLR International Forum on Aeroelasticity and Structural Dynamics IFASD 2005 : M{\"u}nchen, June 28 - July 1, 2005. DGLR-Bericht. 2005,04}, publisher = {DGLR}, address = {Bonn}, isbn = {3-932182-43-X}, pages = {1 CD-ROM}, year = {2005}, language = {en} } @incollection{BraunBouckeBallmann2005, author = {Braun, Carsten and Boucke, Alexander and Ballmann, Josef}, title = {Numerical study of the influence of dynamic pressure and deflected ailerons on the deformation of a high speed wing model}, series = {High performance computing in science and engineering '04. Transactions of the High Performance Computing Center Stuttgart (HLRS) 2004 / Eds.: Egon Krause ...}, booktitle = {High performance computing in science and engineering '04. Transactions of the High Performance Computing Center Stuttgart (HLRS) 2004 / Eds.: Egon Krause ...}, publisher = {Springer}, address = {Berlin}, isbn = {3-540-22943-4}, pages = {225 -- 236}, year = {2005}, language = {en} } @incollection{BrittenBraunHesseetal.2003, author = {Britten, G. and Braun, Carsten and Hesse, M. and Ballmann, Josef}, title = {Computational aeroelasticity with reduced structural models}, series = {Flow modulation and fluid-structure interaction at airplane wings : research results of the Collaborative Research Center SFB 401 at RWTH Aachen, University of Technology, Aachen, Germany / Josef Ballmann (Ed.) Notes on numerical fluid mechanics and multidisciplinary design. Vol. 84}, booktitle = {Flow modulation and fluid-structure interaction at airplane wings : research results of the Collaborative Research Center SFB 401 at RWTH Aachen, University of Technology, Aachen, Germany / Josef Ballmann (Ed.) Notes on numerical fluid mechanics and multidisciplinary design. Vol. 84}, publisher = {Springer}, address = {Berlin}, isbn = {3-540-40209-8}, pages = {275 -- 299}, year = {2003}, language = {en} } @article{BullerschenWilhelmi1991, author = {Bullerschen, Klaus-Gerd and Wilhelmi, Herbert}, title = {Cooling of arc furnace electrodes with heat pipes}, series = {Chemical Engineering \& Technology. 14 (1991), H. 1}, journal = {Chemical Engineering \& Technology. 14 (1991), H. 1}, isbn = {0930-7516}, pages = {45 -- 53}, year = {1991}, language = {en} } @article{BullerschenWilhelmiWimmer1985, author = {Bullerschen, Klaus-Gerd and Wilhelmi, Herbert and Wimmer, W.}, title = {Influence of non-uniform material properties and water cooling on current density and temperature profiles in arc furnace elektrodes}, series = {Steel Research. 56 (1985), H. 11}, journal = {Steel Research. 56 (1985), H. 11}, isbn = {0177-4832}, pages = {559 -- 564}, year = {1985}, language = {en} } @incollection{BusseEschMuntaniol2015, author = {Busse, Daniel and Esch, Thomas and Muntaniol, Roman}, title = {Thermal management in E-carsharing vehicles - preconditioning concepts of passenger compartments}, series = {E-Mobility in Europe : trends and good practice}, booktitle = {E-Mobility in Europe : trends and good practice}, publisher = {Springer}, address = {Cham [u.a.]}, isbn = {978-3-319-13193-1}, doi = {10.1007/978-3-319-13194-8_18}, pages = {327 -- 343}, year = {2015}, abstract = {The issue of thermal management in electric vehicles includes the topics of drivetrain cooling and heating, interior temperature, vehicle body conditioning and safety. In addition to the need to ensure optimal thermal operating conditions of the drivetrain components (drive motor, battery and electrical components), thermal comfort must be provided for the passengers. Thermal comfort is defined as the feeling which expresses the satisfaction of the passengers with the ambient conditions in the compartment. The influencing factors on thermal comfort are the temperature and humidity as well as the speed of the indoor air and the clothing and the activity of the passengers, in addition to the thermal radiation and the temperatures of the interior surfaces. The generation and the maintenance of free visibility (ice- and moisture-free windows) count just as important as on-demand heating and cooling of the entire vehicle. A Carsharing climate concept of the innovative ec2go vehicle stipulates and allows for only seating areas used by passengers to be thermally conditioned in a close-to-body manner. To enable this, a particular feature has been added to the preconditioning of the Carsharing electric vehicle during the electric charging phase at the parking station.}, language = {en} } @article{BecretGrossenTrillaetal.2007, author = {B{\´e}cret, P. and Grossen, J. and Trilla, J. and Robinson, A. and Bosschaerts, W. and Funke, Harald and Hendrick, P.}, title = {Testing and numerical study of a 10 kW hydrogen micro combustor}, series = {International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications <7, 2007, Freiburg, Breisgau> ; PowerMEMS ; 7}, journal = {International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications <7, 2007, Freiburg, Breisgau> ; PowerMEMS ; 7}, pages = {367 -- 370}, year = {2007}, language = {en} } @article{BoehnischBraunMuscarelloetal.2024, author = {B{\"o}hnisch, Nils and Braun, Carsten and Muscarello, Vincenzo and Marzocca, Pier}, title = {About the wing and whirl flutter of a slender wing-propeller system}, series = {Journal of Aircraft}, journal = {Journal of Aircraft}, publisher = {American Institute of Aeronautics and Astronautics}, issn = {1533-3868}, doi = {10.2514/1.C037542}, pages = {1 -- 14}, year = {2024}, abstract = {Next-generation aircraft designs often incorporate multiple large propellers attached along the wingspan (distributed electric propulsion), leading to highly flexible dynamic systems that can exhibit aeroelastic instabilities. This paper introduces a validated methodology to investigate the aeroelastic instabilities of wing-propeller systems and to understand the dynamic mechanism leading to wing and whirl flutter and transition from one to the other. Factors such as nacelle positions along the wing span and chord and its propulsion system mounting stiffness are considered. Additionally, preliminary design guidelines are proposed for flutter-free wing-propeller systems applicable to novel aircraft designs. The study demonstrates how the critical speed of the wing-propeller systems is influenced by the mounting stiffness and propeller position. Weak mounting stiffnesses result in whirl flutter, while hard mounting stiffnesses lead to wing flutter. For the latter, the position of the propeller along the wing span may change the wing mode shapes and thus the flutter mechanism. Propeller positions closer to the wing tip enhance stability, but pusher configurations are more critical due to the mass distribution behind the elastic axis.}, language = {en} } @phdthesis{Boerner2013, author = {B{\"o}rner, Sebastian}, title = {Optimization and testing of a low NOx hydrogen fuelled gas turbine}, publisher = {Universit{\´e} Libre de Bruxelles}, address = {Bruxelles}, pages = {XVI, 144 S.}, year = {2013}, language = {en} } @article{BoernerFunkeHendricketal.2010, author = {B{\"o}rner, Sebastian and Funke, Harald and Hendrick, P. and Recker, E.