TY - JOUR A1 - Bühler, Yves A1 - Christen, Marc A1 - Kowalski, Julia A1 - Bartelt, Perry T1 - Sensitivity of snow avalanche simulations to digital elevation model quality and resolution JF - Annals of Glaciology N2 - 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. KW - snow KW - avalanche Y1 - 2011 SN - 1727-5644 VL - 52 IS - 58 SP - 72 EP - 80 PB - Cambridge University Press CY - Cambridge ER - TY - JOUR A1 - Campen, R. A1 - Kowalski, Julia A1 - Lyons, W.B. A1 - Tulaczyk, S. A1 - Dachwald, Bernd A1 - Pettit, E. A1 - Welch, K. A. A1 - Mikucki, J.A. T1 - Microbial diversity of an Antarctic subglacial community and high‐resolution replicate sampling inform hydrological connectivity in a polar desert JF - Environmental Microbiology Y1 - 2019 U6 - http://dx.doi.org/10.1111/1462-2920.14607 SN - 1462-2920 IS - accepted article PB - Wiley CY - Weinheim ER - TY - CHAP A1 - Carzana, Livio A1 - Dachwald, Bernd A1 - Noomen, Ron T1 - Model and trajectory optimization for an ideal laser-enhanced solar sail T2 - 68th International Astronautical Congress N2 - 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 Y1 - 2017 N1 - 68th International Astronautical Congress: Unlocking Imagination, Fostering Innovation and Strengthening Security, IAC 2017, 2017-09-25 → 2017-09-29, Adelaide, Australia ER - TY - JOUR A1 - Christen, Marc A1 - Bartelt, Perry A1 - Kowalski, Julia T1 - Back calculation of the In den Arelen avalanche with RAMMS: Interpretation of model results JF - Annals of Glaciology N2 - 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. KW - avalanche Y1 - 2010 SN - 1727-5644 U6 - http://dx.doi.org/10.3189/172756410791386553 VL - 51 IS - 54 SP - 161 EP - 168 PB - Cambridge University Press CY - Cambridge ER - TY - CHAP A1 - Christen, Marc A1 - Bartelt, Perry A1 - Kowalski, Julia A1 - Stoffel, Lukus T1 - Calculation of dense snow avalanches in three-dimensional terrain with the numerical simulation programm RAMMS T2 - Proceedings ISSW 2008 ; International Snow Science Workshop. Whistler 2008 N2 - 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. KW - snow KW - avalanche Y1 - 2008 SP - 709 EP - 716 ER - TY - JOUR A1 - Christen, Marc A1 - Kowalski, Julia A1 - Bartelt, Perry T1 - RAMMS: Numerical simulation of dense snow avalanches in three-dimensional terrain JF - Cold Regions Science and Technology N2 - 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 Vallée de la Sionne test site. KW - RAMMS KW - snow KW - avalanche Y1 - 2010 U6 - http://dx.doi.org/10.1016/j.coldregions.2010.04.005 SN - 1872-7441 VL - 63 IS - 1-2 SP - 1 EP - 14 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Czupalla, Markus A1 - Horneck, G. A1 - Blome, Hans-Joachim T1 - The conceptual design of a hybrid life support system based on the evaluation and comparison of terrestrial testbeds JF - Advances in Space Research Y1 - 2005 SN - 0273-1177 VL - 35 IS - 9 SP - 1609 EP - 1620 ER - TY - JOUR A1 - Dachwald, Bernd T1 - Optimization of very-low-thrust trajectories using evolutionary neurocontrol JF - Acta Astronautica. 57 (2005), H. 2-8 Y1 - 2005 SN - 0094-5765 SP - 175 EP - 185 ER - TY - JOUR A1 - Dachwald, Bernd T1 - Minimum Transfer Times for Nonperfectly Reflecting Solar Sailcraft JF - Journal of Spacecraft and Rockets. 