TY - JOUR A1 - Weber, Tobias A1 - Arent, Jan-Christoph A1 - Steffen, Lucas A1 - Balvers, Johannes M. A1 - Duhovic, Miro T1 - Thermal optimization of composite autoclave molds using the shift factor approach for boundary condition estimation JF - Journal of Composite Materials Y1 - 2017 U6 - https://doi.org/10.1177/0021998317699868 SN - 1530-793X VL - 51 IS - 12 SP - 1753 EP - 1767 PB - Sage CY - London ER - TY - CHAP A1 - Otten, D. A1 - Schmidt, M. A1 - Weber, Tobias T1 - Advances in Determination of Material Parameters for Functional Simulations Based on Process Simulations T2 - SAMPE Europe Conference 16 Liege Y1 - 2016 SN - 978-1-5108-3800-0 SP - 570 EP - 577 ER - TY - CHAP A1 - Weber, Tobias A1 - Tellis, Jane J. A1 - Duhovic, Miro T1 - Characterization of tool-part-interaction an interlaminar friction for manufacturing process simulation T2 - ECCM 17, 17th European Conference on Composite Materials, München, DE, Jun 26-30, 2016 Y1 - 2016 SN - 978-3-00-053387-7 SP - 1 EP - 7 ER - TY - JOUR A1 - Weber, Tobias A1 - Arent, Jan-Christoph A1 - Münch, Lukas A1 - Duhovic, Miro A1 - Balvers, Johannes M. T1 - A fast method for the generation of boundary conditions for thermal autoclave simulation JF - Composites Part A N2 - Manufacturing process simulation enables the evaluation and improvement of autoclave mold concepts early in the design phase. To achieve a high part quality at low cycle times, the thermal behavior of the autoclave mold can be investigated by means of simulations. Most challenging for such a simulation is the generation of necessary boundary conditions. Heat-up and temperature distribution in an autoclave mold are governed by flow phenomena, tooling material and shape, position within the autoclave, and the chosen autoclave cycle. This paper identifies and summarizes the most important factors influencing mold heat-up and how they can be introduced into a thermal simulation. Thermal measurements are used to quantify the impact of the various parameters. Finally, the gained knowledge is applied to develop a semi-empirical approach for boundary condition estimation that enables a simple and fast thermal simulation of the autoclave curing process with reasonably high accuracy for tooling optimization. Y1 - 2016 U6 - https://doi.org/10.1016/j.compositesa.2016.05.036 SN - 1359-835X VL - 88 SP - 216 EP - 225 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Hailer, Benjamin A1 - Weber, Tobias A1 - Arent, Jan-Christoph T1 - Manufacturing Process Simulation for Autoclave-Produced Sandwich Structures T2 - Proceedings of SAMPE Europe Conference 2019, Nantes, France Y1 - 2019 SP - 1 EP - 8 ER - TY - CHAP A1 - Weber, Tobias A1 - Englhard, Markus A1 - Hailer, Benjamin A1 - Arent, Jan-Christoph T1 - Manufacturing Process Simulation for the Prediction of Tool-Part-Interaction and Ply Wrinkling T2 - Proceedings of SAMPE Europe Conference 2019, Nantes, France Y1 - 2019 SP - 1 EP - 10 ER - TY - CHAP A1 - Weber, Tobias A1 - Englhard, Markus A1 - Hailer, Benjamin A1 - Arent, Jan-Christoph T1 - Manufacturing Process Simulation for the Prediction of Tool-Part-Interaction and Ply Wrinkling T2 - Proceedings of SAMPE Europe Conference, Amiens , France Y1 - 2015 SP - 1 EP - 10 ER - TY - CHAP A1 - Weber, Tobias T1 - Manufacturing Process Simulation for Tooling Optimization: Reduction of Quality Issues During Autoclave Manufacturing of Composite Parts T2 - Proceedings of SAMPE Europe Conference 2015, Amiens, France Y1 - 2015 SP - 1 EP - 8 ER - TY - CHAP A1 - Otten, D. A1 - Schmid, M. A1 - Weber, Tobias T1 - Advances In Sheet Metal-Forming: Reduction Of Tooling Cost By Methodical Optimization T2 - Proceedings of SAMPE Europe Conference, Amiens , France Y1 - 2015 ER - TY - JOUR A1 - Hoeveler, B. A1 - Bauknecht, André A1 - Wolf, C. Christian A1 - Janser, Frank T1 - Wind-Tunnel Study of a Wing-Embedded Lifting Fan Remaining Open in Cruise Flight JF - Journal of Aircraft N2 - It is investigated whether a nonrotating lifting fan remaining uncovered during cruise flight, as opposed to being covered by a shutter system, can be realized with limited additional drag and loss of lift during cruise flight. A wind-tunnel study of a wing-embedded lifting fan has been conducted at the Side Wind Test Facility Göttingen of DLR, German Aerospace Center in Göttingen using force, pressure, and stereoscopic particle image velocimetry techniques. The study showed that a step on the lower side of the wing in front of the lifting fan duct increases the lift-to-drag ratio of the whole model by up to 25% for all positive angles of attack. Different sizes and inclinations of the step had limited influence on the surface pressure distribution. The data indicate that these parameters can be optimized to maximize the lift-to-drag ratio. A doubling of the curvature radius of the lifting fan duct inlet lip on the upper side of the wing affected the lift-to-drag ratio by less than 1%. The lifting fan duct inlet curvature can therefore be optimized to maximize the vertical fan thrust of the rotating lifting fan during hovering without affecting the cruise flight performance with a nonrotating fan. Y1 - 2020 U6 - https://doi.org/10.2514/1.C035422 SN - 1533-3868 VL - 57 IS - 4 PB - AIAA CY - Reston, Va. ER - TY - JOUR A1 - Götten, Falk A1 - Havermann, Marc A1 - Braun, Carsten A1 - Marino, Matthew A1 - Bil, Cees T1 - Airfoil drag at low-to-medium reynolds numbers: A novel estimation method JF - AIAA Journal N2 - This paper presents a novel method for airfoil drag estimation at Reynolds numbers between 4×10⁵ and 4×10⁶. The novel method is based on a systematic study of 40 airfoils applying over 600 numerical simulations and considering natural transition. The influence of the airfoil thickness-to-chord ratio, camber, and freestream Reynolds number on both friction and pressure drag is analyzed in detail. Natural transition significantly affects drag characteristics and leads to distinct drag minima for different Reynolds numbers and thickness-to-chord ratios. The results of the systematic study are used to develop empirical correlations that can accurately predict an airfoil drag at low-lift conditions. The new approach estimates a transition location based on airfoil thickness-to-chord ratio, camber, and Reynolds number. It uses the transition location in a mixed laminar–turbulent skin-friction calculation, and corrects the skin-friction coefficient for separation effects. Pressure drag is estimated separately based on correlations of thickness-to-chord ratio, camber, and Reynolds number. The novel method shows excellent accuracy when compared with wind-tunnel measurements of multiple airfoils. It is easily integrable into existing aircraft design environments and is highly beneficial in the conceptual design stage. Y1 - 2020 U6 - https://doi.org/10.2514/1.J058983 SN - 1533-385X