}, title = {Control system modifications for a hydrogen fuelled gas-turbine}, series = {ISROMAC 13, 13th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, Honolulu, HI, US, Apr 4-7, 2010}, journal = {ISROMAC 13, 13th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, Honolulu, HI, US, Apr 4-7, 2010}, publisher = {Curran}, address = {Red Hook, NY}, isbn = {978-1-617-38848-4}, pages = {665 -- 670}, year = {2010}, language = {en} } @inproceedings{BoernerFunkeHendricketal.2009, author = {B{\"o}rner, Sebastian and Funke, Harald and Hendrick, P. and Recker, E.}, title = {LES of Jets In Cross-Flow and Application to the "Micromix" Hydrogen Combustion}, series = {XIX International Symposium on Air Breathing Engines 2009 (ISABE 2009) : Proceedings of a meeting held 7-11 September 2009, Montreal, Canada}, booktitle = {XIX International Symposium on Air Breathing Engines 2009 (ISABE 2009) : Proceedings of a meeting held 7-11 September 2009, Montreal, Canada}, isbn = {9781615676064}, pages = {1555 -- 1561}, year = {2009}, language = {en} } @article{BuehlerChristenKowalskietal.2011, author = {B{\"u}hler, Yves and Christen, Marc and Kowalski, Julia and Bartelt, Perry}, title = {Sensitivity of snow avalanche simulations to digital elevation model quality and resolution}, series = {Annals of Glaciology}, volume = {52}, journal = {Annals of Glaciology}, number = {58}, publisher = {Cambridge University Press}, address = {Cambridge}, isbn = {1727-5644}, pages = {72 -- 80}, year = {2011}, abstract = {Digital elevation models (DEMs), represent the three-dimensional terrain and are the basic input for numerical snow avalanche dynamics simulations. DEMs can be acquired using topographic maps or remote-sensing technologies, such as photogrammetry or lidar. Depending on the acquisition technique, different spatial resolutions and qualities are achieved. However, there is a lack of studies that investigate the sensitivity of snow avalanche simulation algorithms to the quality and resolution of DEMs. Here, we perform calculations using the numerical avalance dynamics model RAMMS, varying the quality and spatial resolution of the underlying DEMs, while holding the simulation parameters constant. We study both channelized and open-terrain avalanche tracks with variable roughness. To quantify the variance of these simulations, we use well-documented large-scale avalanche events from Davos, Switzerland (winter 2007/08), and from our large-scale avalanche test site, Valĺee de la Sionne (winter 2005/06). We find that the DEM resolution and quality is critical for modeled flow paths, run-out distances, deposits, velocities and impact pressures. Although a spatial resolution of ~25 m is sufficient for large-scale avalanche modeling, the DEM datasets must be checked carefully for anomalies and artifacts before using them for dynamics calculations.}, language = {en} } @article{CampenKowalskiLyonsetal.2019, author = {Campen, R. and Kowalski, Julia and Lyons, W.B. and Tulaczyk, S. and Dachwald, Bernd and Pettit, E. and Welch, K. A. and Mikucki, J.A.}, title = {Microbial diversity of an Antarctic subglacial community and high-resolution replicate sampling inform hydrological connectivity in a polar desert}, series = {Environmental Microbiology}, journal = {Environmental Microbiology}, number = {accepted article}, publisher = {Wiley}, address = {Weinheim}, issn = {1462-2920}, doi = {10.1111/1462-2920.14607}, year = {2019}, language = {en} } @inproceedings{CarzanaDachwaldNoomen2017, author = {Carzana, Livio and Dachwald, Bernd and Noomen, Ron}, title = {Model and trajectory optimization for an ideal laser-enhanced solar sail}, series = {68th International Astronautical Congress}, booktitle = {68th International Astronautical Congress}, year = {2017}, abstract = {A laser-enhanced solar sail is a solar sail that is not solely propelled by solar radiation but additionally by a laser beam that illuminates the sail. This way, the propulsive acceleration of the sail results from the combined action of the solar and the laser radiation pressure onto the sail. The potential source of the laser beam is a laser satellite that coverts solar power (in the inner solar system) or nuclear power (in the outer solar system) into laser power. Such a laser satellite (or many of them) can orbit anywhere in the solar system and its optimal orbit (or their optimal orbits) for a given mission is a subject for future research. This contribution provides the model for an ideal laser-enhanced solar sail and investigates how a laser can enhance the thrusting capability of such a sail. The term "ideal" means that the solar sail is assumed to be perfectly reflecting and that the laser beam is assumed to have a constant areal power density over the whole sail area. Since a laser beam has a limited divergence, it can provide radiation pressure at much larger solar distances and increase the radiation pressure force into the desired direction. Therefore, laser-enhanced solar sails may make missions feasible, that would otherwise have prohibitively long flight times, e.g. rendezvous missions in the outer solar system. This contribution will also analyze exemplary mission scenarios and present optimial trajectories without laying too much emphasis on the design and operations of the laser satellites. If the mission studies conclude that laser-enhanced solar sails would have advantages with respect to "traditional" solar sails, a detailed study of the laser satellites and the whole system architecture would be the second next step}, language = {en} } @article{ChristenBarteltKowalski2010, author = {Christen, Marc and Bartelt, Perry and Kowalski, Julia}, title = {Back calculation of the In den Arelen avalanche with RAMMS: Interpretation of model results}, series = {Annals of Glaciology}, volume = {51}, journal = {Annals of Glaciology}, number = {54}, publisher = {Cambridge University Press}, address = {Cambridge}, isbn = {1727-5644}, doi = {10.3189/172756410791386553}, pages = {161 -- 168}, year = {2010}, abstract = {Two- and three-dimensional avalanche dynamics models are being increasingly used in hazard-mitigation studies. These models can provide improved and more accurate results for hazard mapping than the simple one-dimensional models presently used in practice. However, two- and three-dimensional models generate an extensive amount of output data, making the interpretation of simulation results more difficult. To perform a simulation in three-dimensional terrain, numerical models require a digital elevation model, specification of avalanche release areas (spatial extent and volume), selection of solution methods, finding an adequate calculation resolution and, finally, the choice of friction parameters. In this paper, the importance and difficulty of correctly setting up and analysing the results of a numerical avalanche dynamics simulation is discussed. We apply the two-dimensional simulation program RAMMS to the 1968 extreme avalanche event In den Arelen. We show the effect of model input variations on simulation results and the dangers and complexities in their interpretation.