@inproceedings{OhndorfDachwaldSeboldtetal.2011, author = {Ohndorf, Andreas and Dachwald, Bernd and Seboldt, Wolfgang and Schartner, Karl-Heinz}, title = {Flight times to the heliopause using a combination of solar and radioisotope electric propulsion}, series = {32nd International Electric Propulsion Conference}, booktitle = {32nd International Electric Propulsion Conference}, pages = {1 -- 12}, year = {2011}, abstract = {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".}, language = {en} } @inproceedings{SchmidtKaschEichleretal.2021, author = {Schmidt, Thomas and Kasch, Susanne and Eichler, Fabian and Thurn, Laura}, title = {Process strategies on laser-based melting of glass powder}, series = {LiM 2021 proceedings}, booktitle = {LiM 2021 proceedings}, pages = {10 Seiten}, year = {2021}, abstract = {This paper presents the laser-based powder bed fusion (L-PBF) using various glass powders (borosilicate and quartz glass). Compared to metals, these require adapted process strategies. First, the glass powders were characterized with regard to their material properties and their processability in the powder bed. This was followed by investigations of the melting behavior of the glass powders with different laser wavelengths (10.6 µm, 1070 nm). In particular, the experimental setup of a CO2 laser was adapted for the processing of glass powder. An experimental setup with integrated coaxial temperature measurement/control and an inductively heatable build platform was created. This allowed the L-PBF process to be carried out at the transformation temperature of the glasses. Furthermore, the component's material quality was analyzed on three-dimensional test specimen with regard to porosity, roughness, density and geometrical accuracy in order to evaluate the developed L-PBF parameters and to open up possible applications.}, language = {en} } @article{LoebSchartnerDachwaldetal.2012, author = {Loeb, Horst Wolfgang and Schartner, Karl-Heinz and Dachwald, Bernd and Ohndorf, Andreas and Seboldt, Wolfgang}, title = {Interstellar heliopause probe}, series = {Труды МАИ}, journal = {Труды МАИ}, number = {60}, publisher = {Moskauer Staatliches Luftfahrtinstitut (МАИ)}, address = {Moskau}, pages = {2 -- 2}, year = {2012}, abstract = {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.}, language = {en} } @incollection{AkimbekovDigelSherelkhanetal.2022, author = {Akimbekov, Nuraly S. and Digel, Ilya and Sherelkhan, Dinara K. and Razzaque, Mohammed S.}, title = {Vitamin D and Phosphate Interactions in Health and Disease}, series = {Phosphate Metabolism}, booktitle = {Phosphate Metabolism}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-91621-3}, doi = {10.1007/978-3-030-91623-7_5}, pages = {37 -- 46}, year = {2022}, abstract = {Vitamin D plays an essential role in calcium and inorganic phosphate (Pi) homeostasis, maintaining their optimal levels to assure adequate bone mineralization. Vitamin D, as calcitriol (1,25(OH)2D), not only increases intestinal calcium and phosphate absorption but also facilitates their renal reabsorption, leading to elevated serum calcium and phosphate levels. The interaction of 1,25(OH)2D with its receptor (VDR) increases the efficiency of intestinal absorption of calcium to 30-40\% and phosphate to nearly 80\%. Serum phosphate levels can also influence 1,25 (OH)2D and fibroblast growth factor 23 (FGF23) levels, i.e., higher phosphate concentrations suppress vitamin D activation and stimulate parathyroid hormone (PTH) release, while a high FGF23 serum level leads to reduced vitamin D synthesis. In the vitamin D-deficient state, the intestinal calcium absorption decreases and the secretion of PTH increases, which in turn causes the stimulation of 1,25(OH)2D production, resulting in excessive urinary phosphate loss. Maintenance of phosphate homeostasis is essential as hyperphosphatemia is a risk factor of cardiovascular calcification, chronic kidney diseases (CKD), and premature aging, while hypophosphatemia is usually associated with rickets and osteomalacia. This chapter elaborates on the possible interactions between vitamin D and phosphate in health and disease.}, language = {en} } @masterthesis{Thomaschik2021, type = {Bachelor Thesis}, author = {Thomaschik, Annika}, title = {Medical Design for Kids: Integration der Bed{\"u}rfnisse von Kindern in medizinische Produkte}, publisher = {FH Aachen}, address = {Aachen}, school = {Fachhochschule Aachen}, pages = {122 Seiten}, year = {2021}, abstract = {Kinder im Kontext von medizinischen Einrichtungen. Kinder sind keine kleinen Erwachsenen und erfordern einen auf sie angepassten Zugang zu medizinischen Behandlungsabl{\"a}ufen. Das Konzept basiert auf dem Gestaltungsprinzip des „Child Centered Design" mit Befragungen von Experten der P{\"a}diatrie und Forschung sowie mit enger Zusammenarbeit mit Kindern. Entstanden ist ein Produkt welches Skepsis und Angst junger Patienten im Alter von 6 bis 14 Jahren bei station{\"a}ren Aufenthalten in Krankenh{\"a}usern mindert und ihren Heilungsprozess positiv unterst{\"u}tzt. Unter Einbezug von digitalen M{\"o}glichkeiten wie Augmented Reality erkl{\"a}rt „ViU", ein Krankenhaus-Companion in Eulen-Optik, den kleinen Patienten Funktionen und das Wirken verschiedenster medizinischer Ger{\"a}te und Behandlungen. So wird nicht nur der Rate an Traumata durch Krankenhausaufenthalte bei Kindern entgegengewirkt, sondern auch das Krankenhauspersonal im Umgang mit Kindern im Klinikalltag entlastet.