41 (2004), H. 4 Y1 - 2004 SN - 0022-4650 N1 - 2. ISSN: 1533-6794 SP - 693 EP - 695 ER - TY - JOUR A1 - Dachwald, Bernd T1 - Optimal Solar Sail Trajectories for Missions to the Outer Solar System JF - Journal of guidance, control, and dynamics. 28 (2005), H. 6 Y1 - 2005 SN - 0162-3192 N1 - 2. ISSN: 0162-3192. - 3. ISSN: 0731-5090 SP - 1187 EP - 1193 ER - TY - JOUR A1 - Dachwald, Bernd T1 - Optimization of Interplanetary Solar Sailcraft Trajectories Using Evolutionary Neurocontrol JF - Journal of guidance, control, and dynamics. 27 (2004), H. 1 Y1 - 2004 SN - 0162-3192 N1 - 2. ISSN: 0162-3192. - 3. ISSN: 0731-5090 SP - 66 EP - 72 ER - TY - JOUR A1 - Dachwald, Bernd T1 - Interplanetary Mission Analysis for Non-Perfectly Reflecting Solar Sailcraft Using Evolutionary Neurocontrol JF - 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) Y1 - 2004 SN - 0-87703-509-1 N1 - Astrodynamics Conference <2003, Big Sky, Mont.> ; American Institute of Aeronautics and Astronautics ; AAS-03-579 SP - 1247 EP - 1262 PB - Univelt CY - San Diego, Calif. ER - TY - JOUR A1 - Dachwald, Bernd T1 - Low-Thrust Trajectory Optimization and Interplanetary Mission Analysis Using Evolutionary Neurocontrol JF - Deutscher Luft- und Raumfahrtkongress 2004 : Dresden, 20. bis 23. September 2004, Motto: Luft- und Raumfahrt - Brücke für eine wissensbasierte Gesellschaft / Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V. (DGLR). [Red.: Peter Brandt (verantwortlich)]. - Bd. 2. - (Jahrbuch ... der Deutschen Gesellschaft für Luft- und Raumfahrt) Y1 - 2004 N1 - Deutscher Luft- und Raumfahrt-Kongress <2004, Dresden> ; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth ; DGLR-2004-116 SP - 917 EP - 926 CY - Bonn ER - TY - JOUR A1 - Dachwald, Bernd T1 - Evolutionary Neurocontrol: A Smart Method for Global Optimization of Low-Thrust Trajectories JF - 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) Y1 - 2004 N1 - American Institute of Aeronautics and Astronautics ; AIAA/AAS Astrodynamics Specialist Conference and Exhibit <2004, Providence, RI> ; AIAA paper number: AIAA-2004-5405 PB - American Inst. of Aeronautics and Astronautics CY - Reston, Va. ER - TY - JOUR A1 - Dachwald, Bernd T1 - Optimal Solar Sail Trajectories for Missions to the Outer Solar System JF - 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) Y1 - 2004 N1 - American Institute of Aeronautics and Astronautics ; AIAA/AAS Astrodynamics Specialist Conference and Exhibit <2004, Providence, RI> ; AIAA paper number: AIAA-2004-5406 PB - American Inst. of Aeronautics and Astronautics CY - Reston, Va. ER - TY - CHAP A1 - Dachwald, Bernd T1 - Low-Thrust Mission Analysis and Global Trajectory Optimization Using Evolutionary Neurocontrol: New Results T2 - European Workshop on Space Mission Analysis ESA/ESOC, Darmstadt, Germany 10 { 12 Dec 2007 N2 - 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 Y1 - 2007 ER - TY - CHAP A1 - Dachwald, Bernd T1 - Global optimization of low-thrust space missions using evolutionary neurocontrol T2 - Proceedings of the international workshop on global optimization N2 - 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. KW - Evolutionary Neurocontrol KW - Spacecraft Trajectory Optimization KW - Low-Thrust Propulsion Y1 - 2005 SP - 85 EP - 90 ER - TY - CHAP A1 - Dachwald, Bernd ED - Knopf, George K. ED - Otani, Yukitoshi T1 - Light propulsion systems for spacecraft T2 - Optical nano and micro actuator technology Y1 - 2017 SN - 9781315217628 (eBook) SP - 577 EP - 598 PB - CRC Press CY - Boca Raton ER - TY - CHAP A1 - Dachwald, Bernd T1 - Solar sail dynamics and control T2 - Encyclopedia of Aerospace Engineering N2 - 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. KW - solar sail KW - sailcraft KW - orbital dynamics KW - orbit control KW - attitude dynamics Y1 - 2010 U6 - http://dx.doi.org/10.1002/9780470686652.eae292 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Dachwald, Bernd T1 - Optimization of very-low-thrust trajectories using evolutionary neurocontrol JF - Acta Astronautica N2 - 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). Y1 - 2005 SN - 1879-2030 VL - 57 IS - 2-8 SP - 175 EP - 185 PB - Elsevier CY - Amsterdam [u.a.] ER - TY - CHAP A1 - Dachwald, Bernd T1 - Radiation pressure force model for an ideal laser-enhanced solar sail T2 - 4th International Symposium on Solar Sailing N2 - 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. Y1 - 2017 N1 - 4th International Symposium on Solar Sailing 17-20 January 2017, Kyōto, Japan SP - 1 EP - 5 ER - TY - CHAP A1 - Dachwald, Bernd T1 - Solar sail performance requirements for missions to the outer solar system and beyond T2 - 55th International Astronautical Congress 2004 N2 - 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. Y1 - 2004 U6 - http://dx.doi.org/10.2514/6.IAC-04-S.P.11 N1 - 55th International Astronautical Congress 2004 - Vancouver, Canada SP - 1 EP - 9 ER - TY - JOUR A1 - Dachwald, Bernd A1 - Ball, Andrew J. A1 - Ulamec, Stephan A1 - Price, Michael E. T1 - 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.] JF - Advances in Space Research. 43 (2009), H. 2 Y1 - 2009 SN - 0273-1177 SP - 317 EP - 324 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Dachwald, Bernd A1 - Baturkin, Volodymyr A1 - Coverstone, Victoria A1 - Diedrich, Ben A1 - Garbe, Gregory A1 - Görlich, Marianne A1 - Leipold, Manfred A1 - Lura, Franz A1 - Macdonald, Malcolm A1 - McInnes, Colin A1 - Mengali, Giovanni A1 - Quarta, Alessandro A1 - Rios-Reyes, Leonel A1 - Scheeres, Daniel J. A1 - Seboldt, Wolfgang A1 - Wie, Bong T1 - Potential effects of optical solar sail degredation on trajectory design T2 - AAS/AIAA Astrodynamics Specialist N2 - 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. Y1 - 2005 N1 - 2005 AAS/AIAA Astrodynamics Specialist Conference, 7-11.08.2005. Lake Tahoe, California https://www.space-flight.org/AAS_meetings/2005_astro/2005_astro.html SP - 1 EP - 23 ER - TY - JOUR A1 - Dachwald, Bernd A1 - Baturkin, Volodymyr A1 - Coverstone, Victoria L. A1 - Dietrich, Benjamin A1 - Garbe, Gregory P. A1 - Görlich, Marianne A1 - Leipold, Manfred A1 - Lura, Franz A1 - Macdonald, Malcolm A1 - McInnes, Colin R. A1 - Mengali, Giovanni A1 - Quatra, Alessandro A. A1 - Rios-Reyes, Leonel A1 - Scheeres, Daniel J. A1 - Seboldt, Wolfgang A1 - Wie, Bong T1 - Potential Effects of Optical Solar Sail Degradation on Interplanetary Trajectory Design JF - 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) Y1 - 2006 UR - http://www.spacesailing.net/paper/200508_LakeTahoe_Dachwald+.pdf SN - 0-87703-527-X N1 - Astrodynamics Conference <2005, South Lake Tahoe, Calif.