}, language = {en} } @inproceedings{ChristenBarteltKowalskietal.2008, author = {Christen, Marc and Bartelt, Perry and Kowalski, Julia and Stoffel, Lukus}, title = {Calculation of dense snow avalanches in three-dimensional terrain with the numerical simulation programm RAMMS}, series = {Proceedings ISSW 2008 ; International Snow Science Workshop. Whistler 2008}, booktitle = {Proceedings ISSW 2008 ; International Snow Science Workshop. Whistler 2008}, pages = {709 -- 716}, year = {2008}, abstract = {Numerical models have become an essential part of snow avalanche engineering. Recent advances in understanding the rheology of flowing snow and the mechanics of entrainment and deposition have made numerical models more reliable. Coupled with field observations and historical records, they are especially helpful in understanding avalanche flow in complex terrain. However, the application of numerical models poses several new challenges to avalanche engineers. A detailed understanding of the avalanche phenomena is required to specify initial conditions (release zone dimensions and snowcover entrainment rates) as well as the friction parameters, which are no longer based on empirical back-calculations, rather terrain roughness, vegetation and snow properties. In this paper we discuss these problems by presenting the computer model RAMMS, which was specially designed by the SLF as a practical tool for avalanche engineers. RAMMS solves the depth-averaged equations governing avalanche flow with first and second-order numerical solution schemes. A tremendous effort has been invested in the implementation of advanced input and output features. Simulation results are therefore clearly and easily visualized to simplify their interpretation. More importantly, RAMMS has been applied to a series of well-documented avalanches to gauge model performance. In this paper we present the governing differential equations, highlight some of the input and output features of RAMMS and then discuss the simulation of the Gatschiefer avalanche that occurred in April 2008, near Klosters/Monbiel, Switzerland.}, language = {en} } @article{ChristenKowalskiBartelt2010, author = {Christen, Marc and Kowalski, Julia and Bartelt, Perry}, title = {RAMMS: Numerical simulation of dense snow avalanches in three-dimensional terrain}, series = {Cold Regions Science and Technology}, volume = {63}, journal = {Cold Regions Science and Technology}, number = {1-2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1872-7441}, doi = {10.1016/j.coldregions.2010.04.005}, pages = {1 -- 14}, year = {2010}, abstract = {Numerical avalanche dynamics models have become an essential part of snow engineering. Coupled with field observations and historical records, they are especially helpful in understanding avalanche flow in complex terrain. However, their application poses several new challenges to avalanche engineers. A detailed understanding of the avalanche phenomena is required to construct hazard scenarios which involve the careful specification of initial conditions (release zone location and dimensions) and definition of appropriate friction parameters. The interpretation of simulation results requires an understanding of the numerical solution schemes and easy to use visualization tools. We discuss these problems by presenting the computer model RAMMS, which was specially designed by the SLF as a practical tool for avalanche engineers. RAMMS solves the depth-averaged equations governing avalanche flow with accurate second-order numerical solution schemes. The model allows the specification of multiple release zones in three-dimensional terrain. Snow cover entrainment is considered. Furthermore, two different flow rheologies can be applied: the standard Voellmy-Salm (VS) approach or a random kinetic energy (RKE) model, which accounts for the random motion and inelastic interaction between snow granules. We present the governing differential equations, highlight some of the input and output features of RAMMS and then apply the models with entrainment to simulate two well-documented avalanche events recorded at the Vall{\´e}e de la Sionne test site.}, language = {en} } @article{CzupallaHorneckBlome2005, author = {Czupalla, Markus and Horneck, G. and Blome, Hans-Joachim}, title = {The conceptual design of a hybrid life support system based on the evaluation and comparison of terrestrial testbeds}, series = {Advances in Space Research}, volume = {35}, journal = {Advances in Space Research}, number = {9}, isbn = {0273-1177}, pages = {1609 -- 1620}, year = {2005}, language = {en} } @article{Dachwald2005, author = {Dachwald, Bernd}, title = {Optimization of very-low-thrust trajectories using evolutionary neurocontrol}, series = {Acta Astronautica. 57 (2005), H. 2-8}, journal = {Acta Astronautica. 57 (2005), H. 2-8}, isbn = {0094-5765}, pages = {175 -- 185}, year = {2005}, language = {en} } @article{Dachwald2004, author = {Dachwald, Bernd}, title = {Minimum Transfer Times for Nonperfectly Reflecting Solar Sailcraft}, series = {Journal of Spacecraft and Rockets. 41 (2004), H. 4}, journal = {Journal of Spacecraft and Rockets. 41 (2004), H. 4}, isbn = {0022-4650}, pages = {693 -- 695}, year = {2004}, language = {en} } @article{Dachwald2005, author = {Dachwald, Bernd}, title = {Optimal Solar Sail Trajectories for Missions to the Outer Solar System}, series = {Journal of guidance, control, and dynamics. 28 (2005), H. 6}, journal = {Journal of guidance, control, and dynamics. 28 (2005), H. 6}, isbn = {0162-3192}, pages = {1187 -- 1193}, year = {2005}, language = {en} } @article{Dachwald2004, author = {Dachwald, Bernd}, title = {Optimization of Interplanetary Solar Sailcraft Trajectories Using Evolutionary Neurocontrol}, series = {Journal of guidance, control, and dynamics. 27 (2004), H. 1}, journal = {Journal of guidance, control, and dynamics. 27 (2004), H. 1}, isbn = {0162-3192}, pages = {66 -- 72}, year = {2004}, language = {en} } @article{Dachwald2004, author = {Dachwald, Bernd}, title = {Interplanetary Mission Analysis for Non-Perfectly Reflecting Solar Sailcraft Using Evolutionary Neurocontrol}, series = {Astrodynamics 2003 : proceedings of the AAS/AIAA Astrodynamics Conference held August 3 - 7, 2003, Big Sky, Montana / ed. by Jean de Lafontaine. - Pt. 2. - (Advances in the astronautical sciences ; 116,2)}, journal = {Astrodynamics 2003 : proceedings of the AAS/AIAA Astrodynamics Conference held August 3 - 7, 2003, Big Sky, Montana / ed. by Jean de Lafontaine. - Pt. 2. - (Advances in the astronautical sciences ; 116,2)}, publisher = {Univelt}, address = {San Diego, Calif.}, isbn = {0-87703-509-1}, pages = {1247 -- 1262}, year = {2004}, language = {en} } @article{Dachwald2004, author = {Dachwald, Bernd}, title = {Low-Thrust Trajectory Optimization and Interplanetary Mission Analysis Using Evolutionary Neurocontrol}, series = {Deutscher Luft- und Raumfahrtkongress 2004 : Dresden, 20. bis 23. September 2004, Motto: Luft- und Raumfahrt - Br{\"u}cke f{\"u}r eine wissensbasierte Gesellschaft / Deutsche Gesellschaft f{\"u}r Luft- und Raumfahrt - Lilienthal-Oberth e.V. (DGLR). [Red.: Peter Brandt (verantwortlich)]. - Bd. 2. - (Jahrbuch ... der Deutschen Gesellschaft f{\"u}r Luft- und Raumfahrt)}, journal = {Deutscher Luft- und Raumfahrtkongress 2004 : Dresden, 20. bis 23. September 2004, Motto: Luft- und Raumfahrt - Br{\"u}cke f{\"u}r eine wissensbasierte Gesellschaft / Deutsche Gesellschaft f{\"u}r Luft- und Raumfahrt - Lilienthal-Oberth e.V. (DGLR). [Red.: Peter Brandt (verantwortlich)]. - Bd. 2. - (Jahrbuch ... der Deutschen Gesellschaft f{\"u}r Luft- und Raumfahrt)}, address = {Bonn}, pages = {917 -- 926}, year = {2004}, language = {en} } @article{Dachwald2004, author = {Dachwald, Bernd}, title = {Evolutionary Neurocontrol: A Smart Method for Global Optimization of Low-Thrust Trajectories}, series = {22nd AIAA Applied Aerodynamics Conference and Exhibit - AIAA/AAS Astrodynamics Specialist Conference and Exhibit - AIAA Guidance, Navigation, and Control Conference and Exhibit - AIAA Modeling and Simulation Technologies Conference and Exhibit - AIAA Atmospheric Flight Mechanics Conference and Exhibit : 16 - 19 August 2004, Providence, Rhode Island / American Institute of Aeronautics and Astronautics. - (AIAA meeting papers on disc ; 2004,14-15)}, journal = {22nd AIAA Applied Aerodynamics Conference and Exhibit - AIAA/AAS Astrodynamics Specialist Conference and Exhibit - AIAA Guidance, Navigation, and Control Conference and Exhibit - AIAA Modeling and Simulation Technologies Conference and Exhibit - AIAA Atmospheric Flight Mechanics Conference and Exhibit : 16 - 19 August 2004, Providence, Rhode Island / American Institute of Aeronautics and Astronautics. - (AIAA meeting papers on disc ; 2004,14-15)}, publisher = {American Inst. of Aeronautics and Astronautics}, address = {Reston, Va.