VL - 58 IS - 7 SP - 2791 EP - 2805 PB - AIAA CY - Reston, Va. ER - TY - JOUR A1 - Khayyam, Hamid A1 - Jamali, Ali A1 - Bab-Hadiashar, Alireza A1 - Esch, Thomas A1 - Ramakrishna, Seeram A1 - Jalili, Mahdi A1 - Naebe, Minoo T1 - A Novel Hybrid Machine Learning Algorithm for Limited and Big Data Modeling with Application in Industry 4.0 JF - IEEE Access N2 - To meet the challenges of manufacturing smart products, the manufacturing plants have been radically changed to become smart factories underpinned by industry 4.0 technologies. The transformation is assisted by employment of machine learning techniques that can deal with modeling both big or limited data. This manuscript reviews these concepts and present a case study that demonstrates the use of a novel intelligent hybrid algorithms for Industry 4.0 applications with limited data. In particular, an intelligent algorithm is proposed for robust data modeling of nonlinear systems based on input-output data. In our approach, a novel hybrid data-driven combining the Group-Method of Data-Handling and Singular-Value Decomposition is adapted to find an offline deterministic model combined with Pareto multi-objective optimization to overcome the overfitting issue. An Unscented-Kalman-Filter is also incorporated to update the coefficient of the deterministic model and increase its robustness against data uncertainties. The effectiveness of the proposed method is examined on a set of real industrial measurements. Y1 - 2020 U6 - https://doi.org/10.1109/ACCESS.2020.2999898 SN - 2169-3536 VL - 8 IS - Art. 9108222 SP - 111381 EP - 111393 PB - IEEE CY - New York, NY ER - TY - JOUR A1 - Maurischat, Andreas A1 - Perkins, Rudolph T1 - Taylor coefficients of Anderson generating functions and Drinfeld torsion extensions N2 - We generalize our work on Carlitz prime power torsion extension to torsion extensions of Drinfeld modules of arbitrary rank. As in the Carlitz case, we give a description of these extensions in terms of evaluations of Anderson generating functions and their hyperderivatives at roots of unity. We also give a direct proof that the image of the Galois representation attached to the p-adic Tate module lies in the p-adic points of the motivic Galois group. This is a generalization of the corresponding result of Chang and Papanikolas for the t-adic case. Y1 - 2020 U6 - https://doi.org/10.1142/S1793042122500099 IS - Vol. 18, No. 01 SP - 113 EP - 130 PB - World Scientific CY - Singapur ER - TY - JOUR A1 - Hein, Andreas M. A1 - Eubanks, T. Marshall A1 - Hibberd, Adam A1 - Fries, Dan A1 - Schneider, Jean A1 - Lingam, Manasvi A1 - Kennedy, Robert A1 - Perakis, Nikolaos A1 - Dachwald, Bernd A1 - Kervella, Pierre T1 - Interstellar Now! Missions to and sample returns from nearby interstellar objects N2 - The recently discovered first high velocity hyperbolic objects passing through the Solar System, 1I/'Oumuamua and 2I/Borisov, have raised the question about near term missions to Interstellar Objects. In situ spacecraft exploration of these objects will allow the direct determination of both their structure and their chemical and isotopic composition, enabling an entirely new way of studying small bodies from outside our solar system. In this paper, we map various Interstellar Object classes to mission types, demonstrating that missions to a range of Interstellar Object classes are feasible, using existing or near-term technology. We describe flyby, rendezvous and sample return missions to interstellar objects, showing various ways to explore these bodies characterizing their surface, dynamics, structure and composition. Interstellar objects likely formed very far from the solar system in both time and space; their direct exploration will constrain their formation and history, situating them within the dynamical and chemical evolution of the Galaxy. These mission types also provide the opportunity to explore solar system bodies and perform measurements in the far outer solar system. Y1 - 2020 SP - 1 EP - 8 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Seefeldt, Patric A1 - Dachwald, Bernd T1 - Temperature increase on folded solar sail membranes JF - Advances in Space Research Y1 - 2021 U6 - https://doi.org/10.1016/j.asr.2020.09.026 SN - 0273-1177 VL - 67 IS - 9 SP - 2688 EP - 2695 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Grundmann, Jan Thimo A1 - Biele, Jens A1 - Dachwald, Bernd A1 - Grimm, Christian D. A1 - Lange, Caroline A1 - Ulamec, Stephan A1 - Ziach, Christian A1 - Spröwitz, Tom A1 - Ruffer, Michael A1 - Seefeldt, Patric A1 - Spietz, Peter A1 - Toth, Norbert A1 - Mimasu, Yuya A1 - Rittweger, Andreas A1 - Bibring, Jean-Pierre A1 - Braukhane, Andy A1 - Boden, Ralf Christian A1 - Dumont, Etienne A1 - Jahnke, Stephan Siegfried A1 - Jetzschmann, Michael A1 - Krüger, Hans A1 - Lange, Michael A1 - Gomez, Antonio Martelo A1 - Massonett, Didier A1 - Okada, Tatsuaki A1 - Sagliano, Marco A1 - Sasaki, Kaname A1 - Schröder, Silvio A1 - Sippel, Martin A1 - Skoczylas, Thomas A1 - Wejmo, Elisabet T1 - Small landers and separable sub-spacecraft for near-term solar sails T2 - The Fourth International Symposium on Solar Sailing 2017 N2 - Following the successful PHILAE landing with ESA's ROSETTA probe and the launch of the MINERVA rovers and the Mobile Asteroid Surface Scout, MASCOT, aboard the JAXA space probe, HAYABUSA2, to asteroid (162173) Ryugu, small landers have found increasing interest. Integrated at the instrument level in their mothership they support small solar system body studies. With efficient capabilities, resource-friendly design and inherent robustness they are an attractive exploration mission element. We discuss advantages and constraints of small sub-spacecraft, focusing on emerging areas of activity such as asteroid diversity studies, planetary defence, and asteroid mining, on the background of our projects PHILAE, MASCOT, MASCOT2, the JAXA-DLR Solar Power Sail Lander Design Study, and others. The GOSSAMER-1 solar sail deployment concept also involves independent separable sub-spacecraft operating synchronized to deploy the sail. Small spacecraft require big changes in the way we do things and occasionally a little more effort than would be anticipated based on a traditional large spacecraft approach. In a Constraints-Driven Engineering environment we apply Concurrent Design and Engineering (CD/CE), Concurrent Assembly, Integration and Verification (CAIV) and Model-Based Systems Engineering (MBSE). Near-term solar sails will likely be small spacecraft which we expect to harmonize well with nano-scale separable instrument payload packages. KW - Small Solar System Body Lander KW - Small Spacecraft KW - PHILAE KW - MASCOT KW - Solar Power Sail Y1 - 2017 N1 - The Fourth International Symposium on Solar Sailing 2017, 17-20 January 2017. Kyoto Research Park, Kyoto, Japan SP - 1 EP - 10 ER - TY - CHAP A1 - Spurmann, Jörn A1 - Ohndorf, Andreas A1 - Dachwald, Bernd A1 - Seboldt, Wolfgang A1 - Löb, Horst A1 - Schartner, Karl-Heinz T1 - Interplanetary trajectory optimization for a sep mission to Saturn T2 - 60th International Astronautical Congress 2009 N2 - The recently proposed NASA and ESA missions to Saturn and Jupiter pose difficult tasks to mission designers because chemical propulsion scenarios are not capable of transferring heavy spacecraft into the outer solar system without the use of gravity assists. Thus our developed mission scenario based on the joint NASA/ESA Titan Saturn System Mission baselines solar electric propulsion to improve mission flexibility and transfer time. For the calculation of near-globally optimal low-thrust trajectories, we have used a method called Evolutionary Neurocontrol, which is implemented in the low-thrust trajectory optimization software InTrance. The studied solar electric propulsion scenario covers trajectory optimization of the interplanetary transfer including variations of the spacecraft's thrust level, the thrust unit's specific impulse and the solar power generator power level. Additionally developed software extensions enabled trajectory optimization with launcher-provided hyperbolic excess energy, a complex solar power generator model and a variable specific impulse ion engine model. For the investigated mission scenario, Evolutionary Neurocontrol yields good optimization results, which also hold valid for the more elaborate spacecraft models. Compared to Cassini/Huygens, the best found solutions have faster transfer times and a higher mission flexibility in general. KW - Spacecraft KW - Reusable Rocket Engines KW - Hybrid Propellants Y1 - 2009 SN - 9781615679089 N1 - 60th International Astronautical Congress 2009 (IAC 2009) Held 12-16 October 2009, Daejeon, Republic of Korea. SP - 5234 EP - 5248 ER - TY - CHAP A1 - Loeb, Horst Wolfgang A1 - Schartner, Karl-Heinz A1 - Dachwald, Bernd A1 - Seboldt, Wolfgang T1 - SEP-Sample return from a main belt asteroid T2 - 30th International Electric Propulsion Conference N2 - By DLR-contact, sample return missions to the large main-belt asteroid “19, Fortuna” have been studied. The mission scenario has been based on three ion thrusters of the RIT-22 model, which is presently under space qualification, and on solar arrays equipped with triple-junction GaAs solar cells. After having designed the spacecraft, the orbit-to-orbit trajectories for both, a one-way SEP mission with a chemical sample return and an all-SEP return mission, have been optimized using a combination of artificial neural networks with evolutionary algorithms. Additionally, body-to-body trajectories have been investigated within a launch period between 2012 and 2015. For orbit-to-orbit calculation, the launch masses of the hybrid mission and of the all-SEP mission resulted in 2.05 tons and 1.56 tons, respectively, including a scientific payload of 246 kg. For the related transfer durations 4.14 yrs and 4.62 yrs were obtained. Finally, a comparison between the mission scenarios based on SEP and on NEP have been carried out favouring clearly SEP. Y1 - 2007 SP - 1 EP - 11 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 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 - Schoutetens, Frederic A1 - Dachwald, Bernd A1 - Heiligers, Jeannette T1 - Optimisation of photon-sail trajectories in the alpha-centauri system using evolutionary neurocontrol T2 - 8th ICATT 2021 N2 - With the increased interest for interstellar exploration after the discovery of exoplanets and the proposal by Breakthrough Starshot, this paper investigates the optimisation of photon-sail trajectories in Alpha Centauri. The prime objective is to find the optimal steering strategy for a photonic sail to get captured around one of the stars after a minimum-time transfer from Earth. By extending the idea of the Breakthrough Starshot project with a deceleration phase upon arrival, the mission’s scientific yield will be increased. As a secondary objective, transfer trajectories between the stars and orbit-raising manoeuvres to explore the habitable zones of the stars are investigated. All trajectories are optimised for minimum time of flight using the trajectory optimisation software InTrance. Depending on the sail technology, interstellar travel times of 77.6-18,790 years can be achieved, which presents an average improvement of 30% with respect to previous work. Still, significant technological development is required to reach and be captured in the Alpha-Centauri system in less than a century. Therefore, a fly-through mission arguably remains the only option for a first exploratory mission to Alpha Centauri, but the enticing results obtained in this work provide perspective for future long-residence missions to our closest neighbouring star system. Y1 - 2021 N1 - 8th ICATT (International Conference on Astrodynamics Tools and Techniques), 23 - 25 June 2021, Virtual SP - 1 EP - 15 ER - TY - CHAP A1 - Seefeldt, Patric A1 - Bauer, Waldemar A1 - Dachwald, Bernd A1 - Grundmann, Jan Thimo A1 - Straubel, Marco A1 - Sznajder, Maciej A1 - Tóth, Norbert A1 - Zander, Martin E. T1 - Large lightweight deployable structures for planetary defence: solar sail propulsion, solar concentrator payloads, large-scale photovoltaic power T2 - 4th IAA Planetary Defense Conference - PDC 2015, 13-17 April 2015, Frascati, Roma, Italy Y1 - 2015 N1 - IAA-PDC-15-P-20 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 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 - CHAP A1 - Grundmann, Jan Thimo A1 - Boden, Ralf A1 - Ceriotti, Matteo A1 - Dachwald, Bernd A1 - Dumont, Etienne A1 - Grimm, Christian D. A1 - Lange, Caroline A1 - Lichtenheldt, Roy A1 - Pelivan, Ivanka A1 - Peloni, Alessandro A1 - Riemann, Johannes A1 - Spröwitz, Tom A1 - Tardivel, Simon T1 - Soil to sail-asteroid landers on near-term sailcraft as an evolution of the GOSSAMER small spacecraft solar sail concept for in-situ characterization T2 - 5th IAA Planetary Defense Conference KW - multiple NEA rendezvous KW - solar sail KW - GOSSAMER-1 KW - MASCOT KW - asteroid sample return Y1 - 2017 N1 - 5th IAA Planetary Defense Conference – PDC 2017 15-19 May 2017, Tokyo, Japan 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 - https://doi.org/10.1002/9780470686652.eae292 PB - Wiley CY - Hoboken ER - TY - CHAP A1 - Seboldt, Wolfgang A1 - Dachwald, Bernd T1 - Solar sails for near-term advanced scientific deep space missions T2 - Proceedings of the 8th International Workshop on Combustion and Propulsion N2 - Solar sails are propelled in space by reflecting solar photons off large mirroring surfaces, thereby transforming the momentum of the photons into a propulsive force. This innovative concept for low-thrust space propulsion works without any