> ; American Astronautical Society ; Number: AAS-05-413 SP - 2569 EP - 2592 PB - Univelt CY - San Diego, Calif. ER - TY - CHAP A1 - Dachwald, Bernd A1 - Boehnhardt, Herrmann A1 - Broj, Ulrich A1 - Geppert, Ulrich R. M. E. A1 - Grundmann, Jan-Thimo A1 - Seboldt, Wolfgang A1 - Seefeldt, Patric A1 - Spietz, Peter A1 - Johnson, Les A1 - Kührt, Ekkehard A1 - Mottola, Stefano A1 - Macdonald, Malcolm A1 - McInnes, Colin R. A1 - Vasile, Massimiliano A1 - Reinhard, Ruedeger T1 - Gossamer roadmap technology reference study for a multiple NEO Rendezvous Mission T2 - Advances in solar sailing N2 - 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. Y1 - 2014 SN - 978-3-642-34906-5 (Print) ; 978-3-642-34907-2 (E-Book) SP - 211 EP - 226 PB - Springer CY - Berlin [u.a.] ER - TY - JOUR A1 - Dachwald, Bernd A1 - Carnelli, I. A1 - Vasile, M. T1 - Low-Thrust Gravity Assist Trajectory Optimization Using Evolutionary Neurocontrollers / I. Carnelli ; B. Dachwald ; M. Vasile ... JF - 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) Y1 - 2006 SN - 0-87703-527-X N1 - Astrodynamics Conference <2005, South Lake Tahoe, Calif.> ; American Astronautical Society ; Number: AAS-05-374 SP - 1911 EP - 1928 PB - Univelt CY - San Diego, Calif. ER - TY - JOUR A1 - Dachwald, Bernd A1 - Carnelli, I. A1 - Vasile, M. T1 - Optimizing low-thrust gravity assist interplanetary trajectories using evolutionary neurocontrollers / I. Carnelli ; B. Dachwald ; M. Vasile JF - IEEE Congress on Evolutionary Computation, 2007 : CEC 2007 ; 25 - 28 September 2007, Singapore Y1 - 2007 SN - 978-1-424-41339-3 N1 - ISBN 10: 1-424-41339-7 ; IEEE Congress on Evolutionary Computation <2007, Singapore> ; Institute of Electrical and Electronics Engineers ; Nebent: CEC 2007 ; Parallel als Online-Ausg. erschienen SP - 965 EP - 972 PB - IEEE Service Center CY - Piscataway, NJ ER - TY - JOUR A1 - Dachwald, Bernd A1 - Carnelli, I. A1 - Vasile, M. T1 - Evolutionary Neurocontrol as a Novel Method for Low-Thrust Gravity Assist Trajectory Optimization / I. Carnelli ; B. Dachwald ; M. Vasile JF - 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] Y1 - 2006 SN - 4-99005-002-9 N1 - International Symposium on Space Technology and Science <25, 2006, Kanazawa> ; ISTS 2006-d-46 SP - 569 EP - 574 PB - JSASS CY - Tokyo ER - TY - JOUR A1 - Dachwald, Bernd A1 - Carnelli, Ian A1 - Vasile, Massimiliano T1 - Evolutionary Neurocontrol: A Novel Method for Low-Thrust Gravity-Assist Trajectory Optimization / Carnelli, Ian ; Dachwald, Bernd ; Vasile, Massimiliano JF - Journal of guidance control and dynamics. 32 (2009), H. 2 Y1 - 2009 SN - 0731-5090 SP - 616 EP - 625 PB - AIAA CY - Reston, Va. ER - TY - CHAP A1 - Dachwald, Bernd A1 - Feldmann, Marco A1 - Espe, Clemens A1 - Plescher, Engelbert A1 - Konstantinidis, K. A1 - Forstner, R. T1 - Enceladus explorer - A maneuverable subsurface probe for autonomous navigation through deep ice T2 - 63rd International Astronautical Congress 2012, IAC 2012; Naples; Italy; 1 October 2012 through 5 October 2012. (Proceedings of the International Astronautical Congress, IAC ; 3) Y1 - 2012 SN - 978-1-62276-979-7 SP - 1756 EP - 1766 PB - Curran CY - Red Hook, NY ER - TY - JOUR A1 - Dachwald, Bernd A1 - Kahle, Ralph A1 - Wie, Bong T1 - Solar Sailing Kinetic Energy Impactor (KEI) Mission Design Tradeoffs for Impacting and Deflecting Asteroid 99942 Apophis JF - 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 ) Y1 - 2006 SN - 1-56347-802-1 N1 - American Institute of Aeronautics and Astronautics ; American Astronautical Society ; AIAA/AAS Astrodynamics Specialist Conference & Exhibit <2006, Keystone, Colo.