}, pages = {2 CD-ROMs}, year = {2004}, language = {en} } @article{Dachwald2004, author = {Dachwald, Bernd}, title = {Optimal Solar Sail Trajectories for Missions to the Outer Solar System}, series = {22nd AIAA Applied Aerodynamics Conference and Exhibit - AIAA/AAS Astrodynamics Specialist Conference and Exhibit - AIAA Guidance, Navigation, and Control Conference and Exhibit - AIAA Modeling and Simulation Technologies Conference and Exhibit - AIAA Atmospheric Flight Mechanics Conference and Exhibit : 16 - 19 August 2004, Providence, Rhode Island / American Institute of Aeronautics and Astronautics. - (AIAA meeting papers on disc ; 2004,14-15)}, journal = {22nd AIAA Applied Aerodynamics Conference and Exhibit - AIAA/AAS Astrodynamics Specialist Conference and Exhibit - AIAA Guidance, Navigation, and Control Conference and Exhibit - AIAA Modeling and Simulation Technologies Conference and Exhibit - AIAA Atmospheric Flight Mechanics Conference and Exhibit : 16 - 19 August 2004, Providence, Rhode Island / American Institute of Aeronautics and Astronautics. - (AIAA meeting papers on disc ; 2004,14-15)}, publisher = {American Inst. of Aeronautics and Astronautics}, address = {Reston, Va.}, pages = {2 CD-ROMs}, year = {2004}, language = {en} } @inproceedings{Dachwald2007, author = {Dachwald, Bernd}, title = {Low-Thrust Mission Analysis and Global Trajectory Optimization Using Evolutionary Neurocontrol: New Results}, series = {European Workshop on Space Mission Analysis ESA/ESOC, Darmstadt, Germany 10 { 12 Dec 2007}, booktitle = {European Workshop on Space Mission Analysis ESA/ESOC, Darmstadt, Germany 10 { 12 Dec 2007}, year = {2007}, abstract = {Interplanetary trajectories for low-thrust spacecraft are often characterized by multiple revolutions around the sun. Unfortunately, the convergence of traditional trajectory optimizers that are based on numerical optimal control methods depends strongly on an adequate initial guess for the control function (if a direct method is used) or for the starting values of the adjoint vector (if an indirect method is used). Especially when many revolutions around the sun are re- quired, trajectory optimization becomes a very difficult and time-consuming task that involves a lot of experience and expert knowledge in astrodynamics and optimal control theory, because an adequate initial guess is extremely hard to find. Evolutionary neurocontrol (ENC) was proposed as a smart method for low-thrust trajectory optimization that fuses artificial neural networks and evolutionary algorithms to so-called evolutionary neurocontrollers (ENCs) [1]. Inspired by natural archetypes, ENC attacks the trajectoryoptimization problem from the perspective of artificial intelligence and machine learning, a perspective that is quite different from that of optimal control theory. Within the context of ENC, a trajectory is regarded as the result of a spacecraft steering strategy that maps permanently the actual spacecraft state and the actual target state onto the actual spacecraft control vector. This way, the problem of searching the optimal spacecraft trajectory is equivalent to the problem of searching (or "learning") the optimal spacecraft steering strategy. An artificial neural network is used to implement such a spacecraft steering strategy. It can be regarded as a parameterized function (the network function) that is defined by the internal network parameters. Therefore, each distinct set of network parameters defines a different network function and thus a different steering strategy. The problem of searching the optimal steering strategy is now equivalent to the problem of searching the optimal set of network parameters. Evolutionary algorithms that work on a population of (artificial) chromosomes are used to find the optimal network parameters, because the parameters can be easily mapped onto a chromosome. The trajectory optimization problem is solved when the optimal chromosome is found. A comparison of solar sail trajectories that have been published by others [2, 3, 4, 5] with ENC-trajectories has shown that ENCs can be successfully applied for near-globally optimal spacecraft control [1, 6] and that they are able to find trajectories that are closer to the (unknown) global optimum, because they explore the trajectory search space more exhaustively than a human expert can do. The obtained trajectories are fairly accurate with respect to the terminal constraint. If a more accurate trajectory is required, the ENC-solution can be used as an initial guess for a local trajectory optimization method. Using ENC, low-thrust trajectories can be optimized without an initial guess and without expert attendance. Here, new results for nuclear electric spacecraft and for solar sail spacecraft are presented and it will be shown that ENCs find very good trajectories even for very difficult problems. Trajectory optimization results are presented for 1. NASA's Solar Polar Imager Mission, a mission to attain a highly inclined close solar orbit with a solar sail [7] 2. a mission to de ect asteroid Apophis with a solar sail from a retrograde orbit with a very-high velocity impact [8, 9] 3. JPL's \2nd Global Trajectory Optimization Competition", a grand tour to visit four asteroids from different classes with a NEP spacecraft}, language = {en} } @inproceedings{Dachwald2005, author = {Dachwald, Bernd}, title = {Global optimization of low-thrust space missions using evolutionary neurocontrol}, series = {Proceedings of the international workshop on global optimization}, booktitle = {Proceedings of the international workshop on global optimization}, pages = {85 -- 90}, year = {2005}, abstract = {Low-thrust space propulsion systems enable flexible high-energy deep space missions, but the design and optimization of the interplanetary transfer trajectory is usually difficult. It involves much experience and expert knowledge because the convergence behavior of traditional local trajectory optimization methods depends strongly on an adequate initial guess. Within this extended abstract, evolutionary neurocontrol, a method that fuses artificial neural networks and evolutionary algorithms, is proposed as a smart global method for low-thrust trajectory optimization. It does not require an initial guess. The implementation of evolutionary neurocontrol is detailed and its performance is shown for an exemplary mission.