Refine
Year of publication
- 2010 (317) (remove)
Document Type
- Article (175)
- Conference Proceeding (67)
- Book (37)
- Part of a Book (20)
- Patent (7)
- Report (4)
- Other (2)
- Contribution to a Periodical (1)
- Doctoral Thesis (1)
- Master's Thesis (1)
- Talk (1)
- Working Paper (1)
Has Fulltext
- no (317) (remove)
Keywords
- Geschichte (2)
- avalanche (2)
- Cardiovascular MRI (1)
- Commercial Vehicle (1)
- Common Rail Injection System (1)
- Diesel Engine (1)
- European Transient Cycle (1)
- Illustration (1)
- Left ventriular function (1)
- MR-stethoscope (1)
- Magnetic field strength (1)
- Magnetic resonance imaging (MRI) (1)
- Process virtualization (1)
- Product bundling (1)
- RAMMS (1)
- Selective Catalytic Reduction (1)
- Services (1)
- Telecommunication (1)
- Transformation (1)
- Typographie (1)
Institute
- Fachbereich Medizintechnik und Technomathematik (68)
- Fachbereich Wirtschaftswissenschaften (41)
- IfB - Institut für Bioengineering (36)
- Fachbereich Elektrotechnik und Informationstechnik (34)
- Fachbereich Energietechnik (31)
- Fachbereich Maschinenbau und Mechatronik (31)
- Fachbereich Chemie und Biotechnologie (26)
- Fachbereich Luft- und Raumfahrttechnik (24)
- Fachbereich Bauingenieurwesen (23)
- INB - Institut für Nano- und Biotechnologien (23)
- Fachbereich Architektur (13)
- Solar-Institut Jülich (13)
- Fachbereich Gestaltung (5)
- Sonstiges (5)
- ECSM European Center for Sustainable Mobility (4)
- ZHQ - Bereich Hochschuldidaktik und Evaluation (2)
- IBB - Institut für Baustoffe und Baukonstruktionen (1)
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.
Sisyphus wird Steiff
(2010)
Biofuels potentially interesting also for aviation purposes are predominantly liquid fuels produced from biomass. The most common biofuels today are biodiesel and bioethanol. Since diesel engines are rather rare in aviation this survey is focusing on ethanol admixed to gasoline products.
The Directive 2003/30/EC of the European Parliament and the Council of May 8th 2003 on the promotion of the use of biofuels or other renewable fuels for transport encourage a growing admixture of biogenic fuel components to fossil automotive gasoline. Some aircraft models equipped with spark ignited piston engines are approved for operation with automotive gasoline, frequently called “MOGAS” (motor gasoline). The majority of those approvals is limited to MOGAS compositions that do not contain methanol or ethanol beyond negligible amounts. In the past years (bio-)MTBE or (bio-)ETBE have been widely used as blending component of automotive gasoline whilst the usage of low-molecular alcohols like methanol or ethanol has been avoided due to the handling problems especially with regard to the strong affinity for water. With rising mandatory bio-admixtures the conversion of the basic biogenic ethanol to ETBE, causing a reduction of energetic payoff, becomes more and more unattractive. Therefore the direct ethanol admixture is accordingly favoured.
Due to the national enforcements of the directive 2003/30/EC more oxygenates produced from organic materials like bioethanol have started to appear in automotive gasolines already. The current fuel specification EN 228 already allows up to 3 % volume per volume (v/v) (bio-)methanol or up to 5 % v/v (bio-)ethanol as fuel components. This is also roughly the amount of biogenic components to comply with the legal requirements to avoid monetary penalties for producers and distributors of fuels.
Since automotive fuel is cheaper than the common aviation gasoline (AVGAS), creates less problems with lead deposits in the engine, and in general produces less pollutants it is strongly favoured by pilots. But being designed for a different set of usage scenarios the use of automotive fuel with low molecular alcohols for aircraft operation may have adverse effects in aviation operation. Increasing amounts of ethanol admixtures impose various changes in the gasoline’s chemical and physical properties, some of them rather unexpected and not within the range of flight experiences even of long-term pilots.