> ; AIAA paper number: AIAA-2006-6178 SP - 1 EP - 20 PB - American Institute of Aeronautics and Astronautics CY - Reston, Va. ER - TY - CHAP A1 - Dachwald, Bernd A1 - Kahle, Ralph A1 - Wie, Bong T1 - Solar sail Kinetic Energy Impactor (KEI) mission design tradeoffs for impacting and deflecting asteroid 99942 Apophis T2 - AIAA/AAS Astrodynamics Specialist Conference and Exhibit N2 - 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. KW - Solar Sail KW - Asteroid Deflection KW - Planetary Protection KW - Trajectory Optimization Y1 - 2006 U6 - http://dx.doi.org/10.2514/6.2006-6178 N1 - AIAA/AAS Astrodynamics Specialist Conference and Exhibit, 21 August 2006 - 24 August 2006, Keystone, Colorado(USA). SP - 1 EP - 20 ER - TY - CHAP A1 - Dachwald, Bernd A1 - Kahle, Ralph A1 - Wie, Bong T1 - Head-on impact deflection of NEAs: a case study for 99942 Apophis T2 - Planetary Defense Conference 2007 N2 - 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 Y1 - 2007 N1 - Planetary Defense Conference 2007, Wahington D.C., USA, 05-08 March 2007 SP - 1 EP - 12 ER - TY - JOUR A1 - Dachwald, Bernd A1 - Leipold, M. A1 - Fichtner, H. T1 - Heliopause Explorer - A Sailcraft Mission to the Outer Boundaries of the Solar System / M. Leipold ; H. Fichtner ; B. Heber ... B. Dachwald ... JF - 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] Y1 - 2003 SN - 92-9092-853-0 N1 - International Conference on Low Cost Planetary Missions <5, 2003, Noordwijk> ; International Academy of Astronautics ; European Space Research and Technology Centre SP - 367 EP - 375 PB - ESA CY - Noordwijk ER - TY - JOUR A1 - Dachwald, Bernd A1 - MacDonald, Malcolm A1 - McInnes, Colin R. T1 - Heliocentric Solar Sail Orbit Transfers with Locally Optimal Control Laws / Malcolm Macdonald ; Colin McInnes ; Bernd Dachwald JF - Journal of Spacecraft and Rockets. 44 (2007), H. 1 Y1 - 2007 SN - 0022-4650 SP - 273 EP - 276 ER - TY - JOUR A1 - Dachwald, Bernd A1 - McDonald, Malcolm A1 - McInnes, Colin R. A1 - Mengali, Giovanni T1 - Impact of Optical Degradation on Solar Sail Mission Performance JF - Journal of Spacecraft and Rockets. 44 (2007), H. 4 Y1 - 2007 SN - 0022-4650 N1 - 2. ISSN: 1533-6794 SP - 740 EP - 749 ER - TY - JOUR A1 - Dachwald, Bernd A1 - Mengali, Giovanni A1 - Quarta, Alessandrao A. A1 - Macdonald, Malcolm T1 - Parametric Model and Optimal Control of Solar Sails with Optical Degradation JF - Journal of guidance, control, and dynamics. 