}, language = {en} } @incollection{Dachwald2017, author = {Dachwald, Bernd}, title = {Light propulsion systems for spacecraft}, series = {Optical nano and micro actuator technology}, booktitle = {Optical nano and micro actuator technology}, editor = {Knopf, George K. and Otani, Yukitoshi}, publisher = {CRC Press}, address = {Boca Raton}, isbn = {9781315217628 (eBook)}, pages = {577 -- 598}, year = {2017}, language = {en} } @incollection{Dachwald2010, author = {Dachwald, Bernd}, title = {Solar sail dynamics and control}, series = {Encyclopedia of Aerospace Engineering}, booktitle = {Encyclopedia of Aerospace Engineering}, publisher = {Wiley}, address = {Hoboken}, doi = {10.1002/9780470686652.eae292}, year = {2010}, abstract = {Solar sails are large and lightweight reflective structures that are propelled by solar radiation pressure. This chapter covers their orbital and attitude dynamics and control. First, the advantages and limitations of solar sails are discussed and their history and development status is outlined. Because the dynamics of solar sails is governed by the (thermo-)optical properties of the sail film, the basic solar radiation pressure force models have to be described and compared before parameters to measure solar sail performance can be defined. The next part covers the orbital dynamics of solar sails for heliocentric motion, planetocentric motion, and motion at Lagrangian equilibrium points. Afterwards, some advanced solar radiation pressure force models are described, which allow to quantify the thrust force on solar sails of arbitrary shape, the effects of temperature, of light incidence angle, of surface roughness, and the effects of optical degradation of the sail film in the space environment. The orbital motion of a solar sail is strongly coupled to its rotational motion, so that the attitude control of these soft and flexible structures is very challenging, especially for planetocentric orbits that require fast attitude maneuvers. Finally, some potential attitude control methods are sketched and selection criteria are given.}, language = {en} } @article{Dachwald2005, author = {Dachwald, Bernd}, title = {Optimization of very-low-thrust trajectories using evolutionary neurocontrol}, series = {Acta Astronautica}, volume = {57}, journal = {Acta Astronautica}, number = {2-8}, publisher = {Elsevier}, address = {Amsterdam [u.a.]}, isbn = {1879-2030}, pages = {175 -- 185}, year = {2005}, abstract = {Searching optimal interplanetary trajectories for low-thrust spacecraft is usually a difficult and time-consuming task that involves much experience and expert knowledge in astrodynamics and optimal control theory. This is because the convergence behavior of traditional local optimizers, which are based on numerical optimal control methods, depends on an adequate initial guess, which is often hard to find, especially for very-low-thrust trajectories that necessitate many revolutions around the sun. The obtained solutions are typically close to the initial guess that is rarely close to the (unknown) global optimum. Within this paper, trajectory optimization problems are attacked from the perspective of artificial intelligence and machine learning. Inspired by natural archetypes, a smart global method for low-thrust trajectory optimization is proposed that fuses artificial neural networks and evolutionary algorithms into so-called evolutionary neurocontrollers. This novel method runs without an initial guess and does not require the attendance of an expert in astrodynamics and optimal control theory. This paper details how evolutionary neurocontrol works and how it could be implemented. The performance of the method is assessed for three different interplanetary missions with a thrust to mass ratio <0.15mN/kg (solar sail and nuclear electric).}, language = {en} } @inproceedings{Dachwald2017, author = {Dachwald, Bernd}, title = {Radiation pressure force model for an ideal laser-enhanced solar sail}, series = {4th International Symposium on Solar Sailing}, booktitle = {4th International Symposium on Solar Sailing}, pages = {1 -- 5}, year = {2017}, abstract = {The concept of a laser-enhanced solar sail is introduced and the radiation pressure force model for an ideal laser-enhanced solar sail is derived. A laser-enhanced solar sail is a "traditional" solar sail that is, however, not solely propelled by solar radiation, but additionally by a laser beam that illuminates the sail. The additional laser radiation pressure increases the sail's propulsive force and can give, depending on the location of the laser source, more control authority over the direction of the solar sail's propulsive force vector. This way, laser-enhanced solar sails may augment already existing solar sail mission concepts and make novel mission concepts feasible.}, language = {en} } @inproceedings{Dachwald2004, author = {Dachwald, Bernd}, title = {Solar sail performance requirements for missions to the outer solar system and beyond}, series = {55th International Astronautical Congress 2004}, booktitle = {55th International Astronautical Congress 2004}, doi = {10.2514/6.IAC-04-S.P.11}, pages = {1 -- 9}, year = {2004}, abstract = {Solar sails enable missions to the outer solar system and beyond, although the solar radiation pressure decreases with the square of solar distance. For such missions, the solar sail may gain a large amount of energy by first making one or more close approaches to the sun. Within this paper, optimal trajectories for solar sail missions to the outer planets and into near interstellar space (200 AU) are presented. Thereby, it is shown that even near/medium-term solar sails with relatively moderate performance allow reasonable transfer times to the boundaries of the solar system.}, language = {en} } @article{DachwaldBallUlamecetal.2009, author = {Dachwald, Bernd and Ball, Andrew J. and Ulamec, Stephan and Price, Michael E.}, title = {A small mission for in situ exploration of a primitive binary near-Earth asteroid / Ball, Andrew J. ; Ulamec, Stephan ; Dachwald, Bernd ; Price, Michael E. ; [u.a.]}, series = {Advances in Space Research. 43 (2009), H. 2}, journal = {Advances in Space Research. 43 (2009), H. 2}, publisher = {Elsevier}, address = {Amsterdam}, isbn = {0273-1177}, pages = {317 -- 324}, year = {2009}, language = {en} } @inproceedings{DachwaldBaturkinCoverstoneetal.2005, author = {Dachwald, Bernd and Baturkin, Volodymyr and Coverstone, Victoria and Diedrich, Ben and Garbe, Gregory and G{\"o}rlich, Marianne and Leipold, Manfred and Lura, Franz and Macdonald, Malcolm and McInnes, Colin and Mengali, Giovanni and Quarta, Alessandro and Rios-Reyes, Leonel and Scheeres, Daniel J. and Seboldt, Wolfgang and Wie, Bong}, title = {Potential effects of optical solar sail degredation on trajectory design}, series = {AAS/AIAA Astrodynamics Specialist}, booktitle = {AAS/AIAA Astrodynamics Specialist}, pages = {1 -- 23}, year = {2005}, abstract = {The optical properties of the thin metalized polymer films that are projected for solar sails are assumed to be affected by the erosive effects of the space environment. Their degradation behavior in the real space environment, however, is to a considerable degree indefinite, because initial ground test results are controversial and relevant inspace tests have not been made so far. The standard optical solar sail models that are currently used for trajectory design do not take optical degradation into account, hence its potential effects on trajectory design have not been investigated so far. Nevertheless, optical degradation is important for high-fidelity solar sail mission design, because it decreases both the magnitude of the solar radiation pressure force acting on the sail and also the sail control authority. Therefore, we propose a simple parametric optical solar sail degradation model that describes the variation of the sail film's optical coefficients with time, depending on the sail film's environmental history, i.e., the radiation dose. The primary intention of our model is not to describe the exact behavior of specific film-coating combinations in the real space environment, but to provide a more general parametric framework for describing the general optical degradation behavior of solar sails. Using our model, the effects of different optical degradation behaviors on trajectory design are investigated for various exemplary missions.