propellant and thus provides a wide range of opportunities for highenergy low-cost missions. Offering an efficient way of propulsion, solar sailcraft could close a gap in transportation options for highly demanding exploration missions within our solar system and even beyond. On December 17th, 1999, a significant step was made towards the realization of this technology: a lightweight solar sail structure with an area of 20 m × 20 m was successfully deployed on ground in a large facility at the German Aerospace Center (DLR) at Cologne. The deployment from a package of 60 cm × 60 cm × 65 cm with a total mass of less than 35 kg was achieved using four extremely light-weight carbon fiber reinforced plastics (CFRP) booms with a specific mass of 100 g/m. The paper briefly reviews the basic principles of solar sails as well as the technical concept and its realization in the ground demonstration experiment, performed in close cooperation between DLR and ESA. Next possible steps are outlined. They could comprise the in-orbit demonstration of the sail deployment on the upper stage of a low-cost rocket and the verification of the propulsion concept by an autonomous and free flying solar sail in the frame of a scientific mission. It is expected that the present design could be extended to sail sizes of about (40 m)2 up to even (70 m)2 without significant mass penalty. With these areas, the maximum achievable thrust at 1 AU would range between 10 and 40 mN – comparable to some electric thrusters. Such prototype sails with a mass between 50 and 150 kg plus a micro-spacecraft of 50 to 250 kg would have a maximum acceleration in the order of 0.1 mm/s2 at 1 AU, corresponding to a maximum ∆V-capability of about 3 km/s per year. Two near/medium-term mission examples to a near-Earth asteroid (NEA) will be discussed: a rendezvous mission and a sample return mission. KW - solar sail KW - low-thrust KW - near-Earth asteroid KW - sample return KW - solar system Y1 - 2003 N1 - Proceedings of the 8th International Workshop on Combustion and Propulsion. Pozzuoli, Italy, 16 - 21 June 2002. ER - TY - CHAP A1 - Dachwald, Bernd A1 - Seboldt, Wolfgang A1 - Häusler, Bernd T1 - Performance requirements for near-term interplanetary solar sailcraft missions T2 - 6th International AAAF Symposium on Space Propulsion: Propulsion for Space Transportation of the XXIst Century N2 - Solar sailcraft provide a wide range of opportunities for high-energy low-cost missions. To date, most mission studies require a rather demanding performance that will not be realized by solar sailcraft of the first generation. However, even with solar sailcraft of moderate performance, scientifically relevant missions are feasible. This is demonstrated with a Near Earth Asteroid sample return mission and various planetary rendezvous missions. Y1 - 2002 N1 - 6th International AAAF Symposium on Space Propulsion: Propulsion for Space Transportation of the XXIst Century, Versailles, France, 14-16 May 2002 ER - TY - JOUR A1 - Loeb, Horst Wolfgang A1 - Schartner, Karl-Heinz A1 - Dachwald, Bernd A1 - Ohndorf, Andreas A1 - Seboldt, Wolfgang T1 - Interstellar heliopause probe JF - Труды МАИ N2 - There is common agreement within the scientific community that in order to understand our local galactic environment it will be necessary to send a spacecraft into the region beyond the solar wind termination shock. Considering distances of 200 AU for a new mission, one needs a spacecraft traveling at a speed of close to 10 AU/yr in order to keep the mission duration in the range of less than 25 yrs, a transfer time postulated by European Space Agency (ESA). Two propulsion options for the mission have been proposed and discussed so far: the solar sail propulsion and the ballistic/radioisotope-electric propulsion (REP). As a further alternative, we here investigate a combination of solar-electric propulsion (SEP) and REP. The SEP stage consists of six 22-cms diameter RIT-22 ion thrusters working with a high specific impulse of 7377 s corresponding to a positive grid voltage of 5 kV. Solar power of 53 kW at begin of mission (BOM) is provided by a lightweight solar array. Y1 - 2012 IS - 60 SP - 2 EP - 2 PB - Moskauer Staatliches Luftfahrtinstitut (МАИ) CY - Moskau ER - TY - CHAP A1 - Ohndorf, Andreas A1 - Dachwald, Bernd A1 - Seboldt, Wolfgang A1 - Schartner, Karl-Heinz T1 - Flight times to the heliopause using a combination of solar and radioisotope electric propulsion T2 - 32nd International Electric Propulsion Conference N2 - We investigate the interplanetary flight of a low-thrust space probe to the heliopause,located at a distance of about 200 AU from the Sun. Our goal was to reach this distance within the 25 years postulated by ESA for such a mission (which is less ambitious than the 15-year goal set by NASA). Contrary to solar sail concepts and combinations of allistic and electrically propelled flight legs, we have investigated whether the set flight time limit could also be kept with a combination of solar-electric propulsion and a second, RTG-powered upper stage. The used ion engine type was the RIT-22 for the first stage and the RIT-10 for the second stage. Trajectory optimization was carried out with the low-thrust optimization program InTrance, which implements the method of Evolutionary Neurocontrol,using Artificial Neural Networks for spacecraft steering and Evolutionary Algorithms to optimize the Neural Networks’ parameter set. Based on a parameter space study, in which the number of thrust units, the unit’s specific impulse, and the relative size of the solar power generator were varied, we have chosen one configuration as reference. The transfer time of this reference configuration was 29.6 years and the fastest one, which is technically more challenging, still required 28.3 years. As all flight times of this parameter study were longer than 25 years, we further shortened the transfer time by applying a launcher-provided hyperbolic excess energy up to 49 km2/s2. The resulting minimal flight time for the reference configuration was then 27.8 years. The following, more precise optimization to a launch with the European Ariane 5 ECA rocket reduced the transfer time to 27.5 years. This is the fastest mission design of our study that is flexible enough to allow a launch every year. The inclusion of a fly-by at Jupiter finally resulted in a flight time of 23.8 years,which is below the set transfer-time limit. However, compared to the 27.5-year transfer,this mission design has a significantly reduced launch window and mission flexibility if the escape direction is restricted to the heliosphere’s “nose". KW - low-thrust trajectory optimization KW - heliosphere KW - ion propulsion Y1 - 2011 N1 - IEPC-2011-051 32nd International Electric Propulsion Conference,September 11–15, 2011 Wiesbaden, Germany SP - 1 EP - 12 ER - TY - CHAP A1 - Borggräfe, Andreas A1 - Dachwald, Bernd T1 - Mission performance evaluation for solar sails using a refined SRP force model with variable optical coefficients T2 - 2nd International Symposium on Solar Sailing N2 - 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. Y1 - 2010 N1 - 2nd International Symposium on Solar Sailing, ISSS 2010, 2010-07-20 - 2010-07-22. New York City College of Technology of the City University of New York, USA SP - 1 EP - 6 ER - TY - CHAP A1 - Schartner, Karl-Heinz A1 - Loeb, H. W. A1 - Dachwald, Bernd A1 - Ohndorf, Andreas T1 - Perspectives of electric propulsion for outer planetary and deep space missions T2 - European Planetary Science Congress 2009 N2 - Solar-electric propulsion (SEP) is superior with respect to payload capacity, flight time and flexible launch window to the conventional interplanetary transfer method using chemical propulsion combined with gravity assists. This fact results from the large exhaust velocities of electric low–thrust propulsion and is favourable also for missions to the giant planets, Kuiper-belt objects and even for a heliopause probe (IHP) as shown in three studies by the authors funded by DLR. They dealt with a lander for Europa and a sample return mission from a mainbelt asteroid [1], with the TANDEM mission [2]; the third recent one investigates electric propulsion for the transfer to the edge of the solar system. All studies are based on triple-junction solar arrays, on rf-ion thrusters of the qualified RIT-22 type and they use the intelligent trajectory optimization program InTrance [3]. Y1 - 2009 N1 - European Planetary Science Congress 2009, 13-18 September, Potsdam, Germany SP - 416 EP - 416 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 - https://doi.org/10.2514/6.IAC-04-S.P.11 N1 - 55th International Astronautical Congress 2004 - Vancouver, Canada SP - 1 EP - 9 ER - TY - CHAP A1 - Kroniger, Daniel A1 - Horikawa, Atsushi A1 - Funke, Harald A1 - Pfäffle, Franziska T1 - Numerical investigation of micromix hydrogen flames at different combustor pressure levels T2 - The Proceedings of the International Conference on Power Engineering (ICOPE) N2 - This study investigates the influence of pressure on the temperature distribution of the micromix (MMX) hydrogen flame and the NOx emissions. A steady computational fluid dynamic (CFD) analysis is performed by simulating a reactive flow with a detailed chemical reaction model. The numerical analysis is validated based on experimental investigations. A quantitative correlation is parametrized based on the numerical results. We find, that the flame initiation point shifts with increasing pressure from anchoring behind a downstream located bluff body towards anchoring upstream at the hydrogen jet. The numerical NOx emissions trend regarding to a variation of pressure is in good agreement with the experimental results. The pressure has an impact on both, the residence time within the maximum temperature region and on the peak temperature itself. In conclusion, the numerical model proved to be adequate for future prototype design exploration studies targeting on improving the operating range. KW - Gas turbine combustion KW - Hydrogen KW - NOx emissions KW - Flame temperature KW - Flame residence time Y1 - 2021 U6 - https://doi.org/10.1299/jsmeicope.2021.15.2021-0237 N1 - International Conference on Power Engineering 2021 (ICOPE-2021). October 17 - 21, 2021. Kobe, Japan (Online) ER - TY - CHAP A1 - Horikawa, Atsushi A1 - Okada, Kunio A1 - Yamaguchi, Masato A1 - Aoki, Shigeki A1 - Wirsum, Manfred A1 - Funke, Harald A1 - Kusterer, Karsten T1 - Combustor development and engine demonstration of micro-mix hydrogen combustion applied to M1A-17 gas turbine T2 - Conference Proceedings Turbo Expo: Power for Land, Sea and Air, Volume 3B: Combustion, Fuels, and Emissions N2 - Kawasaki Heavy Industries, LTD. (KHI) has research and development projects for a future hydrogen society. These projects comprise the complete hydrogen cycle, including the production of hydrogen gas, the refinement and liquefaction for transportation and storage, and finally the utilization in a gas turbine for electricity and heat supply. Within the development of the hydrogen gas turbine, the key technology is stable and low NOx hydrogen combustion, namely the Dry Low NOx (DLN) hydrogen combustion. KHI, Aachen University of Applied Science, and B&B-AGEMA have investigated the possibility of low NOx micro-mix hydrogen combustion and its application to an industrial gas turbine combustor. From 2014 to 2018, KHI developed a DLN hydrogen combustor for a 2MW class industrial gas turbine with the micro-mix technology. Thereby, the ignition performance, the flame stability for equivalent rotational speed, and higher load conditions were investigated. NOx emission values were kept about half of the Air Pollution Control Law in Japan: 84ppm (O2-15%). Hereby, the elementary combustor development was completed. From May 2020, KHI started the engine demonstration operation by using an M1A-17 gas turbine with a co-generation system located in the hydrogen-fueled power generation plant in Kobe City, Japan. During the first engine demonstration tests, adjustments of engine starting and load control with fuel staging were investigated. On 21st May, the electrical power output reached 1,635 kW, which corresponds to 100% load (ambient temperature 20 °C), and thereby NOx emissions of 65 ppm (O2-15, 60 RH%) were verified. Here, for the first time, a DLN hydrogen-fueled gas turbine successfully generated power and heat. KW - industrial gas turbine KW - combustor development KW - engine demonstration KW - fuels KW - hydrogen Y1 - 2021 U6 - https://doi.org/10.1115/GT2021-59666 N1 - ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. June 7–11, 2021. Virtual, Online. Paper No: GT2021-59666, V03BT04A014 ER - TY - CHAP A1 - Kroniger, Daniel A1 - Horikawa, Atsushi A1 - Funke, Harald A1 - Pfäffle, Franziska A1 - Kishimoto, Tsuyoshi A1 - Okada, Koichi T1 - Experimental and numerical investigation on the effect of pressure on micromix hydrogen combustion T2 - Conference Proceedings Turbo Expo: Power for Land, Sea and Air, Volume 3A: Combustion, Fuels, and Emissions N2 - The micromix (MMX) combustion concept is a DLN gas turbine combustion technology designed for high hydrogen content fuels. Multiple non-premixed miniaturized flames based on jet in cross-flow (JICF) are inherently safe against flashback and ensure a stable operation in various operative conditions. The objective of this paper is to investigate the influence of pressure on the micromix flame with focus on the flame initiation point and the NOx emissions. A numerical model based on a steady RANS approach and the Complex Chemistry model with relevant reactions of the GRI 3.0 mechanism is used to