29 (2006), H. 5 Y1 - 2006 SN - 0162-3192 N1 - 2. ISSN: 0731-5090 SP - 1170 EP - 1178 ER - TY - CHAP A1 - Dachwald, Bernd A1 - Mengali, Giovanni A1 - Quarta, Alessandro A A1 - Macdonald, Malcolm A1 - McInnes, Colin R T1 - Optical solar sail degradation modelling T2 - 1st International Symposium on Solar Sailing N2 - 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. Y1 - 2007 N1 - 1st International Symposium on Solar Sailing 27–29 June 2007, Herrsching, Germany SP - 1 EP - 27 ER - TY - JOUR A1 - Dachwald, Bernd A1 - Mengali, Giovanni A1 - Quarta, Alessandro A. A1 - Circi, Christian T1 - Refined Solar Sail Force Model with Mission Application / Giovanni Mengali ; Alessandro A. Quarta , Christian Circi ; Bernd Dachwald JF - Journal of Guidance, Control, and Dynamics. 30 (2007), H. 2 Y1 - 2007 SN - 0162-3192 N1 - 2. ISBN: 0731-5090 SP - 512 EP - 520 ER - TY - CHAP A1 - Dachwald, Bernd A1 - Mikucki, Jill A. A1 - Tulaczyk, Slawek A1 - Digel, Ilya A1 - Feldmann, Marco A1 - Espe, Clemens A1 - Plescher, Engelbert A1 - Xu, Changsheng T1 - IceMole - a maneuverable probe for clean in-situ analysis and sampling of subsurface ice and subglacial aquatic ecosystems : extended abstract / SCAR Open Science Conference 2012, Session 29: Advancing Clean Technologies for Exploration of Glacial Aquatic Ecosystems N2 - The ”IceMole“ is a novel maneuverable subsurface ice probe for clean in-situ analysis and sampling of subsurface ice and subglacial water/brine. It is developed and build at FH Aachen University of Applied Sciences’ Astronautical Laboratory. A first prototype was successfully tested on the Swiss Morteratsch glacier in 2010. Clean sampling is achieved with a hollow ice screw (as it is used in mountaineering) at the tip of the probe. Maneuverability is achieved with a differentially heated melting head. Funded by the German Space Agency (DLR), a consortium led by FH Aachen currently develops a much more advanced IceMole probe, which includes a sophisticated system for obstacle avoidance, target detection, and navigation in the ice. We intend to use this probe for taking clean samples of subglacial brine at the Blood Falls (McMurdo Dry Valleys, East Antarctica) for chemical and microbiological analysis. In our conference contribution, we 1) describe the IceMole design, 2) report the results of the field tests of the first prototype on the Morteratsch glacier, 3) discuss the probe’s potential for the clean in-situ analysis and sampling of subsurface ice and subglacial liquids, and 4) outline the way ahead in the development of this technology. KW - Eisschicht KW - Sonde KW - subsurface ice KW - subglacial aquatic ecosystems Y1 - 2012 ER - TY - JOUR A1 - Dachwald, Bernd A1 - Mikucki, Jill A1 - Tulaczyk, Slawek A1 - Digel, Ilya A1 - Espe, Clemens A1 - Feldmann, Marco A1 - Francke, Gero A1 - Kowalski, Julia A1 - Xu, Changsheng T1 - IceMole : A maneuverable probe for clean in situ analysis and sampling of subsurface ice and subglacial aquatic ecosystems JF - Annals of Glaciology N2 - 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. KW - Antarctic Glaciology KW - Extraterrestrial Glaciology KW - Glaciological instruments and methods KW - Subclacial exploration KW - Subglacial lakes Y1 - 2014 U6 - http://dx.doi.org/10.3189/2014AoG65A004 SN - 1727-5644 VL - 55 IS - 65 SP - 14 EP - 22 PB - Cambridge University Press CY - Cambridge ER - TY - JOUR A1 - Dachwald, Bernd A1 - Ohndorf, A. T1 - 1st ACT Global Trajectory Optimisation Competition : Results found at DLR JF - Acta Astronautica. 