}, language = {en} } @article{DachwaldBaturkinCoverstoneetal.2006, author = {Dachwald, Bernd and Baturkin, Volodymyr and Coverstone, Victoria L. and Dietrich, Benjamin and Garbe, Gregory P. and G{\"o}rlich, Marianne and Leipold, Manfred and Lura, Franz and Macdonald, Malcolm and McInnes, Colin R. and Mengali, Giovanni and Quatra, Alessandro A. and Rios-Reyes, Leonel and Scheeres, Daniel J. and Seboldt, Wolfgang and Wie, Bong}, title = {Potential Effects of Optical Solar Sail Degradation on Interplanetary Trajectory Design}, series = {Astrodynamics 2005 : proceedings of the AAS/AIAA astrodynamics conference held August 7 - 11, 2005, South Lake Tahoe, California / ed. by Bobby G. Williams. - Pt. 3. - (Advances in the astronautical sciences ; 123,3)}, journal = {Astrodynamics 2005 : proceedings of the AAS/AIAA astrodynamics conference held August 7 - 11, 2005, South Lake Tahoe, California / ed. by Bobby G. Williams. - Pt. 3. - (Advances in the astronautical sciences ; 123,3)}, publisher = {Univelt}, address = {San Diego, Calif.}, isbn = {0-87703-527-X}, pages = {2569 -- 2592}, year = {2006}, language = {en} } @incollection{DachwaldBoehnhardtBrojetal.2014, author = {Dachwald, Bernd and Boehnhardt, Herrmann and Broj, Ulrich and Geppert, Ulrich R. M. E. and Grundmann, Jan-Thimo and Seboldt, Wolfgang and Seefeldt, Patric and Spietz, Peter and Johnson, Les and K{\"u}hrt, Ekkehard and Mottola, Stefano and Macdonald, Malcolm and McInnes, Colin R. and Vasile, Massimiliano and Reinhard, Ruedeger}, title = {Gossamer roadmap technology reference study for a multiple NEO Rendezvous Mission}, series = {Advances in solar sailing}, booktitle = {Advances in solar sailing}, publisher = {Springer}, address = {Berlin [u.a.]}, isbn = {978-3-642-34906-5 (Print) ; 978-3-642-34907-2 (E-Book)}, pages = {211 -- 226}, year = {2014}, abstract = {A technology reference study for a multiple near-Earth object (NEO) rendezvous mission with solar sailcraft is currently carried out by the authors of this paper. The investigated mission builds on previous concepts, but adopts a strong micro-spacecraft philosophy based on the DLR/ESA Gossamer technology. The main scientific objective of the mission is to explore the diversity of NEOs. After direct interplanetary insertion, the solar sailcraft should—within less than 10 years—rendezvous three NEOs that are not only scientifically interesting, but also from the point of human spaceight and planetary defense. In this paper, the objectives of the study are outlined and a preliminary potential mission profile is presented.}, language = {en} } @article{DachwaldCarnelliVasile2006, author = {Dachwald, Bernd and Carnelli, I. and Vasile, M.}, title = {Low-Thrust Gravity Assist Trajectory Optimization Using Evolutionary Neurocontrollers / I. Carnelli ; B. Dachwald ; M. Vasile ...}, series = {Astrodynamics 2005 : proceedings of the AAS/AIAA astrodynamics conference held August 7 - 11, 2005, South Lake Tahoe, California / ed. by Bobby G. Williams. - Pt. 3. - (Advances in the astronautical sciences ; 123,3)}, journal = {Astrodynamics 2005 : proceedings of the AAS/AIAA astrodynamics conference held August 7 - 11, 2005, South Lake Tahoe, California / ed. by Bobby G. Williams. - Pt. 3. - (Advances in the astronautical sciences ; 123,3)}, publisher = {Univelt}, address = {San Diego, Calif.}, isbn = {0-87703-527-X}, pages = {1911 -- 1928}, year = {2006}, language = {en} } @article{DachwaldCarnelliVasile2007, author = {Dachwald, Bernd and Carnelli, I. and Vasile, M.}, title = {Optimizing low-thrust gravity assist interplanetary trajectories using evolutionary neurocontrollers / I. Carnelli ; B. Dachwald ; M. Vasile}, series = {IEEE Congress on Evolutionary Computation, 2007 : CEC 2007 ; 25 - 28 September 2007, Singapore}, journal = {IEEE Congress on Evolutionary Computation, 2007 : CEC 2007 ; 25 - 28 September 2007, Singapore}, publisher = {IEEE Service Center}, address = {Piscataway, NJ}, isbn = {978-1-424-41339-3}, pages = {965 -- 972}, year = {2007}, language = {en} } @article{DachwaldCarnelliVasile2006, author = {Dachwald, Bernd and Carnelli, I. and Vasile, M.}, title = {Evolutionary Neurocontrol as a Novel Method for Low-Thrust Gravity Assist Trajectory Optimization / I. Carnelli ; B. Dachwald ; M. Vasile}, series = {Proceedings of the Twenty-Fifth International Symposium on Space Technology and Science (Selected papers) : Kanazawa, [June 4 through June 11, 2006, at Kanazawa-shi Kanko Kaikan in Kanazawa city] / [Japan Society for Aeronautical and Space Sciences. Kohtaro Matsumoto [ed.-in-chief]}, journal = {Proceedings of the Twenty-Fifth International Symposium on Space Technology and Science (Selected papers) : Kanazawa, [June 4 through June 11, 2006, at Kanazawa-shi Kanko Kaikan in Kanazawa city] / [Japan Society for Aeronautical and Space Sciences. Kohtaro Matsumoto [ed.-in-chief]}, publisher = {JSASS}, address = {Tokyo}, isbn = {4-99005-002-9}, pages = {569 -- 574}, year = {2006}, language = {en} } @article{DachwaldCarnelliVasile2009, author = {Dachwald, Bernd and Carnelli, Ian and Vasile, Massimiliano}, title = {Evolutionary Neurocontrol: A Novel Method for Low-Thrust Gravity-Assist Trajectory Optimization / Carnelli, Ian ; Dachwald, Bernd ; Vasile, Massimiliano}, series = {Journal of guidance control and dynamics. 32 (2009), H. 2}, journal = {Journal of guidance control and dynamics. 32 (2009), H. 2}, publisher = {AIAA}, address = {Reston, Va.}, isbn = {0731-5090}, pages = {616 -- 625}, year = {2009}, language = {en} } @inproceedings{DachwaldFeldmannEspeetal.2012, author = {Dachwald, Bernd and Feldmann, Marco and Espe, Clemens and Plescher, Engelbert and Konstantinidis, K. and Forstner, R.