}, language = {de} } @masterthesis{Schrey2021, type = {Bachelor Thesis}, author = {Schrey, Leander}, title = {Less Waste Shelf: Ein M{\"o}bel zur Reduzierung der h{\"a}uslich anfallenden Lebensmittelabf{\"a}lle}, publisher = {FH Aachen}, address = {Aachen}, pages = {177 Seiten}, year = {2021}, abstract = {Mit dem Projekt wird sich dem Problem der weltweiten Lebensmittelverschwendung angenommen und versucht Abf{\"a}lle in Privathaushalten prim{\"a}r industrialisierter Staaten zu reduzieren. Mit j{\"a}hrlich 1,3 Milliarden Tonnen landet circa ein Drittel aller weltweit produzierten Lebensmittel im M{\"u}ll. Einen Großteil dieser Abf{\"a}lle ist vermeidbar, besonders dort, wo man im {\"U}berfluss lebt. Das konzipierte M{\"o}belst{\"u}ck soll die Lagerungsm{\"o}glichkeiten des Nutzers optimieren und somit f{\"u}r die Wertsch{\"a}tzung von Lebensmitteln sensibilisieren. F{\"u}r das M{\"o}belst{\"u}ck werden ausschließlich nat{\"u}rliche Materialien verwendet, welche in ihrer Charakteristik optimal zum Funktionsumfang passen, der f{\"u}r die Lagerung ben{\"o}tigt wird. Das Material Terracotta erm{\"o}glicht es, mittels Verdunstungsk{\"u}hlung stromlos Gem{\"u}se kalt zu halten. Antibakterielles Holz t{\"o}tet sch{\"a}dliche Bakterien ab. Die Konstruktion erm{\"o}glicht somit eine fachgerechte Lebensmittelagerung und erm{\"o}glicht sowohl sehr flexible Nutzung, wie auch leichte Reparatur.}, language = {de} } @masterthesis{Niederschmidt2021, type = {Bachelor Thesis}, author = {Niederschmidt, S{\"o}ren}, title = {Living product: ein Ansatz, lebendige Organismen mit einem Produkt zu vereinen und nutzbar zu machen}, publisher = {FH Aachen}, address = {Aachen}, pages = {57 Seiten}, year = {2021}, abstract = {Diese Arbeit setzt sich mit der Frage auseinander, in welcher Form sich lebendige Organismen - hier insbesondere Pilze - in die Produktwelt integrieren lassen. In welcher Art und Weise beeinflusst ein Organismus das Produkterlebnis? Im Rahmen dieser Arbeit sind vier verschiedene Produkte entstanden, die die St{\"a}rken des Materials Myzelium demonstrieren. Myzelium bezeichnet das sehr dichte Wurzelnetzwerk eines Pilzes. Dieses lebendige Netzwerk kann dazu genutzt werden, um organische Stoffe miteinander zu verwachsen und somit Formen entstehen zu lassen. Die so entstandenen Produkte sind in eine Konzeptumgebung eingebettet, in der der Verbrauchende die Natur durch naturn{\"a}here Produkte (Form, Material und gewachsene Strukturen) neu erlebt. Gezeigt wird ein Packaging f{\"u}r Einmachgl{\"a}ser, ein Kressebeet, ein Wandregal und ein Teelicht.}, language = {de} } @inproceedings{DachwaldSeboldtHaeusler2002, author = {Dachwald, Bernd and Seboldt, Wolfgang and H{\"a}usler, Bernd}, title = {Performance requirements for near-term interplanetary solar sailcraft missions}, series = {6th International AAAF Symposium on Space Propulsion: Propulsion for Space Transportation of the XXIst Century}, booktitle = {6th International AAAF Symposium on Space Propulsion: Propulsion for Space Transportation of the XXIst Century}, pages = {9 Seiten}, year = {2002}, abstract = {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.}, language = {en} } @inproceedings{SeboldtDachwald2003, author = {Seboldt, Wolfgang and Dachwald, Bernd}, title = {Solar sails for near-term advanced scientific deep space missions}, series = {Proceedings of the 8th International Workshop on Combustion and Propulsion}, booktitle = {Proceedings of the 8th International Workshop on Combustion and Propulsion}, pages = {14 Seiten}, year = {2003}, abstract = {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.}, language = {en} } @incollection{Dachwald2010, author = {Dachwald, Bernd}, title = {Solar sail dynamics and control}, series = {Encyclopedia of Aerospace Engineering}, booktitle = {Encyclopedia of Aerospace Engineering}, publisher = {Wiley}, address = {Hoboken}, doi = {10.1002/9780470686652.eae292}, year = {2010}, abstract = {Solar sails are large and lightweight reflective structures that are propelled by solar radiation pressure. This chapter covers their orbital and attitude dynamics and control. First, the advantages and limitations of solar sails are discussed and their history and development status is outlined. Because the dynamics of solar sails is governed by the (thermo-)optical properties of the sail film, the basic solar radiation pressure force models have to be described and compared before parameters to measure solar sail performance can be defined. The next part covers the orbital dynamics of solar sails for heliocentric motion, planetocentric motion, and motion at Lagrangian equilibrium points. Afterwards, some advanced solar radiation pressure force models are described, which allow to quantify the thrust force on solar sails of arbitrary shape, the effects of temperature, of light incidence angle, of surface roughness, and the effects of optical degradation of the sail film in the space environment. The orbital motion of a solar sail is strongly coupled to its rotational motion, so that the attitude control of these soft and flexible structures is very challenging, especially for planetocentric orbits that require fast attitude maneuvers. Finally, some potential attitude control methods are sketched and selection criteria are given.}, language = {en} }