predict the reactive flow and NOx emissions at various pressure conditions. Regarding the turbulence-chemical interaction, the Laminar Flame Concept (LFC) and the Eddy Dissipation Concept (EDC) are compared. The numerical results are validated against experimental results that have been acquired at a high pressure test facility for industrial can-type gas turbine combustors with regard to flame initiation and NOx emissions. The numerical approach is adequate to predict the flame initiation point and NOx emission trends. Interestingly, the flame shifts its initiation point during the pressure increase in upstream direction, whereby the flame attachment shifts from anchoring behind a downstream located bluff body towards anchoring directly at the hydrogen jet. The LFC predicts this change and the NOx emissions more accurately than the EDC. The resulting NOx correlation regarding the pressure is similar to a non-premixed type combustion configuration. KW - NOx emissions KW - hydrogen KW - combustor KW - gas turbine Y1 - 2021 U6 - https://doi.org/10.1115/GT2021-58926 N1 - ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition, June 7–11, 2021, Virtual, Online. Paper No: GT2021-58926, V03AT04A025 PB - ASME CY - New York, NY ER - TY - JOUR A1 - Heiligers, Jeannette A1 - Schoutetens, Frederic A1 - Dachwald, Bernd T1 - Photon-sail equilibria in the alpha centauri system JF - Journal of Guidance, Control, and Dynamics Y1 - 2021 U6 - https://doi.org/10.2514/1.G005446 SN - 1533-3884 SN - 0731-5090 SN - 0162-3192 VL - 44 IS - 5 SP - 1053 EP - 1061 ER - TY - JOUR A1 - German, Laura A1 - Mikucki, Jill A. A1 - Welch, Susan A. A1 - Welch, Kathleen A. A1 - Lutton, Anthony A1 - Dachwald, Bernd A1 - Kowalski, Julia A1 - Heinen, Dirk A1 - Feldmann, Marco A1 - Francke, Gero A1 - Espe, Clemens A1 - Lyons, W. Berry T1 - Validation of sampling antarctic subglacial hypersaline waters with an electrothermal ice melting probe (IceMole) for environmental analytical geochemistry JF - International Journal of Environmental Analytical Chemistry N2 - Geochemical characterisation of hypersaline waters is difficult as high concentrations of salts hinder the analysis of constituents at low concentrations, such as trace metals, and the collection of samples for trace metal analysis in natural waters can be easily contaminated. This is particularly the case if samples are collected by non-conventional techniques such as those required for aquatic subglacial environments. In this paper we present the first analysis of a subglacial brine from Taylor Valley, (~ 78°S), Antarctica for the trace metals: Ba, Co, Mo, Rb, Sr, V, and U. Samples were collected englacially using an electrothermal melting probe called the IceMole. This probe uses differential heating of a copper head as well as the probe’s sidewalls and an ice screw at the melting head to move through glacier ice. Detailed blanks, meltwater, and subglacial brine samples were collected to evaluate the impact of the IceMole and the borehole pump, the melting and collection process, filtration, and storage on the geochemistry of the samples collected by this device. Comparisons between melt water profiles through the glacier ice and blank analysis, with published studies on ice geochemistry, suggest the potential for minor contributions of some species Rb, As, Co, Mn, Ni, NH4+, and NO2−+NO3− from the IceMole. The ability to conduct detailed chemical analyses of subglacial fluids collected with melting probes is critical for the future exploration of the hundreds of deep subglacial lakes in Antarctica. Y1 - 2021 U6 - https://doi.org/10.1080/03067319.2019.1704750 SN - 0306-7319 VL - 101 IS - 15 SP - 2654 EP - 2667 PB - Taylor & Francis CY - London ER - TY - JOUR A1 - Spietz, Peter A1 - Spröwitz, Tom A1 - Seefeldt, Patric A1 - Grundmann, Jan Thimo A1 - Jahnke, Rico A1 - Mikschl, Tobias A1 - Mikulz, Eugen A1 - Montenegro, Sergio A1 - Reershemius, Siebo A1 - Renger, Thomas A1 - Ruffer, Michael A1 - Sasaki, Kaname A1 - Sznajder, Maciej A1 - Tóth, Norbert A1 - Ceriotti, Matteo A1 - Dachwald, Bernd A1 - Macdonald, Malcolm A1 - McInnes, Colin A1 - Seboldt, Wolfgang A1 - Quantius, Dominik A1 - Bauer, Waldemar A1 - Wiedemann, Carsten A1 - Grimm, Christian D. A1 - Hercik, David A1 - Ho, Tra-Mi A1 - Lange, Caroline A1 - Schmitz, Nicole T1 - Paths not taken – The Gossamer roadmap’s other options JF - Advances in Space Research KW - Solar sail KW - Small spacecraft KW - DLR-ESTEC GOSSAMER roadmap for solar sailing KW - GOSSAMER-1 Y1 - 2021 U6 - https://doi.org/10.1016/j.asr.2021.01.044 SN - 0273-1177 VL - 67 IS - 9 SP - 2912 EP - 2956 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kezerashvili, Roman Ya A1 - Dachwald, Bernd T1 - Preface: Solar sailing: Concepts, technology, and missions II JF - Advances in Space Research Y1 - 2021 U6 - https://doi.org/10.1016/j.asr.2021.01.037 SN - 0273-1177 VL - 67 IS - 9 SP - 2559 EP - 2560 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hein, Andreas M. A1 - Eubanks, T. Marshall A1 - Lingam, Manasvi A1 - Hibberd, Adam A1 - Fries, Dan A1 - Schneider, Jean A1 - Kervella, Pierre A1 - Kennedy, Robert A1 - Perakis, Nikolaos A1 - Dachwald, Bernd T1 - Interstellar now! Missions to explore nearby interstellar objects JF - Advances in Space Research N2 - The recently discovered first hyperbolic objects passing through the Solar System, 1I/’Oumuamua and 2I/Borisov, have raised the question about near term missions to Interstellar Objects. In situ spacecraft exploration of these objects will allow the direct determination of both their structure and their chemical and isotopic composition, enabling an entirely new way of studying small bodies from outside our solar system. In this paper, we map various Interstellar Object classes to mission types, demonstrating that missions to a range of Interstellar Object classes are feasible, using existing or near-term technology. We describe flyby, rendezvous and sample return missions to interstellar objects, showing various ways to explore these bodies characterizing their surface, dynamics, structure and composition. Their direct exploration will constrain their formation and history, situating them within the dynamical and chemical evolution of the Galaxy. These mission types also provide the opportunity to explore solar system bodies and perform measurements in the far outer solar system. KW - Interstellar objects KW - Trajectories KW - Missions Y1 - 2022 U6 - https://doi.org/10.1016/j.asr.2021.06.052 SN - 0273-1177 VL - 69 IS - 1 SP - 402 EP - 414 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Grundmann, Jan Thimo A1 - Bauer, Waldemar A1 - Boden, Ralf A1 - Ceriotti, Matteo A1 - Chand, Suditi A1 - Cordero, Federico A1 - Dachwald, Bernd A1 - Dumont, Etienne A1 - Grimm, Christian D. A1 - Heiligers, Jeannette A1 - Herčík, David A1 - Hérique, Alain