61 (2007), H. 9 Y1 - 2007 SN - 0094-5765 N1 - Global Trajectory Optimization ; Results of the First Competition Organised by the Advanced Concept Team (ACT) of the European Space Agency (ESA) SP - 742 EP - 752 ER - TY - JOUR A1 - Dachwald, Bernd A1 - Ohndorf, A. A1 - Gill, E. T1 - Optimization of low-thrust Earth-Moon transfers using evolutionary neurocontrol / Ohndorf, A. ; Dachwald, B. ; Gill, E. JF - IEEE Congress on Evolutionary Computation, 2009. CEC '09. Y1 - 2009 SN - 978-1-4244-2958-5 SP - 358 EP - 364 ER - TY - JOUR A1 - Dachwald, Bernd A1 - Ohndorf, A. A1 - Wie, Bong T1 - Solar Sail Trajectory Optimization for the Solar Polar Imager (SPI) Mission JF - 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 ) Y1 - 2006 SN - 1-56347-802-1 N1 - American Institute of Aeronautics and Astronautics ; American Astronautical Society ; AIAA/AAS Astrodynamics Specialist Conference & Exhibit <2006, Keystone, Colo.> ; AIAA paper number: AIAA-2006-6177 PB - American Institute of Aeronautics and Astronautics CY - Reston, Va. ER - TY - CHAP A1 - Dachwald, Bernd A1 - Ohndorf, Andreas T1 - Global optimization of continuous-thrust trajectories using evolutionary neurocontrol T2 - Modeling and Optimization in Space Engineering N2 - 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. Y1 - 2019 SN - 978-3-030-10501-3 SN - 978-3-030-10500-6 U6 - http://dx.doi.org/10.1007/978-3-030-10501-3_2 N1 - Springer Optimization and Its Applications, vol 144 gedruckt unter der Signatur 21 ZSS 46 in der Bereichsbibliothek Eupener Str. vorhanden SP - 33 EP - 57 PB - Springer CY - Cham ER - TY - JOUR A1 - Dachwald, Bernd A1 - Schmidt, Tanja D. A1 - Seboldt, Wolfgang A1 - Auweter-Kurtz, T1 - Flight Opportunities from Mars to Earth for Piloted Missions Using Continuous Thrust Propulsion / Schmidt, Tanja D. ; Dachwald, Bernd ; Seboldt, Wolfgang ; Auweter-Kurtz, Monika Y1 - 2003 N1 - 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 20-23 July 2003, Huntsville, Alabama ; AIAA 2003-4573 SP - 1 EP - 9 PB - - ER - TY - JOUR A1 - Dachwald, Bernd A1 - Seboldt, W. T1 - Multiple Near-Earth Asteroid Rendezvous and Sample Return Using First Generation Solar Sailcraft JF - Acta Astronautica. 57 (2005), H. 11 Y1 - 2005 SN - 0094-5765 SP - 864 EP - 875 ER - TY - JOUR A1 - Dachwald, Bernd A1 - Seboldt, W. T1 - Optimization of Interplanetary Rendezvous Trajectories for Solar Sailcraft Using a Neurocontroller JF - A collection of technical papers / AIAA Astrodynamics Specialist Conference : Monterey, California, 5 - 8 August 2002. - Vol. 2 Y1 - 2002 SN - 1-56347-549-9 N1 - Astrodynamics Specialist Conference <2002, Monterey, Calif.> American Institute of Aeronautics and Astronautics ; AIAA paper number: AIAA-2002-4989 SP - 1263 EP - 1270 PB - American Institute of Aeronautics and Astronautics CY - Reston, Va. ER - TY - JOUR A1 - Dachwald, Bernd A1 - Seboldt, W. T1 - Solar Sails for Near- and Medium-Term Scientific Deep Space Missions / W. Sebolt ; B. Dachwald JF - In-space propulsion : edited book of proceedings of the 10-IWCP, the 10th International Workshop on Combustion and Propulsion held in Lerici, La Spezia, Italy, 21-25 September 2003 / [ed.: Luigi T. DeLuca] Y1 - 2005 N1 - Paper 31 ; International workshop on combustion and propulsion <10, 2003, Lerici> PB - SP Lab, Politecnico di Milano CY - Milano ER -