}, title = {Enceladus explorer - A maneuverable subsurface probe for autonomous navigation through deep ice}, series = {63rd International Astronautical Congress 2012, IAC 2012; Naples; Italy; 1 October 2012 through 5 October 2012. (Proceedings of the International Astronautical Congress, IAC ; 3)}, booktitle = {63rd International Astronautical Congress 2012, IAC 2012; Naples; Italy; 1 October 2012 through 5 October 2012. (Proceedings of the International Astronautical Congress, IAC ; 3)}, publisher = {Curran}, address = {Red Hook, NY}, organization = {International Astronautical Congress <63, 2012, Napoli>}, isbn = {978-1-62276-979-7}, pages = {1756 -- 1766}, year = {2012}, language = {en} } @article{DachwaldKahleWie2006, author = {Dachwald, Bernd and Kahle, Ralph and Wie, Bong}, title = {Solar Sailing Kinetic Energy Impactor (KEI) Mission Design Tradeoffs for Impacting and Deflecting Asteroid 99942 Apophis}, series = {AIAA Guidance, Navigation, and Control Conference \& Exhibit - AIAA Atmospheric Flight Mechanics Conference \& Exhibit - AIAA Modeling and Simulation Technologies Conference \& Exhibit - AIAA/AAS Astrodynamics Specialist Conference \& Exhibit : [21 - 24 August 2006, Keystone, Colorado ; papers]. - (AIAA meeting papers on disc ; [11.]2006,19-20 )}, journal = {AIAA Guidance, Navigation, and Control Conference \& Exhibit - AIAA Atmospheric Flight Mechanics Conference \& Exhibit - AIAA Modeling and Simulation Technologies Conference \& Exhibit - AIAA/AAS Astrodynamics Specialist Conference \& Exhibit : [21 - 24 August 2006, Keystone, Colorado ; papers]. - (AIAA meeting papers on disc ; [11.]2006,19-20 )}, publisher = {American Institute of Aeronautics and Astronautics}, address = {Reston, Va.}, isbn = {1-56347-802-1}, pages = {1 -- 20}, year = {2006}, language = {en} } @inproceedings{DachwaldKahleWie2006, author = {Dachwald, Bernd and Kahle, Ralph and Wie, Bong}, title = {Solar sail Kinetic Energy Impactor (KEI) mission design tradeoffs for impacting and deflecting asteroid 99942 Apophis}, series = {AIAA/AAS Astrodynamics Specialist Conference and Exhibit}, booktitle = {AIAA/AAS Astrodynamics Specialist Conference and Exhibit}, doi = {10.2514/6.2006-6178}, pages = {1 -- 20}, year = {2006}, abstract = {Near-Earth asteroid 99942 Apophis provides a typical example for the evolution of asteroid orbits that lead to Earth-impacts after a close Earth-encounter that results in a resonant return. Apophis will have a close Earth-encounter in 2029 with potential very close subsequent Earth-encounters (or even an impact) in 2036 or later, depending on whether it passes through one of several so-called gravitational keyholes during its 2029-encounter. Several pre-2029-deflection scenarios to prevent Apophis from doing this have been investigated so far. Because the keyholes are less than 1 km in size, a pre-2029 kinetic impact is clearly the best option because it requires only a small change in Apophis' orbit to nudge it out of a keyhole. A single solar sail Kinetic Energy Impactor (KEI) spacecraft that impacts Apophis from a retrograde trajectory with a very high relative velocity (75-80 km/s) during one of its perihelion passages at about 0.75 AU would be a feasible option to do this. The spacecraft consists of a 160 m x 160 m, 168 kg solar sail assembly and a 150 kg impactor. Although conventional spacecraft can also achieve the required minimum deflection of 1 km for this approx. 320 m-sized object from a prograde trajectory, our solar sail KEI concept also allows the deflection of larger objects. In this paper, we also show that, even after Apophis has flown through one of the gravitational keyholes in 2029, solar sail Kinetic Energy Impactor (KEI) spacecraft are still a feasible option to prevent Apophis from impacting the Earth, but many KEIs would be required for consecutive impacts to increase the total Earth-miss distance to a safe value. In this paper, we elaborate potential pre- and post-2029 KEI impact scenarios for a launch in 2020, and investigate tradeoffs between different mission parameters.}, language = {en} } @inproceedings{DachwaldKahleWie2007, author = {Dachwald, Bernd and Kahle, Ralph and Wie, Bong}, title = {Head-on impact deflection of NEAs: a case study for 99942 Apophis}, series = {Planetary Defense Conference 2007}, booktitle = {Planetary Defense Conference 2007}, pages = {1 -- 12}, year = {2007}, abstract = {Near-Earth asteroid (NEA) 99942 Apophis provides a typical example for the evolution of asteroid orbits that lead to Earth-impacts after a close Earth-encounter that results in a resonant return. Apophis will have a close Earth-encounter in 2029 with potential very close subsequent Earth-encounters (or even an impact) in 2036 or later, depending on whether it passes through one of several less than 1 km-sized gravitational keyholes during its 2029-encounter. A pre-2029 kinetic impact is a very favorable option to nudge the asteroid out of a keyhole. The highest impact velocity and thus deflection can be achieved from a trajectory that is retrograde to Apophis orbit. With a chemical or electric propulsion system, however, many gravity assists and thus a long time is required to achieve this. We show in this paper that the solar sail might be the better propulsion system for such a mission: a solar sail Kinetic Energy Impactor (KEI) spacecraft could impact Apophis from a retrograde trajectory with a very high relative velocity (75-80 km/s) during one of its perihelion passages. The spacecraft consists of a 160 m × 160 m, 168 kg solar sail assembly and a 150 kg impactor. Although conventional spacecraft can also achieve the required minimum deflection of 1 km for this approx. 320 m-sized object from a prograde trajectory, our solar sail KEI concept also allows the deflection of larger objects. For a launch in 2020, we also show that, even after Apophis has flown through one of the gravitational keyholes in 2029, the solar sail KEI concept is still feasible to prevent Apophis from impacting the Earth, but many KEIs would be required for consecutive impacts to increase the total Earth-miss distance to a safe value}, language = {en} } @article{DachwaldLeipoldFichtner2003, author = {Dachwald, Bernd and Leipold, M. and Fichtner, H.}, title = {Heliopause Explorer - A Sailcraft Mission to the Outer Boundaries of the Solar System / M. Leipold ; H. Fichtner ; B. Heber ... B. Dachwald ...}, series = {Proceedings of the Fifth IAA International Conference on Low Cost Planetary Missions : 24 - 26 September 2003, ESTEC, Noordwijk, the Netherlands / [comp. by R. A. Harris]}, journal = {Proceedings of the Fifth IAA International Conference on Low Cost Planetary Missions : 24 - 26 September 2003, ESTEC, Noordwijk, the Netherlands / [comp. by R. A. Harris]}, publisher = {ESA}, address = {Noordwijk}, isbn = {92-9092-853-0}, pages = {367 -- 375}, year = {2003}, language = {en} } @article{DachwaldMacDonaldMcInnes2007, author = {Dachwald, Bernd and MacDonald, Malcolm and McInnes, Colin R.}, title = {Heliocentric Solar Sail Orbit Transfers with Locally Optimal Control Laws / Malcolm Macdonald ; Colin McInnes ; Bernd Dachwald}, series = {Journal of Spacecraft and Rockets. 44 (2007), H. 1}, journal = {Journal of Spacecraft and Rockets. 44 (2007), H. 1}, isbn = {0022-4650}, pages = {273 -- 276}, year = {2007}, language = {en} } @article{DachwaldMcDonaldMcInnesetal.2007, author = {Dachwald, Bernd and McDonald, Malcolm and McInnes, Colin R. and Mengali, Giovanni}, title = {Impact of Optical Degradation on Solar Sail Mission Performance}, series = {Journal of Spacecraft and Rockets. 44 (2007), H. 4}, journal = {Journal of Spacecraft and Rockets. 44 (2007), H. 4}, isbn = {0022-4650}, pages = {740 -- 749}, year = {2007}, language = {en} } @article{DachwaldMengaliQuartaetal.2006, author = {Dachwald, Bernd and Mengali, Giovanni and Quarta, Alessandrao A. and Macdonald, Malcolm}, title = {Parametric Model and Optimal Control of Solar Sails with Optical Degradation}, series = {Journal of guidance, control, and dynamics. 