A1 - Ho, Tra-Mi A1 - Jahnke, Rico A1 - Kofman, Wlodek A1 - Lange, Caroline A1 - Lichtenheldt, Roy A1 - McInnes, Colin A1 - Meß, Jan-Gerd A1 - Mikschl, Tobias A1 - Mikulz, Eugen A1 - Montenegro, Sergio A1 - Moore, Iain A1 - Pelivan, Ivanka A1 - Peloni, Alessandro A1 - Plettemeier, Dirk A1 - Quantius, Dominik A1 - Reershemius, Siebo A1 - Renger, Thomas A1 - Riemann, Johannes A1 - Rogez, Yves A1 - Ruffer, Michael A1 - Sasaki, Kaname A1 - Schmitz, Nicole A1 - Seboldt, Wolfgang A1 - Seefeldt, Patric A1 - Spietz, Peter A1 - Spröwitz, Tom A1 - Sznajder, Maciej A1 - Tóth, Norbert A1 - Vergaaij, Merel A1 - Viavattene, Giulia A1 - Wejmo, Elisabet A1 - Wiedemann, Carsten A1 - Wolff, Friederike A1 - Ziach, Christian T1 - Flights are ten a sail – Re-use and commonality in the design and system engineering of small spacecraft solar sail missions with modular hardware for responsive and adaptive exploration T2 - 70th International Astronautical Congress (IAC) KW - system engineering KW - small solar system body characterisation KW - small spacecraft solar sail KW - small spacecraft asteroid lander KW - responsive space Y1 - 2019 SN - 9781713814856 N1 - 70th International Astronautical Congress (IAC), Washington D.C., United States, 21-25 October 2019 SP - 1 EP - 7 ER - TY - JOUR A1 - Neu, Eugen A1 - Janser, Frank A1 - Khatibi, Akbar A. A1 - Orifici, Adrian C. T1 - Fully Automated Operational Modal Analysis using multi-stage clustering JF - Mechanical Systems and Signal Processing Y1 - 2017 U6 - https://doi.org/10.1016/j.ymssp.2016.07.031 SN - 0888-3270 VL - Vol. 84, Part A SP - 308 EP - 323 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Konstantinidis, K. A1 - Kowalski, Julia A1 - Martinez, C. F. A1 - Dachwald, Bernd A1 - Ewerhart, D. A1 - Förstner, R. T1 - Some necessary technologies for in-situ astrobiology on enceladus T2 - Proceedings of the International Astronautical Congress Y1 - 2015 SN - 978-151081893-4 N1 - 6th International Astronautical Congress 2015: Space - The Gateway for Mankind's Future, IAC 2015; Jerusalem; Israel; 12 October 2015 through 16 October 2015 SP - 1354 EP - 1372 ER - TY - JOUR A1 - Funke, Harald A1 - Keinz, Jan A1 - Kusterer, Karsten A1 - Ayed, Anis Haj A1 - Kazari, Masahide A1 - Kitajima, Junichi A1 - Horikawa, Atsushi A1 - Okada, Kunio T1 - Experimental and Numerical Study on Optimizing the Dry Low NOₓ Micromix Hydrogen Combustion Principle for Industrial Gas Turbine Applications JF - Journal of Thermal Science and Engineering Applications N2 - Combined with the use of renewable energy sources for its production, hydrogen represents a possible alternative gas turbine fuel for future low-emission power generation. Due to the difference in the physical properties of hydrogen compared to other fuels such as natural gas, well-established gas turbine combustion systems cannot be directly applied to dry low NOₓ (DLN) hydrogen combustion. The DLN micromix combustion of hydrogen has been under development for many years, since it has the promise to significantly reduce NOₓ emissions. This combustion principle for air-breathing engines is based on crossflow mixing of air and gaseous hydrogen. Air and hydrogen react in multiple miniaturized diffusion-type flames with an inherent safety against flashback and with low NOₓ emissions due to a very short residence time of the reactants in the flame region. The paper presents an advanced DLN micromix hydrogen application. The experimental and numerical study shows a combustor configuration with a significantly reduced number of enlarged fuel injectors with high-thermal power output at constant energy density. Larger fuel injectors reduce manufacturing costs, are more robust and less sensitive to fuel contamination and blockage in industrial environments. The experimental and numerical results confirm the successful application of high-energy injectors, while the DLN micromix characteristics of the design point, under part-load conditions, and under off-design operation are maintained. Atmospheric test rig data on NOₓ emissions, optical flame-structure, and combustor material temperatures are compared to numerical simulations and show good agreement. The impact of the applied scaling and design laws on the miniaturized micromix flamelets is particularly investigated numerically for the resulting flow field, the flame-structure, and NOₓ formation. Y1 - 2016 U6 - https://doi.org/10.1115/1.4034849 SN - 1948-5093 N1 - TSEA-15-1227 VL - 9 IS - 2 SP - 021001 EP - 021001-10 PB - ASME CY - New York, NY ER - TY - JOUR A1 - Ayed, Anis Haj A1 - Kusterer, Karsten A1 - Funke, Harald A1 - Keinz, Jan T1 - CFD Based Improvement of the DLN Hydrogen Micromix Combustion Technology at Increased Energy Densities JF - American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) N2 - Combined with the use of renewable energy sources for its production, Hydrogen represents a possible alternative gas turbine fuel within future low emission power generation. Due to the large difference in the physical properties of Hydrogen compared to other fuels such as natural gas, well established gas turbine combustion systems cannot be directly applied for Dry Low NOx (DLN) Hydrogen combustion. Thus, the development of DLN combustion technologies is an essential and challenging task for the future of Hydrogen fuelled gas turbines. The DLN Micromix combustion principle for hydrogen fuel has been developed to significantly reduce NOx-emissions. This combustion principle is based on cross-flow mixing of air and gaseous hydrogen which reacts in multiple miniaturized diffusion-type flames. The major advantages of this combustion principle are the inherent safety against flash-back and the low NOx-emissions due to a very short residence time of reactants in the flame region of the micro-flames. The Micromix Combustion technology has been already proven experimentally and numerically for pure Hydrogen fuel operation at different energy density levels. The aim of the present study is to analyze the influence of different geometry parameter variations on the flame structure and the NOx emission and to identify the most relevant design parameters, aiming to provide a physical understanding of the Micromix flame sensitivity to the burner design and identify further optimization potential of this innovative combustion technology while increasing its energy density and making it mature enough for real gas turbine application. The study reveals great optimization potential of the Micromix Combustion technology with respect to the DLN characteristics and gives insight into the impact of geometry modifications on flame structure and NOx emission. This allows to further increase the energy density of the Micromix burners and to integrate this technology in industrial gas turbines. Y1 - 2016 SN - 2313-4402 VL - 26 IS - 3 SP - 