@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{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{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{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{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{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 = {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{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{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 = {AIAA}, address = {Reston, Va.}, 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 = {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} } @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{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} } @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} } @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} } @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} } @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} } @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} } @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} }