29 (2006), H. 5}, journal = {Journal of guidance, control, and dynamics. 29 (2006), H. 5}, isbn = {0162-3192}, pages = {1170 -- 1178}, year = {2006}, language = {en} } @inproceedings{DachwaldMengaliQuartaetal.2007, author = {Dachwald, Bernd and Mengali, Giovanni and Quarta, Alessandro A and Macdonald, Malcolm and McInnes, Colin R}, title = {Optical solar sail degradation modelling}, series = {1st International Symposium on Solar Sailing}, booktitle = {1st International Symposium on Solar Sailing}, pages = {1 -- 27}, year = {2007}, abstract = {We propose a simple parametric OSSD model that describes the variation of the sail film's optical coefficients with time, depending on the sail film's environmental history, i.e., the radiation dose. The primary intention of our model is not to describe the exact behavior of specific film-coating combinations in the real space environment, but to provide a more general parametric framework for describing the general optical degradation behavior of solar sails.}, language = {en} } @article{DachwaldMengaliQuartaetal.2007, author = {Dachwald, Bernd and Mengali, Giovanni and Quarta, Alessandro A. and Circi, Christian}, title = {Refined Solar Sail Force Model with Mission Application / Giovanni Mengali ; Alessandro A. Quarta , Christian Circi ; Bernd Dachwald}, series = {Journal of Guidance, Control, and Dynamics. 30 (2007), H. 2}, journal = {Journal of Guidance, Control, and Dynamics. 30 (2007), H. 2}, isbn = {0162-3192}, pages = {512 -- 520}, year = {2007}, language = {en} } @article{DachwaldMikuckiTulaczyketal.2014, author = {Dachwald, Bernd and Mikucki, Jill and Tulaczyk, Slawek and Digel, Ilya and Espe, Clemens and Feldmann, Marco and Francke, Gero and Kowalski, Julia and Xu, Changsheng}, title = {IceMole : A maneuverable probe for clean in situ analysis and sampling of subsurface ice and subglacial aquatic ecosystems}, series = {Annals of Glaciology}, volume = {55}, journal = {Annals of Glaciology}, number = {65}, publisher = {Cambridge University Press}, address = {Cambridge}, issn = {1727-5644}, doi = {10.3189/2014AoG65A004}, pages = {14 -- 22}, year = {2014}, abstract = {There is significant interest in sampling subglacial environments for geobiological studies, but they are difficult to access. Existing ice-drilling technologies make it cumbersome to maintain microbiologically clean access for sample acquisition and environmental stewardship of potentially fragile subglacial aquatic ecosystems. The IceMole is a maneuverable subsurface ice probe for clean in situ analysis and sampling of glacial ice and subglacial materials. The design is based on the novel concept of combining melting and mechanical propulsion. It can change melting direction by differential heating of the melting head and optional side-wall heaters. The first two prototypes were successfully tested between 2010 and 2012 on glaciers in Switzerland and Iceland. They demonstrated downward, horizontal and upward melting, as well as curve driving and dirt layer penetration. A more advanced probe is currently under development as part of the Enceladus Explorer (EnEx) project. It offers systems for obstacle avoidance, target detection, and navigation in ice. For the EnEx-IceMole, we will pay particular attention to clean protocols for the sampling of subglacial materials for biogeochemical analysis. We plan to use this probe for clean access into a unique subglacial aquatic environment at Blood Falls, Antarctica, with return of a subglacial brine sample.}, language = {en} } @article{DachwaldOhndorf2007, author = {Dachwald, Bernd and Ohndorf, A.}, title = {1st ACT Global Trajectory Optimisation Competition : Results found at DLR}, series = {Acta Astronautica. 61 (2007), H. 9}, journal = {Acta Astronautica. 61 (2007), H. 9}, isbn = {0094-5765}, pages = {742 -- 752}, year = {2007}, language = {en} } @article{DachwaldOhndorfGill2009, author = {Dachwald, Bernd and Ohndorf, A. and Gill, E.}, title = {Optimization of low-thrust Earth-Moon transfers using evolutionary neurocontrol / Ohndorf, A. ; Dachwald, B. ; Gill, E.}, series = {IEEE Congress on Evolutionary Computation, 2009. CEC '09.}, journal = {IEEE Congress on Evolutionary Computation, 2009. CEC '09.}, isbn = {978-1-4244-2958-5}, pages = {358 -- 364}, year = {2009}, language = {en} } @article{DachwaldOhndorfWie2006, author = {Dachwald, Bernd and Ohndorf, A. and Wie, Bong}, title = {Solar Sail Trajectory Optimization for the Solar Polar Imager (SPI) Mission}, series = {AIAA Guidance, Navigation, and Control Conference \& Exhibit - AIAA Atmospheric Flight Mechanics Conference \& Exhibit - AIAA Modeling and Simulation Technologies Conference \& Exhibit - AIAA/AAS Astrodynamics Specialist Conference \& Exhibit : [21 - 24 August 2006, Keystone, Colorado ; papers]. - (AIAA meeting papers on disc ; [11.]2006,19-20 )}, journal = {AIAA Guidance, Navigation, and Control Conference \& Exhibit - AIAA Atmospheric Flight Mechanics Conference \& Exhibit - AIAA Modeling and Simulation Technologies Conference \& Exhibit - AIAA/AAS Astrodynamics Specialist Conference \& Exhibit : [21 - 24 August 2006, Keystone, Colorado ; papers]. - (AIAA meeting papers on disc ; [11.]2006,19-20 )}, publisher = {American Institute of Aeronautics and Astronautics}, address = {Reston, Va.}, isbn = {1-56347-802-1}, pages = {2 CD-ROMs.}, year = {2006}, language = {en} } @incollection{DachwaldOhndorf2019, author = {Dachwald, Bernd and Ohndorf, Andreas}, title = {Global optimization of continuous-thrust trajectories using evolutionary neurocontrol}, series = {Modeling and Optimization in Space Engineering}, booktitle = {Modeling and Optimization in Space Engineering}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-10501-3}, doi = {10.1007/978-3-030-10501-3_2}, pages = {33 -- 57}, year = {2019}, abstract = {Searching optimal continuous-thrust trajectories is usually a difficult and time-consuming task. The solution quality of traditional optimal-control methods depends strongly on an adequate initial guess because the solution is typically close to the initial guess, which may be far from the (unknown) global optimum. Evolutionary neurocontrol attacks continuous-thrust optimization problems from the perspective of artificial intelligence and machine learning, combining artificial neural networks and evolutionary algorithms. This chapter describes the method and shows some example results for single- and multi-phase continuous-thrust trajectory optimization problems to assess its performance. Evolutionary neurocontrol can explore the trajectory search space more exhaustively than a human expert can do with traditional optimal-control methods. Especially for difficult problems, it usually finds solutions that are closer to the global optimum. Another fundamental advantage is that continuous-thrust trajectories can be optimized without an initial guess and without expert supervision.}, language = {en} } @article{DachwaldSchmidtSeboldtetal.2003, author = {Dachwald, Bernd and Schmidt, Tanja D. and Seboldt, Wolfgang and Auweter-Kurtz,}, title = {Flight Opportunities from Mars to Earth for Piloted Missions Using Continuous Thrust Propulsion / Schmidt, Tanja D. ; Dachwald, Bernd ; Seboldt, Wolfgang ; Auweter-Kurtz, Monika}, publisher = {-}, pages = {1 -- 9}, year = {2003}, language = {en} }