290 EP - 303 PB - GSSRR ER - TY - JOUR A1 - Funke, Harald A1 - Beckmann, Nils A1 - Keinz, Jan A1 - Abanteriba, Sylvester T1 - Comparison of Numerical Combustion Models for Hydrogen and Hydrogen-Rich Syngas Applied for Dry-Low-NOx-Micromix-Combustion JF - ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition Volume 4A: Combustion, Fuels and Emissions Seoul, South Korea, June 13–17, 2016 N2 - The Dry-Low-NOₓ (DLN) Micromix combustion technology has been developed as low emission combustion principle for industrial gas turbines fueled with hydrogen or syngas. The combustion process is based on the phenomenon of jet-in-crossflow-mixing. Fuel is injected perpendicular into the air-cross-flow and burned in a multitude of miniaturized, diffusion-like flames. The miniaturization of the flames leads to a significant reduction of NOₓ emissions due to the very short residence time of reactants in the flame. In the Micromix research approach, CFD analyses are validated towards experimental results. The combination of numerical and experimental methods allows an efficient design and optimization of DLN Micromix combustors concerning combustion stability and low NOₓ emissions. The paper presents a comparison of several numerical combustion models for hydrogen and hydrogen-rich syngas. They differ in the complexity of the underlying reaction mechanism and the associated computational effort. For pure hydrogen combustion a one-step global reaction is applied using a hybrid Eddy-Break-up model that incorporates finite rate kinetics. The model is evaluated and compared to a detailed hydrogen combustion mechanism derived by Li et al. including 9 species and 19 reversible elementary reactions. Based on this mechanism, reduction of the computational effort is achieved by applying the Flamelet Generated Manifolds (FGM) method while the accuracy of the detailed reaction scheme is maintained. For hydrogen-rich syngas combustion (H₂-CO) numerical analyses based on a skeletal H₂/CO reaction mechanism derived by Hawkes et al. and a detailed reaction mechanism provided by Ranzi et al. are performed. The comparison between combustion models and the validation of numerical results is based on exhaust gas compositions available from experimental investigation on DLN Micromix combustors. The conducted evaluation confirms that the applied detailed combustion mechanisms are able to predict the general physics of the DLN-Micromix combustion process accurately. The Flamelet Generated Manifolds method proved to be generally suitable to reduce the computational effort while maintaining the accuracy of detailed chemistry. Especially for reaction mechanisms with a high number of species accuracy and computational effort can be balanced using the FGM model. Y1 - 2016 SN - 978-0-7918-4975-0 U6 - https://doi.org/10.1115/GT2016-56430 PB - ASME CY - New York, NY ER - TY - JOUR A1 - Neu, Eugen A1 - Janser, Frank A1 - Khatibi, Akbar A. A1 - Orifici, Adrian C. T1 - Automated modal parameter-based anomaly detection under varying wind excitation JF - Structural Health Monitoring N2 - Wind-induced operational variability is one of the major challenges for structural health monitoring of slender engineering structures like aircraft wings or wind turbine blades. Damage sensitive features often show an even bigger sensitivity to operational variability. In this study a composite cantilever was subjected to multiple mass configurations, velocities and angles of attack in a controlled wind tunnel environment. A small-scale impact damage was introduced to the specimen and the structural response measurements were repeated. The proposed damage detection methodology is based on automated operational modal analysis. A novel baseline preparation procedure is described that reduces the amount of user interaction to the provision of a single consistency threshold. The procedure starts with an indeterminate number of operational modal analysis identifications from a large number of datasets and returns a complete baseline matrix of natural frequencies and damping ratios that is suitable for subsequent anomaly detection. Mahalanobis distance-based anomaly detection is then applied to successfully detect the damage under varying severities of operational variability and with various degrees of knowledge about the present operational conditions. The damage detection capabilities of the proposed methodology were found to be excellent under varying velocities and angles of attack. Damage detection was less successful under joint mass and wind variability but could be significantly improved through the provision of the currently encountered operational conditions. Y1 - 2016 U6 - https://doi.org/10.1177/1475921716665803 SN - 1475-9217 VL - 15 IS - 6 SP - 1 EP - 20 PB - Sage CY - London ER - TY - THES A1 - Keinz, Jan T1 - Optimization of a Dry Low NOx Micromix Combustor for an Industrial Gas Turbine Using Hydrogen-Rich Syngas Fuel Y1 - 2018 N1 - Dissertation submitted for the degree of Doctor of Engineering Sciences and Technology ; in Cooperation with Aachen university of Applied Sciences, Department Aerospace Technology; Thesis director: Prof. P. Hendrick; Thesis co-director: Prof. H. Funke PB - Université Libre de Bruxelles - Brussels School of Engineering Aero-Thermo-Mechanics CY - Brüssel ER - TY - JOUR A1 - Finger, Felix A1 - Braun, Carsten A1 - Bil, Cees T1 - Impact of electric propulsion technology and mission requirements on the performance of VTOL UAVs JF - CEAS Aeronautical Journal N2 - One of the engineering challenges in aviation is the design of transitioning vertical take-off and landing (VTOL) aircraft. Thrust-borne flight implies a higher mass fraction of the propulsion system, as well as much increased energy consumption in the take-off and landing phases. This mass increase is typically higher for aircraft with a separate lift propulsion system than for aircraft that use the cruise propulsion system to support a dedicated lift system. However, for a cost–benefit trade study, it is necessary to quantify the impact the VTOL requirement and propulsion configuration has on aircraft mass and size. For this reason, sizing studies are conducted. This paper explores the impact of considering a supplemental electric propulsion system for achieving hovering flight. Key variables in this study, apart from the lift system configuration, are the rotor disk loading and hover flight time, as well as the electrical systems technology level for both batteries and motors. Payload and endurance are typically used as the measures of merit for unmanned aircraft that carry electro-optical sensors, and therefore the analysis focuses on these particular parameters. Y1 - 2018 U6 - https://doi.org/10.1007/s13272-018-0352-x SN - 1869-5582 print SN - 1869-5590 online VL - 10 IS - 3 SP - 843 PB - Springer ER -